Abstract:Cystatins (CSTs) belong to a protein superfamily the members of which reversibly bind cysteine proteases and inhibit their activity. CSTs are divided into three families:family 1 CSTs are single domain cystatins that do not contain disulfide bridges and carbohydrate side chains; family 2 CSTs possess a single cystatin domain, but their structures have at least two intramolecular disulfide bridges; and family 3 CSTs display a higher degree of structural complexity characterized by the occurrence of multiple cystatin-like domains, each with two disulfide bridges at positions homologous to those in family 2 CSTs. CSTs widely occur in various vertebrates such as mammals, birds, and fishes. CSTs have also been identified in some invertebrates. In many cellular defense systems, the CSTs plays a role in preventing the excessive hydrolysis of cellular proteins by cysteine proteases, and regulate many metabolic processes that depend on cysteine proteases. However, the study of the role of CSTs in the gonads of animals has not yet been reported. is a member of the Palaemonidae family of decapod crustaceans and is widely farmed in China because of its flavor and high nutritive and economic values. To breed superior variety of during actual production, it is necessary to study the characteristics and functions of the gonadal development-related genes of this species. The aims of this study were to identify the sequence information and function of CSTs in the ovary of CST (MnCST) cDNA sequence was cloned using the rapid amplification of cDNA ends (RACE) technology; then, real-time quantitative PCR (RT-qPCR) was used to analyze the expression level of in different tissues and different developmental stages of the ovary; and finally, the role of MnCST in the ovary of was analyzed by RNA interference (RNAi) technology. The results showed that the full-length cDNA of was 6199 bp long, including 1183 bp at the 5'-UTR, 2304 bp at the 3'-UTR, and a 2709 bp open reading frame encoding a peptide of 903 amino acids. The putative peptide contained six cystatin-like domains and 42 phosphorylation sites. Multiple sequence comparison of crustacean CST indicated that MnCST has the highest similarity with the corresponding protein in , while it has the lowest similarity with the corresponding protein in mRNA in nine different tissues of , and the maximum level was detected in the intestine. Moreover, M. nipponense ovary; the maximum level was detected in the stage IV ovary, while the minimum level was detected in the stage Ⅱ ovary. The results of RNAi showed that the expression change of the gene was basically consistent with the expression changes of cathepsin B (M. nipponense, while there was no effect on the expression of vitellogenin ( is likely to inhibit the activities of cathepsins and indirectly regulate the hydrolysis of Vg during ovarian development. This study provides new insights into the role of CSTs in the gonads of crustaceans.

Abstract:DNA Methyltransferase-2 (2) is one of the most widely distributed DNA methyltransferases in eukaryotes and plays important roles in eukaryotic development. In this study, the full-length cDNA of the Portunus trituberculatus) using rapid amplification of cDNA ends (RACE). The length of 2 cDNA is 1291 bp, and contains a 1203 bp open reading frame that is predicted to encode 400 amino acids. Structural domain analysis revealed that the protein of 2 contains a typical methyltransferase structural domain. Homology analysis revealed that the exhibits high identity with those in other species. Phylogenetic analysis showed that the amino acids of Macrobrachium rosenbergii. PtDnmt2 was found to be expressed in all tested tissues, and highly expressed in ovary and heart tissues (2 showed stage-specific expression during embryonic and larval development. No expression was detected in the zygote and multicellular stages. It was, however, detected from the blastula stage, after which expression increased gradually with embryonic development. Expression of 2 changed significantly during gonadal development. During ovarian development, the highest expression occurred in stage Ⅱ after which the level dramatically decreased. During testis development, the expression of 2 increased gradually and reached its peak in stage IV. The results suggest that 2 is important in the regulation of embryonic, larval, and gonadal development, and will provide useful information for further research on the roles of DNA methylation in developmental regulation in .

Abstract:Fragments of the mitochondrial gene (COI and 16S rRNA) and the nuclear marker (H3 and 28S rRNA) regions are suitable for phylogenetic relationship analysis. The phylogenetic relationships among nine S. diphos, S. olivacea, and ) collected from the coastal areas of China was analyzed through the sequencing of COI, H3, 16S rRNA, and 28S rRNA genes. The two mitochondrial genes, COI 16S rRNA, had an obvious AT-skewness, and their GC content were 41.17% and 41.01%, respectively, showing a certain degree of base preference. The overall transition/transversion bias of the four fragments (COI 5.073, 16S rRNA 3.042, H3 1.564, and 28S rRNA 1.480) were much higher than the critical value (0.4), which could offer effective phylogenetic information. As the genetic diversity parameters of all four markers in nine species had higher values (Pi<0.05, Hd<0.5) than most bivalve species, it is suggested that the species may have long history in the localities, and sufficient phylogenetic information. Among the nine species, the genetic average distances based on the COI gene were 0.087-0.331, and the genetic distances within species were 0-0.016. The minimum genetic distance was between , which was much higher than the average value (0.005) between most species of bivalves. The saturation of the nucleotide substitution process in the four markers was calculated as well. The third codon positions of the COI gene's transition and transversion substitutions reached the point of saturation, which means that the third codon positions of the COI gene could not provide effective information. The combined data set T12, including the four molecular markers without the third codon positions of COI, totaled 1555 bp in length. Phylogenetic trees constructed by the Maximum Likelihood (ML) and Bayesian Inference (BI) methods were consistent, and cluster analysis based on the data set T12 showed three separate lineages, corresponding to three morphologically defined subgenera:. Combining morphological and molecular evidence, the results support that has the closest phylogenetic relationship. The study sheds light on the genetic diversity and phylogenetic relationship of species occurring along the coast of China, which may be useful in genetic resource protection and sustainable use.

Abstract:The genes play an important role in the steroidogenesis and gonadal differentiation of teleosts. Therefore, in this study, we chose triploid and diploid rainbow trouts () at 31-68 days post fertilization (dpf) cultured in the same environment as object. In this study, triploid rainbow trouts were used as object and diploid rainbow trouts were used as controls to evaluate the expression of genes and the activity of CYP19A1B enzyme in the brain of rainbow trout. The real-time polymerase chain reaction results showed that the expression of in the diploid rainbow trout was up-regulated during 30-50 dpf and maintained a stable level during this period. Subsequently, during 50-56 dpf, the expression was down-regulated; during 56-68 dpf, the expression was up-regulated again. The expression of in the triploid rainbow trout was up-regulated during 30-35 dpf, down-regulated during 35-47 dpf, and then upregulated during 47-55 dpf; thereafter, until 68 dpf, the expression was maintained at a stable level. The expression of in diploid rainbow trout peaked at 34 dpf and in triploid rainbow trout peaked at 38 dpf. The expression of in the diploid rainbow trout was maintained at a high level during 33-42 dpf and its expression peaked at 38 dpf. The expression of in the triploid rainbow trout was high during 47-59 dpf and peaked at 49 dpf. The expression of in diploid rainbow trout peaked at 37 dpf, and then the expression was down-regulated. In the triploid rainbow trout, the peak value was recorded at 40 dpf, and then the expression was down-regulated, but the expression of in the triploid rainbow trout was lower than that in the diploid rainbow at the same period. The expression of in the diploid rainbow trout was up-regulated at 35-46 dpf and the peak value was recorded at 45 dpf, and then the expression was down-regulated until 69 dpf. However, under the same experimental conditions, the expression of in the triploid rainbow trout was not detected. The results of enzyme-linked immunosorbent assay demonstrated that at 40 dpf, the activity of CYP19A1B enzyme in the diploid and triploid rainbow trout peaked, but during 40-60 dpf, the activity of CYP19A1B enzyme in the diploid rainbow trout was significantly higher than that in the triploid rainbow trout; especially at 45 dpf and 50 dpf, the activity of this enzyme in the diploid trout was 1.15 and 1.12 times higher than that in the triploid trout, respectively. The results suggest that one of the reasons for early gonadal differentiation delay in triploid rainbow trout is the expression of is lower and later than those in the diploid rainbow trout. Moreover, estradiol cannot be synthesized normally in triploid rainbow trout, and therefore, gonadal differentiation is delayed.

Abstract:Na⁺/H⁺-exchanger is a membrane-associated enzyme responsible for the active transport of Na⁺ and H⁺ ions across cell membranes, and generates chemical and electrical gradients. It plays an important role in the aquatic adaptation of aquatic crustaceans. To investigate the function of the Na⁺/H⁺-exchanger in -exchanger 3 cDNA of (GenBank:MF373587), was cloned from the gill tissues of the animal by Reverse Transcription-Polymerase Chain Reaction (RACE). The full-length of cDNA was 3508 bp (base pairs), including a 2805 bp open reading frame (ORF) encoding a 934-amino acid peptide with one signal peptide and 12 transmembrane domains. Comparison with homologous proteins showed that the deduced Carcinus maenas (74%), and along with , were clustered into one group by phylogenetic analysis. Results of RT-qPCR showed that expression level in the gills was significantly higher than in other tissues ( in the gills was up-regulated under low pH stress (pH 5.2) during the entire duration of exposure. The expression level of in the gills was down-regulated during the first 48 h and up-regulated at 72 h under high pH stress (pH 9.1). After the knockdown of expression by RNA interference (RNAi), shrimp mortality was found to be significantly higher under low pH stress when compared with the control group. The results suggest that may play a more important role in regulating acid-base balance under low pH stress than under high pH stress.

Abstract:The swimming crab (), which is an economically important marine crab in China, is a widespread species in coastal Japan, Korea, and China. Neuropeptides have a significant effect on osmoregulation, growth, development, and immunity of crabs. To investigate the function of neuroparsin under low salinity stress in , the neuroparsin gene was cloned by rapid amplification of cDNA ends. The NP gene is 1920 bp long, including a 309 bp open reading frame (ORF) that encodes a 102-aa polypeptide; its isoelectric point was 7.42 and the molecular mass was 10.8 kDa. The NP gene contains 12 cysteine residues, which is a typical characteristic of neuroparsin in decapods. The homology and phylogenetic systematic analyses revealed that the highest homology and similarity (reaching up to 89%) occurred between P. trituberculatus clustered with . The tissue expression analysis showed that the expression of NP gene was relatively high in the brain, followed by the gill and eye, with very little or no expression in the ovaries, muscles, heart, liver, and pancreas. The expression pattern analysis of the NP gene under low salt stress condition showed that low salt stress can significantly change the expression of NP gene in the brain, gill, and eyestalk, and the overall expression was upregulated. In the brain, gill, and eyestalk, the expression of NP was 7.7, 2.8, and 2.6 times higher than that of the control, respectively (NP gene expression in the gills presented an increasing trend after the ablation of eyestalk. Furthermore, the expression of NP after the ablation of bilateral eyestalk was significantly higher than that after the ablation of unilateral eyestalk (NP gene might play a role in the salinity adaptation of , which is regulated by its neuroendocrine system.

Abstract:To explore the morphological characteristics of , the morphological changes in the embryos and larvae were observed using scanning electron and optical microscope. The results obtained were as follows. (1) The embryonic and larval development of included six stages:cleavage, blastula, gastrula, trochophore, pelagospheric larva, and creeping larva. The cleavage, blastula, gastrula, and trochophore stages occurred within the egg envelope. The egg envelope was discarded when the pelagospheric larva was out of the membrane and did not develop into epidermis. (2) At a water temperature of 30℃-31.5℃, the oosperm began to cleave 30 min after fertilization and the gastrula was formed after 2 h. After 4 h, it developed into trochophore. After 24 h, the larva was out of the envelope and developed to a pelagospheric larva. After 8-9 d, the pelagospheric larva developed into creeping larva. (3) exhibited a typical helical complete cleavage. The trochophore larva could swim by rotating. The surface of the embryo body was covered with cilia, and the front of the body had a bundle of long cilia called apical cilia. The cilia which protruded from the body through the center of the egg envelope can be divided into two types-normal and spoon-shaped cilia. The embryo body formed eyespot, nephridioduct, and other organs. (4) The pelagospheric larva swam rapidly and captured phytoplankton. The anterior ciliary ring was short, and the eyespot and ganglion were on the head. The postoral ciliary ring was long; the cilia were also divided into two kinds (normal and scoop-shaped cilia). With development, the muscle bundles of the body wall continued to become strong and formed the square lattice texture. The stomach gradually moved forward to the head, intestine extended and spiraled, and anus was formed in the anterior end of the body. (5) The creeping larva crawled on the surface of the sediment and devoured gravel. The body surface developed a stratum corneum, and the body wall muscle became strong. Flaky protuberances were formed in the anterior part of the body, which developed into tentacles. The introvert had regularly arranged mastoid; it was convex to the central zone of the body, forming a spherical tail. The retractor muscle, ventral nerve cord, fixing muscles organ, and other tissues were obvious. The study provides morphological details of embryonic and larval development in . Furthermore, it provides a theoretical reference for the procreation regulation and artificial breeding of .

Abstract:To determine the effect of main morphological traits on the body weight of and to offer strategies for parent selection during the breeding of , the correlations between the morphometric attributes and body weight of were explored by the correlation, path, and regression analyses. One thousand individuals from each of traditional shell, golden shell, white shell, red shell, and black shell oysters were randomly sampled to measure their body weight (BW, g) and four morphometric attributes, including the shell length (SL, mm), shell height (SH, mm), shell width (SW, mm), and hinge length (HL, mm). The correlation coefficients among all variables were calculated. The path coefficients were calculated by setting the body weight as a dependent variable and other attributes as independent variables via stepwise elimination. The results showed that the four morphometric attributes of the five kinds of oysters extremely significantly (<0.01) correlated with body weight. The shell length presented the highest correlation with the body weight of traditional, white, and red shell oysters, and the shell height showed the highest correlation with the body weight of golden and black shell oysters. The results of the path coefficient analysis showed that the shell length of traditional and white shell oysters, the shell height of golden and red shell oysters, and the shell width of black shell oysters showed the highest correlation with body weight, and exhibited predominant direct effect and determinacy on the body weight for . The multiple regression equations were obtained to estimate body weight as traditional shell golden shell color:BW=-38.661+0.305SL+0.477SH+0.242SW+ 0.375HL; white shell red shell color:BW=-27.307+0.327SL+ 0.321SH+0.252SW+ 0.305HL; black shell color:BW=-40.921+0.278SL+0.335SH+1.076SW+0.269HL. The clustering results showed that the morphological traits were more similar between the traditional and golden shell oysters and between the white, red, and black shell oysters.

Abstract:The Pacific oyster , naturally distributed in the Pacific Coast of Asia, has become a global aquaculture species owing to its high fecundity and strong environmental adaptability. It is also the most highly produced mollusk species worldwide, and China is the top oyster-producing country. Although China is the highest producer of oysters with a long history of oyster aquaculture, there are no well-documented cases of selective breeding. To genetically improve the productivity traits of , we initiated a selective breeding program in 2007, concentrating on the establishment of selected strains by mass selection with fast growth rate. After eight generations of selection, significant genetic gains in growth rate were observed in the selected strains. In 2014, the fast-growing strain of ‘Haida No.1’ was established. However, the genetic parameters of growth-related traits in Haida No.1 are still undetermined. As a result of successive selection in closed population, genetic parameters varied between different generations of selected strains. The estimates of heritability and genetic correlation for growth-related traits in Haida No.1, which experienced numerous generations of selection, is of great benefit to long-term breeding program, contributing to the evaluation of increased genetic gains in future generations. In the present study, genetic parameters were estimated for growth-related traits in Haida No.1 after eight and nine generations of selection. A total of 41 and 28 full-sib families were obtained by a nested mating design (1 sires×3 dams) consisting of 60 and 40 broodstocks, which were obtained from the eighth-and ninth-generation selected strains of Haida No.1 in 2015 and 2016, respectively. The shell height, shell length, shell width, and body weight of 2,070 progeny representing 69 full-sib families were recorded at the age of 330 d. The variance components and genetic parameters were obtained from multi-trait animal models using ASReml 3.0 in the R Programming Language. The growth-related traits of Haida No. 1 had a high value of coefficient of variation, which showed a potential for successive selective breeding. The phenotypic correlations between the growth-related traits were positive and varied among different traits. The genetic correlation between body weight and shell shape-related traits (shell height, width, and length) was positive, ranging from 0.40 to 0.66. The heritability estimates of shell height, shell length, and body weight ranged from 0.16 to 0.37, belonging to moderate and high levels of heritability. These results suggest that the effects of successive mass selection on the genetic parameters of growth-related traits in Haida No. 1 were negligible. The high genetic diversity and stable genetic structure of selected strains of Haida No. 1 might be responsible for the high estimates of growth-related trait heritability. The results provide important information for future breeding programs of ‘Haida No. 1’.

Abstract:Probiotics have been defined as live microorganisms, which confer health benefits to the host when administered in adequate amounts. The probiotics used in aquaculture commonly include effective microorganisms (EM bacteria), sp. The biofloc technology (BFT) is a zero-water exchange and eco-friendly aquaculture system. The BFT can recycle nutrient by introducing additional carbon source to culture water in order to stimulate the growth of heterotrophic bacteria that convert ammonia into microbial biomass. The microbial biomass will further aggregate with other microorganisms and particles to form bioflocs. The bioflocs contain a heterogeneous mixture of diatoms, macroalgae, food and fecal remnants, exoskeletons, bacteria, invertebrates, and other microorganisms. The bioflocs can maintain good water quality, increase fish growth performance, reduce feed cost by recycling feed residues and fecal excrements, aid enzymatic activity, and enhance innate immunity and disease resistance. Meanwhile, the BFT can minimize water exchange to save labor and environmental costs, and reduce water usage and waste generated in aquaculture. It can also avoid drug abuse for disease control, because of the key microorganism in the bioflocs. The BFT has the potential to be used widely in aquaculture. Gibel carp () is one of important freshwater species farmed in China, and it is a representative species of mudflat cultured fish. However, with the rapid development of aquaculture, the waste of water resources, pollution, and diseases seriously affected the sustainable development and aquaculture efficiency of gibel carp. Our previous studies showed that the BFT can be used in gibel carp culture and that it has positive effects on the growth performance and immune response of gibel carp. To further optimize the BFT system in gibel carp culture, a 35-day feeding experiment was conducted to evaluate the effects of probiotics on the growth performance, digestive enzyme activities, and intestinal morphology of gibel carp cultured using the BFT. A total of 1800 normal gibel carps with a mean body weight of 1.60 g were randomly assigned to nine ponds (3.0 m×1.0 m×0.8 m) as three experimental treatments, including the EM bacteria addition group in BFT system (BB), s addition group in BFT system (BI), and BFT without any probiotics addition (B). The results revealed the followings (1) Compared with those of the control group, weight gain and specific growth of gibel carp in the BB and BI groups were significantly higher (<0.05); the weight gain in the BB and BI groups increased by 216.70% and 184.04%, respectively. Furthermore, the specific growth increased by 141.18% and 125.49%, respectively. The weight gain and specific growth in BB group were higher but no significantly different from those in BI group (>0.05). These results indicate that the addition of probiotics to BFT system can promote the growth of gibel carp. Additionally, compound bacteria (EM bacteria) addition showed better efficiency than the addition of single strain . (2) The activity of digestive enzymes (amylase, lipase and protease) in the probiotics addition groups (BB and BI) was significantly higher than those in control group (<0.05), and the highest activities were observed in BB group. The activity of amylase in BB group was significantly higher than that in BI group (<0.05). (3) The thickness of muscularis and submucosa of gibel carp gut in the probiotics addition groups was significantly higher than those in control group (<0.05). The mucosal fold height and fold mesenchyme width of gibel carp gut were not significantly different among the BB, BI, and control groups (>0.05). The results suggest that the addition of probiotics can promote growth of gibel carp and improve their intestinal digestive enzyme activities. Furthermore, the addition of probiotics can also affect the intestinal morphology of gibel carp cultured in BFT system. This study provides some valuable information to promote the usage of BFT in aquaculture.

Abstract:An 8-week feeding trial was conducted to evaluate the effects of yeast hydrolysate (YH) on the growth performance, serum biochemical indices, digestive enzyme activity, and intestinal morphology of . Four isonitrogenous and isolipidic practical diets (42.5% crude protein and 8.5% crude lipid) were formulated to contain 0%, 1%, 3%, and 5% YH (named Y0, Y1, Y3, and Y5, respectively). A total of 480 , with an average initial body weight of about 1.86±0.01 g, were randomly allocated to four groups with four replicates per group and 30 shrimps per replicate. The results indicated that the shrimp fed the diet containing 5% YH had a significantly higher weight gain rate, specific growth rate, and protein efficiency rate than those fed the control diet (<0.05), and that the lowest feed conversion ratio occurred in the Y5 group (<0.05). Crude protein of whole shrimp significantly increased with increasing YH levels in the diet (<0.05). Dietary supplementation with 5% YH significantly increased the contents of total protein and triglyceride and decreased the activities of aspartate aminotransferase and alanine aminotransferase (<0.05). However, serum glucose and total cholesterol were not significantly influenced by YH (>0.05). Shrimp fed the Y3 diet had higher hepatopancreas trypsin and lipase activities than those fed the control diet (<0.05), but there were no significant differences in amylase activity among all the treatments (>0.05). Shrimp fed the Y3 diet had significantly higher fold heights and widths in their intestines than those fed the control diet (<0.05), and microvillus height in the Y5 group was significantly higher than that in the Y0 group. In conclusion, a 3%-5% YH supplementation in shrimp diet can effectively promote digestion and improve the growth performance, feed utilization, and intestinal morphology of .

Abstract:An 8-week feeding trial was carried out to investigate the effects of supplementation on the growth performance, nonspecific immunity-related enzyme activities, and disease resistance-related enzyme mRNA expression in juvenile , with initial average weight of 0.58±0.01 g, was randomly assigned to 7 groups in triplicates, with 40 individuals per replicate. Seven isonitrogenous and isolipid diets were supplemented with 0%, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, and 1.0% in a basal diet, respectively. Following results were observed:nonsignificant difference was found in survival among all the groups (>0.05). Weight gain rate (WGR) and specific growth rate (SGR) increased gradually as dietary supplementation increased up to 0.4%, and then showed decline (<0.05). The minimum feed conversion rate (FCR) was observed on feed supplementation with 0.2% , which was significantly lower than that in the other groups (<0.05), while protein efficiency rate (PER) showed the opposite trend. Serum phenoloxidase (PO), alkaline phosphatase (AKP), and acid phosphatase (ACP) activities increased gradually with increasing dietary levels, and then gradually declined. The maximum values of PO, AKP, and ACP were found in the 0.4%, 0.1%, and 0.2% supplementation groups, respectively (<0.05). Activities of serum catalase (CAT), lysozyme (LSZ), and superoxide dismutase (SOD) of all treatment groups were significantly higher than that of the control group (0%) (<0.05). Gene expression levels of CAT and LZM in all treatment groups were significantly up-regulated when compared with the control group (<0.05). At the end of the feeding trial, the shrimps were challenged by for 96 h. Post-challenge survival rate increased with increasing dietary <0.05). Based on the broken-line regression analysis of WGR, when feed was supplemented with 0.23% of Litopenaeus vannamei were found to significantly improve.

Abstract:The aim of this study was to investigate and analyze quinolone resistance and plasmid-mediated qui­nolone resistance (PMQR) genes in isolated from the commercial aquatic prod­ucts sold in Guangzhou's supermarkets, and to assess the quality and safety of these aquatic products. One hun­dred live tilapias were collected from 14 supermarkets in Guangzhou. The results of high-throughput sequencing analysis indicated that were the dominant bacteria. According to bacterial screening culture methods, 280 strains were isolated from the gills, muscles, and intestinal contents, respectively. All the isolates were evaluated for resistance to enrofloxacin (ENR) and cipro­floxacin (CIP) by agar dilution method. All of the 280 qnr, qepA, aac(6')- genes using PCR. The results showed that 7 (2.50%) isolates were resistant to ENR, while 6 (2.14%) isolates were resistant to CIP. The resistance rates of ENR and/or CIP in isolates obtained from the muscles were much lower than those in the microorganisms isolated from the gills and intestinal contents. All the isolates obtained from different issues were much more resistant to fluoroquinolones than the isolates, 59.89% isolates harbored PMQR genes, and 5 types of PMQR genes were detected, including Aeromonas isolates, 6.79% harbored PMQR genes, and only were detected. Only a few resistant bacteria were screened in the muscles, which form the edible part of the tilapia; so, the food products were considered relatively safe. However, resistant was predominantly isolated from the intestinal contents and gills, and most of the isolates carried various types of PMQR genes, suggesting a potential risk of drug-resistant transmission from these tissues. Therefore, it is important to strengthen monitoring of antimicrobial resistance of bacteria in aquatic products.

Abstract:, one of the important sources of agar, is the third most widely cultivated seaweed in China, after . In recent years, there has been a large-scale decrease in the cultivation of , resulting in huge economic losses for the seaweed cultivation industry. Epiphytes grow as an integral part on the surfaces of large algae, and the variations in the seaweed-associated microbial community compositions are typically associated with disease occurrence. In this study, the 07-2 strain was used as experimental material. DNA of epiphytes from the healthy, adjacent, and bleached fronds was extracted, and the V3 variables amplified from 16S rDNA genes were carried out by denaturing gradient gel electrophoresis (DGGE). Finally, the 23 objective bands were cloned and identified. The number and diversity index of the bacterial community of the epiphytes from the three fronds were calculated after digitization of the experimental results. The similarity among the dominant species in the bacterial communities were compared by non-metric multidimensional scaling (nMDS) and redundancy analysis (RDA). The results show that the colony forming units and bacterial community diversity increased gradually with the aggravation in the degree of lesion in <0.05). The nMDS results indicate that the bacterial community composition of the epiphytes varies between the healthy and bleached fronds, while the composition of adjacent fronds is closer compared with that between healthy fronds. The RDA results reveal that the potential dominant bacteria of the epiphytes of the healthy and adjacent fronds are Pseudoalteromonas, respectively. However, the potential dominant bacteria of the epiphytes of the bleached fronds were not identified. The dominant bacteria of the epiphytes of the bleached attached fronds were . It can be seen from the above results that there is a significant difference between the healthy fronds and the diseased fronds of in terms of the bacterial community composition and dominant bacteria of the epiphytes, while the epiphytic bacterial community composition of the adjacent fronds was more similar than that of the healthy fronds.

Abstract:is a new species of microsporidia found to be affecting shrimp culture. Previous studies have shown that shrimps infected with grow slowly. In recent years, slow growth has been observed in Enterocytozoon hepatopenaei infection has been reported. To study the morphological characteristics of in Jiangsu Province and interpret the differences in context of the reports from other studies conducted abroad, this study used Penaeus vannamei cultured in Jiangsu Province as the research material. Preliminary isolation and purification of through sucrose density gradient centrifugation was performed. A method of diagnosing using Fluorescent Brightener 28 staining was established and the spore morphology was observed under a microscope. The results showed that the spores of were mainly distributed along the sucrose gradient of 35%-40%, and their buoyant density was 1.15g/mL-1.17g/mL. The spores were elliptical or round, bright blue, and small, but countable under the fluorescence microscope. The spores were approximately 1.7 μm×0.9 μm. The spore surface is covered with small folds and there is a large amount of white nodules present on their outer wall, which may be wall protein; the cell wall is composed of a relatively thin, electron-transparent inner wall and an electron dense spore wall. The spores have a nucleus, and 4-6 coils of the pole filament. The morphological structure of in Jiangsu was consistent with the reports abroad. The methods of isolation, purification, and fluorescent staining developed, as well as the morphological data of obtained in this study provide reference for diagnosis and research.

Abstract:With the decrease in traditional economic fish resources, has become one of the dominant fish species in the Haizhou Bay ecosystem, playing an important ecological role in the food web. is a benthic fish species widely distributed in the China seas and Japan Sea, and in the waters around the Korean Peninsula. Using the samples collected from the bottom trawl survey in the Haizhou Bay during the autumn of 2011 and 2013-2015, 733 stomach samples were analyzed to study their feeding ecology, including diet composition, feeding intensity, feeding strategy, and prey selectivity. The results showed that the prey items of included more than 80 species, and shrimp and fish were the predominant prey taxa, with the index of relative importance of 97.14% and 1.15%, respectively. Latreutes planirostris, were the most important prey species. The results of the cluster analysis showed that the diet composition did not change significantly with the increase in body length. The average similarity coefficient of the food composition of was 86.74% among different size classes. This might be because the samples were collected in autumn. The samples reached or were close to adulthood, with their mouth, teeth, gill rake, and other feeding organs developed perfectly. The feeding intensity was described by the percent of empty stomachs and the mean stomach fullness index. The percent of empty stomachs of P> 0.05), but the mean stomach fullness index varied during the growth period ( was higher than that of large individuals. This is because the growth rate of small-sized is faster than adalts; they require more energy from prey. The feeding of fish is generally affected by several variables, including the development status of fish, the type and abundance of prey species, environmental conditions, and other factors. In this study, the generalized additive model (GAM) revealed that the feeding intensity of was affected significantly by salinity, water temperature, and latitude (< 0.05), whereas, the effects of body length, longitude, and water depth were not significant (>0.05). It will help analyze the factors that affect feeding habits of fish, understand the feeding status of fish, and examine the current situation and development of fish and their prey species, in order to make reasonable resource development and utilization decisions. The feeding strategy analysis further revealed that is a generalist predator and mainly feeds on shrimp and fish. The general feeding habit is an adaptive feeding strategy for fish that facilitates the adaptation of fish to variable environmental conditions, regulating the relationships with competitors. By calculating the prey selectivity index, it was found that there was a difference in the composition of favorite prey items and actual feeding prey items. The feeding ecology of is affected not only by the abundance and availability of prey, but also by strong active selectivity. These results will provide basic data to further understand the trophic dynamics in the Haizhou Bay ecosystem. It can also provide scientific reference for the protection and rational utilization of resources in Haizhou Bay.

Abstract:Using ecological experimental methods, the effects of starvation on the behavior and morphological features, and the effects of substrate type and different temperatures on starvation tolerance in newly hatched juveniles were evaluated. The results showed that starvation exerted a significant negative effect on the morphological features, behavior, and activities of juveniles, and all of them died on day 12 of starvation. At a water temperature of 25℃, the the point of no-return time (PNR) of the juveniles in the fine sand, no particulate substrate, and sand-mud groups was 7.5 d, 8 d, and 9.5 d respectively, and the accumulated death rate for the first 7 d was marginally different between different substrate groups. However, after 10 d of starvation, the highest death rate was found in the fine sand group and the lowest was found in the sand-mud group. Simultaneously, the weight loss of juvenile in the three groups was 7.72%±2.80%, 6.95%±2.64%, and 5.30%±2.41%, respectively. When there were no particulate substrates, the accumulated death rate of the 28℃ group was significantly higher than that of the 25℃ and 22℃ groups (<0.05), and the PNR was 7 d, 8 d, and 9.5 d, respectively. After a 10-d starvation period, the weight of the juvenile in the three groups decreased at a rate of 8.90%±1.65%, 6.95%±2.64% and 5.79%±3.54%, respectively, but there were no significant differences in the weight loss between the three groups. The results showed that the sand-mud group with smaller sediment particle size had a positive effect on starvation alleviation in juveniles, but the fine sand group did not. In the temperature range of 22-28℃, the PNR would occur earlier with the increase in water temperature.

Abstract:The main ecological patterns and functioning of estuarine ecosystems are difficult to evaluate owing to natural and human induced complexity and variability on biodiversity. Therefore, there is an increased demand to analyze and predict the relationships between the environment and the distribution of biota in estuarine ecosystems. Biodiversity is viewed as the variety of life, encompassing variations from the gene to ecosystem levels, and is commonly expressed as species richness. The patterns of biodiversity in the Yangtze River Estuary have remained largely unexplored, despite the increasing understanding of the importance of estuarine ecosystems and the existing knowledge on the variability of fish communities within estuaries and their environmental drivers. As a transitional system, the Yangtze River Estuary, a typical ecotone, is the largest estuarine ecosystem in the western Pacific Ocean. It establishes links between the marine and freshwater ecosystems in the East China Sea; persistent environmental fluctuations in this estuarine ecosystem creates considerable physiological demands on the species that inhabit this ecosystem. Predictive modelling techniques are being increasingly used to determine major habitat requirements that affect species distribution. Important technological advancements have benefited predictive distribution modelling, and new and sophisticated methods have been developed for use in statistical models that are applied to ecology. The prediction of fish biodiversity has important scientific implications for evaluating the Yangtze River Estuary ecosystem. Based on fishery and environmental data collected in 2012-2013, a regression tree model was built to predict fish species richness in the Yangtze River Estuary. The node structure of the optimal decision tree model indicated that salinity, dissolved oxygen, and month (i.e. season) were three factors affecting fish biodiversity in the Yangtze River Estuary. In addition, the data observed in 2014 was used to validate the predictive performance of the tree-based model by calculating root mean square error (RMSE), average absolute error (AAE), and average relative error (ARE), which were often used as statistical indicators to compare fitted value and observed value in modelling studies. The results showed that the prediction performance was better in spring and summer than in autumn and winter, and generally, the model presents a fair predictable ability indicating the feasibility to predict fish species richness by utilizing a classification and regression trees (CART) algorithm. Estuarine ecosystems are often considered a complex mosaic of habitat types, and their fish biodiversity are best predicted through a CART algorithm. In the present study, in terms of predictive performance, CART could be viewed as an appropriate technique to predict fish species richness in the Yangtze River Estuary.

Abstract:is caught as one of the main by-catches by deep-sea shrimp trawl. This species plays an important role in maintaining the stability and diversity of ecosystems in the deep sea and continental slopes. Based on samples collected by bottom-water shrimp trawl and mid-water trawl in the continental slope of the northern South China Sea in June and August 2015 and March 2017, the biological parameters of viz., growth, reproduction, and feeding habit, important in terms of fishery, were investigated. Body length ranged from 71 mm to 172 mm, with an average of 118 mm; body weight varied from 5.25 g to 66.20 g, and the mean weight was 26.26 g. The distribution of body length and weight presented significant differences (ANOVA, <0.01) between females and males. Relationship between body length and weight was 2=0.9241, L^2.6883(=558) for the males. The sex ratio was 1:1.76 (female:male), and obviously, there were more males than females. Gonad samples of appeared mainly to be at stage Ⅱ; mature fishes were observed during the investigation, indicating March, June, and August to be the spawning months for in the continental slope of the northern South China Sea. The body length of the female individuals at 50% maturity was estimated to be 145.0 mm. The feeding grades of were mainly in 1 and 2 grades, and this species mainly fed on cephalopods such as , and preyed on small-size mesopelagic fish including , and crustaceans (e.g. mainly live in the bottom of the sea, and generally do not perform normal diel vertical migrations; exceptions include a few immature individuals. is a large species of lantern fish, which has important ecological and economic value in the continental shelf and slope ecosystems, and investigations into their biology and ecology should be further strengthened in the future.

Abstract:The Indian Ocean albacore (), which is widely distributed in the Indian Ocean from 25°N to 40°S, is one of the main target species of the Indian Ocean commercial tuna fishery. In recent years, China longline fleets have also targeted the albacore in the Indian Ocean. At present, several stock assessment models have been used to assess the Indian Ocean albacore tuna to determine the status of their stocks. However, there has been a substantial uncertainty regarding the results of these models. Therefore, in this paper, we have analyzed the factors influencing stock assessment for the Indian Ocean albacore tuna. This paper argues that:(1) substantial uncertainty exists in the catch and catch-at-size or catch-at-age data, because there were no, or incomplete, or incorrectly classified data from some important fleets reported, and the number of samples for size frequency data was very low, or the sampling protocols of the collection of size data changed with time; (2) although the catch per unit effort (CPUE) was standardized, the impacts of the changes in target species and the inhomogeneous distribution of fishing efforts of the fleets have still degraded the quality of the standardized CPUE; (3) because there were very few or limited studies on the biology of the Indian Ocean albacore, knowledge about their population structure, reproduction, growth, and natural mortality is limited, which has led to the values of some important biological parameters in the stock assessment models being set by using the results from the other oceans; (4) although the ocean environment has significant influences on the biomass dynamics and distribution of the Indian ocean albacore, only a few stock assessment models take these influences into account. These aforementioned issues have resulted in great uncertainties of the stock assessment. In the future, we need to further explore approaches to improve the quality of the stock assessment. However, at the same time, we have to develop a management strategy evaluation framework for the Indian Ocean albacore tuna to avoid the impacts of uncertainties of the stock assessment on the sustainable development of the fishery.

Abstract:Based on the survey data of fishery resources and habitat, collected at 63 stations in October 2016 and January 2017 in the southern waters off the Shandong Peninsula, we analyzed spatiotemporal distribution of and examined its relationship with environmental variables, including survey season, water depth, bottom salinity, and bottom water temperature, using generalized additive model (GAM). The results showed significant seasonal variations in the distribution of . The stock had significantly higher density and wider range in autumn than in winter, and stock density was higher in the coastal waters and lower in the offshore waters. In addition, the stock showed more even distribution in the coastal waters, but distribution patterns varied greatly in the offshore waters. GAM identified depth and bottom water temperature as the major environmental factors influencing distribution (<0.05) and the effect of water depth was the most significant. Stock density increased with depth at shallow waters, peaking at the depth of 30-40 m, but decreased with further increase in water depth. The most suitable water temperature range was around 10℃. The temperature effect might be attributed to the migratory habits of this species and the variations in the environmental conditions caused by seasonal changes in the Yellow Sea Warm Current.

Abstract:Correlations of the catch per unit effort (CPUE) (based on the catch data of skipjack tuna, caught using the purse seine technique in the west-central Pacific Ocean) with spatial-temporal factors (year, month, latitude, and longitude) and environmental factors (sea surface temperature, SST; sea surface height, SSH; oceanic nino index, ONI; and chlorophyll-a, Chl-a) were analyzed, and the relative importance of CPUE was estimated using two different types of models (Generalized additive model:GAM, and Boosted regression tree:BRT). The results showed that longitude is the most important factor in determining the importance of CPUE using GAM, accounting for more than 50% of the total CPUE, while latitude, year, and month had decreasing importance in the order mentioned. SSH is the most important environmental factor in GAM, and ONI, SST, and Chl-a are less important in determining the importance of CPUE. The result of BRT was similar to that of GAM; longitude is the most important spatial-temporal factor, accounting for 60% of the total importance of CPUE, while year, latitude, and month were of less importance, with their importance decreasing in the order mentioned. ONI is the most important environmental factor in BRT, followed by SSH, SST, and Chl-a, in that order. In conclusion, the two types of models can effectively reflect the influence of CPUE. ENSO induced oceanographic variation will change the abundance distribution of skipjack tuna; so, ONI should be included in fishery forecasting models to improve the accuracy of prediction in future.

Abstract:On April 2009, a base population (F0) of the Fujian oyster, , was selectively bred from the Fujiang and Guangdong local populations. A successive six-generation selection for golden shell and body weight was carried out to produce "Golden oyster 1#" (F6). In this study, eight microsatellite markers were analyzed in the base population, selected line F6, and wild populations of . The number of alleles per locus ranged from 7 to 24. The average number of alleles and average allelic richness of the three populations at all loci had ranges of 10.3-17.6 and 9.8-16.8, respectively. Expected heterozygosity and observed heterozygosity were 0.655-0.662 and 0.788-0.872, respectively. In the Hardy-Weinberg equilibrium test, for the three populations and eight microsatellites, segregation distortion was significant for 12 of the 18 groups. The inbreeding coefficient (F_st values were 0.0224-0.1627, with an average of 0.0767, indicating that there is a low level of inbreeding within populations and a high level of differentiation. Our results suggested that successive artificial breeding has a certain influence on genetic variation; however, there remains high genetic variability in the mass selection lines.

Abstract:Aggression is an adaptive behavioral trait that is important in the competition for mating partners, food, and territories and in the establishment of social hierarchies. Dominance hierarchies not only reflect fitness, but also prevent the need for continued aggression and associated risk of injury. Therefore, aggression is also a trait under stabilizing selection. From genetics perspective, aggression is a quantitative trait. High heritability estimates for aggressive behavior have been observed in many species, including human being. Similar to other behaviors, the display of extent of aggression is influenced by a combination of genetic and environmental factors. To understand the genetic architecture of aggression, it is necessary to integrate human genetics studies with studies on other organisms. Herein, we reviewed the molecular pathways and gene types related to aggression in fish, including 5-hydroxy tryptamine, dopamine, histamine, somatostatin, nitric oxide, hypothalamo-neurohypophysial, hypothalamo-pituitary-interrenal, and hypothalamo-pituitary-gonadal pathways, and several other genes. Furthermore, we also describe the discriminant method of aggression in fish, which provides a theoretical basis for further studies in the molecular regulation mechanism of aggression in fish.