Abstract:A 120-day experiment was conducted to investigate the effects of different feeding frequencies on the growth, physiology, and hepatic growth hormone (GH) and insulin-like growth factor-I (IGF-I) gene expression levels of (body weight:5.0 g±0.4 g) reared in in-pond raceway culture systems (IPRS). Fish were randomly assigned to one of three feeding frequencies (2, 3 and 4 times/d) following the same ration size. No significant differences were observed in final body weight, weight gain or specific growth rate of fish fed at different feeding frequencies on days 30 and 60 (>0.05). Fish fed 2 times/d showed higher growth than those fed 4 times/d on day 90, and had higher growth than those fed 3 times/d and 4 times/d on day 120. No significant differences were found in serum alanine aminotransferase (ALT), aspartate transaminase (AST), or alkaline phosphatase (ALP) activities, lysozyme, cortisol and triglyceride (TG) content, hepatic total antioxidant capacity (T-AOC), glutathione peroxidase (GSH-Px) activities, nor in malondialdehyde (MDA) content among fish fed at different feeding frequencies (>0.05). Serum total protein (TP) and glucose (Glu) content, and catalase (CAT) activity, decreased, while total cholesterol (TC) content increased with increasing feeding frequency. Fish fed 2 times/d had higher hepatic total superoxide dismutase (T-SOD) than those fed 4 times/d on days 60, 90 and 120 ( gene mRNA expression on days 30, 60 and 120 (<0.05), while no significant difference was found on day 90. No significant difference was found in gene mRNA expression on days 30 and 60, while fish fed 4 times/d exhibited lower P<0.05). Based on the growth, physiology, and hepatic gene expression levels, the optimal feeding frequency for (average body weight:5.0 g±0.4 g) reared in IPRS is 2 times/d. These data are crucial for the optimization of culture conditions and feeding management strategies in IPRS culture operations.

Abstract:Salinity is one of the most important environmental factors affecting the growth and development of sea cucumbers. microRNAs (miRNAs) can regulate the expression of their target genes by specifically binding to target mRNA. The expression profiles of Aja-miR-22 and Aja-miR-27, and two target genes, were detected in sea cucumbers that were under low salt stress. RNA and miRNA were extracted from coelomocytes of sea cucumbers in normal salinity seawater and were, after 3 h, 6 h, 12 h, 24 h, 48 h, and 72 h exposure to salinity stress, analyzed by qRT-PCR. The results showed that the expression profile of Aja-miR-22 was consistent with that of Aja-miR-27 at each time point after initial salinity stress. Two miRNAs were induced to up-regulate and reached maximum expression at 3 h after stress. The expression maximums of Aja-miR-22 and Aja-miR-27 were 36 times and 16 times more than in the control group, respectively. The expression levels of Aja-miR-22 and Aja-miR-27 were higher than those of the control group under salinity stress, and Aja-miR-22 was significantly different from the control group at 3 h and 48 h after initial stress exposure (<0.01). Aja-miR-27 was significantly different from the control group at 3 h, 48 h, and 72 h under salinity stress. The expression of the target gene echinoderm microtubule-associated protein (EMAP; 77 kD) was also consistent with the general transcription factor IIE subunit 2, which reached the minimum value at 3 h under salinity stress. The expression level of EMAP was lower than that of the control group at each time point after salinity stress. The general transcription factor IIE subunit 2 (General Transcription Factor IIE Subunit 2) was significantly different from the control group at 48 h and 72 h under salinity stress (<0.01). The expression trends of Aja-miR-22 and Aja-miR-27 were negatively correlated with their target gene expression patterns before 24 h. The above results indicated that Aja-miR-22 and Aja-miR-27, and their corresponding target genes, are involved in the salinity adaptation mechanism of sea cucumber.

Abstract:is the largest-culturing species of shrimp, which lends to its high economic and natural nutritional value. However, diseases caused by viruses and bacteria often occur in this species, causing huge economic losses to the shrimp farming industry. Since shrimp can only rely on their innate immune system to protect against pathogen invasions, it is important to understand this innate immune system by studying the immune related molecules of shrimp species, such as . This understanding is essential for the prevention and treatment of shrimp diseases. It has been reported that β-thymosins are a class of highly conserved functional peptides that play important regulatory roles in physiological activities such as wound healing, angiogenesis, and antibacterial and antiviral immunity. In this experiment, one β-thymosin gene sequence was successfully cloned from . The full-length cDNA was 1495 bp and the open reading frame (ORF) was 615 bp, which encoded 204 amino acids. It was named because it contained 5 thymosin beta actin-binding motifs (THY). Multiple sequence alignment and phylogenetic tree analysis showed that Penaeus vannamei, and had the highest homology with thymosin β5 of , with a similarity of 77%. Real-time quantitative PCR (qRT-PCR) showed that the gene was expressed in the hepatopancreas, gills, intestine, stomach, muscle and lymphoid organ, and was significantly higher in immune related tissues such as the hepatopancreas and lymphoid organ. The in vitro recombinant protein of Pmβ5 was obtained by a prokaryotic expression technique and the recombinant protein was confirmed to be a Pmβ5 protein by Western Blot analysis. The antibacterial activity of the recombinant protein was further confirmed by the antibacterial experiment (Oxford Cup method). It was found that the recombinant protein had certain antibacterial activity against four bacteria. After 12 hours of inactivation by inactivated was significantly increased, indicating that Pmβ5 may be involved in shrimp resistance to bacterial immunity. In summary, we have found the expression and distribution of and conducted a preliminary study on the function of Pmβ5 in immunity.

Abstract:This study aimed to explore the effect of temperature on the microbial community in recirculating aquaculture water used to raise , as well as to understand the relationship between environmental factors and the microbial community in the aquaculture water. The breeding experiment of was carried out in a recirculating aquaculture system at water temperatures of 18℃, 22℃, 26℃, 30℃, and 32℃. The microbial community composition in the water was analyzed with 16SrRNA gene high- throughput sequencing technology. The results showed that, (1) the diversity index of the bacterial community in the five groups of water samples was t26 > t22 > t30 > t32 > t18, and the species abundance was t22 > t26 > t32 > t30 > t18. Temperature can significantly influence the diversity of microbial communities in aquaculture water, but no direct correlation was found between the two. (2) 31 phyla, 43 classes, 94 orders, 185 families and 351 genera of bacterial communities were obtained from the aquaculture system at five different temperatures. Proteobacteria was by far the dominant phyla in the aquaculture water. When the water temperature of the aquaculture system was 26℃, the content of nitrogen and phosphorus pollutants in the water was relatively high, and the relative abundance of nitrogen and phosphorus removal by bacteria in the water was significantly higher than at the other four temperatures tested. (3) Similarity analysis using petaline graphs and UPGMA cluster analysis showed that the aquaculture water's microbial community responded well to the temperature change. The overall similarity of the bacterial community structure was low among the five groups of water samples, and the bacterial community structures at the highest temperature of 32℃ and the lowest temperature of 18℃ were the most similar. (4) The correlation analysis of microbial community structure and environmental factors in the water showed that total phosphorous (TP) and NO₃^--N have significant effects on the characteristics of the microbial communities, with temperature being the main reason for the differentiation of nitrogen and phosphorus in the water. The above research results preliminarily explain the effect of temperature on the microbial community in recirculating aquaculture systems, and provide a reference for further study on the relationship between environmental changes and microbial diversity in recirculating aquaculture systems.

Abstract:It is well known that niacin plays an important role in metabolism with regards to protein, lipid and carbohydrates. Fish fed with a niacin deficient diet may show poor growth, lower feed conversion, skin or fin damage, and anemia. So far, reports regarding the effects of niacin on growth, flesh quality and antioxidant function in hybrid sturgeon () are relatively few in number. Therefore, this study was undertaken to evaluate the effects of dietary niacin on growth performance, muscle composition, muscle quality and antioxidant function of juvenile hybrid sturgeon. Four test diets were prepared by adding 0 mg/kg, 30 mg/kg, 120 mg/kg and 1200 mg/kg of niacin, respectively. The juvenile hybrid sturgeon, which had an initial body weight of (54.41±0.79) g, were fed for 12 weeks. The experiment was divided into four treatments, each treatment with three replicates and 15 fish in each replicate. The results showed that weight gain rate was significantly affected by the dietary niacin level (<0.05). The weight gain rate of the 0 mg/kg niacin group was significantly lower than that of the 30 mg/kg, 120 mg/kg and 1200 mg/kg niacin groups (>0.05), and no significant differences were observed among the other niacin groups. The survival rate, feed conversion rate, and viscerosomatic index were not affected by the dietary niacin level (>0.05). The condition factor of the 120 mg/kg niacin group was significantly lower than that of the 0 mg/kg, 30 mg/kg and 1200 mg/kg niacin groups (>0.05), and there was no significant difference between the 0 mg/kg, 30 mg/kg and 1200 mg/kg niacin groups (>0.05). The hepatosomatic index of the 120 mg/kg niacin group was significantly lower than that of the 0 mg/kg and 1200 mg/kg niacin groups (<0.05), and no significant differences were observed between the 30 mg/kg and 120 mg/kg niacin groups (>0.05). The muscle hardness and springiness increased first and then decreased with increasing dietary niacin. The muscle hardness and springiness of the 1200 mg/kg niacin group was significantly lower than that of other niacin groups (<0.05). The muscle chewiness, resilience and gumminess of the 30 mg/kg niacin group was the highest among all groups, and was significant higher than that of the 0 mg/kg, 120 mg/kg and 1200 mg/kg niacin groups (<0.05). The muscle cohesiveness of the 30 mg/kg niacin group was significant higher than that of the 0 mg/kg, 120 mg/kg and 1200 mg/kg niacin groups (<0.05), and there was no significant difference between the 0 mg/kg, 120 mg/kg and 1200 mg/kg groups (>0.05). The muscle composition of crude protein, crude lipid, ash and moisture content were not affected by the dietary niacin level (>0.05). The muscle T-SOD activity of the 30 mg/kg niacin group was significant higher than that of the 0 mg/kg and 120 mg/kg niacin groups (<0.05), but there was no significant difference between the 1200 mg/kg and 120 mg/kg niacin groups (>0.05). Similarly, the muscle T-AOC activity of the 30 mg/kg niacin group was significant higher than that of the 0 mg/kg, 120 mg/kg and 1200 mg/kg niacin groups (<0.05), and there was no significant difference in T-AOC activity between the 0 mg/kg, 120 mg/kg and 1200 mg/kg niacin groups (>0.05). The key finding here is that dietary niacin (≥ 30 mg/kg) can improve the growth, muscle quality and antioxidant capacity of hybrid sturgeon.

Abstract:Based on the data obtained from four cruise investigations during 2016-2017, the secondary production and the P/B ratio of the macrobenthos in Jiaozhou Bay were analyzed using Brey's empirical formula (first devised by Brey in 1990), and the relationship between environmental factors and secondary productivity was analyzed with Pearson's correlation. The results showed that the annual mean abundance was 19.17 ind/m², mean biomass in ash-free dry weight (AFDW) was 20.57 g/m², mean secondary productivity in AFDW was 9.64 g/(m²·a), and the mean ratio was 0.47/a. In terms of spatial distribution, sampling stations with high secondary productivity were mainly located in areas near aquaculture systems and coastal sea areas, highlighting these as high productivity centers. For seasonal distribution, the seasonal variation of secondary productivity was spring > winter > summer > autumn. The correlation analysis indicated that the relationship between environmental factors and secondary productivity was not significant (>0.05). The secondary productivity near the aquaculture area in the bay was closely correlated with sediment type, while being greatly correlated with dissolved oxygen outside the bay. Comparing the results of the present study with other similar studies, secondary productivity in Jiaozhou Bay was higher than that of most sea areas of North China, but the ratio was lower. The results showed that species with small body size, short life and quick metabolism were accounted for less in the community composition of Jiaozhou Bay.

Abstract:Cephalopod species are well documented for fast growth rate, short life span, and high sensitiveness to their ambient marine environments. Energy accumulation is central to the life history of organisms, indicating their levels of energy reserves and resilience to ongoing environmental changes. In order to enhance our understanding of the adaptability of to its habitats, the energy density determination technique, coupled with the generalized additive model (GAM), was applied to investigate energy accumulation in the somatic and gonad tissues, in relation to oceanographic variables, in from the equatorial water of the eastern Pacific. The results showed that the soma energy of male and female individuals increased significantly with growth and development, and was mainly influenced by geographic latitude and sea surface temperature (SST). Significant differences in the gonadal tissue energy were found between immature and mature animals. The energy accumulated in the gonadal tissue was significantly related to the geographic latitude and longitude, SST, and chlorophyll-a concentration. These lines of evidence indicate that the somatic and gonadal tissues of in the equatorial water of the eastern Pacific continuously accumulate energy during the course of sexual maturation. There was tissue-specific energy accumulation in relation to ambient environments, in which the soma energy was significantly correlated with SST. Not only does SST significantly influence energy accumulation in gonadal tissues, but also chlorophyll-a concentration is an important environmental variable influencing gonadal tissue energy. Also, gonadal energy accumulation in female animals showed an obvious increasing trend with the westward geographic longitudes, indicating that the life history of includes offshore feeding migration.

Abstract:Stable isotope analysis has become increasingly popular in the determination of trophic relationships in marine ecosystem. In this study, based on bottom trawl surveys, 33 species of fish and 18 species of invertebrates were collected in February and May 2016 in the offshore waters of southern Zhejiang. All of these species accounted for 90% of the total catch biomass, highlighting them as being the dominant fish species and invertebrates in the offshore waters of southern Zhejiang. Stable isotope ratios of carbon (δ¹³C) and nitrogen (δ¹⁵N) of the fishery organisms were calculated with an element analysis-isotope ratio mass spectrometer (EA-IRMS), and the δ¹⁵N values were applied to estimate their trophic levels. The results revealed that the major fishery organisms had great variations in their composition of stable carbon and nitrogen isotopes, especially the fish species, with statistical difference (C values of the fishery organisms ranged from -19.71‰ to -14.01‰, with an average of -17.06‰, and the δ¹⁵N values ranged from 7.05‰ to 13.69‰, with the average of 10.98‰. Filter-feeding bivalves were set as the baseline. The average trophic levels of fish, crustaceans, cephalopods and gastropods were 2.66-4.21, 3.08-3.72, 2.83-3.49 and 3.54-3.62, respectively. The major fishery organisms were mainly in the range of 3.0 to 4.0, most of which were primary and intermediate carnivorous species. Cluster analysis on the stable isotope results of the major fishery organisms produced organism groups that could be interpreted with trophic and feeding information. Based on hierarchical cluster analysis and feeding literatures, five feeding groups of the major fishery organisms from the offshore waters of southern Zhejiang were classified:zooplankton feeding, omnivorous, benthic feeding, mixed feeding and nekton feeding. The trophic structure of the food web could be divided into four trophic groups, which includes primary consumers, secondary consumers, intermediate consumers and senior consumers. According to the characteristics of trophic structure, the primary consumers were composed of omnivorous species, and the secondary consumers mainly included small fish, shrimps and cephalopods. The intermediate consumers were mainly benthic crabs, gastropods and mixed carnivorous fish, while the senior consumers were carnivorous fish. In this study, the continuous trophic spectrum of fishery organisms in the offshore waters of southern Zhejiang was established to provide an important reference for the study of energy flow and matter cycles in marine food webs.

Abstract:Cyprinid herpesvirus 3 (CyHV-3), also known as koi herpesvirus (KHV), is a highly contagious and lethal virus. At present, a kind of commercial attenuated vaccine has been used in Israel against this virus. However, this vaccine, as well as other reported gene-modified attenuated vaccines against CyHV-3 infection, cannot exclude the risk of reversion to virulence. In contrast to live vaccines, DNA vaccines are easy to produce and safe to apply. CyHV-3 has a genome of 295 kb, which is predicted to encode 164 different open reading frames (ORFs). Among them, ORF148 encodes a glycosylated type I membrane protein and bioinformatics analysis has shown that this protein has good immunogenicity. During our previous study, CyHV-3 ORF148 was inserted into pEGFP-N1, generating a pEGFP-ORF148 recombinant plasmid. In the present study, it was confirmed that a pORF148-EGFP fusion protein could be successfully expressed by transfection assay and immunofluorescence analysis, respectively. The carps, n=45), were intramuscularly injected with the pEGFP-ORF148 recombinant plasmid, pEGFP-N1 and PBS three times at two-week intervals. The results of ELISA showed that immunization with the pEGFP-ORF148 recombinant plasmid could significantly (<0.01) improve the tire of specific antibodies against CyHV-3. The RT-qPCR revealed that injection with the pEGFP-ORF148 recombinant plasmid caused 145.30-, 131-, 52.27-, 12.16-, 4.19-, 3.05-, 4.03-fold increases of , gene expression in the head kidney, respectively, when the PBS immunized carps served as a control group. In the spleen, the expression of from pEGFP-ORF148 recombinant plasmid injected carps were 22.44-, 4.63-, 6.14-, and 4.23 times higher than those of control group. Post-infection with CyHV-3, the survival rates of carps immunized with PBS, pEGFP-N1, and the pEGFP-ORF148 recombinant plasmid were 30%, 35% and 85%, respectively, suggesting that immunization with the pEGFP-ORF148 recombinant plasmid significantly protected the carps against the CyHV-3 infection (<0.01). In conclusion, DNA vaccination based on the pEGFP-ORF148 recombinant plasmid could elicit the activation of an immune response and production of a specific antibody to produce effective protection against CyHV-3 infection. Thus, this study highlights a potential DNA vaccine candidate against CyHV-3.

Abstract:Fish growth is one of the most important traits in fish farming and is of great significance to the economic development of aquaculture. By investigating different farmed fish, a large number of studies have shown that growth is mainly affected by environment, genes, and gene-environment interactions; specifically:(1) The environment is the external cause of growth trait regulation, and its impact on growth has generally presented a pattern of dosage effect. Excessive or insufficient amounts of several major environmental factors, such as temperature, light and nutrition, may have adverse effects on the growth of fish. Therefore, seeking optimal conditions becomes the ultimate goal of setting the best aquaculture environment. Additionally, regulating various environmental factors in modern aquaculture possesses significant application potential. (2) Genes are the internal factors that regulate growth traits, and their effects on growth have shown, largely, a relationship of causal effect. Single nucleotide polymorphisms, gene structural variations, ploidy changes, and transgenes of certain genes have shown statistically significant effects on fish growth. Since growth is a complex quantitative trait that is controlled by multiple genes, finding the major genes and then using them in selective breeding becomes an important method for improving growth. The technology of next generation sequencing presents strong advantages in the screening of growth-related candidate genes and in molecular-assisted selection. (3) The influence of gene-environment interactions on growth mainly derives from the different adaptability of genotypes to different environmental conditions, which is characterized by specificity and complexity. Therefore, quantitative research into gene-environment interactions is very limited at present. However, it may be important to consider the gene-environment interactions before developing a program of large-scale commercial breeding. In summary, a full understanding of the impacts of environment, genes, and gene-environment interactions on growth can facilitate better management of fish growth, thereby minimizing cultivation costs and maximizing the ecological benefits.