Abstract:By using the growth superiority demonstrated by the female individuals of the cultured grass carp, the method of breeding the whole female grass carp species by sex reversal is discussed, which has a good application prospect. The 17α-methyltestosterone (17α-MT) was selected to induce female-to-male as the male hormone, and set 4 concentration gradients evenly mixed with feed, i.e. 0 mg/kg, 50 mg/kg, 100 mg/kg, 200 mg/kg, which were respectively fed for 150 days. The objective of this study was to investigate the effects of different MT-treated diet on gonadal development and the changes of estradiol-17β (E₂), testosterone (T) and 11-ketotestosterone (11-KT), and further the characteristics in the process of grass carp sex reversal. The morphological changes of grass carp were investigated by observing the changes of gonadal structure and serum steroid hormone content at different treatment levels to explore the sex reversal. Histological sections of gonads results showed that spermatogonia began to appear in the ovaries of all treatment groups from the 30 th day after feeding. With the prolongation of feeding time, 50 mg/kg MT treatment group can inhibit the formation and maturation of oocytes, resulting in developmental delay; The inhibition of germ cells in 100 mg/kg MT treatment group was higher than that in 50 mg/kg MT treatment group, the gonads had been occupied by a large number of spermatogonia, and there was a tendency of developing testis at 210 d. The ovaries-testes state of 200 mg/kg MT treatment group at 210 d was more obvious than 50 mg/kg MT treatment group, but the number of spermatogonia was less than 100 mg/kg MT treatment group, while the control group ovary did not exhibit spermatogonia. The results of serum steroid hormone revealed that E₂ increased significantly which to some extent depended on the MT dosages, reached the highest value at 45 days and then decreased steadily, but was still significantly higher than that of the control group, however. With the development of early stage testis, E₂ level of control male also gradually increased. With the prolongation of MT feeding time, the concentrations of T in each treatment group decreased to different extents, and the biggest drop occurred in all treatment groups at 45 days, which was positively correlated with the MT concentration. The 11-KT increased to varying degrees. The results show that: 100 mg/kg was more suitable concentration to bring about sex reversal, MT can cause the early female fish serum E₂ to increase, and exert the effect of androgen, thereby promoting ovarian egg cell degradation, and spermatogonia proliferation.

Abstract:Kisspeptins are a family of neuropeptides encoded by the Kiss genes and play important roles in the reproduction and the regulation energy balance in vertebrate. In order to identify the sequence information of Trachinotus ovatus Kiss1 (ToKiss1) and its expression response to the different feed types, ToKiss1 was cloned from the T. ovatus based on its genome sequences and transcriptome sequences, then the expression level of ToKiss1 in liver and intestine tissues were analyzed by qRT-PCR. ToKiss1 is approximately 2 768 bp in length with 3 exons and 2 introns. The whole length of ToKiss1 cDNA was 505 bp, including a 312 bp open reading frame (ORF) encoding 104 amino acids, in which there are a signal peptide and one kisspeptin-10 domain (YNLNSFGLRY). Its tertiary structure consisted of two α-helices and was similar to a pail. Phylogeny analysis proved that the kisspeptin-1 in Osteichthyes has distant relationship with the kisspeptin-1 in Mammalia, Amphibian and Reptilia. The qRT-PCR tissue expression analysis indicated that ToKiss1 mRNA was expressed in brain, intestine, stomach, spleen and muscle with the highest expression level in brain. Feed types significantly affected the expression profile of intestinal ToKiss1 mRNA. The transcription level of intestinal ToKiss1 mRNA in T. ovatus fed with pelleted feed was higher than in those fed with iced fish, and the T. ovatus fed with iced squid had lowest ToKiss1 mRNA expression. However, feed types did not significantly affect the expression profile of hepatic ToKiss1 mRNA. All those results indicated that kisspeptin may play a critical role in digestion and absorption functions of the T. ovatus. The research for the first time focuses on expression difference of ToKiss1 mRNA in liver and intestine of Osteichthyes by feeding different feed types, which benefits further studies on the feeding regulation physiological mechanism of Kiss1 gene of teleost fish.

Abstract:Japanese Spanish mackerel (Scomberomorus niphonius) during spawning seasons were collected from Lüsi spawning ground in the southern Yellow Sea, then transverse sections of otoliths were analyzed from its core to the margin by using laser ablation ICPMS. Element:calcium ratios were integrated with microstructural analysis to produce profiles of different life stages for measured elements. The results revealed that the detected Li, Na, Mg, Fe, Co, Sr and Ba were all heterogeneously distributed on the otolith. However, Ba:Ca ratio fluctuated sharply with a range of 2.13–5.05 μmol/mol. The Ba concentration was normally high in the otolith cores (0–40 μm), declining rapidly in 40–320 μm areas and being low in the remaining areas (320–1 440 μm). Therefore, Ba:Ca ratio showed significant difference between life stages: it was significantly higher in hatching stage than in wintering and spawning stages. It indicated that variation in Ba:Ca ratio was most informative and S. niphonius seemed to prefer high Ba concentrations habitats at the stages of embryonic development and hatching before they soon swam away from this habitat at the stage of post-hatching development. Low Ba concentrations habitats seemed to be preferable for the stage of wintering and spawning. These results provided further evidence for the common migration trajectory.

Abstract:To study the effects of culture temperature on antioxidant capacity and inflammatory responses of Larimichthys crocea macrophages, macrophages were isolated from head kidney of L. crocea and resultant monolayer was maintained at 16 ℃, 22 ℃ and 28 ℃, respectively. After adding 25 μg/mL LPS medium to macrophage monolayer for 2 h, cell viability, respiratory burst activity, antioxidant enzyme activities and gene expressions together with IL-1β and Hsp70 mRNA expressions of macrophage cultured at different temperatures were evaluated. Results showed that cell viability of macrophages placed at 16 ℃ and 22 ℃ was significantly higher than cells cultured at 28 ℃ after incubation for 36 h. LPS could significantly promote the respiratory burst activity and inhibited the activities of SOD and CAT enzymes. Macrophage incubated at high temperature (28 ℃) showed significantly higher CAT enzyme activity and gene expression, whereas no significant difference was found in SOD enzyme activity and gene expression. LPS triggered potent pro-inflammatory response with IL-1β being the indicative parameter, which was inhibited by high culture temperature. However, transcript levels of Nrf2 and Hsp70 increased with the rise of temperature to a significant extent, and both gene expressions were markedly enhanced by LPS compared to control groups. Taken together, all the results in the present study indicated that temperature may regulate the antioxidant capacity and inflammatory responses of LPS-induced macrophages from head kidney of L. crocea through pathways involving Nrf2 and Hsp70.

Abstract:The North Pacific albacore tuna (Thunnus alalunga) is one of the main target species of tuna longline fisheries, and the conservation and management of this species have been increasingly concerned by tuna regional management organizations, such as WCPFC. T. alalunga is a kind of highly migratory species mainly living in the tropical and subtropical waters. This species which lives in the North Pacific Ocean generally spawns at the western and central part of the tropics and subtropics in spring and early summer. In the juvenile period of T. alalunga, a number of albacores migrate from the North Pacific to the temperate waters of the eastern Pacific. The spawns will migrate to the western tropical and subtropical regions of the Pacific to spawn. This set of patterns of movement will be juvenile fish recorded. The migratory characteristics of this species can provide an important basis for its sustainable utilization and management. Since the difficulty of sample collection, studies for the age identification of the North Pacific T. alalunga were few. Therefore, we studied the age and growth of T. alalunga in the North Pacific by the species’ spines data from the survey of the long-spines tuna fishery in the North Pacific during the years of 2013 and 2014. The fin rays are the newest manifestation of the biological information of T. alalunga in the North Pacific, providing useful information for the sustainable utilization and management of T. alalunga in the North Pacific. Information on the age and growth is very important for conducting stock assessment of this species. Based on 258 fin ray samples collected on the Chinese tuna longliner “Tianxiang 16” operated in the North Pacific between October 19, 2013 and April 5, 2014, the age and growth of the North Pacific T. alalunga were studied. Three different cutting positions were involved in the processing of section selection, and three functions, the linear function, exponential function and exponential function respectively, were also used to fit the relationships between the fork length and fin ray radius. The Von Bertalanffy growth function of the North Pacific albacore was L_t=112.231×[1-e^{–0.277(t+1.435)}].

Abstract:In order to understand the biological function of glucocorticoid receptors (GRs) of Megalobrama amblycephala, we explored the expression characteristics of grs in different tissues and the expression changes of grs and some function genes in the recovery process after stress. Results show that the gr1 was highly expressed in gill, spleen and head kidney, while gr2 was highly expressed in pituitary, liver, intestinal, and so on. During the recovery process, on HPI axis, the expression of gr1 had fluctuations, gr2 significantly up-regulated at the 0 h, and the value of gr1/gr2 was gradually increasing in hypothalamus. The expression of gr1 and gr2 all rose first and then decreased, gr1/gr2 value reached the peak at 2 h in pituitary. The expression of gr1 had fluctuations, whereas gr2 had a low expression at 0 h and 2 h compared with the other time points, gr1/gr2 value gradually decreased in head kidney. In liver, gr1 rose in the early time (0 h and 2 h), and gr2 presented a fluctuating situation, and there was a tendency to reduce the the value of gr1/gr2. At the similar time point the expression of pepck peaked. In gills gr1 rose first, and then decreased, while the expression of gr2 was subdued in the early time (0 h and 2 h), gr1/gr2 value maintained at a large value during 2-8 h, while the occ expression peaked at 2 h. In skin gr1 and gr2 rose significantly in 2 h, gr1/gr2 in 2-8 h also maintained at a large value, and the occ expression rose first and then decreased. Histology research shows that gill filament was hyperplasia, lymphocyte-like cells increased kidney tissues, while other organizations examined had no obvious pathological changes. All the results indicate that GRs have a complex regulatory mechanism in the stress, and the histological analysis shows that the risks of pathological changes come from the stress.

Abstract:Manganese superoxide dismutase (MnSOD), a transition-metal-containing antioxidant enzyme that dismutates the superoxide radicals to either ordinary molecular oxygen (O₂) or hydrogen peroxide (H₂O₂), widely existed in many aerobic organisms. In this study, the cDNA of MnSOD, identified from Nibea albiflora, was 958 bp in length including 5′-untranslated region (UTR) of 47 bp, 3′-UTR of 233 bp and an open reading frame (ORF) of 678 bp encoding a polypeptide of 225 amino acids. The deduced amino acid sequence analysis showed that MnSOD contains a putative signal peptide in the N-terminus (1-27 aa), four Mn binding sites (His 53, 101, 190 and Asp 186) and a Mn/Fe SOD signature sequence (186-193 aa). Phylogenetic tree analysis indicated that N. albiflora has the closest relationship with Larimichthys crocea, and was classified into the same cluster with other teleosts (Epinephelus coioides, Takifugu fasciatus, Paralichthys olivaceus, Danio rerio and Anguilla japonica). Quantitative real-time qRT-PCR analysis showed that the mRNA transcripts of MnSOD were detected in all examined tissues and the predominant distribution was in heart, followed by brain, liver, gill, kidney, intestine, stomach, head-kidney, muscle and swim bladder, and the minimum level was displayed in spleen. Moreover, during the acute toxic experiment of ammonia nitrogen or nitrite nitrogen, N. albiflora showed more sensitive to ammonia nitrogen, and the 96 h median lethal concentration (LC₅₀) value was found to be 20.23 mg/L for ammonia nitrogen (or 0.57 mg/L for non-ionic ammonia) with safe concentration (SC) values of 2.02 mg/L (or 0.06 mg/L for non-ionic ammonia) and 99.08 mg/L with SC of 9.91 mg/L for nitrite nitrogen, successively. Furthermore, the temporal expression of MnSOD was significantly up-regulated in the liver, gill and head-kidney of N. albiflora. The expression features of the MnSOD suggested its important role in scavenging oxygen free radicals caused by ammonia nitrogen/nitrite nitrogen and could be used as an early biomarker for detection of environmental pollution.

Abstract:It is known to all that age and growth study of crustacean is a problem. However, this problem has been solved to some extent as growth increments were found in hard structures such as eyestalk and gastric mill of crustacean. Fenneropenaeus chinensis as one of important economic shrimp, the study of age and growth has been widely concerned. This paper collected 69 F. chinensis from the coastal waters of Nantong, Jiangsu Province. The microstructures of eyestalks of these F. chinensis were analyzed, and the relationship between growth bands of the eyestalks and the weight of F. chinensis was studied. Research shows that the eyestalks consists of four parts: epicuticle, exocuticle, endocuticle and membranous layer. Eyestalk has growth bands and growth increments obviously. Among 44 clear microstructure samples, there are 33 samples with 0 growth band, and 11 samples with 1 growth band. The number of growth increments in one growth band is 25 to 37. The number of growth increments and the length and weight of F. chinensis showed Logistic relation. We conclude that the formation of growth bands of eyestalk in F. chinensis is yearly. However, the formation of growth increments is not daily. Whether the formation period of growth increment is different from the individual differences and the growth environment differences of F. chinensis needs further experimental verification. The results not only lay the foundation for the future identification of F. chinensis, but also provide a new method for the domestic identification of shrimp and crabs and their growth.

Abstract:In order to study the roles of R-spondin1(Rspo1) gene in the sex determination and differentiation of the Qihe crucian carp (Carassius auratus), a natural gynogenesis triploid fish, we cloned its cDNA by using reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA 5′ and 3′ ends (RACE). We also examined Rspo1 spatio-temporal expression profiles by real-time PCR, at the same time, expression level of Rspo1 in the testis induced by Letrozole or high temperature treatment was also examined. The results showed that the cDNA of Rspo1 was 1243 bp including a 318 bp 5′-untranslated region (UTR), a 127 bp 3′UTR, and a 798 bp open reading frame (ORF) encoding a polypeptide of 265 amino acids. Sequence analysis revealed that Rspo1 from Qihe crucian carp showed the highest similarity with Cyprinidae fish, while had low similarity with other vertebrates including mammalians and reptiles. Tissue distribution by real-time PCR revealed that Rspo1 was abundantly expressed in the muscle, and then in the ovary, gill, intestine, and was barely detectable in other tissues. The expression of Rspo1 was gradually downregulated from fertilization stage, and then upregulated from the tailbud stage, so Rspo1 might be a maternal factor. Ontogenic analysis demonstrated that Rspo1 was expressed abundantly from 20 days after hatching (dah) in the gonad. However, Rspo1 was upregulated in the gonad of sex-reversed males by Letrozole or high temperature treatment, indicating that Rspo1 exhibited a sexual dimophic expression pattern. These results suggested that, as a maternal factor, Rspo1 might be involved in both the ovarian differentiation and spermatogenesis in the testis of C. auratus.

Abstract:In order to investigate salt tolerance and immune response under high-salt stress in postlarvae of Litopenaeus vannamei, a 30-day feeding trial was conducted with different high-salt stress (40, 50, 60, 65 and 30 as CK). Body weight were detected at the start and end of the trial to get average daily gain, and the activities of T-ATPase, Na⁺-K⁺-ATPase, ACP, AKP, SOD, CAT, LZM and MDA were detected at the end of the trial. The results showed that high-salt stress significantly inhibited average daily gain of postlarvae. The average daily gain showed decreasing trend with the increase of salinity, those of salinity 40, 50, 60, 65 were 84.53%, 60.99%, 46.19% and 27.71% compared with 30, respectively; Survival rate decreased significantly as salinity increased. The T-ATPase activity of postlarvae showed a tendency to decrease first and then stabilize at about 1.4 U/mg prot with salinity increasing. However, the change trend of Na⁺-K⁺-ATPase activity was opposite to T-ATPase activity. When salinity was 60 and 65, the activity of Na⁺-K⁺-ATPase was stable. In addition, high-salt stress also significantly affected the activities of non-specific immunity enzymes of L.vannamei postlarvae. With the increase of salinity, the enzymes activities of T-SOD and CAT had the same trend, rising first and decreasing then. Their highest values, 16.118 U/mg prot and 1.378 U/mg prot respectively, were detected at the salinity of 50. The changes of ACP and AKP activities were positively correlated with salinity. Under different salt stress treatments, the content of MDA changed significantly, and LZM content did not significantly change at all salinity levels. The result indicated that the higher salinity, the slower the growth rate and the increase of the energy for osmotic regulation of L.vannamei postlarvae. In a certain salinity range, high-salt stress can stimulate some non-specific immunity enzymes to cope with the salt stress environment and reduce the damage to the body.

Abstract:Marine fishery fishing operations are carried out in different spatial and temporal scales, and the distribution of fish may vary with the spatial-temporal scale. Spatial and temporal scales play a vital role in the study of marine fishery habitat, but there were few researches on the comparison of habitat suitability index models in different spatial-temporal scales. In this study, based on the statistical data of Scomber japonicus from July to September in 2003—2011, combined with the data of sea surface temperature (SST) and sea surface height (SSH) obtained by ocean remote sensing, using arithmetic mean model (AM) and the relationship between SST and SSH to build habitat suitability index model (HSI). The study divided the sea surface temperature (SST) and sea surface height (SSH) into different spatial and temporal scales. Spatial scales included 0.25°×0.25°, 0.5°×0.5° and 1°×1°, temporal scales included weekly, ten days and monthly. A total of 9 HSI models were constructed in different spatial-temporal scales. The results indicated that spatial scale of 1°×1° and temporal scale of monthly were the most optimum spatial-temporal scales. When HSI value was greater than 0.6, the percentage of fishing effort was 75.42%, and when HSI value was less than 0.4, the percentage of fishing effort is 12.93%. According to the optimum spatial-temporal scales, using the data from July to September in 2012 to verify the optimum model, when HSI value was greater than 0.6, the percentage of fishing effort was 60.89%, and when HSI value was less than 0.4, the percentage of fishing effort is 13.88%. In summary, the spatial and temporal scales of fishing and marine environment factors should be considered during the construction of fishery habitat suitability index model.

Abstract:we developed a method to separate the GC and SGC of Cherax quadricarinatus by using discontinuous Percoll density gradient centrifugation. The dilution buffer and the combination of density gradient were optimized. We found that the density gradient should be diluted in anti-clotting buffer to prevent hemocytes aggregation, and the discontinuous Percoll density gradient that consisted of 20%, 65% and 100% of Percoll provided the best result compared with others. After centrifugation at 1 810 r/min for 20 min, the hemocytes were separated into two layers, corresponding to SGC and GC, respectively. Flow cytometry analysis showed that the purities of both fractions were >95% and the cell mortalities were <1.5%. The isolated cells were in good status and could be readily used for further analysis. This simple and effective method will facilitate the study on the function of different hemocytes and thus provide information for disease control.

Abstract:Five complete cDNA sequences related to Wnt/β-catenin signal pathway, designated wnt2, wnt2bb, wnt3a, wnt8a and ctnnb1, were amplified by RT-PCR and RACE approaches from yellow catfish (Pelteobagrus fulvidraco). The validated cDNAs encoding wnt2, wnt2bb, wnt3a, wnt8a and ctnnb1 were 1 743, 2 133, 1 379, 1 508 and 2 636 bp in length, encoding peptides of 351, 372, 291, 387 and 791 amino acid residues, respectively. The amino acid alignment and phylogenetic analysis revealed that these sequences were relatively conserved among vertebrates, and Wnt/β-catenin genes of P. fulvidraco were more closely related to those of Astyanax mexicanus. All Wnt/β-catenin mRNAs were expressed in nine tested tissues (brain, spleen, kidney, gill, heart, muscle, mesenteric fat, liver and ovary), but at variable levels. Effect of waterborne Cu exposure on ovarian mRNA levels of the five genes of P. fulvidraco were determined. On day 28, wnt3a mRNA levels in the ovary significantly decreased with increasing waterborne Cu concentration, but wnt8a showed the opposite trend. On day 56, mRNA levels of these five genes from the ovary of P. fulvidraco showed no significant differences among the three groups. The present study may be helpful to understand the physiological functions of Wnt/β-catenin pathway in fish.

Abstract:Because of improving resource utilization and reducing environmental pollution, IPA (Intensive Pond Aquaculture) technology has been widely promoted as a new breed aquaculture technology. In order to improve the efficiency of pollution collection and discharge in the process of aquaculture, the method of constructing negative slope bottom is used to reconstruct aquaculture tanks. By establishing a two-dimensional simplified model of aquaculture tank and combining the CFD-DEM simulation and KPLS (Kernel Partial Least-Squares Regression) modeling method, a model that can reflect the relationship between the vertical velocity distribution and the bottom slope was established. On this basis, the model of the particle incipient velocity and the single wide suspended load transport rate in the tank was obtained by the theory of sediment motion. After setting up two performance indexes of particle motion and transportation, the DP-MOPSO (Preference-based Multi-objective Particle Swarm Optimization) method was used to get the optimal bottom slope. The optimization results show that with the increase of the bottom roughness, the optimal gradient is slightly reduced and the range is about 0.013-0.015. The simulation results show that the optimal bottom slope can effectively improve the moving probability and the transport capacity of particles, and for the rough surface, the superiority of the slope bottom is more significant. It shows that it is reasonable to optimize the discharge performance of aquaculture tanks by constructing the bottom slope to change the flow structure.

Abstract:Giant freshwater prawn (Macrobrachium rosenbergii) is an important cultured species in China. Molting is closely related to the growth and breeding of M. rosenbergii. Chitinase, a member of the glycoside hydrolase family 18, plays vital physiological roles in crustaceans, including molting, digestion, and immunity. The molting cycle of M. rosenbergii consisted of five stages, named postmolt Ⅰ (A), postmolt Ⅱ (B), intermolt (C), premolt (D), and molt (E). To understand the characteristics and molecular dynamics of chitinase in the molting cycle of M. rosenbergii, the chitinase gene of M. rosenbergii (MrChi3B) was cloned. Thereafter, polyclonal antibody against the chitinase was generated in rabbit. The cDNA of MrChi3B spans 1 143 bp that encodes a protein of 380 amino acids (aa) with a predicted molecular weight of 41.91 ku. Phylogenetic analysis revealed that chitinase contains the GH18 family catalytic domain, and it was closely related to chitinase of M. nipponense with 94% homology at the aa level. The expression profile of MrChi3B in six different tissues (eyestalk, gill, stomach, muscles, endocuticle, intestine) and at different stages of the molting of M. rosenbergii was investigated by quantitative real-time PCR (qRT-PCR) and Western blot (WB) analysis. The results showed that the MrChi3B was ubiquitously expressed in all the tested tissues, whereas its expression was significantly increased in stomach, skin, and muscle at A, B stages. At the stage C, highest expression of MrChi3B was observed in the stomach. At the stages A, B, the expression of MrChi3B in the endocuticle and muscle reached the highest. The expression of MrChi3B in the intestine has increased during the stage D and E. Relative lower expression of MrChi3B was observed in the eyestalk at all the stages. The results will shed a new light on the further study of the function of MrChi3B from M. rosenbergii.

Abstract:In order to establish a quick and accurate determination method of whether the oocyte of Chinese mitten crab (Eriocheir sinensis) is mature or not, a series of experiments were carried out referred to the clearing solution’s ingredients of oocyte in zebrafish. Finally, we found that the mixture of 60 percent of ethanol, 1 percent of acetic acid and 30 percent of formaldehyde was useful for the oocyte of Chinese mitten crab. White spots could be observed in immature oocytes after treated with the mixture, while in mature oocytes, no white spot could be seen. And it is consistent with the result of optical microscopy and H.E staining. Obviously, the mixture of 60 percent of ethanol, 1 percent of acetic acid and 30 percent of formaldehyde could be used to determine whether the oocyte of E. sinensis is mature.

Abstract:The Chinese mitten crab (Eriocheir sinensis) is an important aquaculture species and food source in Eastern Asia. At the present, pond-reared broodstock are used for seed production of E. sinensis, and the reasonable utilization of wild-caught broodstock is conducive breeding and selection of E. sinensis. Reproductive performance is one of the most important indicators for the evaluation of broodstock quality in aquatic animals. This study was designed to determine and compare the reproductive performance, egg quality, colouration, proximate and fatty acid composition of wild-caught and pond-reared E. sinensis broodstock. The results showed that: ①the wild-caught E. sinensis broodstock had the slightly higher egg production, fecundity and reproductive effort than the pond-reared females, but there was no significant difference between two treatments. The egg diameter, wet weight and dry weight of individual egg were similar between two treatments. ② The eggs from pond-reared E. sinensis broodstock had significantly higher redness (a*), yellowness (b*) and total carotenoids contents than those of the eggs produced by the wild-caught broodstock, however, there are no significant differences for lightness (L*) and colour difference (dE*). ③ As for proximate composition of eggs, no significant differences were found for the moisture, total protein and total lipid contents between the wild-caught and pond-reared treatments. The eggs from wild-caught broodstock had the significantly higher percentages of C18:1n9, C18:1n7, C20:4n6, C22:5n3 and C22:6n3 than the eggs produced by the pond-reared broodstock, but the C18:2n6 and C18:3n3 of the wild caught broodstock were significantly lower than those of the pond-reared broodstock. In conclusion, these results indicated that the reproductive performance and egg proximate composition were similar between wild-caught broodstock and pond-reared broodstock with similar body weight, but significant differences were found on redness (a*), yellowness (b*), total carotenoids content and fatty acid composition in the eggs. These results could provide valuable information for the broodstock selection, evaluation of reproductive performance and artificial breeding of E. sinensis in the future.

Abstract:Nitrite nitrogen is toxic to the aquatic animals. Monitoring the concentration of nitrite nitrogen is very critical for the culture of aquatic animals. Due to the high cost of the current commercial electrode sensor which is used to measure the concentration of nitrite nitrogen in water, this kind of sensor is very difficult to be popularized on a large scale. Therefore, it is an urgent need to develop another novel method to predict the concentration of nitrite nitrogen in water. In this paper, taking the advantage of the established online water monitoring system in our laboratory, the temperature, pH value, dissolved oxygen and oxidation-reduction potential were recorded from the water in tanks. Meanwhile, the actual concentration of nitrate nitrogen in water was measured using alpha-naphthalene colorimetric method. The data after pretreatment were used as the original data to be used for SAE neural network training. Thereafter, unsupervised greed training method was applied. The learnt characteristics were used for the supervision and training of BP neural network. The model was optimized using the back propagation (BP) algorithm. The prediction model R² of the nitrite nitrogen after training was 0.95, and root mean square error of the prediction (RMSEP) was 0.099 71, indicating that the model could accurately predict the concentrations of nitrate nitrogen in water. The established model will pave a new way for developing online system for monitoring the water nitrate nitrogen concentration in the future.

Abstract:Bromodomain-containing protein (BCP) is a highly conservative protein, which belongs to the bromodomain and extraterminal (BET) protein superfamily. BCP can regulate gene replication and transcription by recruiting different chromosome modifying proteins, and the change of its expression is often associated with the occurrence of tumor and inflammation. Based on the transcriptomic analysis, a cDNA sequence of BCP gene (Lv-BRD), 2 229 bp in length, was isolated from the hemocytes of Litopenaeus vannamei in this study. The sequence has been deposited in GenBank with accession number of MH638256. Using online tools, the sequence was characterized. The deduced protein sequence of Lv-BRD has a conservative bromine domain, indicating that it may be involved in the regulation of cell cycle. Tissue/organ expression was analyzed by qPCR and the result showed that Lv-BRD was mainly expressed in hemocytes, hepatopancreas and gills of shrimp. Expression of Lv-BRD in hemocytes increased significantly in the early stage (0.5–12 hours past infection, hpi) challenge by white spot syndrome virus (WSSV), B. thuringiensis and V. parahemolyticus, suggesting that Lv-BRD is involved in the innate immune response to pathogens in shrimp. These results provided a basis for further studies on the function and mechanism of Lv-BRD in antiviral immunity and interferon regulation of L. vannamei.

Abstract:The development and exocytosis of the ring-shaped granules (RG) during the process of fertilization membrane (FM) formation in Scylla paramamosain were investigated by transmission electron microscope. The results are as follows: FM, the second envelope between oocyte and chorin, formed during a complex cortical reation initiated after fertilization. The cortical reation includes the successive exocytosis of two morphologically different granules. Firstly the dense granules underwent exocytosis and formed a thin membrane. After that, RG underwent several rounds of massive and rapid exocytosis, and the material from RG fused and formed a thick membrane. Every round of exocytosis of RG participated in three stages as the placid, the thickening and the swelling of FM. The development of RG happened both in the cortex and the nearby endoplasm mainly at the thickening phase of FM. Numerous RG formed and shifted to the edge of plasm membrane to participate in FM formation by explosive exocytosis. Our study showed that the development of RG was closely connected with two kinds of yolk granules and lipid drops, and mitochondria only appeared at cortex. So we inferred that there may be two kinds of RG forming mechanics in cortex and endoplasm in S. paramamosain. Finally, FM was composed of the two layers, and the newly formed plasma membrane became an inlaying membrane (the third envelope). The importance of yolk and lipid drops and RG in participating in FM formation was discussed at the end of this paper.

Abstract:To investigate the possibility of feeding the red swamp crayfish (Procambarus clarkii) with biofloc technology, a 30-day short-term experiment was conducted to farm juveniles (9.70±0.32) g using biofloc technology and feeding normal diet. This experiment compared the hydrochemical indexes of two experimental groups during experimental period and compared the growth performance, muscle and hepatopancreas nutrient composition, the digestive enzyme activities in stomach, intestine, hepatopancreas tissues, the antioxidant capacity in hepatopancreas and muscle tissues of two groups’ juveniles at the end of the experiment. The results showed that the concentration of total nitrogen (TN), nitrite nitrogen (NO₂^--N), nitrate nitrogen (NO₃^--N) of the biofloc group were all kept at a low level during experimental period. The final weight of the juvenile shrimps, the weight gain rate (WG), the specific growth rate (SGR) and survive rate (SR) showed no significant difference in the two experimental groups under this experiment condition. The content of crude protein of the biofloc was 36.8% which could meet the protein requirement of P. clarkii. However, the crude lipid content of biofloc was significantly lower and affected the crude lipid content of muscle from biofloc group juveniles. The α-amylase (α-AL), lipase (LPS) and cellulase (CL) activities in hepatopancreas of the biofloc group juveniles were significantly higher than that of the diet group juveniles, respectively, while α-AL activity in stomach and intestine was higher in the diet group. No significant difference was found in the pepsin activity between the two experimental groups. Comparing the antioxidant capacity of crayfish juveniles from the two experimental groups, the activity of superoxide dismutase (SOD) in hepatopancreas of juveniles from the biofloc group was significantly higher, and the content of malondialdehyde (MDA) was much lower than that from the diet group. No differences were found in the activities of total antioxidant capacity (T-AOC), catalase (CAT), glutathione reductase (GR) and lysozyme (LZM) in hepatopancreas of juveniles from two experimental groups. In conclusion, the biofloc technology had a positive effect on farming of the red swamp crayfish. And this technology could achieve the same or even better affect than the normal diet feeding.

Abstract:E75 is an important regulator of the ecdysone signaling pathway in shrimp. In order to gain insight into the structure and function of this gene, we screened and analyzed all E75 gene transcripts based on the transcriptome and genome data of Litopenaeus vannamei, and identified 6 alternatively spliced LvE75 isoforms (named LvE75-1, LvE75-2, LvE75-3, LvE75-4, LvE75-5 and LvE75-6). LvE75-1/2/4/5/6 contained DBD and LBD domains consistent with E75A/C of Drosophila melanogaster, and LvE75-3 only had LBD domains consistent with Drosophila E75D. During molting process, LvE75s were highly expressed in D3–D4 stage. In adult tissues, various isoforms of LvE75 were expressed in all tissues and were highly expressed in the epidermis, gut and gill, with only LvE75-3 being highly expressed in hepatopancreas, blood cells and lymphoid tissues. According to the conserved domain sequence, we designed primers for double-stranded RNA (dsRNA) interference. In LvE75 gene RNAi samples, qRT-PCR results showed that spo, phm and dib were down-regulated, and shd was up-regulated, indicating that LvE75 might regulate Halloween genes to influence ecdysone synthesis. Br-C and Ftz-f1 were down-regulated and HR3 was up-regulated after LvE75 were interfered, indicating LvE75 might influence the downstream early response genes of ecdysone signal pathway. After continued interference in LvE75 for 12 days, the molting rate was significantly lower compared with control group, but the death rate of dsLvE75 group was significantly higher, suggesting LvE75 gene played an important role in shrimp molting and survival.

Abstract:In order to analyze the lipid compositions and antioxidant activities of Hemicentrous pulcherrimus and Strongylocentrotus nudus gonads, the lipid and fatty acid compositions were analyzed by NMR and GC-MS, and the antioxidant activities were determined by the methods of DPPH radical scavenging, hydroxyl radical scavenging and superoxide anion radical scavenging in this paper. The experimental results indicated that the triacylglycerols and phospholipids were the predominant lipid components of H. pulcherrimus and S. nudus gonads, while the contents of free fatty acids, cholesterol and cholesteryl esters were relatively low. Meanwhile, C20:4n-6 and C20:5n-3 were the major polyunsaturated fatty acids, and the total contents of C20:4n-6 and C20:5n-3 reached respectively 35.88% in H. pulcherrimus and 34.98% in S. nudus. The remarkable differences were observed in the fatty acid compositions of neutral lipids and polar lipids. Neutral lipids were chiefly composed with C14:0 and C16:0, whereas polar lipids mainly of C20:4n-6 and C20:5n-3. H. pulcherrimus and S. nudus gonad lipids exhibited great scavenging activity on DPPH radical and hydroxyl radical. The IC₅₀ values of H. pulcherrimus and S. nudus gonad lipids to DPPH radical were 2.75 and 1.98 mg/mL, and were 0.33 and 0.29 mg/mL to hydroxyl radical, 0.33 and 0.31 mg/mL to superoxide anion radical, respectively. The results suggested that H. pulcherrimus and S. nudus gonad lipids had high nutritional values and antioxidant activities, and could be the important dietary sources of C20:4n-6, C20:5n-3 and phospholipids.

Abstract:Anaerobic ammonium oxidation and denitrification are the main processes of biological nitrogen removal from sediments. Carbon sources are the key factors regulating anaerobic ammonium oxidation and denitrification. In this study, the static carbon release of lignite and its effect on nitrogen removal from pond sediment were studied. The results show that the carbon release rule of lignite at room temperature accords with the second-order kinetic equation and has the feasibility of being a denitrification carbon source.In the denitrification experiment, it was found that lignite promoted the removal of nitrite nitrogen (NNO₂^--N) in the overlying water. The removal rate of N\${\rm{O}}_2^ - $\-N increased with the increase of lignite concentration. When the mass concentration of lignite was 40 g/L, the removal rate of NNO₂^--N was up to 99.61%. At this time, the concentration of nitrate nitrogen (NO₃^--N) was also the lowest; at the same time, it was found that the optimum concentration of ammonia nitrogen (NH₄⁺-N) in water was 10 g/L, and the removal rate was 99.39%. Illumina high-throughput sequencing of anaerobic ammonium oxidizing bacteria in the sediment found that the proportion of Fusarium was the largest (39.6%-71.8%), and the dominant genus was Candidatus Brocadia (13.9%-35.8%), Desulfovibrio (17.1%-34.8%), the proportion of Candidatus Scalindua added to the lignite group was higher than that of the unadded group; fluorescence quantitative PCR showed that with the increase of lignite mass concentration, the abundance of denitrifying bacteria in the sediment increased, while the abundance of anaerobic ammonium oxidizing bacteria was lower than that in the zero-brown coal addition group, indicating that the addition of lignite promoted the sediment denitrification. It has a certain inhibitory effect on anaerobic ammonium oxidation. Studies have shown that lignite has the conditions of denitrifying carbon source and can be used for denitrification of pond culture sediments.

Abstract:In order to study more about the molecular mechanism of nacre formation, we cloned a novel shell matrix protein hic9 (accession no. MF508725) from freshwater mussel Hyriopsis cumingii. We analyzed the gene expression by RT-PCR and in situ hybridization.The result indicated that hic9 was expressed most highly in adductor muscle and mantle, and the strong signals occurred in the whole outer epithelial cells of outer fold, and also occurred in the crust groove between out fold and middle fold. This result indicated that hic9 is a multifunctional matrix protein involved in the cuticle, prism layer and nacre layer of the shell. The amino acid sequence of hic9 featured high proportion of Gly (14.81%)、Pro (13.58%) and Ala (12.35%) residues, and formed the "Gly-X-X" structure in the middle of the sequence (X is any amino acid). And there is the continuous repetitive structure of alanine (polyA) structure close to the C terminal of the sequence, together giving the sequence of hic9 similar characters of spider silk protein. The Hic9 C terminus is composed of a hydrophobic sequence, "LAWMLFV", and this sequence is presumed to form a beta folding structure. Next to this sequence, the 89–91 bit is the "Asp-Leu-Asp" sequence, which is a typical Ca²⁺ binding site.In addition, the expression of hic9 in primary pearl sac was detected by real-time quantitative PCR in the early stage of pearl formation. Expression levels of hic9 in the pearl sac during 3–15 days after implantation maintained roughly the same, and the expression level of hic9 had a significant increase during 18–25 days in the period of transition from irregular to orderly in calcium carbonate deposits,which indicates that hic9 participates in this process and plays a key role in the formation of the macreous layer.

Abstract:Seaweed Gracilariopsis lemaneiformis is mainly used as the bait for abalone and raw material for agar production in China. This macroalga is widely cultivated along the coasts of China from south to north, but its cultivation period is limited by high temperature in summer. In the current study, the effects of heat and phytohormone treatments on Rubisco large subunit (rbcL) and heat shock protein 70 (HSP70) were investigated by using quantitative real-time PCR and Western blot technologies in G. lemaneiformis. The results showed that transcript and protein levels of rbcL in G. lemaneiformis were inhibited by heat stress (33 ℃), however, 100 μmol/L salicylic acid (SA100) and 50 μmol/L methyl jasmonate (MJ50) treatments reduced the inhibition of high temperature on the expression of rbcL. In SA100 and MJ50 groups, the transcriptional expression of rbcL increased to 1.31- and 1.32-fold at 3 h, and the protein levels of rbcL were enhanced to 1.36- and 2.10-fold at 24 h compared to the heat-stress group, respectively. Moreover, SA100 and MJ50 effectively alleviated the inhibition effect of heat stress on Rubisco activity, and recovered the Rubisco activation states. However, the addition of 50 μmol/L abscisic acid (ABA50) mainly inhibited rbcL expression and Rubisco activity. Heat stress stimulated the transcript and protein levels of HSP70; hsp70 transcript expression further rose by 0.53–1.00 times at 3 h, and its protein expression enhanced by 0.93–2.45 times at 24 h in the heat-stress group after applying SA100, MJ50 or ABA50. In conclusion, SA, MJ and ABA play a certain role in regulating the inhibition of photosynthesis enzyme and the induction of heat shock proteins caused by heat stress.

Abstract:In order to study the relationship between bacterial community composition and Ctenopharyngodon idella growth in the periphyton substrate systems, the ratios of substrate surface area to pool water surface area were set at 50%, 100% and 150% (S-50, S-100 and S-150). Firstly, the growth traits of C. idella in three systems and control groups were measured, and then the high-throughput sequencing technology was used to analyze the bacterial community composition in the water and the substrates, finally, the relationship between bacterial community and C. idella growth in the culture system was explored. The results showed that the weight gain rate and specific growth rate of C. idella in S-100 and S-150 groups were significantly higher than those in S-50 and control group. The survival rate of S-100 group was significantly higher than other groups. The feed conversion rates of the S-100 and S-150 groups were significantly lower than the control group. Bacterial community analysis demonstrated that 1) the proportion of Gammaproteobacteria increased in the substrates compared with the water, and the bacteria was significantly higher in the S-100 group than the other groups; 2) the bacteria in the water mainly consist of Flavobacterium, Rhodobacte, Cetobacterium and Planctomyces, and in the substrates Acinetobacter, Pseudomona and Chryseobacterium accounted for a high proportion, and the latter three bacteria were significantly higher in the S-100 group than those in the other groups; 3) at the identifiable species level, Pseudomonas alcaligene and Bacillus cereu were mainly in the substrates, and Pseudomonas faecalis was the highest in the S-100 and S-150 groups. Comprehensive analysis of C. idella growth, bacterial community composition and substrate cost, showed that the best effect was the 100% substrate group, in which there were the high bacterial diversity and potential probiotics ratio, the minimum feed coefficient and the highest of C. idella survival rate and weight gain rate. These data from this study provided the scientific data for the practical application of substrates in the aquaculture.

Abstract:In order to elucidate the transformation rule of fatty acids in body of female Coilia nasus during the spawning migration process, the fatty acid content and its components were determined in different tissues at different ovarian developmental stages (from stage Ⅲ to stage Ⅴ) of female C. nasus collected from the lower reaches of the Yangtze River. The changes in the components and contents of various fatty acids in the ovary, muscle and hepatopancreas were analyzed. The results showed that the total fatty acids content in ovary increased by 148.89 mg/g, in muscle decreased by 109.57 mg/g and in hepatopancreas decreased by 160.58 mg/g, respectively, during the period of ovarian development from stages III to V. The fatty acids components of ovary, muscle and hepatopancreas are basically the same at different ovarian developmental stages. They all contain three types and 24 kinds of fatty acids, including 9 saturated fatty acids (SFA), 6 monounsaturated fatty acids (MUFA) and 9 polyunsaturated fatty acids (PUFA). Among all the fatty acids, the content of oleic acid (C18:1n9c) was the highest, accounting for more than 18% of the total amount of fatty acids in each tissue. During the ovarian development from stage Ⅲ to stage Ⅴ, the content of oleic acid decreased by 86.36% in muscle, increased by 2.62 times in ovary; the content of essential fatty acids C18:2n6 and C18:3n3 decreased by 74.00% and 82.26% in muscle respectively, but increased by 225.87% and 183.96% respectively in ovary; the content of DHA decreased by 2.6 times in muscle, while increased by nearly 3 times in ovary. All of these showed that these fatty acids are closely related to reproductive activities. The present study also found that, the values of ARA/EPA in ovary of stage Ⅳ and stage Ⅴ were all less than 0.46, which means that female C. nasus in the Yangtze River had a good egg quality.

Abstract:In order to explore the optimum spectral components for growth and development of thallus of Pyropia haitanensis, the effects of different light qualities (white light, WL; blue light, BL; green light, GL; red light, RL) from light-emitting diode (LED) illuminations on the vegetative growth, developmental differentiation, maximal quantum efficiency of PSⅡ photochemistry and photosynthetic pigment contents of female thalli were studied. Results showed that the average length and fresh weight of thalli under WL after 25 days culturing were 2.42-3.86 and 2.64-4.50 times higher than those of thalli cultured in monochromatic light qualities, respectively. The growth rate of thalli was fastest when cultured in polychromatic WL, while it was limited in the monochromatic lights (BL, GL and RL). RL and GL were significantly adverse for the synthesis of phycobiliproteins. Compared to WL, the phycoerythrin contents of thalli under RL and GL decreased by 44.1% and 43.2%, respectively, and the phycocyanin contents of thalli decreased by 11.6% and 12.5%, respectively. However, the phycoerythrin and phycocyanin contents of thalli under BL were increased by 94.3% and 16.2%, respectively, compared with that under WL, and the highest F_v/F_m values kept on a continuous uptrend through the whole culturing period suggested that thallus had long-term acclimation to BL. It was noteworthy that both GL and BL accelerated cell differentiation and rapidly motivated the parthenogenetic development in the apical parts of thalli, while WL and RL never had such effects. The pathway of parthenogenetic spores developing into normal parthenogenetic conchocelis were promoted by BL, but blocked by GL. All of the parthenogenetic spore germlings in GL overflowed their cell inclusions and finally hollowed and demised. These results indicated that monochromatic lights limited the vegetative growth of thalli, and significantly affected the photosynthetic pigment components and the maximum photochemical efficiency (F_v/F_m) of PSⅡ, yet BL was favourable for parthenogenetic development of unisexual thalli. It also provided a reference for the further studies on the light adaptation mechanism of the thallus in P. haitanensis.

Abstract:To understand the current population genetic structure of half-smooth tongue sole and explore the trend and status of effective population size (N_e) in half-smooth tongue sole, in this paper, 800 4-month-old half-smooth tongue sole were identified by gender-specific genetic markers, and 297 genetic females were selected. Then64 416 SNP markers were obtained by simplified genome sequencing method (2b-RAD). The genome-wide linkage disequilibrium (LD) was used to obtain the linkage disequilibrium distribution on each chromosome. The effective population size was calculated based on the different physical distances between the markers for each historical generation. In order to analyze the genetic structure of the population of half-smooth tongue sole selected by natural and artificial means, the sizes of 7 different chromosomal fragment lengths were detected. And the results showed that the effective population size two generations ago was only about 29. The high-throughput 2b-RAD sequencing method was first applied to the estimation of the effective population size of aquatic animals, which provided a reference for the breeding work of other aquatic species. The effective population sizes decreased when the historical generation was closer. It is important for half-smooth tongue sole breeding and conservation to estimate the effective population size for current generation.

Abstract:With the development of aquaculture, far more attention has been paid to safety in fish drugs usage. In order to find alternatives to antibiotics, silver nanoparticles (AgNPs) were synthesized using extracts of Ginkgo leaves with AgNO₃ in this study. The synthesized silver nanoparticles were characterized by UV-Visible spectrophotometer, transmission electron microscope and X ray diffraction spectrum. The antibacterial efficacy was assessed against Staphylococcus aurous, Escherichia coli and common bacterial pathogens in aquacuture including Edwardsiella tarda and Aeromonas hydrophila, by using cylinder plate method, broth macrodilution method and bacteriostasis kinetic experiments. The results showed that the absorbance maximum was observed at 460 nm corresponding to the plasmon absorbance of the AgNPs. Transmission electron microscope revealed that the AgNPs had an average size below 10 nm.The X-Ray Diffraction (XRD) spectrum of the nanoparticles confirmed the formation of metallic silver.The AgNPs synthesised in this research exhibited good antibacterial efficacy against the test pathogens. This investigation demonstrated that the green synthesis of AgNps with leaves of Ginkgo biloba was not only fast and convenient but also cost effective and ecofriendly, which has good prospects in control of aquaculture diseases.

Abstract:A 12-week feeding trial was conducted to investigate the effects of dietary soyasaponins on the growth performance, activities of digestive enzymes, intestinal morphology and intestinal bacterial community of turbot (Scophthalmus maximus). Two isonitrogenous and isolipidic experimental diets (based on 67% fish meal) containing 0% and 0.3% soyasaponins were formulated. The results showed that the growth performance was not affected by dietary soyasaponins, while the activities of intestinal pepsin and amylase were significantly depressed by dietary 0.3% soyasopnins. No obvious changes of intestinal histology were observed between two groups. However the gene expression of intestinal tight junction protein occludin was significantly declined when 0.3% soyasaponins was added. The analysis of intestinal microbiota showed that Proteobacteria and Halomonas were the most dominant phylum and genus in S. maximus intestine, respectively. LEfSe and MetaStat analysis showed that the abundance of dominant bacteria (Proteobacteria and Shewanella) was significantly increased by dietary 0.3% soyasaponins. Meanwhile, dietary soyasaponins significantly increased the abundance of intestinal saponin-hydrolyzing bacteria. In addition, the abundance of some intestinal potential pathogenic bacteria such as Methylobacterium, Moraxella and Photobacterium, was increased while that of some other pathogenic bacteria such as Ralstonia was decreased by dietary soyasaponins. In conclusion, dietary 0.3% soyasaponins depressed the activities of digestive enzymes, and the gene expression of intestinal tight junction protein Occludin, and altered the intestinal microbiota of S. maximus. Thus, the effects of soyasaponins on fish intestine health, especially intestinal flora, cannot be ignored and deserve funther study.

Abstract:We analyzed the growth characteristics of the hybrids named Yunlong grouper, derived from Epinephelus moara and E. lanceolatus, and in this paper, we conducted the comparison of the growth characteristics among three groupers, including Yunlong grouper, E.moara and the Zhenzhulongdan grouper, which were cultivated in the factory condition. After establishing the family of two kinds of grouper, we were investigate the fertilization rate, normal development rate and malformation rate of Yunlong grouper, and measured the growth characteristics of Yunlong grouper and E. moara during 45-245 days. At the same time, we counted the growth index and survival rates of the Yunlong grouper and Zhenzhulongdan grouper during 2-13 month after hatching, and counted the survival rate in 13 months. We adopted One-Way ANOVA and Multiple Comparative Analysis to compared the growth characteristics, and fitted the growth model by Excel software. The results show that the average fertility rate, normal development rate, deformity rate of Yunlong grouper was 55.5%±26.7%, 33.9%±23.6%, 8.3%±0.9%, respectively. Until 245 days old, the body weight and body length of Yunlong grouper was (316.7±57.3) g, (22.5±1.7) cm, respectively, About E. moara, measured length (16.8±1.3) cm, weight (123.2±30.2) g. Yunlong grouper grew faster than E. moara, the body weight of Yunlong grouper was as 2.6 times as E. moara’s, and the body length was about 1.3 times. The growth curve of Yunlong grouper during 45-245 days old was W=0.039 2L^{2.891 2}(R²=0.986 9), which reveals that Yunlong grouper was at allometric growth state in this phase, E. moara’s growth curve was W=0.025 5L^{3.021 6} (R²=0.990 8), which reveals that it was in lsogony growth pattern in this phase; after 12 months contrast cultivation between Yunlong grouper and Zhenzhulongdan grouper, the result reveals that the survival rate of Yunlong grouper was 97.2%, while Zhenzhulongdan grouper’s was 93.2%-94%, and the body weight and total length of Yunlong grouper was (700.0±247.2) g, (35.3±4.1) cm, respectively. However, the Zhenzhulongdan grouper’s was (28.6±3.5) cm, (550.0±224.8) g, Yunlong grouper’s weight is 1.3 times the weight of Zhenzhulongdan grouper with 1.2 times total length. The result of this study reveals that E. moara (♀) ×E. lanceolatus (♂) is a ideal hybrid combination, and Yunlong grouper has the advantages of fast growth, low deformity rate, and high survival rate, providing the basis for the study of heterosis, and providing scientific basis for the promotion of Yunlong grouper.

Abstract:In order to discuss the microbial community diversity of vinasse liquid during processing of vinasse fish, the large yellow croaker (Larimichthys crocea) was chosen as a material to produce vinasse fish with traditional pickling technology, and the bacterial flora of vinasse liquid was measured by Illumina HiSeq2500 high-throughput sequencing technique. The results showed that the pH value slightly increased in the first 5 or 10 days and then gradually decreased with different salt dosage (2%, 5% and 10%). The TVB-N value was all lower than 30 mg/100 g after 30 days of processing and the lowest value was found in 5% salt group. The variation of the pH and TVB-N value in the 5% salt group were basically the same in different ratios of fish to vinasse (1:1, 1:1.5 and 1:2), which indicated that the quality of this vinasse fish was stable during processing. High-throughput sequencing results of 5% salt group showed that the Chao index of the vinasse liquid of 1:2 was the largest (167), which indicated the highest community richness. The Shannon index of the vinasse liquid of 1:1 was the largest (2.75) and the Simpson index was the lowest (0.109), which indicated the highest bacterial diversity. The main microbial domains of the vinasse liquid involve 17 phyla, 1 unclassified phylum and 143 genera. Proteobacteria, Cyanobacteria and Firmicutes were dominant, of which Proteobacteria was absolutely dominant. Vibrio, Chloroplast norank and Enterobacter were dominant, and Vibrio was absolutely dominant in the early fermentation. The results could provide theoretical basis for the study of microbial community diversity of vinasse fish liquid and references for the control of hygienic safety of drunk aquatic products.

Abstract:The study was conducted to investigate the effects of different dietary taurine concentrations on growth performance, body composition, tissue mRNA expression of taurine transporter (TauT) and key enzyme activities of taurine synthesis (cysteine sulfinic acid decarboxylase and cysteine dioxygenase, i.e. CSD and CDO) in juvenile grouper (Epinephelus coioides). Four diets at 0 (0DT), 0.5% (0.5DT), 1.0% (1.0DT) and 1.5% (1.5DT) taurine levels were formulated using casein and gelatin as the protein source. A total of 320 juvenile fish with an average weight of (13.85±0.25) g were randomly divided into 4 groups with 4 replicate tanks at a stock density of 20 fish per tank, and each group of fish was fed one of the same experimental diets to apparent satiation each time during a feeding period of 84 days. Results showed that the feed efficiency, feeding rate, weight gain rate and whole-body crude protein content for fish fed the diets with taurine administration were significantly increased, but hepatosomatic index and whole-body crude lipid content were significantly decreased in comparison with 0DT. The dietary taurine addition significantly upregulated tissue mRNA expression levels of TauT and 1.0DT had the highest level of tissue mRNA expression, which declined with concentrations of taurine, but still was significantly higher than 0DT and 0.5DT. There was a positive correlation between concentrations of taurine in serum, liver, intestine and muscle of juvenile E. coioides and dietary taurine content. The CSD activities in liver, muscle and the CDO activities in plasma, liver, intestine and muscle were significantly decreased by dietary taurine administration, however, the plasma CSD activity was not affected by dietary taurine administration. The results suggested that dietary taurine addition could improve the growth performance of juvenile E. coioides, increase whole-body protein deposit, decrease whole-body lipid deposit, enhance the expression level of TauT mRNA and taurine content in tissues, reduce key enzyme actvities of taurine synthesis. The optimal dietary taurine content for juvenile E. coioides was 0.92% based on the regression analysis between weight gain rate and dietary taurine content.

Abstract:Family selection has emerged as the essential manner of selective breeding in aquaculture. The current artificial selection for Japanese scallop (Patinopecten yessoensis) is primarily focused on the apparent characters, e.g. growth, shell color and survival rate. However, the selective breeding in terms of nutritional value of adductor muscle has been rarely reported. Based on the adductor muscle dry weight and fatty acid profile of P. yessoensis, the families harboring higher growth rates were screened out initially and the vital nutritional indicators, i.e. the relative abundances of EPA as well as DHA of total fatty acids, and the ratio of ω-3/ω-6 fatty acids, were further assessed. Among a total of 12 selected families, the growth rates and adductor muscle ratio of B04, B05 and B10 were prominently higher than other families. The relative abundances of EPA and DHA of total fatty acids were all above 45% and the ratio of ω-3/ω-6 fatty acids varied between 10.94 and 12.69 in any individual family. The families, B03, B05, B06, B07, B10, B11 and B12, exhibited superior nutritional performance involving fatty acids of adductor muscle. The highest-quality families of P. yessoensis, i.e. B05 and B10, were successfully selected on a basis of the comprehensive comparative analyses. These results revealed that it was feasible to perform artificial selection in terms of the growth performance and the equally critical fatty acid composition of P. yessoensis. This study provides valuable insights into selective breeding of scallops in aquaculture.

Abstract:To compare microbial community structure, diversity and metabolic potential, and analyze their relationships with the spoilage characteristic between Scomber japonicus and Larimichthys crocea, Illumina MiSeq sequencing technology was used to sequence the 16S rRNA V3-V4 hypervariable region of bacteria, and the physicochemical and microbiological indices including pH, total volatile basic nitrogen (TVB-N), histamine and aerobic plate count (APC) were detected. The correlation between microbes and fish spoilage and histamine producing was investigated by Pearson analysis, and the relationship between bacterial community composition and metabolic function was also predicted by phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt). The results showed that the pH, TVB-N, histamine content and APC in both fish fillets increased with the storage time extention, however their values in S. japonicus fillet increased faster and kept higher than those in L. crocea throughout storage. TVB-N and histamine content reached 76.34 mg/100 g, 59.92 mg/100 g in S. japonicus, while 59.98 mg/100 g, 3.11 mg/100 g in L. crocea at the end of storage, respectively. An increase tendency was observed in richness and diversity of bacteria in S. japonicus muscle and then followed by a decrease during the storage, while a sustained increase tendency was observed in that of L. crocea. Shewanella was the dominant bacteria in fillets of both S. japonicus and L. crocea. Twelve types of bacteria in S. japonicus were screened as TVB-N correlation bacteria, ten of which also showed significant correlation with the histamine producing, meanwhile seven types of bacteria in L. crocea were screened as TVB-N correlation bacteria, however, no bacterium showed correlation with histamine producing. Amino acid metabolism and carbohydrate metabolism were higher than other metabolism during the storage. The abundance of function genes related to amino acids metabolism and carbohydrate metabolism in S. japonicus was enormously higher than that in L. crocea throughout the storage period such as histidine, arginine and proline metabolism and butanoate metabolism, propanoate metabolism and pyruvate metabolism, respectively. This may partially explain why S. japonicus was more perishable than L. crocea from the level of metabolism of the bacterial community. Our study provided a new method to understand the spoilage characteristics of different aquatic products from the perspective of bacterial community and their metabolism related function genes.

Abstract:The purpose of this experiment was to investigate the effect of low-fishmeal diet with Bacillus subtilis on growth performance, digestive enzyme activity, antioxidant enzyme activity and its mRNA expression of juveniles Epinephelus lanceolatu♂×E. fuscoguttatus♀. A total of 720 grouper with average initial weight of (7.00±0.02) g were randomly assigned into 8 groups in triplicates with 30 individuals per replicate. Eight diets were prepared by adding 0 (normal fishmeal control group), 0 (low fishmeal control group), 0.10%, 0.25%, 0.50%, 0.75%, 1.00% and 1.25% Bacillus subtilis in a diet with low fishmeal (15%), and were formulated by an optimum fishmeal group (35%) as positive control group. The results showed that there was no significant difference in survival rate (SR) among all the treatments. The weight gain rate (WGR) and specific growth rate (SGR) were increased firstly and then decreased with the B. subtilis level increasing. The feed conversation ratio (FCR) in 0.75% group has the lowest value, while the protein efficiency ratio (PER) showed the opposite trend compared to FCR. The activities of trypsin (TRY) and amylase (AMY) firstly increased and then decreased. The activities of serum catalase (CAT) and superoxide dismutase (SOD) in 0.75% group has the maximum value. The highest CAT and glutathione reductase (GR) mRNA expression in liver of fish were observed in 0.50% and 0.75% group, respectively. Grouper were challenged by Vibrio harveyi for the next 7 days, the survival rate of grouper increased significantly with the B. subtilis level increasing. It can be concluded that the supplementation of 0.63% B. subtilis (1.0×10⁸ cfu/mL) can significantly enhance the growth performance, disease resistance, digestive enzymes, serum CAT and SOD activity and mRNA expression related to immunity of grouper, which is estimated with WGR as the evaluation index.

Abstract:In order to induce triploid using cytochalasin B (CB) in Crossostrea sikamea, three effecting factors, including CB concentration, initial time of induction, and duration time of induction, were optimized by the cleavage rate, D larvae rate, and triploidy rate. In addition, the variations of survival rate and triploidy rate were also compared for larvae and adults. The results suggested that the optimal method of triploid induction were 0.5 mg/L CB, 40% first polar body releasing for initial time of induction, and 20 min for duration time of induction. The triploidy rate of 87% was obtained by the optimal method. The first effecting factor for cleavage rate, D larvae rate, and triploidy rate was CB concentration, duration time of induction and initial time of induction, and duration time of induction, respectively. Furthermore, there was insignificant negative relationship between triploidy rate and cleavage rate. Whereas, the positive relationship was significant between triploidy rate and D larvae rate. As a result, high triploidy rate and high larvae production could be obtained by decreasing both CB concentration and duration time of induction. The survival rates were 71.27% and 96.09% at 3 days, and 34.14% and 58.80% at 15 days for triploid and control groups, respectively. Comparatively, the survival rate were 53.62% and 44.67% for adults at 450 days (September) in triploid and control groups, respectively. The triploidy rate declined from 87% to 77% during the period of 3 to 9 days. Whereas, the triploidy rate was 59.21%±4.99% on average from 90 to 450 days, suggesting that there was no correlativity between triploidy rate and survival rate, with a small variation of triploidy rate for adults. This study provides valuable data for further exploration into triploidy of C. sikamea.

Abstract:By comparing the changes of the microflora during salted-dried processing of the red-fleshed fish (Decapterus maruadsi) and the white-fleshed fish (Trichiurus lepturus), the dominant bacterium with antioxidant activity was also studied. In this paper, MiSeq sequencing technology was utilized in two kinds of fish in different processing phases. The results showed that the microflora of the two fishes was mainly distributed in Bacteroidetes and Proteobacteria. At the family level of the initial material, there were 7 and 15 colonies in D. maruadsi and T. lepturus, respectively. All the species in round scad were totally in T. lepturus and Enterbacteriaceae was as common dominant bacteria, accounted for 47% and 26% in D. maruadsi and T. lepturus respectively. From the start of salting, the number of bacteria in both fishes was greatly reduced. Vibrionaceae and Bacillaceae were the common dominant bacteria, the former accounted for an average of 40.3% and 42.2% of D. maruadsi and T. lepturus, and the latter accounted for an average of 16.7% and 13.3%. Among the raw materials, four spoilage bacteria of Enterobacteriaceae, Pseudomonas, Vibrionaceae, and Shewanellaceae were showed in both fishes. The dominant spoilage bacteria in both fishes during salt-dried processing was Vibrionaceae. Lactic acid bacteria (LAB), including Streptococcaceae and Lactobacillaceae, only appeared in T. lepturus. Therefore, during salt-dried processing, the degree of reduction of bacteria in hairtail was greater than that of round scad, and they all showed a decrease. The two fishes contained common bacteria and dominant bacteria, but showed significant differences. The spoilage bacteria of both fishes have been greatly reduced, suggesting that salt-dried processing is beneficial to reducing the possibility of fish corruption. T. lepturus could be selected for LAB isolation for subsequent antioxidant studies.

Abstract:In order to clarify the physiological basis of fast growth traits of an excellent black-shell strain of the Pacific oyster (Crassostrea gigas), feeding and metabolism between the black-shell strain and wild population of C. gigas were compared. Results indicated that at the test temperature (16-32 ℃), temperature had significant effects on clearance rate (CR), oxygen consumption rate (OCR) and ammonia excretion rate (AER) of C. gigas. With the increasing of temperature, the CR of the black shell strain of C. gigas began to rise, reached the maximum at 28 ℃ and then declined, while the CR of the wild population of C. gigas reached the maximum at 24 ℃. The OCR and AER of black shell strain and wild population increased with temperature, no significant turning point was found. There were significant differences in CR and AER between black shell strain and wild population of C. gigas. The black shell strain had higher CR and lower OCR than wild population, and had significantly lower AER than wild population at 32 ℃. At the test salinities of 15 to 35, salinity had significant effects on CR, OCR and AER of C. gigas. CR, OCR and AER of C. gigas increased firstly and then decreased with increasing salinity. There were significant differences in CR between the black shell strain and wild population of C. gigas. The black shell strain had higher CR than wild population, and its AER was lower than that of wild population in range of salinity 15 to 25. The O:N ratio of C. gigas reached the maximum at 16 ℃ and salinity 35, increase in temperature or decrease in salinity reduced O:N ratio. In the temperature experiment, the O:N ratio of the black shell strain ranged from 10.52-29.31. In the salinity experiment, the O:N ratio of the black shell strain ranged from 11.51-22.98. The present results demonstrated that the black shell strain of C. gigas could adapt to high temperature and low salinity environment, and selective breeding of black shell strain of C. gigas could produce oysters that have higher intake of energy and lower metabolic costs.

Abstract:The present study investigated the effect of two states (hunger and refeeding) on the growth performance, body composition and related metabolism of Litopenaeus vannamei. There were 5 treatments in the experiment, which were starvation group (S0), control group (C), experimental group named S1, S2 and S3 (sugar sources: glucose, sucrose, cornstarch, respectively), while the juvenile L. vannamei (1.84±0.23) g continue to feed for 12 days after 12 days of starvation. The results showed that starvation affected body composition of juvenile L. vannamei postlarvae and related enzymes [lipase (LPS), phosphofructokinase (PFK), hexokinase (HK), glutamine synthetase (GS)] significantly; shrimp liver and muscle glycogen were repeated movements, after 8 d starvation glycogen dropped to the lowest value, muscle glycogen decreased significantly after a brief rebound. The weight gain in S3 group was the highest after refeeding 4 days, the experimental groups were lower than the C group significantly and it was not significant among the experimental groups. The liver glycogen, muscle glycogen content in S1 was significantly lower, The activity of LPS and HK increased greatly during the early days of refeeding, and there was no significant difference in the content of LPS and PFK between the experimental groups. After refeeding 12 days, the activity of LPS and HK in S3 was significantly higher the other experimental groups; there was no significant different between GS and PFK content in experimental groups. The study showed that the glycogen and fat were first used for energy supply during the starvation of L. vannamei, and the refeeding was partly compensated for growth, and the effect of corn starch sugar source feed was the best.

Abstract:In the experiment, cartilaginous proteins of Raja porosa were prepared using guanidine-HCl extraction and acetone precipitation, and two antioxidant peptides (RCPE-A and RCPE-B) were subsequently isolated from the tryptic hydrolysates of cartilaginous proteins using ultrafiltration, anion-exchange chromatography, gel filtration chromatography and reversed phase high performance liquid chromatography (RP-HPLC). The amino acid sequences and antioxidant activities including free radical scavenging activity and lipid peroxidation inhibition were also measured. The results indicated that the amino acid sequences of RCPE-A and RCPE-B were identified as Gly-Glu-Glu-Gly-Pro-Arg-Gly (GEEGPRG) and Gly-Glu-Glu-Gly-Thr-Met-Gly-Leu (GEEGTMGL) with molecular weights of 700.71 and 792.87 u, respectively. RCPE-A and RCPE-B exhibited good scavenging activity on DPPH· (EC₅₀ 2.94 and 1.16 mg/mL), HO· (EC₅₀ 0.34 and 0.54 mg/mL), ABTS⁺· (EC₅₀ 0.34 and 0.10 mg/mL), and O₂^-· (EC₅₀ 0.11 and EC₅₀ 0.03 mg/mL). In addition, RCPE-A and RCPE-B were effectively against lipid peroxidation in a linoleic acid model system. The antioxidant activities of RCPE-A and RCPE-B were due to the smaller size and the presence of antioxidant amino acids including Gly, Glu, Pro, Arg, Met and/or Leu within their peptide sequences. These results suggested that RCPE-A and RCPE-B might serve as potential antioxidants and be used as food additives and functional foods.

Abstract:The pharmacokinetics of enrofloxacin in Chinemys reevesii was studied following intramascular injection and oral administration by HPLC-MS/MS. Enrofloxacin is the third generation of quinolones and the first animal-specific drug. Now, it is also the commonly used drug for reptiles. C. reevesii is a common native turtles in China, it is not only used as medicine or food, but also for ornament. It is another economic turtle species in addition to Trionyx sinensis. As the scale of farming has expanded each year, disease problem have gradually highlighted, but the technical problems encountered in clinical medicine has become the bottleneck of industrial development. At present, enrofloxacin is often used in the treatment of diseases of C. reevesii, such as respiratory diseases and urinary system diseases. However, there are few reports about pharmacokinetic of enrofloxacin in C. reevesii, and this experiment filled the gap.In this experiment, 20 healthy Chinese pond turtles were selected from a farm in Wuxi, Jiangsu Province. All turtles were female. After holding for two weeks, they were selected and followed by a single dose of enrofloxacin (10 mg/kg) by intramascular injection and forced oral administration (gastric intubation) respectively. Blood samples were collected continuously for the same subject 13 times from the jugular sinus. Samples were obtained and assayed by HPLC-MS/MS, and the corresponding pharmacokinetic parameters were calculated with non-compartmental models by Kinetic 4.4. The main pharmacokinetic parameters of forced oral administration were C_max: 7.49 μg/mL, T_max: 12 h, T_1/2λz: 99.85 h and AUC_0-∞: 531.67 μg/(mL·h); The main pharmacokinetic parameters of intramuscular injection were C_max:5.85 μg/mL, T_max: 4 h, T_1/2λz: 30.42 h and AUC_0-∞: 193.6 μg/(mL·h). The results showed that enrofloxacin was absorbed faster by intramuscular injection, but was absorbed better and comprehensivly by forced oral administration in Chinemys reevesii. And the retention time of forced oral administration was longer. So in the control of Chinese turtle disease, enrofloxacin is more suitable for oral administration. When we need to quickly achieve the effect, intramuscular injection of enrofloxacin will be better. When we need to continue to administer and the turtle metabolic state is normal, it is recommended to use forced oral administration of enrofloxacin by gastric intubation.

Abstract:In order to investigate the effect of triacontanol on growth of Sargassum horneri, different concentration of triacontanol applied continuously for 20 days, or the thalli were immersed in triacontanol solution at concentration of 0.1, 0.5, 1.0 and 2.0 mg/L) for 24 h and then cultured in normal conditions for 20 days, and then the relative growth rate (RGR), physiological and biochemical indexes (photosynthetic pigment, soluble protein, soluble sugar) and fucoxanthin contents were determined, respectively. The results showed that after continuous application of 5 days, the RGR, chlorophyll a (Chl-a), carotenoid (Car), soluble protein, soluble sugar contents were significantly higher than the control; on the 15^th day, the growth of the 2.0 mg/L group was inhibited, and all the physiological indexes decreased significantly; on the 20^th day, the growth of the 0.1 mg/L group was still promoted, the other three higher concentration groups were inhibited by different degrees, and the higher concentration of triacontanol, the more obvious inhibitory effect. The immersed group after 5 days of culture, the RGR, Chl-a, Car, soluble protein and soluble sugar contents increased significantly; on the 10^th day, the RGR of 0.5 and 1.0 mg/L groups were significantly higher than the control; on the 15^th day, there was no significant difference with the control, and considering the physiological and biochemical indexes, 1.0 mg/L group was the most obvious effective group, and the promotion effect could maintain about 10 days after treatment. Fucoxanthin contents were significantly higher than control in treatment groups except continuous application with 2.0 mg/L triacontanol for 20 days, among which the fucoxanthin content increased 79.5% on the 10^th day after immersed treatment in 1.0 mg/L triacontanol solution for 24 h. Therefore, continuous application of low concentration of triacontanol (0.1 mg/L) or immersed in 1.0 mg/L triacontanol solution for 24 h every 10 days could significantly promote the growth and accumulation of fucoxanthin of S. horneri.

Abstract:In order to identify the pathogen which caused mass mortality in farmed Cyprinus carpio var. specularis in Deyang district of Sichuan Province, China, the pathogen of this event was determined following bacteriology, parasite morphological observation, histopathology and PCR detection. The results showed that bacteriological examination was negative whereas parasite was positive with Thelohanellus kitauei. Histologically, intestinal damage is the most serious, where a large number of parasitoid cysts were noted. Morphological observation showed that the total length and width of the spores were about 23–30 μm and 10–15 μm, respectively. In addition, the polar capsule was 11–15 μm long and ovalellipsoidal, which accounted for about 1/3–1/2 of spores. The outer layer of the spores covered with a thin colorless and transparent film. One pyriform macronucleus was in the upper part and two globular micronuclei near the iodinophilous vacuole. Tissue DNA from infected intestine was identified as T. kitauei (TKF-1) by nest polymerase chain reaction amplification of the 18S SSUrRNA gene and the sequenced 18S SSUrRNA gene of TKF-1 has a homology up to 100% with T. kitauei in GenBank. According to the results we confirmed that the death of C. carpio var. specularis in this region was caused by T. kitauei.

Abstract:Modern marine ranching is a new type of achieving marine environmental protection and efficient production of fishery resources, which is of great significance in accelerating the shift in driving forces for economic development. We illustrated the development history of modern marine ranching concept, the history and current situation of modern marine ranching construction, and proposed strategic concept to promote the sustainable development of China’s modern marine ranching from the perspectives of innovation drive, technology leader and project demonstration. This review aims to provide reference for the upgrading and transformation of China’s marine fishery.

Abstract:The objective of this study was to assess the optimal dietary lipid requirement of advanced genetically improved farmed tilapia (GIFT Oreochromis niloticus), reared at 34 ℃ water temperature. In present study, 360 fish with average initial body weight of (50.88±1.57) g were randomly divided into 6 groups with 3 replicates of 20 fish in each replicate. Fish in each group were hand-fed a purified diets containing different lipid levels [0.22% (control group), 2.83%, 4.98%, 7.45%, 9.23% and 12.47%] reared at 34 ℃ water temperature for 56 days. At the end of feeding trial, growth performance, body composition, serum biochemical indexes and the activities of lipid metabolism enzyme in liver were measured. The results showed as follows: with the increase of lipid levels, weight gain rate (WGR), specific growth rate (SGR), protein efficiency rate (PER) and protein retention rate (PRR) of GIFT O. niloticus were increased at first and then decreased, but feed conversion ratio (FCR) and the feeding intake rate (FIR) presented the opposite trend. The highest hepatosomatic index (HSI) was in 12.47% diet group, the other groups were not significantly different in HSI. During the feeding trial, no fish died. Increasing dietary lipid levels contributed to increased whole body and muscle lipid levels. With dietary lipids levels increased (i.e., from 2.83% to 9.23%), liver crude lipid concentrations were significantly lower than that in the control group. Serum triacylglycerol (TG) and total cholesterol (TCHO) levels tended to increase first then decrease with increasing dietary lipids level. Meanwhile, lipoprotein lipase (LPL) and hepatic lipase activities increased as the level of lipid increased, and were highest in 12.47% diet group; hepatic lipase (HL) activities tended to first increase and then to decrease as the level of dietary lipid increased, and was highest in 2.83% diet group. Regression analysis showed the optimum dietary lipid level for maximum WGR and PER was 4.92% and 5.67%, respectively, and for the lowest FCR was 6.49% when GIFT reared at 34 ℃ water temperature.

Abstract:In this experiment, two strains of probiotics, i.e. Enterobacter hormaechei (E3) and Lactobacillus (R3) were used to feed Litopenaeus vannamei for 4 weeks. The diversity of intestinal microflora of L. vannamei in experimental group and blank group was compared and analyzed by Biolog-ECO method in the later period of feeding, in order to evaluate the effect of probiotics on the metabolic function of intestinal microflora of L. vannamei. The results showed that AWCD in the experimental group was significantly higher than that in the blank group, indicating that probiotics enhanced the intestinal microbial activity; the ability of intestinal microorganisms to utilize carbon source was significantly enhanced, which indicated that the digestive enzyme secreted by probiotics increased the digestibility and absorption rate of prawn feed, thus promoting the rapid growth of L. vannamei. There were significant differences in intestinal microbial diversity index (including Shannon, Simpson and McIntosh indexes), which indicated that different strains had different effects on intestinal microflora richness of L. vannamei. The results of sampling on the 1st and 5th day after stopping adding E. hormaechei showed that Shannon index decreased significantly and Simpson index and McIntosh index increased significantly, and lactic acid bacteria was stopped from adding. The results of sampling on the 1st and 5th day showed that there was no significant difference in Shannon index and McIntosh index, but there was no significant difference between them on the 10th day. The results showed that the addition of probiotics to the feed could change the number and structure of the original microflora in the intestinal tract of L. vannamei and promote the complex interaction between the microbial communities in the intestinal tract of L. vannamei. In turn, it plays an important role in maintaining or promoting the health of L. vannamei. It also showed that the two probiotics should stay in the intestines of aquatic animals for at least 5 days.

Abstract:A 16-week feeding experiment was conducted to study the effects of different dietary carbohydrate sources (wheat, barley, corn, white sorghum, cassava) on growth, body composition, overwintering and serum indexes of large-size grass carp (Ctenopharyngodon idella) [initial body weight (400.77±7.45) g]. Every diet was randomly fed by triplicate cages, and each cage (2 m×2 m×2 m) was stocked with 30 fish. After the feeding trail, 15 fishes were kept in original cage for overwintering experiment in 16 weeks . Results show as follows: the weight gain rate (WGR) and protein efficiency ratio (PER) of grass carp in corn group was the lowest among experimental groups, and the feed coefficient ratio (FCR) was the highest, but other four groups had no significant difference; the condition factor (CF) in wheat group, was the highest, body weight (VSI) in corn group, and the hepatic body ratio (HSI) and intestine ratio (ISI) in cassava group were the highest, and these were highest among experimental groups; blood glucose (GLU) in wheat group and total cholesterol (T-CHO) in barley and white sorghum groups were the highest among other groups. The triglyceride (TG) content in the cassava group was significantly lower than that in the other groups. The crude fat of muscle in wheat, barley and corn groups was significantly higher than white sorghum and cassava groups. The crude protein content of muscle in cassava group was significantly lower among other four groups. Hepatic glycogen was significantly higher in the white sorghum and cassava groups than other groups. Muscle glycogen was significantly higher in the barley and white sorghum groups than other groups. After wintering, the weight loss of barley grass carp was significantly higher than that of other groups. The decrease rate of HSI was significantly lower than other groups. The hepatic glycogen content was significantly increased, and the decrease of GLU was significantly less than that of other groups. The crude muscle protein decreased most rapidly. There were no significant differences in weight loss after winter in other groups. The CF was the highest drop rate in wheat group, the HSI decline in corn and cassava groups was significantly greater than other groups. Corn group had the largest decrease in VSI. In conclusion, under the puffing process conditions, wheat, cassava, and white sorghum are suitable sugar to be sources to be added in feed for large-size grass carp, and cassava has the lowest weight-increasing costs with growth, weight gain cost, and overwintering as evaluation indicators.

Abstract:In this paper, a new and highly efficient denitrifying bacterium strain from Poyang Lake was screened and named X10. The physiological and biochemical characteristics, 16S rDNA gene sequence analysis, and the effects of nitrite concentration, pH value, temperature and inoculum size on the growth and nitrogen removal ability of the strain were researched. Meanwhile, the nitrite degradation capacity of X10 in aquaculture water was also studied. The results showed that the strain X10 was identified as Acinetobacter xylosoxidans. The optimal incubation conditions for the aerobic denitrifying strain X10 were: pH, 7.0; inoculation size, 3%; temperature, 30 ℃; nitrite concentration, 300 mg/L. Under this circumstance, the degradum rate of nitrite reached peak after 48 h, up to 99.8%. When X10 bacteria (2×10⁸ CFU/mL) were added into cultured pond water (28℃), the degradation rate of nitrite was 82.6% after 96 h. The safety evaluation test showed that the high concentration of X10 (5 × 10⁸ CFU/mL) had no lethal effect on Danio rerio and no hemolysis was found. These results indicated that X10 can be applied widely in aquaculture.

Abstract:An 8-week feeding trial was conducted to evaluate the effects of dietary yeast culture supplementation on growth performance, nonspecific immunity and intestinal health of Pelteobagrus fulvidraco. Yeast culture YC1 (50% crude protein), yeast culture YC2 (55% crude protein) with 0, 1% and 2%, respectively were added to basic diet, and five practical diets with iso-nitrogenous and iso-lipidic (42% crude protein and 8% crude lipid) were prepared, named C, YC1-1, YC1-2, YC2-1 and YC2-2, respectively. A total of 375 P. fulvidraco with an average initial body weight about (4.87±0.00) g were randomly allocated into five groups with three replicates per group and 25 fish per replicate. The results indicated that fish fed the diets containing YC2-1 and YC2-2 had higher weight gain rate (WGR) than that fed the control diet of P. fulvidraco, and the highest specific growth rate (SGR) was observed at YC2-2 treatment among all treatments. Fish fed the diets containing YC2-1 and YC2-2 had higher productive protein value (PPV) than that fed the control diet of P. fulvidraco. Protein efficiency rate (PER) increased at first and then decreased with the increase of yeast culture addition level, and YC2-1 treatment had the highest PER among all treatments. Fish fed the diets containing YC2-1 and YC2-2 had lower feed coefficient rate (FCR) than that fed the control diet of P. fulvidraco, and YC2-2 treatment had lower FCR than that the YC2-1 treatment. Fish fed the diets containing YC2-1 and YC2-2 had higher activity of lysozyme (LSZ) and superoxide dismutase (SOD) than that fed the control diet in the liver of P. fulvidraco. Fish fed the diets containing YC2-1 had higher height of intestinal folds than that fed the YC1-1 diet of P. fulvidraco, and fish fed the diets containing YC2-1 had greater width of folds and height of epithelial cells than that the YC2-2 treatment of P. fulvidraco. In the experiment of Aeromonas hydrophila challenge, fish fed the diets containing yeast culture had lower average cumulative mortality rates (CMR) than that fed the control diet of P. fulvidraco, and the lowest CMR was observed at YC2-1 treatment among all treatments. In conclusion, under the experimental conditions, adding yeast culture YC2 to diet can effectively improve the nonspecific immune function of P. fulvidraco, improve its antioxidant capacity, maintain intestinal health and improve its ability to resist A. hydrophila infection.

Abstract:In order to determine the pathogen and pathogenic characteristics of Ctenopharyngodon idella haemorrhagic septicemia in a farm of Nanchang, a strain of pathogenic bacteria A1310 was isolated from the liver lesions of the diseased C. idella. The phenotypic characteristics of the isolated strain A1310 included the morphological characteristics, physiological and biochemical characteristics, pathogenicity, susceptibility test. In addition, the whole genome sequencing, phylogeny-based on multilocus sequence typing (MLST) and virulence gene were examined. According to morphological, biochemical characteristics, the pathogen was identified as Aeromonas hydrophilia. Artificial infection experiments showed that it is pathogenic to C. idella after being infected with the 1.0×10⁶ CFU/mL bacteria strains culture. Antibiotic sensitivity test using 20 antimicrobial agents showed that the isolate was resistant to 7 antibiotics including penicillin, but was sensitive to 5 antibiotics including Kanamycin. The A1310 strain genome sequence contains a total of 96 genes related to toxicity and defense, and most of them are multidrug resistance efflux pump genes, about 22%. MLST typing showed that this isolate was genetically related to the American channel catfish isolates (S15-242, S15-458, S15-591, S15-700). Moreover, the comparative genomic analysis showed that A1310 has at least 80% of the core proteins necessary for a complete T6SS, lacking a segment of vgrG and a segment of vca0109. In conclusion, A. hydrophila A1310 from C. idella was genetically related to the American channel catfish isolates genetically and contains multiple reported virulence genes of A. hydrophilia. This study broadened our knowledge to understand the biological traits of A. hydrophlia. This can provide some reference for the effective inspection, prevention, and in-depth study of A. hydrophilia, and it has some significance for the prevention and control of C. idella disease and will be a basis for the disease control during C. idella culture.

Abstract:In order to investigate the effects of feed bamboo charcoal on muscle nutrition composition and lipid metabolism-related gene expression in juvenile red tilapia, the healthy juvenile red tilapia with an average body weight of (7.07±0.01) g were randomly divided into 5 groups, with 3 replicates in each group and were kept for 60 days. The quantity of bamboo charcoal in the feed was 0%, 0.5%, 1%, 2% and 4%, respectively. The results showed that: the activity of ALT in the 0.5% and 1% groups was significantly lower than that in the control group. The activity of alkaline phosphatase (ALP) and serum total protein (TP) activities were significant increased in the 1% group. The aspartate aminotransferase (AST), triglyceride (TG) and serum total cholesterol (TC) concentrations in the experimental groups were significantly lower than those in the control group. High density lipoprotein (HDL) increased significantly with the increase of bamboo charcoal concentration. 1% bamboo charcoal group muscle moisture content was significantly lower than the control group; crude protein content of 1%, 2% and 4% treatment groups was significantly lower than that of the control group. Crude fat content and muscle ash that of increased compared with the control group, 1% and 4% groups significantly increased compared with the control group. Feed bamboo charcoal can increase the content of total unsaturated fatty acid (UFA) in fish muscle, but only 4% group's total unsaturated fatty acid content increased significantly, on the contrary, the content of saturated fatty acids (SFA) in 4% group was significantly lower than that of the control group; C18: 2 and C18: 3n3 treatment in 4% bamboo charcoal treatment group increased significantly compared with the control group, and the C22: 6 in 1% bamboo charcoal treatment group was significantly lower than the control group. With the increase of bamboo charcoal feed, LPL gene and MDH gene expression increased compared with the control group, but only 1% group MDH gene compared with the control group were significantly different. Studies have shown that adding appropriate concentrations of bamboo charcoal can improve the crude fat content, total unsaturated fatty acid (UFA) content, LPL gene and MDH gene expression in fish, and help to change the nutrient composition of fish.

Abstract:Lysozyme is an important immune effector present in phylogenetically diverse organisms, and plays important roles in bacteria elimination. In this study, two I-type lysozymes from Ruditapes philippinarum (designated as VpILYZ-1 and VpILYZ-2, respectively) were recombinantly expressed in Escherichia coli BL21 (DE3). The recombinant proteins rVpILYZ-1 and rVpILYZ-2 showed broad spectrum of antimicrobial activities. Especially, the rVpILYZ-1 displayed high lytic activities against V. parahaemolyticus, V. splendidus and M. luteus, while rVpILYZ-2 showed strong microbicidal activities against V. parahaemolyticus. The antibacterial activities of rVpILYZs may be performed by both the enzymatic way and non-enzymatic ways. The optimum pH and temperature for the lytic activities of rVpILYZ-1 were 6.5 and 20 ℃, and the highest antimicrobial activities of rVpILYZ-2 was detected at pH 4.5 and 10 ℃. Moreover, both rVpILYZ-1 and rVpILYZ-2 possessed the opsonic activities, and the phagocytic activities of hemocytes were boosted after being incubated with rVpILYZ-1 or rVpILYZ-2. These results suggested that VpILYZ-1 and VpILYZ-2 played important roles in the immune responses of R. philippinarum.