Abstract:Some species of Sciaenidae were the important fishes in the artificial propagation and breeding in the world. The health of intestinal flora played a significant role in the nutrition, growth and immunity of cultured fishes. However, only a few studies on intestinal flora of cultured croakers have been reported. Investigation of intestinal flora of related species was helpful to the understanding of the influence of host genetic factors on the formation and maintenance of intestinal flora. In order to explore the interspecific structural characteristics, differences of intestinal flora of cultured croakers and the influence of host genetic factors on intestinal microflora, the 16S rDNA V3-V4 region of intestinal microflora was amplified from 5 kinds of yelloe croaker (Larimichthys crocea, Nibea albiflora, N. miichthyoides, Miichthys miiuy, Sciaenops ocellatus) cultured in Sandu Bay, Ningde, Fujian Province and then were sequenced based on Illumina Hiseq2500 sequencing platform. The number of unique tags obtained from these samples were from 20351 to 43347, and the species mentioned above obtained 479, 626, 603, 518 and 556 OTUs, respectively. The classification annotation results showed that they belongded to 33 phyla and 273 genera. Proteobacteria, Bacteroidetes and Firmicutes were the dominant microflora that accounted for about 70% of the total number of the bacteria. The proportion of Spirochetes in the intestinal flora of L. crocea was 26.19%, and it was the dominant flora in the intestinal of L. crocea. Bacillus, Photobacterium, Vibrio, Chryseobacterium, Sphingomonas, and Pseudomonas were the predominant genera of the reared croakers, but great differences in percentages of these genera existed among the microflora of these fish species. The analysis of the microflora diversity of cultured croakers showed that Shannon’s diversity index of the intestinal flora: N. albiflora > N. miichthyoides > S. ocellatus > M. miiuy > L. crocea. The microflora diversity of the intestinal contents of these fishes was higher than that of the intestinal wall. According to the variation analysis of microflora between these species, N. miichthyoides and M. miiuy had the most similar intestinal microflora structure. Then they clustered with the flora of N. albiflora. The intestinal flora of L. crocea was more similar to them than that of S. ocellatus. At the same time, the comparative analysis of the intestinal flora structure showed that the phylogenetic factors were important in the forming of fish’s intestinal microflora. In summary, the intestinal flora of the 5 species of mariculture croakers had core flora with its own characteristics. Although the fishes sampled in this study belonged to relative species and the diets habits were similar, they still had great differences in the intestinal microflora structure. The difference in intestinal flora structure was similar to the phylogenetic relationship between species, which proved that intestinal flora structure was closely related to host genetic factors. Studies on maintaining the intestinal health of aquaculture fish and providing better nutritional feed would improve economic benefits of aquaculture industry. In addition, they can also provide a huge space for the development of new fish feed supplements. This study would provide scientific basis for the development of both feed and probiotics for cultured croakers. In the meantime, the results would be helpful to the control of fish disease and providing relevant experimental evidence on proving host genetics had influence on intestinal flora.

Abstract:Intensive aquaculture is generally characterized by the addition of nutritionally enriched diets. High-protein feed inputs thus lead to an inefficient use of nitrogen, and the waste of the natural resources, mostly fishmeal, from which this nitrogen originated. With increasing concentration, ammonia and nitrite can be toxic to aquatic life. Previous studies demonstrated that Houttuynia cordata floating bed could significantly reduce ammonia and nitrogen (N) in tilapia intensive aquaculture, but little information is available about the effective planting density or proportion of H. cordata and its effects on water quality and microbiota in tilapia co-culturing pond system. For this, this study constructed two aquaponic models (M1 and M2) based on H. cordata and tilapia, and respectively investigated their effects on water quality and bacterial microbiota in the tilapia intestinal tract and the pond water system. The M1 model included four density treatments (350 g/m², 450 g/m², 600 g/m², and 0 g/m²): the control 0 g/m² (no H. cordata floating bed), treatment 350 g/m² (planting 350 g H. cordata per square meter pond water), treatment 450 g/m², and treatment 600 g/m². The M2 model included four cover ratio treatments: the control 0 % (with no H. cordata floating bed), treatment 5 % (growing 5% H. cordata with floating bed), treatment 10%, and treatment 15%. Results showed in the M1 model the water quality trends based on chemical oxygen demand (COD), ammonia nitrogen(NH₄⁺-N), nitrite nitrogen (NO₂^--N), nitrate nitrogen (NO₃^--N), total nitrogen (TN), total phosphorus (TP) and ortho phosphate (PO₄^3–-P) in treatment groups were significantly lower than those in the control groups. And in the three experimental months, the effect of treatment 450 g/m² was relatively more stable than treatments 350 g/m² and 600 g/m². High-throughput sequencing analysis based on α-diversity indices (Chao1, ACE, Shannon and Simpson) showed different H. cordata floating bed treatments (350 g/m², 450 g/m², and 600 g/m²) could significantly improve the bacterial microbiota composition and increase the bacterial microbiota diversity. And these effects were more obvious along with the extension of co-cultured time. In same month, the effects of treatments 450 g/m² and 350 g/m² (P<0.05) were more stable than that of treatment 600 g/m² (P>0.05). Among different months, the effect from seasonal variation on bacterial composition of fish gut or water was greater than the effect from H. cordata floating bed. In the M2 model, results showed that the H. cordata floating bed with different cover ratios could effectively improve the pond water quality and increase the bacterial community richness and diversity in tilapia ponds and fish guts. And the effect of treatment 10% was relatively more stable. These results demonstrated that using H. cordata floating beds in aquaponics could improve the pond water quality and increase the richness and diversity of the bacterial community in tilapia ponds and in fish guts. In this study, the density 450 g/m² was more stable than densities of 350 g/m² and 600 g/m², and a 10% cover ratio of H. cordata floating bed was superior to ratios of 15% and 5%. These results provide a scientific basis for the application of aquaponics based on H. cordata and tilapia.

Abstract:The scallop (Pationopecten yessoenisis) is one of the most important aquaculture species in China. The main cultured areas are distributed in Chang-Shan archipelagos of Liaoning. But since 2007, the raft culture scallops P. yessoenisis disease outbreak has caused massive mortality in Changhai, Liaoning. The moribund scallops exhibited severe disease signs including brown deposit on the inner shell. So the cause of brown deposit symptom and the relationship with death of P. yessoenisis were analyzed. The epidemiological investigation and experiment of avoiding bite were used for researching the preliminary cause and formation of brown deposition syndrome. The infrared spectroscopy scanning was also used for studying the components of brown deposit. The result show that the cumulative mortality of P. yessoenisis cultured in aquaculture cage for avoiding bite was 87.60%, and the proportion of brown deposition syndrome was 74.50%. So biting or mechanical abrasion between scallops was not the cause of brown deposition syndrome; the FITR spectra of brown deposit was consistent with the FTIR of BSA, and had protein characteristic peaks of amide Ⅰ and amide Ⅲ, and the main component of brown deposit was protein; the brown deposition syndrome often happened in mid late June and early July when the temperature of seawater was 17 °C. 2017–2019, the proportion of brown deposition syndrome was 85.7%, 1.54% and 10.9% respectively, and the cumulative mortality of P. yessoenisis cultured in ordinary cage was 90.40%, 49.20% and 48.16%, and the proportion of brown deposition syndrome was significantly associated with the cumulative mortality of P. yessoenisis. So pathogenic infection may be the cause of brown deposition syndrome, and it had relationship with the massive mortality of P. yessoenisis.

Abstract:As an effective, safe and eco-friendly aquaculture mode, biofloc technology (BFT) is receiving more and more attention nowadays. So far, the impacts of BFT on perfomances of Litopenaeus vannamei regarding organic carbon sources, C/N ratio and culture density have been reported, which especially focusing on water quality and biofloc microflora. However, the effect of molasses on the aquatic microbiota during shrimp culture has not been systematically evaluated. In order to investigate the effects of molasses on shrimp growth and aquatic microbiota during culture of L. vannamei, high-throughput sequencing of 16S rDNA amplicons was used to compare the differences of bacterial community structure between the treatment group with molasses (C/N=16.0) and the control group (C/N=8.5) on the 4th, 13th and 34th days respectively, and the microflora function was predicted by PICRUSt2. The results showed that although molasses addition had no significant effects on body length and body weight of shrimp, the shrimp survival rate was significantly enhanced. Compared with the control group, the Shannon diversity and evenness indices of aquatic microbiota in treatment group increased significantly on the 4th day, while decreased markedly on the 13th and 34 th days. After adding molasses, the relative abundances of α-Proteobacteria and Actinobacteria in the treatment group were very significantly higher than those in the control group, whereas the abundances of Cyanobacteria and γ-Proteobacteria presented an opposite trend. The abundance of β-Proteobacteria was also significantly lower than that of the control group on the 4th and 34th days. Additionally, the abundance of Bacteroidetes was significantly higher and lower than that of the control group on the 4th and 13th days, respectively. At the family level, the relative abundance of Microbacteriaceae in the treatment group was significantly higher than that in the control group on the 4th, 13th, and 34th days. On the 4th day, the relative abundances of Rhodobacteraceae and Flavobacteriaceae were extremely significantly higher than those of the control group, while the abundances of Devosiaceae, Alcaligenaceae and Lewinellaceae exhibited conversely. On the 13th day, the abundances of Halieaceae and Cyclobacteriaceae were significantly lower than that of the control group. On the 34th day, the abundance of Demequinaceae was significantly higher than that of the control group. The abundances of dominant genera such as Gemmobacter and Demequina in the treatment group were significantly higher than those in the control group, while the abundances of some genera such as Haliea decreased significantly. The functional prediction of aquatic microflora showed that the top 20 items in the treatment group presented extremely significant metabolic function enrichment on the 34th day, and eight of these items, including glycolysis/gluconeogenesis, were highly enriched, which mainly act on carbohydrate or energy metabolism. The results indicated that the proper amount of molasses could significantly affect the relative abundances of dominant bacterial communities in rearing water of L. vannamei, optimize the microflora structure by enriching the functions of carbohydrate and energy metabolism pathways, and thus improve the survival rate of shrimp. This study provides key and practical references for application of molasses as an organic carbon source in shrimp biofloc aquaculture.

Abstract:In order to explore microbial community structure and the correlation between environmental factors and community structure on Hole-Rotten disease of kelp Saccharina japonica in coastal regions of Putian, in this study, 16S rRNA gene amplicon sequencing technology was used to analyze the samples of healthy (HT) S. japonica, S. japonica with Hole-Rotten disease (DT), seawater from area of cultivated healthy S. japonica (HS) and seawater from area of cultivated S. japonica with Hole-Rotten disease (DS). The interactions between seawater microbial and environmental factors were analyzed by redundancy analysis (RDA) as well. The results showed that the Ace index, Shannon index and Heip index were significantly different between HT and DT samples (P<0.05), the Ace index and Shannon indes were significantly different between HS and DS samples (P<0.05), while the Heip index was not significantly different (P>0.05). The results of principal co-ordinate analysis showed that the microbial community of each sample was obviously partitioned. Microbial community composition analysis showed the relative abundance of Halomonadaceae in the HT and DT samples were 1.63% and 49.01%, the relative abundance of Cyanobacteria in the HS and DS samples were 74.45% and 3.89%, respectively. The relative abundance of Pseudoalteromonadaceae in DS samples is 30.87%, nevertheless, less than 1% in HS samples. The results of correlation analysis of environmental factors showed the salinity and temperature were significantly different in the association between HS and DS samples (P<0.05), and the explanations for the variation of seawater microbial communities were 46.75% and 42.42%, respectively. The dominant Cyanobacteria in seawater was positively correlated with salinity and negatively correlated with temperature; the dominant Flavobacteriaceae, Rhodobacteraceae, Pseudoalteromonadaceae and Vibrionaceae, were negatively correlated with salinity and positively correlated with temperature. In summary, the occurrence of Hole-Rotten disease may be intimately related to the Halomonas in S. japonica epiphytes and the Cyanobacteria and Pseudoalteromonadaceae in seawater microorganisms. Salinity and temperature might be the key environmental factors leading to the change of seawater microflora.

Abstract:Scientific researchers have done a lot of research about the influence of morphological traits of Macrobrachium rosenbergii on body weight of different ages, but the effect of phenotypic traits such as body length before and after sexual maturity on body weight of M. rosenbergii has not been studied. This study aimed to explore the relationship among the phenotypic traits of cultured population M. rosenbergii, before and after sexual maturity. A total of 1 106 samples were collected from a hatchery (Gaoyou), and 15 traits including body weight, total length, and body length were measured, and correlation and path analyses were used to clarify the influence of morphological traits on body weight. The results showed that the key traits that affect body weight and the constructed key phenotypic traits multiple regression equations were extremely between before and after sexual maturity, and between male and female groups. According to the coefficient of determination of individual traits on body weight before sexual maturity of M. rosenbergii, total length, body length, carapace width, carapace depth, abdominal depth and length of second leg should be focused on during selective breeding. Carapace length, carapace depth, the weight of second leg and abdominal weight could be used as key parameters for selective breeding after sexual maturity. Before sexual maturity, body length, carapace width, carapace depth, abdominal length, abdominal depth and length of second leg should be considered during breeding in males while total length, body length, rostrum length, abdominal width, abdominal depth and length of second leg could be considered in females. After sexual maturity, carapace width, carapace depth, abdominal depth, weight of second leg and abdominal weight could be selected in females while considering carapace length, abdominal weight and weight of second leg in males. The present study also indicated that the traits affecting body weight were different between males and females even if in the same growth environment and age, and that males and females had distinct sexual dimorphism. Except for the length of second leg and weight of second leg, in which males were significantly larger than females, and the female’s total length, body length, rostrum length, carapace depth, abdominal length, abdominal depth, and abdominal weight were significantly larger than those of males, which may be related to the fertility enhancement of females. Meanwhile, the multiple correlation coefficient between the retained traits and body weight was higher than 0.85, indicating that the key morphological traits affecting the body weight of each population were verified. In conclusion, the sexual maturity status of M. rosenbergii and the excellent phenotype of males and females could be considered as key factors during breeding practice. This study can provide a reference for the selective breeding of M. rosenbergii.

Abstract:In order to investigate the characteristic volatile flavor components in the muscle of channel catfish (Ictalurus punctatus) by in-pond raceway system (IPRS), and the traditional pond system (TPS) served as control. The volatile flavor components of I. punctatus selected randomly under the two modes were extracted and identified by the headspace solid phase microextraction combined with comprehensive two- dimensional gas chromatography-time of flight mass spectrometry, and the characteristic components were determined by ROAV (relative odor activity value). The results showed that 49 and 50 components were identified under the IPRS and TPS, respectively, which were mainly composed of aldehydes, hydrocarbons, alcohols and lipids. The relative contents of alcohols and ketones by IPRS were higher than those by TPS, and 1-pentanol, 1-penten-3-ol, vinyl acetate, 2-nonone, 2,3-octanedione, 1,3-pentadiene and n-pentadecane were significantly higher or very significantly higher than those of TPS (P<0.05 or P<0.01). Some aldehydes, such as hexanal, tended to present unpleasant odor when the content was high, the advantage of IPRS in the study were obvious. The characteristic volatile flavor components by IPRS were composed of 1-octen-3-ol, hexanal, heptanal, octanal, 2,6-nonadienal, nonanal, decanal, 2,4-decadienal and (E, E)-2,4-nonadienal, among them, the heptanal and 2,6-nonadienal were the particular components. In conclusion, the culture mode had a great influence on the volatile flavor components and relative contents, The composition of volatile flavor components under IPRS was better than that under TPS, which was suitable for intensive and high-density cultivation of I. punctatus.

Abstract:Suppressor of cytokine signaling (SOCS) is a class of intracellular proteins that inhibited cytokine signaling in JAK/STAT pathway. To explore the function of SOCS in fish immune response, hybrid yellow catfish “Huangyou-1” and its female parent Pelteobagrus fulvidraco and male parent P. vachell were selected as the research object in this study. The immune related genes SOCS1, SOCS2 and SOCS3 of hybrid yellow catfish “Huangyou-1” were cloned and preliminarily analyzed by bioinformatics. The Quantitative Real-time PCR (qRT-PCR) technology was used to detect the expression patterns of these three genes after infection of Aeromonas hydrophila and Edwardsiella ictaluri into hybrid yellow catfish “Huangyou-1” and its parents. The results show that the ORF length of SOCS1, SOCS2 and SOCS3 genes of hybrid yellow catfish “Huangyou-1” was 561, 735 and 672 bp, encoding 186, 244 and 223 amino acids respectively, and prediction results revealed that SOCS1, SOCS2 and SOCS3 proteins contained SH2 conserved domains and SOCS box. The expression pattern of SOCS1, SOCS2 and SOCS3 genes showed tissue specificity in hybrid yellow catfish “Huangyou-1”, P. fulvidraco and P. vachell. After being challenged with A. hydrophila or E. ictaluri, the transcripts of SOCS1, SOCS2 and SOCS3 were all significantly increased, reached the peak at 24 h and then gradually returned to normal levels in liver, gill and head kidney in hybrid yellow catfish “Huangyou-1” and its parents (P<0.05). In addition, compared with parent P. fulvidraco and P. vachell, hybrid yellow catfish “Huangyou-1” had higher mRNA levels in SOCS1, SOCS2 and SOCS3 after the infection of E. ictalurid, showing a stronger immune regulation ability and having pathogen specificity. Our study provides a basis for the analysis of the immune defense regulation mechanism of the SOCS family of Pelteobagrus.

Abstract:Barnacle is an important marine biofouling organism and its attachment to the surface of marine engineering equipment has a strong impact on the use of the equipment and causes huge economic losses. The development of environmentally friendly antifouling technology against barnacle is inseparable from fundamental studies of the molecular regulatory mechanism underlying the larval attachment and metamorphosis process which has not been fully studied. The attachment of barnacle larvae involves many complex processes, such as the growth and development of the larvae, the exploration of the substrate for permanent attachment, the metamorphosis process and the secretion of barnacle glue. These processes are difficult to be analyzed in detail by the traditional methods of cell biology and molecular biology. In recent years, transcriptomics and proteomics based on high-throughput sequencing technology have played an important role in studying the attachment process of marine biofouling organisms, and have accumulated a large amount of data in revealing the attachment mechanism of barnacle larvae. In the present paper, recent studies on the barnacle adhesion mechanism at home and abroad were reviewed. We mainly focused on omics studies on the attachment and metamorphosis of the barnacle larvae, composition and curing of the barnacle glue. The collective archives have revealed an increasing application of omics tools in the biofouling field since the pioneering work of Anthony Clare’s group. Transcriptome and proteome data provide insights into the signaling pathways in barnacle larval adhesion. It was found that receptor tyrosine kinases and mannose receptors may be involved in signal perception. In addition, many receptors related to vision, auditory and mechanical senses were identified and supposed to be involved in cyprid searching and attachment. Some studies focused on the water-soluble pheromone which are crucial for the aggregation of barnacles. As for the identification of the cement proteins, proteome analyses were commonly applied, which yielded characterization of biomineralization-related and adhesion-related proteins, as well as some proteins involved in other cellular processes. These findings inferred that the attachment of the cyprids and adult barnacles was a complex biochemical reaction coupling several physiological responses. At last, we briefly discussed the future perspectives of antifouling technology. Much attention has been paid to developing antifouling coatings with prevalent and long-term effects. However, the tests were usually conducted in the lab, while the real scenarios are extremely complex where multi-factors are coupled. And we suggest that individualized antifouling design according to the local marine environment, work site and other factors, rather than a cure-all, may improve efficiency and reduce the cost in the future.

Abstract:Filament amplification is a key step in artificial seedling cultivation of Scytosiphon lomentaria. In order to optimize the growth conditions of the filament of S. lomentaria, a Box-Behnken design (BBD) was employed for experimental design and analysis of the results to obtain the best possible combination of temperature (X₁: 17–23 °C), light intensity [X₂: 43.2–100 μmol/(m²·s)], and added nitrogen: phosphorus (N∶P) ratio (X₃: 7–17). The results show that the mathematical model has a good fitting degree and good regression property. The model predicted and optimized reaction parameters as follows: temperature 20.45 °C, light intensity 78.13 μmol/(m²·s), added N∶P ratios 16.19. Under the condition of the amplification for 10 d, the increasing ratio of filament biomass was 299.21%±13.58%, which was significantly higher than that measured in the single factor experiment and Box-Behnken design experimental conditions. In order to evaluate the development of filaments of S. lomentaria after optimized culture, the filaments were induced for 20 days. The results showed that the sporangium ratio after optimized culture (26.37%±5.22%) was higher than that of unoptimized culture (18.10%±3.51%). Meanwhile, the average sporangium diameter under optimized conditions was (19.75±0.21) μm, which was also higher than that before optimized culture [(16.91±0.36) μm]. The results showed that the high amplification rate and the development of sporangia of filaments could be achieved by purposeful regulation of environmental conditions and appropriate nutrient concentration.

Abstract:In order to explore the immune function of Strawberry Notch1 gene (SBNO1) in crustaceans, the full length of SBNO1 gene cDNA sequence, phylogeny, tissue distribution, the expression of SBNO1 and related genes in Notch signaling pathways by Vibrio parahaemolyticus (VP) injection were studied in this paper. The results showed that the cDNA sequence of SBNO1 was 4 353 bp, encoding a total of 1380 amino acids. The predicted molecular weight of protein is 158.91 ku and theoretical isoelectric point is 4.8. According to the RT-qPCR analysis, it can be found that SBNO1 was expressed in all tested tissues, among which hepatopancreas had the highest level and gonad followed. Futhermore, after RNAi interference, compared with the non-inference group, the death rate of the inference group injected with VP was significantly higher. The transcription of SBNO1, Numb and Delta in the hepatopancreas in Notch signaling was obviously influenced by VP. However, there was no significant difference in the expression of Jagged. In the group injected with VP, the expression levels of SBNO1 and Numb increased first and then decreased over time, while the expression of Delta decreased first and then increased. The results indicate that Notch signaling pathway plays an important role in the immunity of E. carinicauda by VP injection. This study helps to clarify the mechanism of invertebrate innate immunity and provides a theoretical basis for molecular breeding of E. carinicauda.

Abstract:As a new type of filler, biochar membrane frame has a higher unit specific surface area, which is conducive to the attachment of denitrification microbial community and has a strong ability to purify sewage. Therefore, it has a broad prospect in the application of constructed wetlands in the future. However, it is not clear whether environmental changes in aquaculture and aquatic medicine will hinder the full use of fillers in constructed wetlands. In order to investigate the influence of external factors on the decontamination capacity of biochar membrane frame, different pH values (E1: 6.5, E2: 7.5 and E3: 8.5) and commonly used aquatic medicines (F1: florfenicol, 6 mg/L; F2: oxytetracycline, 20 mg/L) were applied in this study. The results showed that: ① Nitrospirae had the highest relative abundance among the nitrification bacteria; ② the ammonia-oxidizing rates of E1, E2 and E3 groups were 0.247, 0.249 and 0.305 mg/(L·h), respectively, which were lower than those of the control group (pH=8.2), 0.323 mg/(L·h). At low pH, the relative content of Nitrospira spp. was slightly decreased, but the relative content of Athiobacillus spp. nitrification had no significant difference; ③ the ammonia oxidizing rates in F1 and F2 groups were 0.172 mg/(L·h) and 0.172 mg/(L·h), respectively, which were lower than those in the control group (0.323 mg/(L·h). Compared with the control group, the relative contents of Helicobacter nitrificatus and Athiobacter denitrificatus had no significant change. It was inferred that the florfenicol and oxytetracycline inhibited their activities and reduced the ammonia oxidizing rate. In conclusion, slightly alkaline water is beneficial to the purification of water quality by biocar filler, and florfenicol and oxytetracycline can affect the abundance and activity of denitrification microorganisms on the biofilm and inhibit the ability of ammonia oxidizing rate. Therefore, when antibiotics are used for treatment, other water quality regulation measures should be taken to control the ammonia nitrogen content of aquaculture water, to ensure the safety of aquaculture objects, and maximize the purification effect of biochar fillers for aquaculture effluent.

Abstract:This study aimed to explore the molecular mechanism of foot color difference to guide the selective breeding of high-quality Paphia textile. In this study, the foot transcriptomes of P. textile with different colors were analyzed by the second and third-generation sequencing technology. Analysis of gene differential expression was also performed in the orange and the white feet of P. textile. The second-generation sequencing results showed that a total of 44.82 Gb of clean data were obtained from six samples, GC content was 35.30%-38.21%, and the percentage of Q30 base was 94.43% or above. The results of third-generation sequencing showed that the orange foot group and light white group obtained 16 968 and 21 611 high quality transcripts, respectively. Among them, high quality transcript sequences were compared with the major databases, 5058 full-length transcripts with annotated information were obtained. Three generation full-length transcripts were regarded as reference sequences, and the second-generation data were aligned back to the reference sequence. A total of 57 differentially expressed transcripts were obtained, including 34 up-regulated and 23 down-regulated genes in orange group. 12 randomly selected transcripts were validated with realtime fluorescence quantitative PCR (qPCR), which showed that they were consistent with the qPCR analysis results. Subsequently, through bioinformatics analysis, it was found the regulation of foot color was affected by fatty acid biosynthesis and metabolism, muscle composition, energy metabolism energy metabolism in P. textile. Among them, peroxisome proliferators-activated receptors (PPARs) regulated fatty acid biosynthesis and metabolism. Troponin is an important component of muscle. Arginine kinase (AK) is involved in energy supply during pigment deposition. It is speculated that PPARs, Troponin, and AK play an important role in the pigment deposition. The results of this study may pave the way for further exploring the molecular mechanism of color-related genes and assist selective breeding practices in P. textile.

Abstract:Staphylococcus sciuri is a common zoonotic pathogen to humans, animals and fish. It can cause a variety of diseases and a high fatality rate to aquatic animals. Carassius auratus is one of the most important aquaculture species in the world, and can be used as a good aquatic animal model. In order to explore the pathogenicity and inactivated vaccine protectivity of S. sciuri JS-1 on C. auratus, we designed the JS-1 injected infection experiment, the JS-1 supplemented feeding experiment, and the inactivated vaccine protection experiment, and samples were detected by histopathological observation, quantitative real-time PCR (qPCR) and enzyme activity detection. Results showed that in the JS-1 injected infection samples, C. auratus showed systemic hemorrhage, and its liver was congested and enlarged, and the 96-hour LD₅₀ was 5×10⁶ CFU/mL. In the JS-1 supplemented feeding experiment, the liver of C. auratus showed congestion and enlargement with irregular nucleus shape, the spleen was congested and had serious necrosis, the renal corpuscle was swollen and the space of renal capsule was enlarged, and the transaminase in serum increased at first and then decreased, and reached the highest level on day 14. The high concentration group showed the most obvious decrease trend, and the activity of lysozyme was significantly increased, compared with control group. On day 14, the lysozyme activity of the high concentration group was significantly higher than that of the control group (P<0.05), on day 28, the lysozyme activity of the low concentration group was significantly increased (P<0.05). The expression of TNF-α and IFN-γ genes in the liver and spleen of C. auratus increased at first and then decreased, and was significantly higher than that of the control group, and on day 21, the difference still existed. After injection of the inactivated vaccine, the activity of lysozyme in serum was significantly higher than that in the control group, while activities of alkaline phosphatase, transaminase, and superoxide dismutase were significantly lower than those in the control group, and the catalase activity was significantly increased; the specific IgM and total IgM in the serum immunized with inactivated vaccine were significantly higher than those in the control group. The content of specific IgM accounts for 50%-60% of the total IgM content, and the survival rate of crucian carp reached 83.3% on 10th day after JS-1 injection. This study showsed that S. sciuri JS-1 is highly pathogenic to C. auratus, causing systemic hemorrhage and internal organ damage, and inactivated vaccine of S. sciuri can stimulate the body to produce a strong immune response. The immune protection rate is more than 80%, and its inactivated vaccine can provide effective protection for C. auratus. This study provides a research basis for the development of S. sciuri vaccine.

Abstract:In this experiment, a comparative study of the physiological states of short-term starvation and feeding of mandarin fish was carried out under the conditions of water temperature [(13±1) °C] with reference to the winter water temperature in Guangdong Province. Ninety mandarin fish with the initial body weight of (84.13±0.14) g were selected and randomly divided into starved group (starved 15 days) and feeding group (feeding 15 days). Physical and chemical indexes were measured after the trial. The results showed: ① the final body weight, liver glycogen, crude protein and crude lipid of the whole body and muscle in feeding group were significantly higher than those in starved group. The weight gain rate in feeding group was 7.54% while the weight loss rate in the starved group was 8.39%. ② The activities of alanine transaminase and aspartate transaminase in plasma of mandarin fish in feeding group were significantly lower than those in starved group, but the concentration of triglyceride was significantly higher than that in starved group and there was no significant difference between the number of various blood cells and glucose level. ③ The activity of digestive enzyme and the development of intestinal tissue structure in the feeding group were significantly higher and better than those in starved group. ④ Feeding group had a better antioxidant capacity than starved group, moreover, liver cell in starved group had an obvious structural damage and the number of lipid droplets in starved group was significantly lower than that in feeding group. ⑤ The activity of lysozyme in plasma and the content of IgM in plasma, spleen and kidney in feeding group were significantly higher than those in starved group. ⑥ There was no significant difference in amino acid composition of dorsal muscle of mandarin fish between feeding group and starved group. However, there were significant differences in the composition of fatty acids. The total saturated fatty acids and monounsaturated fatty acids in the dorsal muscle of mandarin fish in feeding group were significantly lower than those in starved group, while the total polyunsaturated fatty acids and high unsaturated fatty acids in feeding group were significantly higher than those in starved group. In conclusion, under this experimental conditions, the difference between the feeding group weight gain and starved group weight loss was 15.93%, in addition, in the starved group, the digestive and immune ability were decreased, the antioxidant ability of liver was weakened and the cellular structure was damaged while in the feeding group, the digestion, immunity and liver function of the mandarin fish were relatively normal. The contents of dorsal muscle protein and lipid were higher than those in starved group, and the composition of fatty acids was improved and the composition of amino acids was stable.

Abstract:Heat shock protein (HSP) is a ubiquitous and highly conserved stress protein, and its expression changes are associated with the health status of fish. Hsp60 is a member of the heat shock protein family with a molecular weight of about 60 ku, which is mainly distributed in mitochondria of eukaryotic cells. Hsp60 was up-regulated during stress or cell injury and recognized by pattern recognition receptors as a danger signaling molecule. Previous studies showed that cytoplasmic Hsp60 could interact with caspase-3 to increase stress tolerance and maintain cell homeostasis. However, excessive accumulation of Hsp60 can also accelerate the activation of caspase-3, induce the release of cytochrome C and promote cell apoptosis. Hsp60 can refold and repair damaged proteins under stress by ATP binding and hydrolysis. Therefore, it is very important to study the function of Hsp60 in fish during bacterial infection. Fish in natural water are threatened by environmental pollution, natural toxins and microbial infection, and bacterial infection was a common disease. Schizothorax prenanti is a unique sub-cold-water economic fish in China and an essential variety of proliferation and release in the Yangtze River’s upper reaches. S. prenanti is a special economic animal with high content of umami amino acids and good content and ratio of amino acids and fatty acids. In recent years, the techniques of artificial domestication and breeding have been relatively mature, but the specific immune system is poor. Streptococcus agalactiae is an important pathogen that harms S. prenanti and the typical clinical symptoms of infection are exophthalmic protrusion and subcutaneous abscess on the body surface. However, the early infection of S. agalactiae is not easy to detect. As an important pathogen, S. agalactiae can spread to the whole body through blood and eventually cause pathological manifestations of edema and sepsis. After entering the blood circulation, S. agalactiae can bind with serum complement C3b through polysaccharide, transforming the activated C3b into an inhibited state to avoid non-specific immune clearance of the host. Besides, S. agalactiae can also avoid phagocytosis and clearance of macrophages through polysaccharide in the capsule, thus causing damage to the visceral tissues and organs. In this study, the molecular characteristics and response to bacterial infection were investigated to explore S. prenanti Heat shock protein 60 (SpHsp60). The 2 277 bp SpHsp60 cDNA sequence was cloned using RACE technology, which encoded 575 amino acids and had relatively conserved spatial conformation with vertebrates. Then, the analysis of tissue expression pattern showed that the expression level of SpHsp60 was the highest in hepatopancreas, followed by blood, and the lowest in skin, muscle, and intestines. Furthermore, the mRNA expression of SpHsp60 in blood, hepatopancreas, trunk kidney and spleen had significant differences in 6 h after S. agalactiae infection. Compared with the control group, the mRNA expression of SpHsp60 in hepatopancreas and trunk kidney expression significantly increased from 6 h to 72 h post-infection, while those in the spleen were significantly decreased. Our results suggested that SpHsp60 could play an early warning role in bacterial infection, providing primary data for Hsp60 mRNA expression in hepatopancreas and trunk kidney as a warning signal for S. agalactiae infection in S. prenanti.

Abstract:In order to study the effects of aquaculture density on the growth performance of juvenile Siberian hybrid sturgeons [Acipenser baerii (♀)×A. schrenckii (♂)] in Jinggangshan region, this study took juvenile Siberian hybrid sturgeons with an initial body weight of (7.89±0.45) g as the research object. Three density groups [low density group (1.16 kg/m³), medium density group (1.74 kg/m³) and high density group (2.32 kg/m³)] were set for 90 days of production test. Through the comparative analysis of different density groups of Siberian hybrid sturgeon growth indexes and body composition content, antioxidant enzyme activity and related gene expression levels, it was found that low density group of larval final body weight, weight gain rate and specific growth rate of low density group was significantly higher than those of medium density and high density group (P<0.05), the density experiment fish survival rate had no significant difference; water content and ash content increased with the increase of culture density, and there were significant differences, but crude fat and crude protein did not show significant differences. The activities of superoxide dismutase (SOD) and glutathione sulfur transferase (GSH-ST) in liver in low and medium density groups were significantly higher than those in high density group at the end of experiment (P<0.05). With the increase of breeding density, the content of MDA in liver of juvenile fish increased continuously, and the activity of catalase (CAT) decreased. There was no significant difference between MDA and CAT during the trial. The results also showed that the expression levels of growth-related growth hormone receptor gene (GHR), insulin-like growth factor-1 gene (IGF-1) and insulin-like growth factor-2 gene (IGF-2) were significantly decreased in the high-density group (P<0.05). The expression level of stress-related heat shock protein 70 gene (HSP70) in high density group was different after 45 days (P<0.05), and after 90 days, high density group was significantly higher than low density group (P<0.05).The expression level of heat shock protein 90 gene (HSP90) in low density group was significantly lower than those in medium and high density groups on day 30 (P<0.05). At the end of the experiment, there were significant differences among the three density groups (P<0.05). The results showed that the juvenile Siberian hybrid sturgeon showed good growth performance under medium and low density conditions. Therefore, it is suggested to control the breeding density of juvenile Siberian hybrid sturgeon in Jinggangshan Mountains region between 1.16 and 1.74 kg/m³.

Abstract:Oligochitosan (OCS) has many important physiological functions, however, the underlying mechanisms on immune regulation of groupers are not well characterized. A feeding trial was conducted in triplicates with the control diet supplemented with OCS at different concentrations (0, 200, 400, 800 and 1600 mg/kg). The effects of OCS on the grouper growth, immune responses and gut microbes were explored after juvenile hybrid groupers [Epinephelus fuscoguttatus (♀)× E. lanceolatu (♂)] were cultured for 4 weeks. The results showed that OCS significantly increased weight gain rate and decreased feed coefficient of hybrid groupers, but had no significant effect on condition factor and survival rate. To elucidate the immune responses stimulated by OCS using qRT-PCR, the mRNA expression levels of inflammation-associated cytokines (TNF-α, IL-1β, TGF-β1, TOR, and TLR3) from midgut were all significantly up-regulated in the 800 mg/kg group compared to the control. At the same time, OCS significantly improved the antioxidant capacity by increasing the expression of GPx, CAT and MnSOD while they also significantly increased the expression of tight junction proteins (ZO-1, ZO-2, ZO-3, and Claudin-3α). To characterize the gut bacterial flora by high-throughput sequencing of 16S rRNA, microbe samples were collected from the foregut, midgut, and hindgut, respectively. We found that although there was no significant differences in the relative abundance and α diversity of intestinal bacterial dominant groups between the OCS and the control group, the abundance of probiotics were increased in the 800 mg/kg group. Additionally, the results of principal coordinate analysis showed that β diversity of bacterial community in 800 mg/kg group was significantly different from that in control group, which indicated that OCS could alter the bacterial assembly of hybrid groupers. To further test the antibacterial ability of hybrid groupers fed with OCS, when the hybrid groupers were challenged with Vibrio harvey, intestinal morphology was greatly improved and the mortality rate of groups fed with 800 m/kg OCS was significantly lower than that of the control. Taken together, appropriate dietary OCS could improve the growth, immune responses and change the bacterial assembly in the gut of hybrid groupers, so as to play a role in the bacterial resistance.

Abstract:Toxic organisms are widely distributed in natural environment and receive much attention from researchers. Ichthyotoxic fishes are one of the largest groups of toxic vertebrates, which refers to fish whose organs or tissues contain toxins or whose tissues can secrete toxins. However, the existent researches on ichthyotoxic fishes have been rather limited for a long time, especially for the freshwater ichthyotoxic fishes. Up to now, the risk assessment system for freshwater ichthyotoxic fishes is scarce at home and abroad, This would greatly hinder the development and utilization of ichthyotoxic fishes. Given that, to increase people’s awareness of freshwater ichthyotoxic fishes, enhance public awareness of prevention, reduce unnecessary losses, and lay a foundation for in-depth research on ichthyotoxic fishes, this study has preliminarily established a risk assessment system for ichthyotoxic fishes and it was applied to 18 known ichthyotoxic fishes in the Jialing River. This risk assessment system was focused on toxic property, population property, and social property of ichthyotoxic fishes. A total of three first-level indexes, eight second-level indexes, and 26 third-level indexes were included in the risk assessment system. By assigning values to the indices of each ichthyotoxic fishes, the score of risk assessment for each ichthyotoxic fishes was calculated according to the determined weight of each index. Finally, the risk grade was confirmed by the score for risk assessment of each ichthyotoxic fish. Results showed that Cyprinus carpio gained 36 points, which is the highest score. On the contrary, Glyptothorax fukiensis obtained 21 points, which is the lowest score. Acrossocheilus yunnanensis acquired 25 points. Among other 15 ichthyotoxic fish species, 7 of them scored between 26 to 30 points and 8 of them scored range from 31 to 35 points. Results of risk grade indicated that four fish species belonged to high risk grade among 18 ichthyotoxic fishes in the Jialing River, and they are Ctenopharyngodon idella, C. carpio, Silurus asotus, and Siniperca chuatsi, respectively. The other 14 ichthyotoxic fishes were divided into medium risk grade. This study has also made effort to examine the intrinsic connection between risk levels and the ecological factors of ichthyotoxic fishes in the Jialing River. Nevertheless, Chi square test (χ²) result showed that there were no significant difference between different risk grades of ichthyotoxic fishes in the Jialing River in respect to feeding habits, distribution water layer, and distribution range. More work could be done in the next research to explore the relationship between ichthyotoxic fishes risk level and their ecological factors. In summary, the risk evaluation system for the freshwater ichthyotoxic fishes we proposed in this study has certain practical value. However, due to limited knowledge for ichthyotoxic fishes, this risk assessment system will inevitably have deficiencies. In the future, the research on ichthyotoxic fishes should be strengthened and the risk assessment system should be constantly improved. Generally, this study has enriched the basic knowledge of freshwater ichthyotoxic fishes, and strengthened people's understanding of ichthyotoxic fish, and provided support for the management of ichthyotoxic fishes. At the same time, it has laid a foundation for further research.