Abstract:exists widely in aquatic environments throughout the world. It is highly pathogenic and infection with this bacterium entails extremely high mortality. To facilitate the prevention and treatment of the diseases caused by AH10 (CCTCC AB2014155), to fully understand its information structure and functions and to provide a basis for future molecular pathology research. Genomic DNA was extracted from strain AH10, and a library was constructed and sequenced. The raw data were filtered and their quality was assessed, the sequence was assembled, and the genome was annotated and analyzed comparatively. The full-length genome of strain AH10 is 4.91 Mb, with a G+C content of 61.1%, and encodes 4570 predicted genes, including 3351 genes with a clear biological function, 2592 genes found in the Clusters of Orthologous Groups (COG) database, 1281 genes related to metabolic pathways, and 31 genomic islands. The study of comparative genomics showed that AH10 has 102481 single-nucleotide polymorphisms (SNPs), 402 insertions/deletions, and a linear genomic organization most similar to ATCC7966, the standard strain in the USA. The pathogenicity of AH10 is closely associated with the hemolysin gene (), serine protease gene (). These genes are highly homologous in different strains. Autoinducer-2 (AI-2) quorum sensing (QS) and AhyI/ QS are found in AH10, but there is no type Ⅲ secretion system (TTSS). With a comparative analysis, we demonstrate the specificity of the A10 genomic structure, its SNPs, and the pathogenic system differences in different strain. Our analysis not only provides a guide to distinguishing the specificities of different species, but also a reference for the analysis of the genomic information of genome has accelerated related studies of its pathogenicity. Identifying the causes of disease requires that the accuracy of their clinical diagnosis be effectively improved. This, in turn, will offer clues to their pathogenic mechanisms in humans. The study of genome also provides the foundation to the research of proteomics. According to the specific functional areas of protein conservative sequences, setting up a corresponding protein database can help to quickly find the protein function area. In this way, we can not only study the cell wall composition and the functions of the membrane proteins and secreted proteins of , but can also predict the functions of related proteins based on genomic information. This research provides unlimited opportunities for the development of new drugs that not only effectively avoid the generation of drug resistance, but also circumvent the abuse of antibiotics, thus providing people with a healthy environment. Studies of the genome should also promote vaccine research. With the comparison of homologous sequences, effective antigen can be rapidly identified and vaccines prepared, efficiently reducing the incidence of disease. Genomic information has potentially wide applications, and its use in the prevention and treatment of the diseases caused by will continue to increase.

Abstract:Parentage assignment is a powerful tool for pedigree analysis and family selection in aquatic animals. Eleven polymorphic microsatellite markers were used to perform a parentage assignment for 417 fast-growth progeny with normal color and 52 red progeny from 26 full-sib families of Yellow River carp, . The average number of alleles for the 11 microsatellites was 8.2, and the mean values of observed heterozygosity, expected heterozygosity, and polymorphism information content were 0.792, 0.792, and 0.76, respectively. The combined probability of exclusion reached 99.79% when both parents were unknown (confidence level, 95%). Among the carp progeny, 29 were not assigned, but 388 fast-growth progeny and 52 red progeny were accurately assigned parental pairs, resulting in an identification rate of 93.82%. By comparison of growth performance among seven families with 20 or more progeny, we identified several favorable parents and families that should be kept for further selection. For body color, two parents with recessive alleles for the red color were identified. These results provide the basis and molecular tools for further selection towards breeding new varieties of fast-growing Yellow River carp with the typical slim body shape and golden color.

Abstract:The full-length cDNA encoding ) using the rapid amplification of cDNA ends technique (RACE). The complete cDNA was 1257 bp long, and contained an open reading frame (ORF) of 1056 bp, a 23-bp 3' untranslated region, and a 178-bp 5' untranslated region. The ORF encoded a polypeptide of 351 amino acids containing a serine/threonine kinase domain and a T-loop. An homology analysis revealed that the Cdk7 of had high identity with those from other species. Quantitative real-time PCR analyses showed that transcripts were present in all of the tissues examined, with the highest transcript levels in the ovary. The high transcript level of in the ovary was consistent with its role in regulating cell division. The mRNA levels in oogonia were higher in the first and the second stages than in the other stages of overy development, indicating that may play an important role in oogonial mitosis. After eyestalk ablation, the transcript levels of significantly increased in the ovary to peak on day 4, and then decreased. Together, these results suggested that Cdk7 may play important roles in ovarian development, especially oogenesis, in . These data provide useful information for further research on the regulation of gonad development in this species and other crustaceans.

Abstract:The pen shell is a large, fan-shaped bivalve that is widely distributed in the Indian and western Pacific oceans. However, little is known about the molecular regulation of its gonad development. The (wingless-type MMTV integration site family, member 4) gene, a member of the family, encodes a growth factor that plays an important role in gonad differentiation and development. In this study, the complete cDNA sequence of ovary by homology-based cloning and rapid amplification of cDNA ends techniques. The full-length cDNA sequence of was 1493 bp long and included an open reading frame of 1074 bp encoding a 357-amino acid protein with a predicted molecular weight of 39.5 kD and a theoretical isoelectric point of 8.94. Multiple alignment and phylogenetic analysis of wnt proteins showed that the wnt4 sequence contained conserved domains of the wnt family. In the phylogenetic analysis, the Chlamys farreri and lower similarity to the wnts of echinoderms, amphibians, and mammals. Quantitative real-time polymerase chain reaction analysis revealed that transcripts were present at higher levels in the female mantle and gonad of wnt4 transcripts was related to gonad maturity, and the transcription of was significantly ovary-predominant during the entire reproductive cycle. These patterns of transcription suggested that A. pectinata. During the early larval development stage of was detected in early embryogenesis (morula stage and gastrula stage), when it was 500 times that in adults, and then the transcript level fell sharply during the trochophore and D-shaped stages. Therefore, wnt4 may be involved in the formation of certain organs in the stages of early larval development. When the sex steroid estradiol-17 through feedback regulation ( treatment significantly induced transcription of , regulated by estradiol-17, is involved in a variety of biological processes in different tissues, especially during early embryogenesis and gonad development. Further research is required to verify whether the transcript level of can be used as an index of testis development.

Abstract:Proliferating cell nuclear antigen (PCNA) is a member of the sliding clamp protein family that plays important roles in DNA replication, and is strongly expressed in proliferating tissues. Several studies have discovered other biological roles of PCNA, for example, in DNA repair, cell cycle regulation, and chromosome recombination. When culturing shrimp, the first problem is how to induce maturation of the ovary; therefore, it is important to understand ovarian development. We focused on PCNA because it plays an important role in cell proliferation. The PCNA gene ( using the rapid amplification of cDNA ends technique. The sequence encoded a protein of 260 amino acids that showed high homology to PCNA proteins from other species. The full-length cDNA was 978 bp long and contained a 5'-untranslated region (UTR) of 135 bp, a 3'-UTR of 60 bp, and an open reading frame of 783 bp. The protein was predicted to have a molecular weight of 28.83 kDa and an isoelectric point of 4.59. Analyses of transcript levels by quantitative real-time PCR indicated that it was transcribed in all tissues, with high transcript levels in the ovary and brain. During ovarian maturation, there were higher transcript levels of <0.05). Previous research has shown that 5-hydroxytryptamine (5-HT) can stimulate ovary growth and development. Injection of 5-HT resulted in increased transcript levels of in the ovaries, with the peak transcript levels at 48 h post-injection. The PmPCNA protein was successfully expressed in a prokaryote, providing a platform for further research. These results provide important information on the role of in the development of the shrimp ovary.

Abstract:, which is distributed along the coast of China, is one of the most economically important marine aquaculture species. With the expansion of breeding, diseases caused by bacteria and viral pathogens have become more widespread and serious. The disease caused by the bacterial pathogen has become an obstacle in the development of half-smooth tongue sole aquaculture. Therefore, it is important to understand the defense mechanisms of the host, , against this pathogen. The CD40 protein, which is a member of the tumor necrosis factor receptor superfamily 5, is an important receptor molecule that plays a key role in the host's immune system and participates in several immune signaling pathways. In this study, using the whole-genome sequence of half-smooth tongue sole, we obtained one homolog using the rapid amplification of cDNA ends technique. The full-length cDNA was 2098 bp long and included an open reading frame (ORF) of 1011 bp, a 5'-untranslated region (UTR) of 44 bp, and a 3'-UTR of 1043 bp. The ORF of encoded a 336-amino acid protein with a predicted molecular weight of 37.27 kDa and a theoretical isoelectric point of 5.355. The 3'-UTR included two instability motifs (ATTTA) and one polyadenylation signal (ATTAAA) located 28 bp upstream of the polyA tail signal (AATAAA). The putative amino acid sequence contained one signal peptide, one trans-membrane region, two N-glycosylation sites, and four conserved cysteine-rich domains. The deduced amino acid sequence of shared 28%-47% identity with the CD40s from other teleost fish, mammals, and amphibians, with higher similarity to CD40s of bony fish. The phylogenetic tree constructed based on the amino acid sequences demonstrated that the CD40 clustered in one branch with other teleost fish. Real-time quantitative PCR analyses detected transcripts in a wide range of tissues in healthy adult fish. There were higher transcript levels of V. harveyi. After challenge with the pathogen, the peak transcript levels of CD40 were at 12 h in the liver, and at 6 h in the spleen and the kidney, before a second peak in transcript levels at 48 h in the three tissues. These results indicate that to the bacterial pathogen .

Abstract:Many genes that play roles in shrimp vitellogenesis, such as that encoding nuclear autoantigenic sperm protein (NASP), have been identified by suppression subtractive hybridization. In shrimp, NASP plays an important role in ovarian maturation. In this study, the using the rapid amplification of cDNA ends technique. The full-length cDNA of consisted of 2258 bp with a 92-bp 5'-untranslated region (UTR), a 174-bp 3'-UTR, and a 2019-bp open reading frame, which encoded a protein of 673 amino acids with a predicted isoelectric point of 4.46 and a predicted molecular weight of 74.18 kDa. The sequence has been submitted to GenBank under the accession number KT274811. The putative protein had two conserved regions:SHNi-TPR and TPR_2. A sequence alignment analysis revealed that the Penaeus monodon (GenBank accession number:FJ040859.1). We constructed a phylogenetic tree based on NASP sequences to evaluate the evolutionary relationships of NASPs between L. vannamei was in the same branch as that of were investigated in the ovary and hepatopancreas of at different overy developmental stages by real-time fluorescent quantitative PCR. The results showed that transcripts were present at all stages, with the highest levels at the second stage and the lowest levels at the third stage. The NASP transcript levels were higher in the ovary than in the hepatopancreas, in which the transcript level was negligible. These results provide the basis for further research on the role of NASP in ovarian development in .

Abstract:To investigate the role of progesterone receptor membrane component 1 (PGRMC1) in oocyte maturation in the half-smooth tongue sole (PGRMC1 from the ovary using homology cloning and rapid amplification of cDNA ends methods. The full-length cDNA of was 1335 bp long with an open reading frame of 546 bp encoding a 181 amino acid preprohormone with a deduced molecular mass of 20.64 kDa and a theoretical isoelectric point of 4.67. The precursor was a single transmembrane protein with an N-terminal transmembrane domain. The predicted transmembrane domain was located at positions 13-35 of the deduced PGRMC1 protein. Sequence alignment of the PGRMC1 precursor protein with corresponding sequences from other species revealed that the highest identity (82.87%) was with the PGRMC1 from (81.22%). In a phylogenetic analysis, the PGRMC1 clustered with its counterparts in the Cyprinodontiformes and Tetraodontiformes. The transcript levels of were high in the ovary, moderate in the liver and brain, and low in other tissues. We also monitored changes in transcript levels in the pituitary, brain, and ovary at different ovarian developmental stages. The mRNA levels increased sharply in the brain at stage Ⅲ, remained at high levels until stage V, and then decreased at stage VI. In the pituitary, the transcript levels of increased to peak at stage V and decreased significantly after ovulation (stage VI). Similarly, in the ovary, the levels increased gradually to peak at stage V and then decreased markedly after spawning (stage VI). Taken together, our results shed light on the role of PGRMC1 in oocyte maturation and in regulating reproductive endocrine function in .

Abstract:Common carp ( L.) is an important economic fish species with very rich genetic resources, and it has been used to develop many carp varieties in China. The FFRC strain (FR) and the Yuxuan Yellow River (YX) strains of common carp have higher growth performance and improved body shape, and have been certified by the National Certification Committee for Aquatic Varieties. Currently, these two carp varieties occupy a pivotal position in fresh water aquaculture because they are farmed in most provinces of China and have brought significant economic profits. Therefore, it is important to evaluate the genetic diversity of the conservation populations of these strains to maintain growth performance and make further genetic improvements. The objective of this study was to analyze the genetic structure of the breeding populations, and to evaluate the genetic distance between female and male individuals using microsatellite markers. A total of 160 and 131 alleles were detected with 23 microsatellite markers in FR (=96), respectively. For FR, the average values of number of effective alleles (), expected heterozygosity (), and polymorphism information content (PIC) were 4.559, 0.695, 0.741, and 0.702, respectively, suggesting that there is a high level of polymorphism in this strain. For YX, the mean values of , and PIC were 3.620, 0.665, 0.642, and 0.600, respectively, indicating a high level of diversity in this strain. The significantly lower P<0.01) suggested that more alleles were derived from different parents in FR with its hybrid breeding background than in YX with its systematic selection background. There was no significant difference in between FR (0.695) and YX (0.665), which indicated that YX maintains high genetic heterozygosity. The genetic distance(GD) between females and males in each population showed a normal distribution. The GD ranged from 0.8 to 1.0 and accounted for 37.39% of variability in FR, and ranged from 0.5 to 0.7 and accounted for 49.33% of variability in YX. Therefore, to construct families in breeding programs, the GD threshold is 0.8-1.0 for FR and 0.5-0.7 for YX.

Abstract:Pacific oyster, , is the most widely cultured oyster in the world. China produces more than 4.35 million tons of oysters annually. However, nearly all of the oyster broodstock in China remains unselected. This leads to many problems such as low growth rate, high mortality rate, and irregular shell shape. A selective breeding program is an effective way to resolve these problems, and Pacific oyster culturing would undoubtedly benefit from selective breeding for productivity traits such as rapid growth and high yield. Growth-related traits are of particular interest to farmers because of their economic importance. Color polymorphisms are relatively common in marine shellfish including , and consumers are willing to pay more for seafood with specific colors. During the period of 2010-2013, four successive generations of four shell-color families (white, black, golden, purple) were produced. None of the specifically colored lines showed superior productivity, and so truncation selections for shell height were initiated based on five fourth-generation black-shell and five fourth-generation white-shell families in 2014. Applying the same intensity of selection in the upward direction, two selected and two control lines were created. These lines were reared under the same environmental conditions at the larvae, spat, and grow-out stages. The progeny of the mass-selected lines were compared to those of controls in a 490-day farming experiment. Mean shell height and mean wet weight of the selected lines were significantly greater than those of the controls from day 120 onwards (<0.05). At harvest on day 490, the black-shell and white-shell oysters had mean shell height of (102.06±10.46) mm and (102.84±14.90) mm, respectively, and mean wet weight of (83.14±18.85) g and (84.46±16.98) g, respectively. The increase in shell height for selected blackshell oysters and white-shell oysters compared with that of the control was 9.04% and 9.01%, respectively, and the increase in wet weight was 9.33% and 10.50%, respectively. The estimated gain was consistent with the expected gain for mollusk species (10%-20% per generation). In the black-shell and white-shell mass-selected lines, the realized heritability of shell height was 0.353±0.093 and 0.405±0.111, respectively, the realized heritability of total weight was 0.297±0.12 and 0.377±0.190, respectively, the average selection response of shell height was 0.545±0.143 and 0.625±0.171, respectively, and the average selection response of total weight was 0.297±0.124 and 0.377±0.190, respectively. The total genetic gain of total weight for the black-shell and white-shell lines was (10.16±3.64)% and (11.34±1.94)%, respectively, indicating that total weight had improved markedly during selection for shell height. In conclusion, growth improvement for the two mass selected lines can be achieved by selecting the individuals with the greatest shell height. The relatively high realized heritability estimates obtained for the two mass-selected lines indicate that there is genetic variation in the two stocks, and that mass selection could be used to select for rapid growth in the next generations.

Abstract:The eastern keeled mullet ( genus (Mugilidae, Mugilformes), is an economically important coastal fish in China. For a long time in China, the eastern keeled mullet was considered to be , but many lines of research suggested that this was incorrect. To address this problem, we analyzed based on morphological characters and DNA barcoding, and compared it with other fishes in the genus. During October 2013 to December 2014, we collected samples from Chinese coastal waters, including Ningde, Jinjiang, Xiamen, Jinmen, Humen, Zhanjiang, and the Beibu Gulf. The specimens included in this study had the following morphological characteristics:pectoral fin length/body length ratio of 15.0%-18.3% and head length/body length ratio of 22.5%-25.1%, consistent with data reported by Senou (1987) for (14.5%-18.4% and 22.1%-26.9%, respectively), and different from those obtained for (19.8%-23.9% and 27.0%-31.3%, respectively). A partial sequence of the mitochondrial cytochrome oxidase subunit I (COI) gene was used in a phylogenetic analysis. The net genetic distance between recorded at GenBank is 13.11%. A neighbor-joining tree showed that our samples clustered with from GenBank with a genetic distance of 0.08%. However, the genetic distance between our samples and was 13.06%, greater than the threshold for species delimitation. The phylogenetic analysis strongly supported the validity of in China at the genetic level. As a result, we propose that the eastern keeled mullet is really exists in Chinese coastal waters. Although the task of identifying and describing new species is ultimately achieved through comprehensive taxonomic work, DNA barcodes can significantly facilitate this process. The conventional taxonomic workflow, which usually requires the collection of morphological and ecological data, can vary for different taxonomic assemblages (i.e., taxonomic identification of birds and fish require different methods and skills), whereas analysis can be applied in a more or less standardized way across large domains (i.e., all animal taxa). As a result, the identification and description of fish species should combine conventional taxonomic methods such as morphological analysis with molecular identification techniques such as DNA barcoding. Japanese and Chinese ichthyologists have traditionally used the name Mugil carinatus or for a mugilid fish with a keel on its back that is commonly found in these regions, ever since Oshima erroneously identified M. affinis was described by Günther (1861) on the basis of a specimen from Amoy, China. Although his description is detailed, he did not describe a keel on its back. Recently, Song reviewed the Chinese mugilids and used the name Valenciennes, 1836). We think this may explain why for so long. The origin, evolution, patterns of speciation, and unique features of genome divergence among the lineages of this species are topics for further research.

Abstract:The Chinese mitten crab, , is one of the most important aquaculture species in China, with a commercial yield of 729 900 tons in 2013. The main culture areas are located in three main drainage basins, i.e., the Liaohe River, the Huanghe River, and the Yangtze River. The Yangtze delta is the largest culture area among the three drainage basins. Although pond-reared populations of originated from their native habitats, i.e., the Liaohe River, Yellow River and Yangtze River, the Yangtze River population generally has the largest body size of adult crabs, the best growth performance, and superior taste among the three populations. To date, however, it is unclear whether there are any differences in gonadal development and nutritional composition of adult male among the three populations when they are cultured under similar pond conditions. In this study, we analyzed the gonadosomatic index (GSI), hepatosomatic index (HSI), meat yield (MY), total edible yield (TEY), and relative fatness (RF) of pond-cultured male , comparing the Yangtze River, Yellow River, and Liaohe River populations. Then, the proximate composition, fatty acids and amino acids composition, and essential amino acid score were compared among the three edible parts (gonad, hepatopancreas, and muscle). The results showed that the GSI was slightly higher in the Yellow River population than in the other populations, while the Yangtze River population had higher HSI, MY, TEY, and RF than those of the other two populations. However, there were no significant differences in these indicators among the three populations. The protein content in the gonad was significantly higher in the Liaohe River population than in the other two populations (<0.05), but moisture, lipid, and ash contents did not differ significantly among the three populations. The hepatopancreas of the Yangtze population had the lowest moisture content, but had higher protein, lipid, and ash contents than those of the other two populations. Compared with the Liaohe River population, the Yellow River population had significantly lower lipid content in the muscle (<0.05). The ash content in the muscle was significantly higher in the Yellow River population than in the other two populations (<0.05). The moisture and protein contents in muscle did not differ significantly among the three populations. The polyunsaturated fatty acids (PUFA) levels in the gonad were similar among the three populations, and the Yangtze population had the highest percentage of ΣPUFA, Σn6PUFA, and total highly unsaturated fatty acid (HUFA) among the three populations. For the hepatopancreas, the percentages of all PUFAs, ΣPUFA, and ΣHUFA were similar among the three populations. Compared with the Liaohe River population, the Yellow River population had significantly higher levels of C18:3n3 (LNA) and C20:5n3 (EPA) in the muscle (<0.05). The Liaohe River population had significantly higher methionine and cysteine contents in the gonad, compared with the other two populations (<0.05), and the highest contents of total essential amino acids (ΣEAA), total nonessential amino acids (ΣNEAA), and total amino acids (TAA) in the gonad. Among the three populations, the Yangtze population had the highest ΣEAA, ΣNEAA, and TAA contents in the muscle. Lysine, valine, and tryptophan were the limited amino acids in the gonad of the Liaohe River population. This population had the lowest mean essential amino acid score (EAAS) for the gonad among the three populations. In all three populations, the muscle of male crabs contained balanced amino acids and no amino acids were limiting. Together, these results suggest that there are differences in gonadal development and nutritional composition among the three populations, and that these differences may be related to different developmental stages and genetic factors.

Abstract:Pacific white shrimp, , is one of the most important commercially farmed species worldwide because of its rapid growth and osmoregulatory capacity. Abiotic factors such as freshwater inflow, rainfall, and seasonal variations result in fluctuations in water salinity in various aquaculture environments such as ponds and estuaries. To determine the response of to periodic salinity fluctuations, a 30-day experiment was conducted in the laboratory. In this experiment, two salinity fluctuation amplitudes of 4 (S4 group) and 10 (S10 group) were designed, using constant salinity of 30 (S0 group) as the control. The free amino acids (FAA) content, and the transcript levels of genes related to water, ion channels and FAA metablism were determined. Fluctuations in salinity strongly affected the transcript levels of genes related to ion and water channels. With increasing amplitude of salinity fluctuations, the transcript levels of genes encoding Na⁺/K⁺-ATPase α and β, carbonic anhydrase, and V-H⁺-ATPase 1 significantly increased, while the transcript levels of the gene encoding aquaporin 4 significantly decreased (+-ATPase 1 and the Na⁺/H⁺ exchanger were in the S4 group (<0.05). The transcript level of the gene encoding chloride channel protein did not differ significantly among the three groups (>0.05). However, the FAA total content in the gill was significantly increased by increasing salinity fluctuations (<0.05). Compared with the control shrimps (salinity of 30; S0 group), those in the S10 group showed significantly increased transcript levels of the gene encoding alanine transaminase, and significantly decreased transcript levels of the genes encoding aminomethyltransferase and proline dehydrogenase ( generates an active response to salinity fluctuations at the transcriptional level. With the increasing amplitude of salinity fluctuations, the osmoregulation capacity can increase. These results provide a scientific reference for further research on the osmoregulation of shrimps in stressful environments and also for the regulation of water quality in aquaculture.

Abstract:Saline-alkaline water is relatively prevalent throughout China, where there are about 99.07 million hm² of saline-alkaline land and more than 30.67 million hm² of saline-alkaline waters. Because of the complex ion composition and high pH value, only a few bodies of saline-alkaline waters have been used to farm freshwater fish. Many of these ventures have been unsuccessful, and so the fish farms have fallen into a state of neglect. Consequently, it is important to find ways to develop and use saline-alkaline soil and water resources. In recent years, has become one of the most important and extensively farmed shrimp species. Because of its strong ability to adapt to harsh environmental conditions, including ammonia nitrogen and pH stresses, could be the ideal species for farming in saline-alkaline waters. Therefore, the aim of these experiments was to explore the effects of water carbonate alkalinity on the survival, growth, reproduction, and immune enzyme activities of E. carinicauda individuals (LC₅₀) was determined in an acute stress experiment. For the LC₅₀ experiment, individuals of were subjected to various levels of carbonate alkalinity (3.5, 5, 6.5 and 8 mmol/L) and then their growth and reproduction were evaluated. The LC₅₀ was 8.73 mmol/L at 96 h. With increasing carbonate alkalinity, the mortality rate, specific growth rate, spawning rate, egg incubation rate, ovarian maturation, and metamorphosis larval survival rate of decreased. In another set of experiments, the carbonate alkalinity levels were set to 5, 6.5, and 8 mmol/L, and the activities of acid phosphatase, alkaline phosphatase, and superoxide dismutase were determined at 0, 3, 6, 12, 24, 48, and 72 h. The activities of all three enzymes in the gill and hepatopancreas of first increased and then decreased over time during carbonate-alkalinity stress. Our results indicated that can adapt to a highly alkaline environment by regulating the activity of immune enzymes. can be farmed in water with 3.5 mmol/L carbonate alkalinity, but cannot grow or develop normally in water with >5 mmol/L carbonate alkalinity. Therefore, water with high carbonate alkalinity must be treated to render it suitable for farming . This study provides a scientific basis for the development of aquaculture in saline-alkaline waters.

Abstract:The aim of this study was to investigate the growth and energy allocation responses of juvenile brown flounder, , to a period of limited dissolved oxygen (DO) supply and recovery. This information is important to understand the adaptive strategy of brown flounder to fluctuations in DO. Juvenile brown flounder were kept in a recirculating system and the DO supply was limited by controlling the water velocity. Two experiments were designed to measure the growth responses and energy allocation. Across a wide range of DO (2.24-6.94 mg/L), the body weight, daily growth coefficient, feeding rate, and feed conversion efficiency (in wet weight) were positively related to DO (<0.05). Individual energy ingestion decreased as the DO level decreased, and the highest percentages of growth energy were recorded at a DO level of 5.38 mg/L. Energy of feces increased and energy of excretion also increased slightly as the DO level decreased. The energy of metabolism decreased as the DO level decreased, then increased when the DO level fell below 5.38 mg/L. Energy allocation to metabolism was minimal at DO 5.38 mg/L (37.66%). For energy allocation per 1 g body weight, all parameters were positively related to DO and increased as the DO level increased. The growth of juvenile brown flounder was depressed during 10 d in low-DO conditions[2 mg/L(S₂) and 4 mg/L (S₄)]. However, when the fish kept in low-DO conditions were transferred to control conditions, their body weight recovered to that of control fish within 10 d. Compared with the fish in the control, those kept in low-DO conditions showed a higher feeding rate during the recovery period and slightly higher feed conversion efficiency. There were no significant differences among the different treatments in energy ingestion, growth energy, and energy of metabolism during the recovery period (>0.05). However, compared with control fish, the fish kept in low-DO conditions showed slightly higher energy ingestion and growth energy, and slightly lower energy of metabolism. Energy of excretion was lower in the S₂ group than in the other groups. Low DO levels decreased the feeding rate and feed conversion efficiency of juvenile brown flounder by depressing the energy supply, leading to depressed growth. These results show that juvenile brown flounder can adapt well to a short period of low DO, and completely compensate for the growth depression in a short period of recovery by improving their feeding rate.

Abstract:Salinity is an important ecological factor in the environment. The geographical distribution of Chinese mitten crab, , is affected by the levels of salinity and dissolved oxygen (DO). These factors also affect the hatching, development, and larval growth of E. sinensis. To study the effects of salinity on the standard metabolism of , juveniles were added to bottles with different salinity levels (0, 4, 8, 12, 16, and 20) and kept under the following conditions:average water temperature, (24±0.5)℃; average DO is (8.12±0.23) mg/L; pH, 7.5±0.18. The oxygen consumption, CO₂ discharge, and NH₃-N excreted into the water in each bottle were measured every 0.5 h during the experiment. Then, regression analyses were conducted for the oxygen consumption rate, CO₂ removal rate, and NH₃-N excretion rate. The response of the juveniles was divided into three stages:the free movement stage (DO>2.33 mg/L), the survival stage (0.33 mg/L < DO < 2.33 mg/L), and the asphyxia stage (DO<0.33 mg/L). Salinity significantly affected the oxygen consumption rate, CO₂ discharge rate, and NH₃-N excretion rate of juvenile <0.05). However, salinity did not significantly affect the oxygen consumption rate, CO₂ discharge rate, or NH₃-N excretion rate ( at the asphyxia stage. The results also showed that the fat was the main energy source under high-DO conditions. Under low-DO conditions, fat and carbohydrates provided energy, and the proportion of protein decreased as energy-providing substances were consumed. Together, these results showed that salinity affects the behavior and metabolism of juvenile . The overall aim of this study was to obtain baseline information on the standard metabolism of juvenile .

Abstract:The aim of this study was to comprehensively assess the nutritional value and safety of cultured and wild as prawn feed, with the ultimate aim of promoting the rational development and utilization of these sandworms. We investigated and compared the basic nutritional composition of the cultured and wild sandworms, determined their amino acid, fatty acid, and heavy metal contents, and evaluated their infection status with WSSV (white spot syndrome virus) and IHHNV (infectious hypodermal and hematopoietic necrosis virus). The results showed that the fat content was significantly higher in the cultured sandworms than in the wild ones (<0.05), but there was no significant difference in the contents of crude protein, moisture, and ash (>0.05). In both groups of nereids, the ratios of essential amino acids/total amino acids for shrimp feed were about 40%, and the ratios of essential amino acids/non-essential amino acids for shrimp feed were above 60%, which met the FAO/WHO standard for high-quality protein. Based on the amino acid score and chemical score of the two groups, the content of the most limiting amino acid was higher in the cultured sandworms than in the wild ones. The contents of unsaturated fatty acids and highly unsaturated fatty acids were significantly higher (<0.05) in the cultured group[(67.75±3.77)% and (54.11±2.58)%, respectively] than in the wild group[(56.13±6.60)% and (43.28±5.50)%, respectively]. The contents of common heavy metals (chromium, copper, cadmium, lead, arsenic, mercury) were significantly lower in the cultured sandworms than in the wild ones, and the arsenic content in the wild group significantly exceeded the standard. The cultured group was not infected with WSSV or IHHNV, while the wild group was infected with WSSV but not IHHNV. These findings indicated that wild sandworms may carry WSSV. In conclusion, based on their nutritional value and safety, cultured sandworms are better prawn feed than wild sandworms.

Abstract:Phenylalanine (Phe) is one of the essential amino acids for fish. It is an essential component of proteins that participate in many important physiological and metabolic processes, including growth and development. A deficiency or excess of phenylalanine in the diet can significantly affect the growth performance and/or feed utilization of farmed fish. Therefore, it is necessary to ensure that dietary levels of Phe meet, but do not exceed, the requirements of the fish. The GIFT strain of (Nile tilapia) is becoming an important and economically valuable farmed freshwater species. The aim of this study was to determine the optimal dietary Phe requirement of the GIFT strain by evaluating its growth performance, feed utilization, body composition, muscle amino acid composition, and digestive enzyme activities in a 60-day growth experiment. Triplicate groups of experimental tilapia (initial body weight, 52.70±1.80 g) were cultured in freshwater in 15 floating net cages (1.0 m×1.0 m×1.5 m). Six isonitrogenous (30.10% crude protein) and isocaloric (17.73 MJ/kg gross energy) diets were formulated with protein sources including fish meal, gelatin, peanut meal, soybean meal, casein, and crystalline amino acids. The measured Phe levels in the experimental diets were 0.78%, 0.95%, 1.09%, 1.34%, 1.51%, and 1.72%. The dietary amino acid pattern, except for Phe, was adapted to the muscle amino acid pattern of the GIFT strain. The results showed that with increasing dietary Phe levels, the weight gain rate, specific growth rate, protein efficiency ratio, and protein deposition efficiency increased significantly (<0.05) with the highest values in the 1.34% Phe group. The feed conversion ratio decreased significantly (<0.05) with increasing dietary Phe levels, and showed the lowest value in the 1.09% Phe group. The hepatosomatic index, viscerosomatic index, and condition factor of the GIFT strain all increased significantly (<0.05) as dietary Phe levels increased from 0.78% to 1.34%, but decreased when dietary Phe levels exceeded 1.34%. The highest whole body crude lipid and whole body ash contents were in the 1.34% dietary Phe group. There were no significant differences (>0.05) among the six groups in whole body moisture content, whole body crude protein content, muscle moisture content, muscle crude protein content, muscle crude lipid content, and muscle amino acids contents. The muscle ash content of the group fed 0.98% dietary Phe was significantly (<0.05) lower than that of the group fed 1.72% dietary Phe, but was not significantly different (>0.05) from those of the other groups. The serum chemistry analysis showed that dietary Phe significantly affected the glucose, total cholesterol, triglyceride, and alanine aminotransferase contents (>0.05). The dietary Phe levels also significantly affected the activities of intestinal protease, intestinal lipase, and Na⁺-K⁺-ATPase (<0.05), but not intestinal amylase activity. The quadratic regression analyses of weight gain rate, feed conversion ratio, and protein efficiency ratio showed that the optimum dietary Phe requirement of GIFT is 1.17%-1.21% of the diet or 3.89%-4.02% of dietary proteins.

Abstract:In this paper, we discuss the geographical isolation and population dynamics of the largehead hairtail () populations in the East China Sea (ECS), Yellow Sea (YS), and Bohai Sea (BS). The results showed that only two largehead hairtail populations exist in the nearshore regions of the ECS, YS, and BS. The largehead hairtail population in the Northern Yellow Sea and Bohai Sea was designated as the Yellow Sea and Bohai Sea population (YSBSP), and the other population in the South Yellow Sea and the East China Sea was designated as the East China Sea population (ECSP). By evaluating moving images of largehead hairtail, we found that the YSBSP rear-ended the population in Jiangsu's northern nearshore waters at 34°00'N, 121°00'E. However, the largehead hairtail output from the overlapping waters accounted for only 1.16% of the total output. The two populations shared the same overwintering ground, and so these populations were mixed in the offshore waters to the west of Cheju Island. Only 1.16% of the total output was fished during the month in which the two populations mixed. We present six lines of evidence that there are two main populations of largehead hairtail in the studied waters. First, the output of largehead hairtail from the overlap waters is small, accounting for less than 5.51% of the total output in the same month. Second, the two groups do not produce hybrids when in overlapping waters because each group follows its own migratory route back to its wintering grounds. Third, the groups of largehead hairtail only mix in overlapping waters and not in spawning grounds, which is another reason why hybridization between the two populations is unlikely. Fourth, the two populations show different trends in their quantitative dynamics; for example, the outputs differ markedly between the two populations, suggesting that the ECSP did not contribute to the YSBSP in recent years. Fifth, there is significant geographical isolation between YSBSP and ECSP, except those in the overlapping waters. Sixth, the two different populations of largehead hairtail showed different migration patterns. Together, all of these results indicate that largehead hairtail inhabiting the East China Sea, Yellow Sea, and Bohai Sea belong to two different populations:the Yellow Sea and Bohai Sea population, and the East China Sea population.

Abstract:Japanese Spanish mackerel () is a large pelagic species that widely distributes in the Bohai Sea, the Yellow Sea, and the East China Sea. Xiangshan Bay is one of the most important spawning grounds of . In each year, the spawning stocks swim into Xiangshan Bay and prepare to spawn in early April. In this study, we analyzed the temporal and spatial distribution of fish eggs, larvae, and juveniles of in Xiangshan Bay to test their relationships with surface temperature, salinity, and depth. Ultimately, an understanding of the characteristics of the spawning and nursery grounds is essential for resource protection and sustainable utilization. Fourteen sampling stations were established, and eggs, larvae, and juveniles of were collected using small plankton trawls (1 m×2 m, 1.0 mm mesh size) each week from April 3rd to June 3rd in 2015. The temperature, salinity, and depth at each sampling site were also measured at each sampling time. The results showed that spawned in Xiangshan Bay from early April to early June, with peak spawning from mid-April to early May. Larvae and juveniles appeared later than eggs, but were only present for a short time. The abundance of larvae and juveniles was high from early May to mid-May. Eggs, larvae and juveniles of were mainly distributed in the outside and middle area of the bay. The distributions of eggs, yolk-sac larvae, and preflexion larvae of were similar, and mainly concentrated in the deeper waters. The distributions of postflexion larvae and juveniles of were similar, and their densities were relatively high in shallow waters. Temperature, salinity, and depth were significantly related to the abundance of eggs. Depth was positively related to the abundance of eggs ( tend to spawn in the profundal zone (15-30 m) of Xiangshan Bay. The results showed that surface temperatures of 15-19℃ were suitable for the incubation of , and the optimum surface salinity for eggs was 25.5-26.0. The abundance of larvae and juveniles was significantly related to surface temperature, but not to surface salinity and depth. The optimum surface temperature for larvae and juveniles was 18-19℃.

Abstract:To understand the nutritional quality of planktonic food for marine fish, the fatty acid composition of plankton collected from the Yellow Sea was investigated and compared between winter and spring. As soon as the plankton were collected at sea, they were size-fractionated into six groups:100, 200, 300, 500, 1000, and 2000 μm, and then immediately stored in liquid nitrogen. The fatty acid contents of the plankton were determined using capillary column gas chromatography in the laboratory. Compared with the spring-collected plankton, the winter-collected plankton in all size groups had higher total saturated fatty acid (SFA) contents, but lower contents of total monounsaturated fatty acids (MUFA), total polyunsaturated fatty acids (PUFA), and the fatty acids 16:1ω7, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and 20:1+22:1. The different size groups of plankton collected in both winter and spring were compared. The contents of ω3PUFA, EPA, DHA, and 20:1+22:1 were higher in large plankton (>500 μm) than in small plankton (<500 μm). However, the contents of the fatty acids 16:0 and 18:0 were higher in small plankton than in large ones. Among the nutritional quality indicators (DHA/EPA, 16:1/16:0, and Σ16/Σ18 ratios), the Σ16/Σ18 ratio was higher in winter-collected plankton than in spring-collected plankton, while the DHA/EPA and 16:1/16:0 ratios were higher in spring-collected plankton than in winter-collected plankton. The DHA/EPA ratios reached to 2 in the 500 μm and 1000 μm groups in winter, but were greater than or close to 2 in all size groups in spring. Multiple analyses showed that the seawater temperature had the strongest effect on the fatty acid composition of plankton in the Yellow Sea, especially the MUFA and PUFA contents in plankton of the 100-1000 μm size groups. The results of this study show that winter-collected plankton of >500 μm could meet the nutritional requirements of marine fish, especially larvae and juveniles. Spring-collected plankton in size groups from 100 μm to 2000 μm, which have higher DHA/EPA ratio and ω3 PUFA content, are also suitable food sources for marine fish. It may be inferred that the size spectrum of plankton suitable as food for marine fishes is wider in spring than in winter in the Yellow Sea.

Abstract:In October 2015, an infectious disease characterized by hemorrhaging from the eyeball, jaw, and operculum, along with neurological symptoms or sudden death with no other clinical symptoms emerged in farms of (Kessler) culture in Ya'an, Sichuan Province, China. A Gram-positive, chain-forming coccus was found in visceral smears. Two bacterial isolates (ZYW151011 and ZYW151012) were isolated from the liver, spleen, and kidney of the diseased pathogenic test, PCR detection of the Streptococcus agalactiae, and sequence analysis of the 16S rRNA gene. Both bacterial isolates were identified as . A 16S rRNA gene sequence analysis by BLAST in GenBank indicated that the two isolates (GenBank accession numbers KU308396 and KU308396) showed high levels of similarity to (99.8%). Drug sensitivity test results showed that both strains were sensitive to ceftriaxone and quinolones, but were not sensitive to doxycycline, florfenicol, and amoxicillin. Serotyping and sequence typing of the two isolates was achieved using capsular polysaccharide serotyping and multilocus sequence typing (MLST), respectively. The serotype of both isolates was pathogenic type Ia. The two isolates were identified as a new sequence type (ZST-1), closely related to ST-261. The allele gene sequence has been submitted to the MLST database under the new allele number 81 (ID, BIGSdb_20151110081850_13025_35759) based on this new variation of in the novel sequence type ZST-1.