Abstract:The nuclear ribosomal RNA (nrRNA) genes of eukaryotes are organized in clusters of tandem repeat units, including three genes (18S, 5.8S, and 28S) and two internal transcribed spacers (ITS1 and ITS2). The ITS2 is located between the 5.8S and 28S genes. Because multiple copies of ITS2 have different intra-and inter-species evolution rates, ITS2 is often used as the molecular marker to identify species or to infer the phylogenetic relationship at the rank of species or genera. In this study, 11 species from five families of Perciformes were selected as the representatives to investigate the characteristics and the evolutionary pattern of the ITS2 in fishes. A total of 444 cloning sequences of ITS2 were obtained from 24 samples through PCR and cloning methods. The length of these sequences ranged between 332-515 bp. A comparison of sequences within species found that the length of (32 bp) were extremely varied, and that of others, less than 14 bp, were relatively conservative. The evolutionary pattern of ITS2 of 11 species within species were conjectured based on the difference in several polymorphism characteristics, including the difference in length, conserved and variable sites, parsimony-informative site, the number of haploid type, proportion of conserved and variable sites, haploid type diversity index, nucleotide diversity and genetic diversity. The two out of 11 species () had obvious differences, especially the three different sequence types (Type A, Type B and Type C) detected in three individuals, suggesting a non-concerted evolution. Although, to a certain extent, length and variable sites were observed in four other species (, and S. leptolepis and , therefore, the four species were not subjected to strict concerted evolution (no-strict concerted evolution). The five other species (Toxotes chatareus, and ) almost had no intraspecific variations, suggesting a concerted evolution process. Meanwhile, there was no correlation between the evolution pattern of 11 species and the taxonomic system. In addition, sequence comparison revealed that transitive sequences between concerted evolution and non-concerted evolution were observed in , all three evolutionary patterns (concerted evolution, no-strict concerted evolution and non-concerted evolution) were detected in three individuals. Based on 444 cloning sequences of ITS2 from 11 species with as the outgroup, two phylogenetic trees were constructed using the neighborjoining and maximum likelihood methods. The results showed that both trees were largely congruent with each other. The topology showed that sequences from the same species clustered together and sequences from each genus of seven genera in Carangidae claded together. These results supported that the ITS2 is applicable as a molecular marker for species identification, but also useful for phylogenetic relation analysis at the rank of genus in Carangidae.

Abstract:Only a few of the world's 275 species of Sciaenidae live in fresh water throughout their life; one of which, is the freshwater drum that is wildly distributed in North American. The study of its morphological and internal anatomical characters have great value to the phylogeny and evolution of Sciaenidae. In present study, the external morphological characters of the juvenile freshwater drum were systematically measured, and the anatomical structure of the main internal organs and sagittae otoliths were observed. The results indicated that there were two kinds of scales covering the body of the freshwater drum, except for the front of the snout, chin, and isthmus. Small cycloid scales were found on its operculum and around the eyes on both sides of the head, and ctenoid scales covered the body including the posterior head and jugular. The lateral line scales extended from the back of the head to half of the caudal fin. Some transition types of cycloid and ctenoid scales existed at the junction of the head and the dorsum. The first membrane of the ventral fin extended slightly to form a specific fin-silk. The juvenile freshwater drum had canine-like jaw teeth and pharyngeal teeth with different sizes, but all bent in an inward internal direction of the pharyngo-oral cavity. The upper pharyngeal disc was divided into two symmetrical parts, whereas the lower pharyngeal disc was fused into one. There were only five mental pores symmetrically distributed on the chin, which were Sciaena-form. The digestive tract consisted mainly of the pharyngo-oral cavity, a short esophagus, a divination-type stomach, the intestine with two bend, and the anus. There were seven circular digital pyloric caecas existing at the junction of the stomach and the intestine. The morphological characteristics of the sagittal otoliths of freshwater drum were similar to those of . Based on the external morphology and internal anatomical characteristics, the freshwater drum has a closer evolutionary relationship with the Sciaena and should belong to low-grade benthic carnivorous fish, which consisted with its specific ecological habits and food consumption characteristics. This study not only provided an important foundation for the artificial domestication of freshwater drum and the large-scale parasitic breeding of pink heelsplitters in China, but also provided the basic material for the study of the evolution of the geographical evolution pattern of Sciaenidae in marine and freshwater regions.

Abstract:is an extremely destructive ciliate parasite of marine fishes, which results in severe economic costs in mariculture. Its life history is divided into three stages:trophont, tomont, and theront. Tubulin is a major component of the cytoskeleton, cilia, and flagella, which plays an important role in maintaining cell morphology, intracellular trafficking, cell division, ciliary, and flagella motility. At the same time, many studies showed that tubulin has immunogenicity and can be used as a target antigen vaccine. In this study, the α-tubulin gene fragment was obtained from the transcriptome data in our laboratory. Full-length cDNA of α-tubulin was cloned for the first time by 5'RACE and 3'RACE. The results showed that full-length cDNA of α-tubulin is 1602 bp containing a 1356 bp open reading frame, which encodes proteins with 451 amino acids. The predicted molecular mass of α-tubulin is 49.78 kD. Bioinformatics analysis showed that it is a hydrophilic non-transmembrane protein. The amino acid sequence at positions 142-148 has a unique conserved GTP nucleotide binding site (GGGTGSG). Multiple sequence alignment analysis and phylogenetic analysis revealed that the α-tubulin in was integrated with other protozoa in the phylogenetic tree and had 94%-95% sequence identity with Naegleria gruberi, and . The real-time quantitative PCR technique was used to detect the expression of α-tubulin gene in the life history of . The results showed that α-tubulin gene expression was significantly higher in the theront stage than in the tomont and trophont stages ( < 0.05). Furthermore, the α-tubulin recombinant expression vector was constructed and transformed into the BL21 (DE3) and Rosetta (DE3) of the expression strain for prokaryotic expression. SDS-PAGE analysis showed that the molecular weight of the recombinant protein was approximately 50 kD, which was consistent with the predicted result, indicating that α-tubulin protein induced expression successfully. The results of this study laid the foundation for the subsequent preparation of an effective subunit vaccine.

Abstract:The freshwater fish is a rare, endemic and economic species, only distributed in the middle and upper reaches of the Nujiang River (Upper Salween River) in China. Potential cascade hydropower development in the Nujiang River will threaten the survival of . The potential for drastic changes in the water flow, water temperature and food supply of their habitat may lead to extinction of . Therefore, biological research on future conservation and resource utilization is imperative. Herein, the histology and ultra-structure of the gill in the teleost was investigated using the optical and electron microscopic imaging techniques. The results showed that the basic structure of the gills consisted of the gill raker, gill arch, gill filament and lamellae, which was similar to other teleost fishes. Different parts of the gill possess distinct histological structures and cell types. The pavement cells (PVC) covered the filament epithelium and lamellae of the gills, showing three distinct morphological features of micro-ridges in the different parts of the gill. There was only one type of mitochondrial rich cells (MRC) observed in the gill, which were located at the base of lamellae. All these MRC have a large number of big, round mitochondria and exhibit apical shallow-basin with microvilli. Our results suggested that the morphological feature and functional diversity of PVC and MRC in the gill of were in accordance with its habitat. These observations enrich the basic biological knowledge of and can provide a reference for clarifying the relationship between the specific structural characteristics of the fish and their living habits.

Abstract:The Amur sturgeon () is one of the eight species of Acipenseriformes that occur in China. The range of the Amur sturgeon is mainly restricted to the middle and lower Amur River. Sometimes sturgeons enter the Ussuri River, but they rarely occur in the Sungari River. This species supports fisheries, but stocks are declining significantly because of overfishing. Developing artificial cultures could reduce market dependence on wild fish and would assist in conservation of the wild stock. Although Amur sturgeons are gonochoristic, they exhibit no apparent sexual dimorphism and have no indicators of their sex for their first 1-2 years of life. Currently, the most reliable method of determining sex and gonad maturation in Amur sturgeons at an early age is through a surgical incision and visual examination of the gonads. The eggs of artificial spawning are also commonly obtained via an abdominal incision or caesarian section. The incisions may not always heal properly; thereby, causing infections, inflammation, and ulcerations that lead to adhesions or in some cases to mortality. Thus, it is critical to close the incisions for the recovery of Amur sturgeons post-surgery. The goals of this research were to study the process of incision healing, through visual and histological evaluations of the surgical incision at different stages post-surgery, to explore the repair capability of Amur sturgeons, and to provide data for the establishment of post-surgery system management. A total of 30 2-year-old Amur sturgeons were anesthetized quickly by immersion into a tank containing a 150 mg/L solution of tricaine methanesulfonate (MS-222). Once the fish reached a surgical plane of anesthesia, a sterile surgical blade was used to make a 5 cm incision through the ventral middle skin and linea alba into the coelomic cavity. The incisions were closed with three simple interrupted stitches. Samples were taken at 4, 7, 14, 28, 42, and 56 days post-surgery. A study on the healing of the incisions was conducted, through visual assessments and histological observations. The results indicated that the epidermal cells migrated into the coelomic cavity along the edge of incision and had contact with the peritoneum at 4 to 7 days post-surgery. The inflammatory infiltrate and Type Ⅲ collagen appeared at the incision margin. The incisions healed, and redness and swelling indexes significantly decreased ( < 0.05) from 14 to 42 days post-surgery. The epidermis covered the incision, and there was an overlap between the epidermis on the front of both sides. The epidermal cell layers at the incision margin significantly increased and were greater than that around the incision and the control. A large number of fibroblasts gathered at the edge of the incision, and new capillaries were regenerated, forming granulation. From 42 to 56 days post surgery, the epidermis healed completely, exhibiting no differences from that of the control. In the granulation, type I collagen substantially increased, but fibroblasts and capillaries decreased and disappeared. A scar remained. These results indicated that the Amur sturgeon had a strong repair capability. It took 56 days to close the surgical incisions. The surgical incision healed mainly during the period from 14 to 42 days post-surgery. It took longer to complete healing of the dermis and hypodermis, compared with that of the epidermis. The healing of the dermis and hypodermis was constraint with the progress of incision closure.

Abstract:in China and is uniquely endemic to the Yarlung Tsangpo River system. With the rapid dwindling of its populations and gradually shrinking distributions due to overfishing and the impact of water conservancy projects and foreign fish invasion in recent years, it is considered a critically endangered (CR) species by the Red List of Chinese vertebrates (2015). It is the only one of the 77 known Chinese sisorid species to be ranked on this list. In this study, the broodstock were captured in the four Yarlung Zangbo River sections of Shigatse, Tibet, including Xaitongmoin, Lhatse, Ngamring, and Saga. The altitude distribution range of the four sampling sites is approximately 3900-4500 m. From mid-May 2015 to mid-June 2015, 79 females were artificially induced to spawn, another 7 females naturally produced eggs and about 57440 eggs were spawned. At the same time, 15 males were dissected and their testes were broken for use in artificial insemination. Approximately 42208 fertilized eggs of were obtained. The fertilized round, demersal eggs were slightly yellowish with strong viscosity. The fertilized eggs were laid flat on a special sieve net and hatched in a small trough of a running water. In Lahsa, Tibet, the entire embryonic development process from fertilized egg to hatching was observed and the effective accumulated temperature of the embryonic development was calculated. In the fertilized egg and cleavage stage, the same batch of fertilized eggs were sampled, observed, photographed and recorded every 30 min. After the cleavage stage, samples were taken every 1 h. At each time point, 10 fertilized eggs were taken and the stages of embryonic development and the period for entry into each were examined by microscopy. More than 50% of the embryos appeared to have corresponding characteristics. It was found that the timing sequence for embryonic development of was consistent with the general rule of teleosts, divided into eight stages-fertilized egg, blastoderm formation, cleavage, blastula, gastrula, neurula, organogenesis and hatching stages-and further subdivided into 28 phases according to the morphological characteristics of each stage. Myomere and optic vesicles were formed before the blastopore and its closure, optic capsules, heart rudiment, digestive tract, otoliths, eye lens, pectoral fin rudiments formed successively in the organogenesis stage. The red blood cells were found after the heart started beating. Meanwhile, the observation records revealed an average temperature of about 13.8℃, and the effective accumulated temperature 2963.2-3132.4 h·℃, with a hatching rate of approximately 70%. However, unlike the eggs of the six common fish in the Yarlung Zangbo River, the fertilized eggs had a two-layer membrane that formed immediately at the point of water absorption and disappeared completely at the neurula stage. The two-layer egg membrane as a special structure may be responsible for environmental adaptability. The outer membrane may play a role in the adhesion, fixation and buffer protection in the process of egg transmission and incubation. This study may contribute to understanding the characteristics and laws of , embryonic development and provide a theoretical reference for artificial breeding and scientific protection of the species.

Abstract:Growth and resistance are the most important agricultural traits for genetic breeding in aquaculture animals. The growth trait of Rainbow trout is central to the economic development in scaled production. Launched from strains of Bohai, Denmark, Norway, Donaldson and California, family selection of the rainbow trout was performed for four consecutive generations based on biallele crossing design. Only data from the fourth generation was selected for this study. Dynamic genetic analysis was conducted using 19299 records repeated body weight (BW) and body length (BL) measurements, which were obtained to genetically evaluate the growth traits of 4368 samples for the fourth generation at their 516 days of age, 608 days of age, 668 days of age, 883 days of age and 1036 days of age. According to the Bayesian information criterion (BIC), Legendre polynomials of three orders were selected as the most optimized submodel to fit changes in additive genetic and permanent environmental effects on both BW and BL. With a bivariate random regression model (RRM), both traits were analysed simultaneously. The heritabilities were estimated to exhibit a downward tendency between 400 and 1000 days of age, from 0.288 to 0.164 and from 0.469 to 0.186 for BW and BL, respectively, while BL was inherited in a consistently higher manner than BW. The genetic correlation of BW and BL showed a tendency towards the decrease of heritabilities with the enlarged growth space. However, the traits in the initial and later days of age showed higher correlation for both traits which are all above 0.75, especially for BW, which is higher than 0.85. The genetic correlations in the same growth days of age for both traits are equal to or above 0.75, but decreased from 0.83 to 0.63 in different growth days of age. In summary, the genetic correlation of a single trait or both traits between paired day-ages decreased with the increasing age-interval. However, the consistent genetic correlation between paired day-ages makes the genetic selection for BW feasible at an early stage. These results provide the theoretical basis for breeding selection focused on BW and BL growth traits. At the same time, this research also provides accurate genetic analysis results which is most fitted for the combined selection. Due to the existing higher genetic correlations between early and later stage for BW and BL, the combined selection is suggested from early 400-growth-day. In addition, the big population with couple families will be artificially divided into several individual subpopulations and repeated random measurements for growth points series will be executed for every subpopulation. This technique will satisfy the requirements for an improved fitting with the growth curve and also save money, including from decreased labour costs.

Abstract:, which is also known as white shrimp, is one of the main farmed shrimp species in China. It is native to the coastal line of Central and South America and was, instead of , introduced into China in the 1990's. The yield of white shrimp increases annually significantly because of its fast growth, adaptability to a wide range of salt and temperatures, strong disease resistance and low demand for dietary protein. However, in recent years, the success rate of white shrimp farming in China has declined because almost 70% of white shrimp seedlings are from inbreeding produced by hatchery farm without systematic selection, resulting in inadequate growth performance and stress resistance. The very small quantity of quality broodstock imported from abroad is unable to meet market demand. Meanwhile, the dominant trait of broodstock selected by other research institutes in China is not stable. The selection of high-quality broodstock is critical to improving shrimp farming in China. Collection of different basic populations is the basis for white shrimp selective breeding and inbreeding should be avoided. In this study, in order to analyse the effect of wild population introducing on the growth trait and stress resistance of the 1 which was imported from Ecuador (EC) and an inbreeding population (ZG) using a complete diallel cross to construct four F₁ populations including EC♂×EC♀ (EE), ZG♂×ZG♀ (GG), EC♂×ZG♀ (EG), ZG♂×EC♀ (GE). The survival rate of post-larvae after exposure to acute low salinity or nitrite, the antioxidant enzymes activities under microcystin-LR (MC-LR) exposure and the growth speed were compared between these four F₁ populations. The results showed that the survival rates under acute low salinity (from 30‰ to 2‰) for 24 h to 48 h were significantly different between the four F₁ populations (EE > GE > EG > GG, <0.05), with the survival rate of the EE population as the highest and the GG population as the lowest. The survival rates of the four F₁ populations under acute nitrite treatment (35 mg/L) after 60 h were different (GE > EE > EG > GG), with GE as the highest and GG again as the lowest. After exposure to 8 mg/L MC-LR, the antioxidant enzyme activities of SOD and CAT were significantly upregulated at 24 h or 36 h; activities of GP_X, GST and GR, which are involved in removing secondary metabolites such as H₂O₂ and ROOH, were also up-regulated; the GSH contents in hepatopancreas decreased because of consumption and the resistance to MC-LR was significantly different between the four F₁ populations (EE > GE > EG > GG). The growth trait analysis showed that the growth speed of the EE and GE populations during 0-40 d was slower than the other two populations, while these two populations showed higher growth speed during 40-83 d, and the EE population had the best growth trait after 83 d (EE>GE>EG>GG). The heterosis rates of hybrid population GE under acute low salinity, nitrite or MC-LR treatment were 31.83%, 77.01%, and 2.77%, respectively, and the performance was better than the mean values of the parents. While the heterosis rates of the EG population were -19.21%, -8.01% and -8.14%, the performance was weaker than the mean values of the parents. In conclusion, the stress resistance and growth trait of the four F₁ populations was EE > GE > EG > GG. The results revealed that maternal inheritance was dominant for hybrid populations; the trait depression in hybrid offspring could be caused by using female individuals from inbreeding population; and improving the dominant traits depended on more and more basic populations for white shrimp selective breeding.

Abstract:We induced the gynogenetic offspring of the breeding grass carp (YZ) using UV-inactivated grass carp sperm and cold shock method to inhibit extrusion of the second polar body. Twelve pairs of microsatellite primers were used for amplification and genetic analysis of the YZ population and control population (YS). A total of 194 alleles were detected in the YZ and YS populations, of which 75.8 were effective alleles. The average number of alleles in the YZ, YS and CH populations was 13.0, 12.6, and 4.7, respectively; the average number of effective alleles was 7.7, 6.6, and 2.3, respectively; the average expected heterozygosities were 0.87, 0.82, and 0.56, respectively; and the average polymorphism information content was 0.84, 0.79, and 0.49, respectively. Homozygosity was analyzed for the microsatellite loci:the homozygosity of individuals in the YZ population was 0.00-0.33, the homozygosity of individuals in the YS population was 0.00-0.42, and the homozygosity of individuals in the CH population was 0.42-0.92. The results showed that the genetic diversity of the CH population was significantly lower than that of the YZ population and the YS population, and the homozygosity of the CH population at each locus was higher than that of the common grass carp groups. This suggests that artificially induced meiotic gynogenesis can accelerate the homozygosity of most grass carp gene loci and is an effective means of rapidly establishing a high purity strain. At the same time, this study screened and used microsatellite loci combinations to establish a simple and efficient identification technique for the genetic relationship among different families and their female parent, laying a foundation for the marker-assisted breeding of gynogestidium.

Abstract:An additive effect is the main genetic determinant of the phenotypic value of a quantitative trait, but it is a direct genetic effect (DGE) of the trait itself, ignoring the genetic influence of social interaction among individuals in the same group. The expression of genes of an individual has an influence on the phenotypic values of others in the same group, which is an indirect genetic effect (IGE). IGE is generated by social interaction among individuals in the group. IGE has been widely reported in animals and plants. For aquatic animals, IGE has been determined in Nile tilapia, Atlantic cod, and the Pacific white shrimp. The Chinese shrimp () is one of the most representative aquaculture species in China. In , cannibalism and frequent attacks are common phenomena. Attacks among individuals under environmental stress and the fight for food may affect the growth of shrimps. In order to study the indirect genetic effects of body weight in under restrictive feeding conditions, 103 families of the eleventh generation of the breeding population were tested using a multi-family by multi-group design. They were reared for about three months with limited feed and harvest body weight was measured for each individual. Genetic parameters of harvest body weight were estimated using an extended animal model, including IGE. The results showed that the IGE of body weight was significant, with a contribution to the total genetic variance reaching up to 75.03%. There was a negative covariance (-2.1900) between DGE and IGE. Based on the model with IGE, the ratio of total genetic variance to phenotypic variance was 0.524±0.212, which was less than the traditional estimate of heritability (0.616±0.074). In addition, there was a negative genetic correlation between the direct and indirect genetic effects (-0.495), implying that the existence of competitive effects may be detrimental to selective responses. This study demonstrated strong social interaction (competition among individuals) exists in a population of under restrictive feeding conditions, which had a heritable effect on body weight. Considering that the indirect genetic effect under the competitive environment has a greater negative impact on selection, it is inadvisable to conduct breeding programs under a competitive environment.

Abstract:Salinity is an important ecological factor in the environment. It not only affects growth but also survival rate, osmotic pressure, and non-specific enzymes in juveniles of E. sinensis in the Yangtze Estuary, the effects of salinity on survival rate, osmotic pressure, and non-specific enzymes of juvenile were studied. Juveniles were added to circular glass fiber cylinders with different salinity levels (0, 4, 8, 12, 16, 20, and 24) and maintained under the following conditions:average water temperature 23-24; pH 7.2℃ -7.8; and average DO>5 mg/L. The survival rate, tissue homogenate supernatant Na⁺, Cl^-, and K⁺ concentrations, Na⁺-K⁺-ATPase activity, oxyhemoglobin content, and the activities of total superoxidase (SOD), alkaline phosphatase (AKP), and phenoloxidase (PO) were analyzed after 3 days of the experiment. The results showed that the salinity 8 experimental group had the highest survival rate and hemocyanin content, which were 89% and (0.253±0.023) mg/mL, respectively, and were significantly higher than those of other experimental groups (<0.05) but were minimized in the freshwater and salinity 24 groups. Na⁺, Cl^-, and K⁺ concentrations, Na⁺-K⁺-ATPase activity, and non-specific immune enzyme activity were divided into three stages. Firstly, these indicators decreased significantly with increasing salinity (0-8), gradually increased with higher salinity (8-12), and finally stabilized at the highest salinity (12-24). It had its lowest index values in the salinity 8 experimental group, the concentrations of Na⁺, Cl^- and K⁺ were (40.897±1.700) mmol/mL, (8.340±2.130) mmol/mL, and (1.842±0.158) mmol/mL, and the activity of Na⁺-K⁺-ATPase was (3.153±0.735) U/mg, and the activities of SOD, AKP, and PO were (129.026±3.496) U/mg, (1.326±0.173) U/mg, and (16.366±0.065) ng/mL, respectively. Together, the results revealed that the juveniles were highly adaptable in low salinity (4-8), whereas fresh water and high salinity water weakened its osmotic regulation and immune defense function. The goals of this study were to reveal the physiological characteristics during feed-bait migration and provide a scientific basis for resource conservation and environmental assessment of juvenile .

Abstract:This study aimed to investigate different feed type and feeding frequency on growth and muscle quality of juvenile channel catfish (). A 2×2 design with three replicates was performed in this trial, which included feed type (extruded feed, EF; pellet feed, PF) and feeding frequency (twice daily, F2; three times daily, F3). In an 8-week trial, regular feeding twice (7:30 and 16:30) or three times (7:30, 12:00, 16:30) daily occurred, and the amount of feed was adjusted to keep all cages consistent. The results showed that the final weight and weight gain rate of channel catfish were influenced by the feeding frequency, the results from the F2 group were significantly higher than that of the F3 group (<0.05); meanwhile, feed type did not affect the growth of channel catfish (>0.05). The crude fat content, cohesiveness, and resilience of the pelleted feed group were significantly lower than that of the extruded feed group (<0.05), whereas the hardness was significantly higher than the extruded feed group (<0.05). The hardness, adhesiveness, and chewiness of the F3 group were significantly higher than that of the F2 group (<0.05). The relative expression of myogenic factor 5 (Myf5) and myostatin (MSTN) genes in the pelleted feed group was significantly lower than that in the extruded feed group ( gene in muscle of the F3 group was significantly higher than that of the F2 group, but the relative expression of the myogenin (MyoG) gene showed the opposite trend. The present study indicated that the growth of channel catfish fed extruded feed was similar to those fed pelleted feed with the same formula. Fish fed pellet feed had higher hardness, whereas fish fed extruded feed had higher muscle fat content. The optimum feeding frequency of channel catfish was twice daily in this study.

Abstract:We evaluated the growth performance and hepatoprotective and antioxidant effects of curcumin against carbon tetrachloride (CCl₄)-induced liver injury in based on an 8-week feeding trial. A basal diet was supplemented with 0 (control), 15, 30, 60, 120, and 240 mg/kg curcumin to formulate six experimental diets. At the end of the feeding trial, the growth performance was determined. Subsequently, CCl₄ was used for the model experiment. The plasma and liver were collected for the test after 72 h. Then, the expression levels of total protein (TP), albumin (ALB), total antioxidant capacity (T-AOC), glutamic oxaloacetic transaminase (GOT), and glutamic pyruvic transaminase (GPT) of plasma and liver superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), malondialdehyde (MDA), and glutathione (GSH) activities were detected. The liver tissues were also collected for anatomical analysis. The change of liver tissue structure was observed under a microscope. Results showed that there was a significant (<0.05) increase in weight gain rate (WG) and special growth rate (SGR) of fish fed diets supplemented with 60 and 120 mg/kg curcumin. When fish were exposed to CCl₄ after 72 h, fish fed diets supplemented with 60 and 120 mg/kg curcumin had significantly (<0.05) lower plasma GOT and GPT activities and MDA content, and higher contents of plasma TP and ALB, and activities of liver SOD, GSH, GSH-Px, and plasma T-AOC than those in other treatment groups. Curcumin (120 mg/kg curcumin per diet) obviously inhibited the damage of liver tissue structure caused by CCl₄ and resulted in the liver tissue structure returning to normal. Overall, the results indicated that appropriate dietary curcumin supplementation could enhance the growth (especially 60 and 120 mg/kg curcumin per diet) of fish and effectively protect the liver against CCl₄-induced injury (especially 120 mg/kg curcumin per diet). Therefore, curcumin can promote the growth of fish and increase the protective effect on liver injury of fish in a certain extent. However, as a Chinese herbal medicine, curcumin is complex, we need to further study its pharmacological mechanism in detail. Especially, because curcumin is insoluble in water, easy to metabolize, and not readily absorbed by the body, we need to develop a new formula to improve its solubility, pharmacological action, and medicinal administration. With an in-depth study of its pharmacological action and further elucidating the mechanism of action, curcumin will definitely play a bigger role in the treatment of fish diseases in the future.

Abstract:Berberine was one kind of Chinese herbal additive, which extracted from the stems and roots of various Berberis species, such as (Huanglian) and so on. It possessed a series of biological activities, including antioxidant, anti-inflammatory, reducing blood glucose and lipid level. In addition, it had been proved that berberine could improve lipid deposition and glucose metabolism in diabetes. Recently, berberine had been applied to aquaculture diets as an herbal feed additive in Asian area. Our laboratory conducted many vivo experiments to study the function of berberine. The current study demonstrated that berberine added in high-fat diet could mitigate oxidative stress, inhibit the apoptosis and enhance disease resistance of fish. However, it was found that the growth performance of fish fed with normal diet supplied berberine was significantly enhanced but immunity was not improved. In order to solve this problem, the study was aimed to explore the effect of different concentrations of berberine on cell activity, oxidative stress and apoptosis of grass carp () hepatopancreas cell in vitro experiment. Cultured cells were treated with different concentrations of berberine (0, 5 μmol/L, 25 μmol/L, 50 μmol/L, 100 μmol/L) for 0, 6 h, 12 h, 24 h. Then, the optimal concentration of berberine was showed by detecting cell viability in CCK-8 assay. Results showed that the cell activity was affected by interaction of time and berberine concentration (<0.05) affected cell activity in a dose-dependent manner. According to the cell activity data, the remaining indicators were selected to data of 12 hours for analyzing related indicators, including glutamate oxalate transaminase (GOT) and glutamate pyruvate transaminase (GPT) activity, malondialdehyde (MDA) and ROS content, apoptosis, caspase-3, caspase-8 and caspase-9 mRNA expression. Compared with control group, GOT and GPT activity in group of 100 μmol/L berberine concentration were significantly (<0.05) increased. Meanwhile, the content of MDA and ROS were significantly increased with increasing concentration of berberine. The tendency of content of MDA and ROS were same as that of GOT and GPT activity (<0.05). In addition, compared with control group, the total cell apoptosis rate in group of 25 μmol/L and 50 μmol/L berberine concentration were significantly (<0.05) increased while cell apoptosis rate in 100 μmol/L berberine group was significantly (-3 in group of 50 μmol/L and 100 μmol/L berberine group were significantly enhanced (<0.05). In summary, the safety concentration of berberine in stimulating fish liver cells should be 25-50 μmol/L. When the concentration was more than 50 μmol/L, it would have toxicity to normal growth cells and affect cell function.

Abstract:Based on four bottom trawl surveys conducted in the Bohai Sea from August 2009 to May 2011, 2979 stomach samples of small yellow croaker with body lengths of 38-218 mm were collected. Stomach contents analysis, the Kruskal-Wallis test and the cluster analysis were used to study their feeding habits and ontogenetic, temporal and spatial variations. The results indicated that small yellow croaker fed on more than 40 prey species. Euphausia pacifica, were the dominant prey item. With the increase of fish size, there is a corresponding change in the feeding strategy of the Bohai Sea small yellow croaker. According to the feeding intensity, as indicated by the percentage of empty stomachs (PES) and mean stomach fullness index (MSFI), MSFI was low at the smaller fish size, resulting in the small yellow croaker increasing the feeding intensity as observed by the low PES. With the increase of fish size, the feeding intensity was enhanced by increasing MSFI. According to the prey items, the mean number of prey per fish decreased significantly with the increased fish size, while the mean weight of prey items per fish increased. According to diet compositions, the feeding habits of small yellow croaker had significant ontogenetic variations. Small yellow croaker less than 60 mm in body length mainly fed on the zooplanktivores copepoda, euphausiacea and mysidacea. At 60-99 mm long, it mainly fed on demersal shrimps and copepoda. The frequency of demersal shrimps in the food increased gradually with the increasing fish size, whereas the frequency of copepod decreased. Thus, fish with a 60-99 mm body length belonged to the generalist predators group. At 100-119 mm long, it belonged to shrimp predators group, mainly feeding on demersal shrimps at a frequency of more than 60%, and fish. It still mainly fed on demersal shrimps and fish at greater than 120 mm in body length with the frequency of fish in the food increasing gradually, and ultimately more than the frequency of demersal shrimps (beyond 60%). Thus, fish greater than 120 mm long included shrimp/fish predators and piscivores. The feeding intensity varied significantly across seasons. The feeding intensity of spring was lowest and the feeding intensity of summer and autumn were higher. The difference in the feeding rate was higher (PES was lower) in summer and the feeding amount (MSFI) was higher in autumn. Seasonal variations were also discovered in diet composition. were the dominant preys in spring, were the dominant preys in summer, whereas was the dominant prey in autumn. By analyzing historical data, we found that the feeding habits of small yellow croaker in the Bohai Sea were closely related to the composition and abundance of dominant prey organisms. The temporal and spatial variations in the feeding habits of small yellow croaker is closely related to the fluctuation of dominant prey species in the environment.

Abstract:In order to provide data support for stock assessment and fishery management of , the spatiotemporal variations of the length-weight relationships for this species were studied, based on the survey data from the bottom-trawl surveys in Shandong coastal waters in the four seasons:autumn (October 2016), winter (January 2017), spring (May 2017) and summer (August 2017). One generalized linear model and 9 linear mixed effect models were constructed to study the length-weight relationships () and their spatiotemporal variations. According to the principle of minimum AIC value, the most complex linear mixed effect model (i.e. regions and seasons have random effects on parameter ) was the best. Cross validation results showed that the prediction effect of this model is the most reliable one among the 10 candidate models. -test between the best model and the generalized linear model revealed that the spatiotemporal variations of the length-weight relationships were significant ( value of the individuals in spring was the largest, followed by autumn and winter, and finally summer; the trend of the increased with latitude, without an obvious trend for depth, which might be resulted from limited sample size. The fixed value of (2.77) was less than 3, indicating the negative allometric growth pattern of . The fatness was negatively related to length and tended towards a slender body. This study showed that season and latitude have significant influences on the length-weight relationships of . The mixed effect model could reflect the heterogeneity of regions and seasons in a single model more accurately and conveniently, which could be applied to more heterogeneity studies of fish life history traits.

Abstract:is widely distributed in the Bohai Sea, Yellow Sea, and East China Sea. The species is of commercial importance, with an annual catch of over 100000 t in the Bohai and Yellow Seas. As the recent recession in traditional fishery resources becomes more serious, plays an increasingly important role in Chinese fisheries. Studies on the biological characteristics of were reported in the 1980s and 1990s in China, but have been rare in recent years. Information on biological characteristics such as growth and maturity may change with the recession of fishery resources. Therefore, better knowledge of biology is needed to inform the scientific management of this species in the China Sea. The biological characteristics of were studied on the basis of 350 samples of spawning stocks collected from April to May 2016 and April 2017 in the Bohai and Yellow Seas. The fork length of this spawning stock ranged from 406 to 1010 mm, and the body weight ranged from 533 g to 7245 g. The ages of ranged from 1+ to 10+ years, in which individuals of 1 and 2 years old accounted for 39.2% and 33.7% of the population, respectively. The parameters of the von Bertalanffy growth equation, , respectively. The sex ratio was 1:1.49 (female:male) in the survey area. There are more males than females under the age of 3 years, and more females than males after age 3. The reproduction of occurs from April to June and is concentrated in April and May. Individual absolute fecundity ranged from 91.6 to 1275.2 thousand eggs/individual, and the mean value was 504.5 thousand eggs/individual. The absolute fecundity increased with age and fork length and then began to decline after 7 years old. The dominant prey organisms were tended to have a lower age structure, miniaturized body size, and decreased fecundity compared to previous studies, and there were substantial changes in their dietary composition and breeding season.

Abstract:Knowledge about swarm dynamics and underlying causes is essential to understand the ecology and distribution of . We examined swarms across the South Orkney Islands in March and April 2017 using the Simrad EK60 (38 and 120 kHz) echosounder, concurrent with net sampling. The acoustic data were analyzed by applying a swarm-identification algorithm, and then filtering out all non-krill targets. A total of 2539 krill swarms with swarm characters including swarm height and length, packing density, swimming depth, and inter-swarm distance were extracted, of which 1389 were daytime swarms and 1150 night swarms. Compared with those of the night swarms, krill aggregated in deep waters during the daytime with lower packing density and smaller inter-swarm distance. There were significant differences between day and night krill swarms. Through the multivariate analysis, the krill swarms were divided into three categories, which differed in both their dimensions and packing density. Group A presented the highest swarm density[(19.24±27.00) ind/m³], Group B swarms presented the deepest distribution depth[(174.74±53.30) m], Group C presented the largest swarm area[(2868.62±2149.75) m²] with the longest swarm length[(258.76±322.88) m]. There was no significant difference in swarm length between Groups A and B and no significant difference in swarm depth between Groups A and C. Group A swarms were mainly distributed in deep water areas in the north and northwest regions of the South Orkney Islands at a depth of >1000 m, and mainly occurred during daytime. Groups B and C swarms were distributed throughout the survey area; Group B swarms were aggregated in the continental shelf at a water depth of <200 m. The results suggest that the majority of krill were contained within a minor fraction of the total number of swarms, and there was a positive correlation between packing density and inter-swarm distance. The results also provide valuable information on the distribution of krill swarms in this area and basic data for the current feedback krill resource management of Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). In the future, studies on the correlation between krill swarms and external factors, such as environmental factors and predators, can help understand the swarm structure and formation mechanism more accurately and predict the distribution of krill resources.

Abstract:Trachinotus ovatus) causing rot body disease in the deep-sea cage aquaculture area in Houshui Bay, 2016. Building a more rapid, accurate, and convenient technical detection analysis rather than the conventional methods, for example, physiological and biochemical identification, 16S rRNA gene sequence analysis, and immunodiagnostic technique, which are labor-intensive and time-consuming, is of great importance to disease prevention and control. According to the principle of the LAMP method, real-time loop-mediated isothermal amplification (RT-LAMP) techniques were developed for detection of fish pathogenic V. harveyi QT520 after adding fluorescent dye SYTO-9 to the reaction system. The results showed that this method could effectively distinguish the , and the detection limit of this method for with both of pure cultures and DNA concentrations were found to be 10³ CFU/reaction and 100 fg/uL, being equivalent to real-time PCR (RT-PCR), which was 1000 and 10 times that of general PCR, respectively. Furthermore, the detection process through this method only took 40 min and the results could be displayed on the LCD panel. Thus, it has high specificity, high sensitivity, and the interpretation of results is simple and objective. Furthermore, it has simple operation characteristics, being suitable for application and promotion in basic levels of fishery technology promotion departments and fishery professional cooperatives.

Abstract:The cDNA and genome of Frizzled1 from was cloned by the RACE technique. The full-length cDNA of -Fzd1 was 2387 bp, containing an open reading frame (ORF) of 1761 bp encoding a poly-peptide with 586 amino acid residues. SMART analysis showed that -Fzd1 shared common features of the Frizzled family, including a putative signal peptide with 23 amino acid residues, the N-terminal extracellular cysteine-rich domain (CRD) with 10 conserved cysteine residues, a transmembrane region composed of seven transmembrane segments, and a C-terminal "tail" with five key phosphorylation sites. The deduced amino acid sequence of -Fzd1 had high homology and may share a common ancestor with that of Frizzled1 in Cnidaria from Nematostella vectensis, and that of Frizzled1, Frizzled2, and Frizzled7 in vertebrates, including Danio rerio, by the multiple sequence alignment and phylogenetic analysis. None of the introns were included in the genome of -Fzd1. Quantitative real-time PCR analysis revealed that the expression of -Fzd1 transcript was detected in all four developmental stages. The mRNA expression level of <0.01) of that in the medusa. Furthermore, the -Fzd1 transcript was revealed in the tentacle and occurrence sites of strobilation in strobila by whole mount -Fzd1 should be involved in the regulation of asexual reproduction and occurrence of strobilation in .

Abstract:Describing predator-prey relationships among organisms is essential in the food web studies of aquatic ecosystems. The traditional method of food web research is based on the morphological observation of the stomach contents. With the development of science and technology, new methodological approaches such as stable isotope analysis, fatty acid profiling, and DNA barcoding effectively avoid the limitations of stomach content analysis, provide a deeper understanding of the feeding characteristics of aquatic organisms, and have been widely used in feeding ecology studies. In this paper, the development trend of the research methods used to study aquatic food webs was introduced. The current status of stable isotope analysis, fatty acid profiling, and DNA barcoding techniques, combined with stomach content techniques, were reviewed, focusing on the application and development of the four methods, the comparison of their advantages and limitations, their applicable scope and assumptions, and the requirements for available experimental samples. These areas are discussed in terms of the assumptions made when applying these techniques to the study of aquatic ecology and the combinations of these techniques that investigators use for different study objectives. Recommendations are made for future aquatic feeding ecology experimental work that would improve understanding of food web structures and the functioning of aquatic ecosystems. As the traditional research method, stomach content analysis remains an irreplaceable technique in the study of feeding ecology. Stable isotopes, fatty acid profiling, DNA barcoding, and other molecular techniques are strong complements to stomach content analysis and provide additional useful information for reconstructing aquatic food webs, which would be helpful in ecosystem-based fishery management.