Abstract:The sea cucumber Holothuria leucospilota is an edible sea cucumber species, which is widely distributed in the shallow waters of tropical and subtropical Indo-Pacific Ocean. Nowdays, H. leucospilota has become an important fishery resource owing to the continuously increasing market demand, however, overfishing activities will put this species at risk of extinction in the future. Artificial breeding of H. leucospilota is considered as a useful strategy to solve this problem. The use of suitable substitute diets is an economical and efficient approach for breeding of planktonic larvae of sea cucumbers. In this study, the microalgae Chaetoceros muelleri and Rhodotorula sp. were fed to planktonic larvae of sea cucumber H. leucospilota, either singly or in combination, to evaluate their nutritional quality. C. muelleri and Rhodotorula sp. were mixed in 4∶0, 3∶1, 2∶2, 1∶3 and 0∶4, by volume, and they were labeled as groups A, B, C, D and E, respectively. Results showed that larvae in group A, which fed solely on C. muelleri, exhibited the fastest growth and development among the five groups, larvae could develop to the auricularia stage on the 10th day and the doliolaria stage on the 18th day; meanwhile, survival of the larvae in group A was the highest, and the survival rate in this group was 58.73%±2.75% at the end of the experiment. By contrast, the larvae in groups D and E always stayed in the early auricularia stage, and individuals in these two groups could not form the hyaline spheres during the whole study period. The larvae in group E exhibited negative growth during the whole study period, and survival rate of this group was only 22.22% ±5.50% at the end of the experiment. In general, negative effects on the development, growth and survival of the planktonic larvae of H. leucospilota were found with the increase in the proportion of the Rhodotorula sp. in the diet, and therefore Rhodotorula sp. was not a suitable substitute for breeding of H. leucospilota.

Abstract:The aim of this paper is to investigate the effects of inner-pond raceway aquaculture (IPRA) on the growth performance, antioxidant enzymes, digestive enzymes, digestive tract structure, and bacterial flora of Micropterus salmoides. There were four tanks in a pond with a recirculating flowing water culture, two of them were set up as the treatment group with flowing water, and the other two were set up as the control group with still water. The experiment lasted for 153 days. Relevant growth, biochemical indicators, and histomorphological structures were measured at the midway and the end of the culture period, and the microorganisms in the digestive tract were analyzed using the Illumina Miseq sequencing platform. Results showed that, ① Halfway through the culture period, the weight gain rate, specific growth rate, and condition factor of the treated group were lower than those of the control group. At the end of the culture period, the weight gain rate, specific growth rate, and condition factor of the treated group continued to decrease, although the treatment group’s survival rate was always higher than that of the control group. ② Halfway through the culture period, liver SOD and CAT in the treated group were significantly higher than those in the control group. MDA (0.16±0.01, 0.14±0.01 μmol/mg) in the treatment group was significantly lower than that in the control group (0.19±0.02, 0.21±0.02 μmol/mg), while digestive enzyme activity in the treatment group was significantly higher than that in the control group. By the end of the culture, antioxidant enzymes and digestive enzyme activity were declining to some extent, while SOD (55.11±3.91, 58.18±4.52 μmol/mg) in the treated group were still obviously higher than those (46.57±3.41, 48.84±3.62 μmol/mg) in the control group. ③ The height and density of intestinal villus in the treated group were significantly higher than those in the control group, and more digestive enzymes were secreted midway through the culture, which strengthened the digestive and absorptive functions of the intestine. ④ Halfway through the culture, there was a significant increase in the species diversity and evenness of the gastrointestinal flora of the M. salmoides in flowing water. However, by the end of the culture, the gastrointestinal diversity and evenness indices of the treated group were decreasing. In addition, midway through the culture, the stomachs of the treated group and the control group contained Helotiales and Cyanobacteria. The dominant bacteria found in the stomachs of the threatment group and control group were Proteobacteria and Firmicutes respectively, while the dominant bacteria found in the intestines of the control group were Firmicutes and then Proteobacteria. Towards the later stages of culture, the dominant bacteria found in the stomachs and intestines of both the treatment group and control group were Helotiales, while the dominant bacteria present in the culture water were Proteobacteria and Actinobacteria. The present study shows that continuous movement of water under IPRA can reduce the growth indexes.

Abstract:In order to investigate the effects of different dietary threonine levels on growth performance, glucose and lipid metabolism, immunity and utilization rate of poultry by-product meal (petfood grade) in largemouth bass(Micropterus salmoides), three isonitrogenous and isolipid diets were designed using M. salmoides with an initial body weight of (4.16±0.06) g as the research subjects (TC diet: threonine control group, LT diet: low threonine group and TS diet: threonine supplementation group) were cultured for for 8 weeks. Present results showed that compared with the TC diet, the LT diet significantly decreased the growth performance, feed efficiency and body nutrient composition, threonine addition could promote those differential effects caused by fishmeal totally substituted by poultry by-product meal. Moreover, the LT diet also suppressed the concentration of plasma nutrients and free amino acids compared with the control diet. TS diet had significant effects on elevating the plasma free amino acids concentration and made no notable difference compared to the TC diet. The mRNA expression level demonstrated that threonine supplementation markedly ameliorated the inhibition of anabolism, aggravation of catabolism and cellular inflammation caused by complete replacement of fishmeal with poultry by-product meal. Studies have shown that appropriate threonine supplementation could promote the growth performance by improving nutrient anabolism and immune response and inhibiting catabolism in M. salmoides.

Abstract:This study was conducted to investigate the effects of various levels of dietary mannan oligosaccharides (MOS) on growth performance, antioxidant capacity, immunity and intestinal microbiota of the Pacific white shrimp, Litopenaeus vannamei, at low salinity (salinity 3). Juvenile shrimp (0.68 ±0.01 g) were selected and fed experimental diets containing different MOS concentration (2, 4, or 8 g/kg) for 42 days. The shrimp fed 0 g/kg MOS diet at salinity 25 and 3 were served as seawater control and low salinity control, respectively. The results showed that: 1) The weight gain rate and specific growth rate of shrimp in low salinity control were significantly reduced compared with those in seawater control (P < 0.01). When compared with low salinity control, these parameters together with condition factor in 8 g/kg MOS group and specific growth rate in 4 g/kg MOS group were significantly increased (P < 0.05). 2) Compared with the seawater control, total superoxide dismutase activity and glutathione S-transferase activity of hepatopancreas in all low salinity groups were decreased significantly (P < 0.05). Malondialdehyde content in shrimp fed the 0 and 2 g/kg MOS diets were significantly increased (P < 0.05), while that returned to seawater control level in 4 and 8 g/kg MOS groups (P > 0.05). 3) α-diversity analysis showed that hyposaline stress had no significant effect on Shannon, Simpson, ACE and Chao1 indexes (P > 0.05), while ACE and Chao1 indexes in shrimp fed the 4 and 8 g/kg MOS diets were more significantly improved than two control groups (P < 0.05). In addition, β-diversity analysis showed that the intestinal microbiota of shrimp in seawter control was clearly separated from those 4 groups under hyposaline stress. 4) Compared with two control groups, the relative abundance of Proteobacteria in shrimp fed 2 and 4 g/kg MOS diets were significantly decreased (P < 0.05), while Firmicute and Verruccomicrobiota were increased significantly (P < 0.05). 5) Function prediction analysis by Tax4Fun showed that, compared with seawater control, low salinity stress had a subtle effect on intestinal microbial-mediated functions. While in 4 g/kg MOS group, most pathways related to energy metabolism and immunity at L3 level were significantly improved (P < 0.05). To sum up, all results suggest that dietary MOS can promote the growth performance, improve antioxidant capacity, and immune system in L. vannamei at low salinity, and shape intestinal microbiota structure and composition to help L. vannamei cope with hyposaline stress, and dietary 4 g/kg MOS supplementation can be optimal for the healthy culture of L. vannamei at low salinity.

Abstract:Long non-coding RNA (lncRNA) is a type of RNA with a length of over 200 nucleotides that can interact with DNA, RNA, or proteins to regulate target genes at the transcriptional, post-transcriptional, and epigenetic levels. Based on the previous transcriptome sequencing data of Cyprinus carpio var. koi skin tissues, we screened four lncRNAs that were significantly differentially expressed in three skin tissues (black, red and white). In order to further explore the function of these lncRNAs in skin color differentiation and synthesis, a preliminary study of the relationship between their functions and miRNAs was also conducted. Firstly, the target binding sites between lncRNA172145 and miR-206 in the melanogenesis pathway were identified through RNAhybrid and TargetScan target gene tools. Then, the coding ability of lncRNA172145 was detected by CPC, CPAT, and CNIT software, and the results confirmed that this sequence was lncRNA with no protein coding ability. The temporal and spatial expression levels of this sequence were further analyzed by qRT-PCR, and it was demonstrated that the levels were significantly higher in the eyes, black skin, fins and blood than those in other tissues; and the expression levels started to increase significantly from the gastrulation stage, and the high-level trend continued until 20 days after hatching. Additionally, with the help of dual luciferase reporter assay, the existence of a targeted regulatory relationship between lncRNA172145 and miR-206 was further verified. Finally, miR-206 was silenced in vivo by synthesizing miR-206 antagonist, and the results showed that the expression level of lncRNA172145 in the miR-206 antagonist group, was significantly higher compared to the negative control antagonist group and the PBS group. These findings suggest that lncRNA172145 could be involved in the regulation of the melanogenesis pathway by targeting to miR-206, providing the fundamental information for further research into the specific molecular mechanisms of their roles in the melanogenesis pathway, as well as the role of long non-coding RNAs in regulating fish body pigmentation and differentiation.

Abstract:Frequent typhoons bring large amounts of precipitation, causing drastic changes in water salinity and stress to aquatic animals. The large number of free radicals generated by stress may lead to aquatic animal mortality, which causes huge economic losses. Although Pacific white shrimp, Litopenaeus vannamei is tolerant to salinities of 1 to 50, drastic salinity changes may be detrimental to their health status. As a new type of protein, yeast-like substances contain a variety of functional substances and nutrients such as nucleic acids, small peptides, oligosaccharides, free amino acids, and rich B vitamins, which can improve the growth performance and health of animals, for example Epinephelus coioides, Scophthalmus maximus, Penaeus monodon. Previous studies have shown that the addition of yeast hydrolysate to feed can improve the non-specific immunity, the diversity of intestinal flora, the digestive enzyme activity, and the ability to utilize sugars and lipids in L. vannamei. It is interesting that yeast-like substances seem to play an active role in the immunoregulation response of aquatic animals to environmental stresses. This study aimed to investigate the effect of yeast hydrolysate addition to feed on the non-specific immune and antioxidant capacity of L. vannamei under salinity stress conditions.Shrimps [initial weight (15.82 ±0.08) g] were randomly divided into 2 groups. The control group was fed with basic feed (Y0), and the experimental group was fed with experimental feed (Y3) supplemented with 3% yeast hydrolysate. After 15 days of culture, they were transferred to the water of salinity 4 (S4) and salinity 28 (S28) for low salinity stress with 3 replicates tanks of each group and 30 individuals in each tank. Groups were named Y0S4, Y0S28, Y3S4, Y3S28 according to different combinations of feed and salinity conditions. The results showed that there was no significant difference in the survival rate of the groups after transferring the shrimp to water with salinities of 4 and 28. The addition of yeast hydrolysate to the feed had no significant effect on serum phenoloxidase (PO) and total nitric oxide synthase (TNOS) activities in L. vannamei. At 1.0 h of low salinity stress, PO and TNOS activities were significantly higher in the Y3S4 group than in the Y0S4 group. The salinity factor had a significant effect on PO and TNOS activities, PO, TNOS activities were significantly higher in the S28 group than in the S4 group at 1.0 h. What’s more, the addition of 3% yeast hydrolysate to the feed significantly increased the hepatopancreas superoxide dismutase (SOD) activity of the shrimps. The studies have shown that the addition of yeast hydrolysate to the feed can increase the hepatopancreas SOD activity of L. vannamei and improve the antioxidant capacity of the shrimp. In the event of low salinity stress, the shrimp can quickly restore the PO and TNOS activities to normal levels, thus improving the resistance of L. vannamei to adverse environments.

Abstract:In different species of fish, the number and distribution of pigments are specific, which results in the diversity of body colors. The pigments in fish have lots of functions such as avoiding predators, protecting fish from radiation, and changing their body color for courtship. The diversity of pigments can make fish better adapt to the natural environment. According to the theory of natural selection, the process of formation of pigments of different groups may genetically be differentiated due to the selection effect of environment light and so on. Oryzias curvinotus is a kind of small oviparous fish and its body length is about 2-4 cm. O. curvinotus has strong fertility, a short generation cycle, sensitivity to water quality and environmental changes, and wide adaptability to salinity. O. curvinotus were used to living in the layer water, which is widely distributed in Guangdong coastal areas. Because the embryos of O. curvinotus are transparent, which makes them become the ideal materials for pigment research and gene function research. At present, there have been researches on the resources survey, development, and function of O. curvinotus which is expected to be developed as a model species for monitoring coastal water environment in China. To test the above hypothesis, in this study, different latitude groups (Raoping, Gaoqiao and Sanya) of O. curvinotus were bred under the same conditions, and their progenies (F₆) were used as materials. The iridophores and melanophores of embryos of O. curvinotus were observed by stereo fluorescence microscope, in addition, the expression of four main genes (tyr, alk, sox10 and pax3) in the early development of the Gaoqiao population was analyzed by real-time fluorescence quantitative PCR (qRT-PCR), and the observation results were verified. The results of observation showed that the melanophores and iridophores of embryos in high latitude Raoping embryos were concentrated in 8 and 10 somites stages, accounting for 81.9% and 52.1% respectively; Accordingly, the melanophores and iridophores of the embryo in Gaoqiao embryos were concentrated in 7 and 11 somite stages, accounting for 47.7% and 42.1%, respectively; And the melanophores and iridophores of the embryo in Sanya embryos were concentrated in 8 and 12 somites stage, accounting for 44.0% and 62.2%. qRT-PCR analysis of Gaoqiao embryos confirmed that the expression of tyr, the rate-limiting enzyme of melanin formation, was up-regulated from the 7 to 9 somites stage, and then tended to be stable; And the sox10 and pax3 genes, which inhibit the formation pathway of melanin and initiate the differentiation of iridescent cells, showed the single peak expression pattern from the 10 to 14 somites stage as the downstream alk genes. In conclusion, this study supports that the pattern of melanin and iridescent pigments in the early development stage of O. curvinotus is consistent with the classical pathway of fish, which is regulated by the orderly expression of tyr, alk, sox10, pax3 genes, and the iridescent cells in the low latitude population generally occur later, which supports the existence of population genetic differentiation, but the specific mechanism remains to be studied in the future.

Abstract:To explore the flavor characteristics of traditional shrimp sauce from different places of China and to explore the formation mechanism of the flavor, the flavor characteristics of traditional shrimp sauce from different areas were studied by using gas ion migration spectrum and headspace solid phase microextraction gas chromatography/mass spectrometry. There were significant differences in the volatile flavor of traditional shrimp sauce from different places. The gas ion migration spectrum and GC-MS could be used to characterize the odor difference. The volatile components of shrimp sauce from different places are significantly different. 2-ethyl-hexanol, 3-ethyl-2,5-methylpyrazine, dimethylamine, dimethyl trisulfide and 3-methylthiopropionaldehyde are the characteristic volatile compounds of shrimp sauce. QDA results showed that the color and flavor score of shrimp sauce produced in Guangdong, Hong Kong and Macao were better, and the content of protein and free amino acids was higher than that of other samples, but the fishy smell of shrimp sauce was also obvious. There was no significant correlation between the crude fat content of shrimp sauce and QDA score. When the moisture content is between 18% and 28% (W%), the viscosity of shrimp sauce is the highest. The characteristic aroma compounds of shrimp sauce produced in Guangdong and Hong Kong are pyrazines, such as 2,6 dimethylpyrazine, 2-ethyl-6-methylpyrazine, etc. Trimethylamine and dimethylamine are the characteristic flavor compounds of traditional shrimp sauce. Sulfur compounds are the characteristic flavor compounds of fermented aquatic seasoning, but they may also be derived from the spices such as onion and garlic in the ingredients.

Abstract:The population size of horseshoe crab is decreasing year by year in China. In order to achieve the protection and sustainable utilization of horseshoe crab resources, it is urgent to study the hematopoietic mechanism of the horseshoe crab, and to make the rapid recovery of hemopoietic lymphocytes from the horseshoe crab. Therefore, strengthening the recovery of horseshoe crabs blood lymphocytes is expected to reduce the loss of horseshoe crabs wild resources. In this study, N-acetylcysteine (NAC) and Vibrio anguillarum (V) were injected into horseshoe crab to compare the changes of reactive oxygen content and non-specific immuno enzyme activity in total lymphocytes of Chinese horseshoe crab at 0, 6, 12, 24, 48 hours after injection. The results showed that compared with the control group, the total hemocyte counts (THC), reactive oxygen species (ROS), malonyldialdehyde (MDA) of horseshoe crabs after NAC injection showed downward trends, while the activity of superoxide dismutase (SOD), catalase (CAT), total antioxidant capacity (T-AOC), lysozyme (LZM), and alkaline phosphatase (AKP) showed upward trends. Under the stimulation of NAC and V. anguillarum at different concentrations, the decrease trend of THC, ROS, MDA in horseshoe crab was slowed down compared with single injection of NAC, while the activities of other enzymes were increased. However, HC showed no significant change during the whole experiment. At 6-48 hours, THC, ROS in the NAC group showed a decreasing trend compared with the V. anguillarum group and Co-stimulation groups between NAC and V.anguillarum, the SOD activity of NAC and V. anguillarum was significantly higher than other groups. At 48 hours, CAT, T-AOC showed no significant difference at the NAC group, V. anguillarum group and co-stimulation groups, but both of them were significantly higher than the control group. The NAC+10⁶V group had the lowest MDA in 48 hours. The activity of AKP increased from 12 to 48 hours, and the activity of LZM in NAC group was the highest at 48 hours. There is a negative correlation between THC, ROS, MDA, HC and SOD, CAT, T-AOC, LZM, AKP. NAC can lower the value of horseshoe crab THC, ROS, NAC and co-stimulation with the V. anguillarum can mitigate the decline. However, the above results showed that inactivated V. anguillarum can increase THC, ROS of horseshoe crab，and antioxidant and immunoenzyme activities were increased in all treatment groups. Therefore, it can be concluded that NAC can reduce THC, ROS of horseshoe crab and co-stimulation of N-acetylcysteine with V. anguillarum can alleviate the decreasing trend，however, inactivated V. anguillarum could increase THC, ROS of horseshoe crab, and the activity of antioxidant and immunoenzyme was increased in all treatment groups. This indicated that when NAC reduced ROS content in horseshoe crab, hemolytic cells in the body also decreased, while NAC combined with V. anguillarum inactivated, ROS, THC decreased less than the NAC group. It can be concluded that NAC and V. anguillarum can stimulate the immune functions of horseshoe crabs, meanwhile, ROS may play an important role in the proliferation and regeneration of blood lymphocytes of the horseshoe crabs.

Abstract:In the context of large-scale enhancement and releasing, in order to study the stability of fishery ecosystem and the change of community structures in the waters off southern Shandong Peninsula, based on the waters off Southern Shandong Peninsula fisheries resources investigation and fishery species feeding literature data from 2016 to 2018, through the food web topology structure and social network analysis, we studied the southern Shandong Peninsula sea fishery resources structure and interannual variability of keystone species. The results showed that, a total of 20-22 fish species were involved in the food web of the waters off southern Shandong Peninsula, which covered 59-65 prey-predator relationships, and these are no obvious interannual changes. Based on the dominance analysis, the dominance of Larimichthys polyactis, Trichiurus lepturus, Scomberomorus niphonius increased significantly in 2018 after the adjustment of summer fishing moratorium.The topological structure density of these food webs ranged from 0.3048 to 0.3684, and interspecies connectivity was 0.1451 to 0.1634. From 2016 to 2018, the keystone species in the fish community in the waters off Southern Shandong Peninsula were Engraulis japonicus and Lophius litulon. E. japonicus as the key prey and L. litulon as the key predator, they were both the dominant species 2016-2018, however, the dominance of E. japonicus decreased with each passing year, and Liparis tanakae has been the dominance species since 2017. The results showed that the food web structure in the waters off southern Shandong Peninsula was relatively stable, with little inter-year differences, and the keystone species did not change, but the energy flow and information transfer in the community gradually evolved from high trophic species to low trophic species.

Abstract:Cyclina sinensis is an important marine economic shellfish. The clam C. sinensis are widely distributed in the coastal beaches and estuaries of China, Japan and North Korea, and have been widely cultivated and proliferated in China. In this paper, the research progress in the exploration, evaluation and utilization of the germplasm resources of C. sinensis was systematically reviewed from the aspects of genomics, systematic classification, population diversity, genetic development, seedling breeding, aquaculture ecology, physiology and biochemistry, nutrition and medicinal value. The future development direction of wild resource protection and evaluation, seedling technology and breeding, green and efficient breeding and carbon sink fishery, and nutritional value and deep processing were put forward.

Abstract:The purpleback flying squid (Sthenoteuthis oualaniensis), which is one of the main fishing objects for light attracting falling-net fishing vessels, has abundant resources in the South China Sea. In this study, samples of medium-form and dwarf-form of S. oualaniensis were collected in the Nansha Islands area. Traditional stomach contents analysis and carbon and nitrogen stable isotope analysis were used to study feeding habit, trophic level, trophic niche and their relationship with feeding organisms. Consequently, S. oualaniensis mainly fed on fish, cephalopods and crustaceans, and the food composition was different at different growth stages. The medium-form smaller than 90 mm ML and the dwarf-form smaller than 100 mm ML fed on zooplankton and small fish. The medium-form ranging 90-129 mm ML and the dwarf-form ranging 100-119 mm ML fed mainly on crustaceans, cephalopods and fish. The food intake was mostly by fish and cephalopods for the medium-form larger than 130 mm ML and the dwarf-form larger than 120 mm ML. Besides, the δ¹³C value of the medium-form ranged from –19.61‰ to –18.10‰ and the δ¹⁵N value ranged from 7.17‰ to 10.13‰. The δ¹³C value of the dwarf-form ranged from –19.63‰ to –17.81‰ and the δ¹⁵N value ranged from 6.48‰ to 10.12‰. Analysis showed that there was an overlap of trophic niches between the medium-form and the dwarf-form, which indicated that the squids had competition for food resources. The trophic niche of dwarf-form was larger than medium-form, and there was lower overlap between the dwarf- male group and the other three groups. In addition, the mean trophic level was 2.97 and ranged from 2.54 to 3.41 for the medium-form, and the mean trophic level was 2.87 and ranged from 2.34 to 3.41 for the dwarf-form. The trophic level of the dwarf-male group was relatively low and quite different compared with other groups, which may be closely related to body size.

Abstract:As more and more microplastics are found in the marine environment and creatures，marine microplastics pollution has attracted more and more attentions. In this study, the types, distribution, toxicity and the ingestion characteristics of marine microplastics in marine fishes of different feeding habits and habitats were summarized, and the future research direction was expected. The results show that the distribution of microplastics was wide and of a great variety almost everywhere in the ocean, the vertical distribution characteristics of microplastics in the ocean was as follows: the sediment was the highest, followed by bottom and upper layers, and the middle layers were the least in the vertical direction, and the estuary zones were higher, the flow field zones were the second, oceanic zones were the least in the horizontal direction. The toxicity of microplastics mainly consists of self-toxicity and joint toxicity. Marine fishes had certain selectivity to ingest microplastics. The ingestion types and quantity of microplastics of different habitats and feeding habits marine fishes were different, and the ingestion of different habitats fishes in types were mainly related to the density of microplastics. The ingestion quantity is mainly related to the distribution of microplastics in the ocean. The ingestion of different feeding habits fishes in types and number were mainly related to the feeding habits, and it also has certain correlation with the size of fish, mouth slit and the amount of water filtrated. Microplastics could reduce the reproductive rate and increase the death rate of marine fishes. However, microplastic will be redistributed in the water after a long time of evolution, meaning the diversification of types and quantity of microplastic pollution. In the future, the fishery biology and fishery ecology, physical oceanography and marine chemistry could be combined to further understand the existence, distribution and transmission of microplastics in the ocean and its impact on marine fish and other marine creatures.