Abstract:Rhomboid domain-containing protein 3 (Rhbdd3) has been identified as playing an essential role in innate mammalian immunity. However, the products and functions of the gene in aquatic animal cells, especially its antiviral characteristics, remain unknown. Spring viraemia of carp virus (SVCV) is a highly pathogenic agent, responsible for significant mortalities in several economically important Cyprinidae fish species. Infectious pancreatic necrosis virus (IPNV) is the causative agent of an acute, highly contagious, and destructive disease named infectious pancreatic necrosis (IPN). The cumulative mortality of young infected salmon can exceed 90%. SVCV and IPNV are difficult to eradicate and there are currently no effective therapeutic strategies or drugs for either viruses. Thus, new interventions need to be developed. Innate immunity also plays an important role in the protection of fish against early viral infections. In the present study, we aimed to obtain the coding region of the common carp ( gene. Furthermore, we sought to determine the function of Rhbdd3 in fish cells and explore the effects of Rhbdd3 on aquatic viral infections. Firstly, the gene of common carp was amplified by RT-PCR, with primers designed according to the conserved regions of the predicted fish gene was cloned into the eukaryotic expression vector pCI-neo, to construct the pCI- plasmid. Next, EPC (Epithelioma Papulosum Cyprinid) and CHSE-214 (Chinook Salmon Embryo) cells were transiently transfected with pCI-, and the expression of Rhbdd3 was detected using western blot analysis. The viability of the transfected cells was examined at 12 h, 36 h, and 72 h post transfection with a CCK-8 kit. SVCV and IPNV infections were conducted at 24 h post pCI- transfection. Viral productive replication was assessed via immunofluorescence microscopy, western blot, and RT-qPCR analyses. The results indicated that the ORF of common carp is 1050 bp, which encodes a putative peptide of 349 amino acids. Overexpression of Rhbdd3 was verified using western blot analysis post pCI- transfection, and the overexpression did not affect the viability of EPC and CHSE-214 cells. Meanwhile, the immunofluorescence microscopy, western blot, and RT-qPCR detection results all showed that Rhbdd3 overexpression inhibited SVCV and IPNV infections. Collectively, our data indicate that Rhbdd3 can inhibit fish viral infections without affecting fish cellular viability. The results presented in this study will facilitate the development of aquatic broad-spectrum antiviral drugs and provide a new insight into the function of Rhbdd3.

Abstract:is a single-season breeder, which dies soon after reproduction. It is important to study the reproduction of . Male size plays an important role in mating competition. This study set out to explore the differences in courtship, competition, and mating behavior between different size male . An experiment with three treatment groups (1L1S, 1L2S, and 1L4S; where L and S represent large- and small-size males, and the number represents the amount of experimental male ) was conducted. A video camera was used to record the reproductive behaviors of during the experimental process. Four different types of behaviors (mate behavior, aggressive behavior, submissive behavior, and accompany behavior) were analyzed over a 2-day period. It was shown that exhibited clear territorial and guarding behaviors during the breeding season. With the increasing proportion of smaller males in the treatment groups, the dominance hierarchy of the large-sized males changed, in which the duration of guarding behaviors and number of successful mating attempts decreased among the large males, while those for the smaller males increased. When there were not enough smaller males in the treatment group, the larger males often actively attacked the smaller ones. When the number of smaller males increased, they actively attacked the larger males to strive for the chances of guarding and mating. The results show that male size has a significant influence on competition and mating behaviors, which potentially corresponds with the determination of male sizes and male-female ratio during breeding. These results may improve the breeding efficiency and contribute to the stock enhancement and development of .

Abstract:In this study, oocyte characteristics were observed during ovarian development of the spotted steed ( sampled from 2015 to 2017, under light and scanning electron microscopy. A total of 190 fish were sampled, with body length between 7.12 cm and 32.21 cm and body weight between 10.55 g and 330.22 g. Our results showed that oocyte development can be divided into five distinct stages. Oocytes in phase I are considered to be in an oogonial proliferation stage. The second phase of oocyte development for the spotted steed is equivalent to the primary growth stage, and this oocyte development stage is characterized by the presence of a follicular layer. Stage III is marked by the appearance of cortical vacuoles, and the zona radiata (ZR) can be differentiated from the follicular layer. Stage IV oocytes enter the late growth stage, and the yolk granules increase. In electron micrographs, the pore-like structures of the ZR were clearly observed, which are believed to be related to nutrient accumulation. Stage V oocytes are characterized by mature oocytes and a completely degenerated nuclear membrane. Following ovulation, the space between the oocyte and ovary membrane is evident. During the reproductive season, the gonadosomatic index (GSI) ranged from 13.78% to 17.04%. The obtained data will consequently facilitate the artificial propagation and breeding of this commercially important species.

Abstract:Animals that inhabit intertidal areas long-term can sense the local tidal rhythm, forming a tidal memory. However, to date, no studies have investigated the mechanism of tidal rhythm sensing in in the laboratory using low-frequency tide sounds. The cDNA sequence of the gene was cloned by RACE-PCR, after which bioinformatics analysis and qRT-PCR experiments were performed. The results showed that the full-length cDNA of the gene was 2321 bp (366 bp 5' non-coding region (UTR), 1337 bp 3' non-coding region (UTR), and 618 bp open reading frame (ORF), which encoded a total 206 amino acids. The gene that encodes polypeptide chains was predicted with an atomic number of 3165, a molecular weight of approximately 23029.64 kD, a theoretical isoelectric point of 4.64, a molecular formula of C₁₀₁₈H₁₅₄₄N₂₇₄O₃₂₀S₉, and an N-terminal signal peptide composed of 29 amino acids. The phylogenetic tree was constructed via amino acid sequence alignment. The results suggest that the like gene of , which is consistent with traditional morphological classification. The distribution of genes in different tissues was detected using qRT-PCR. The results indicated that , but the expression of ganglion was significantly higher than dorsal skin, pleopod, intestines, liver, mouthparts, and albumen gland (<0.05). We speculated that it may be involved in the plasticity regulation of the ganglion system. The quantitative fluorescence results indicated that the genes were highly expressed, underlying the stimulation of low frequency sound waves at 25 Hz and 50 Hz for 12.4 h, respectively, for which it was presumed that could sense the 25-50 Hz sound frequency. This may be related to the tidal memory formed by the long-term immersion in the 12.4 h half-day tidal cycle rhythm in the intertidal zone. This study will lay the foundation for further understanding of the molecular mechanisms of sensing tidal rhythm, and provide a basis for exploring the environmental adaptation mechanism of marine animals from ocean to land evolution.

Abstract:China has become the largest producer of sturgeon in the world. Hybrid sturgeon[)] is one of the dominant aquacultures organisms in China. However, the feeding strategy for hybrid sturgeon has not been clearly outlined. To determine the optimum feeding rate and frequency for juvenile hybrid sturgeon, an experiment was conducted to study the effects of different feeding rates and frequencies on the growth performance, body composition, and biochemical parameters of juvenile hybrid sturgeon. The fish were randomly assigned into 10 groups with 3 replicates per group, including 5 groups (initial body weight:335.87±0.82 g) treated with different feeding rates (0.4%, 0.8%, 1.2%, 1.6%, and 2.0%) and another 5 groups (initial body weight:334.77±1.06 g) treated with different feeding frequencies (once, twice, three times, four times, and five times a day). After the 10-week feeding trail, the increased feeding rate significantly improved the weight gain rate (WGR), specific growth rate (SGR), hepatosomatic index (HSI), viscerosomatic index (VSI), and condition factor (CF) of hybrid sturgeon (<0.05). In addition, the crude protein and lipid content in muscle, crude lipids in the liver, pepsin activities, serum alanine aminotransferase (ALT), and aspartate aminotransferase (AST) also increased significantly with the increasing feeding rate (<0.05). However, the feed efficiency (FE), whole body moisture, and muscle moisture decreased significantly with the increasing feeding rate (<0.05). Meanwhile, the whole body crude lipids, total protein (TP), albumin (ALB), and high density lipoprotein cholesterol (HDL-C) in the serum firstly increased with the increasing feeding rate, but then decreased (<0.05). On the other hand, the feeding frequency had no significant effects on the WGR, SGR, or FE of hybrid sturgeon after the 10-week feeding trail (>0.05). The VSI, CF, and content of whole body crude lipids of the fish fed once a day were significantly lower than that of the other groups (<0.05). In addition, a significantly higher content of the whole body crude protein was observed in the fish fed twice a day compared with that of the other groups (<0.05). No significant effects of the feeding frequency were found on the digestive enzyme activities in the stomach and intestine or the serum biochemical parameters, except for the glucose level (>0.05). Overall, according to the results of this study, the optimum feeding strategy with regards to the feeding rate and feeding frequency for juvenile hybrid sturgeon (300-600 g) was suggested to be 1.2%-1.6% of the body weight with meals twice per day.

Abstract:With the improvement of people's living standards, fish has become more popular as a high-protein, low-fat food. As cold-water fish, salmon and trout have gradually attracted people's attention owing to their taste and nutritive value. Atlantic salmon (), and golden trout () are three common species of culture, but the differences concerning the flesh quality need further study. To evaluate the flesh quality of the three species, the texture characteristics and pH value of the flesh were analyzed. The crude protein, crude fat, ash, and moisture of the flesh were assayed using biochemical analysis methods. The muscular texture profile parameters were analyzed using a texture analyzer. The results showed that the moisture content in the flesh of the Atlantic salmon, triploid rainbow trout, and golden trout was 62.91%, 67.15%, and 73.02%, respectively. The crude protein content was 22.39%, 21.03%, and 22.11%, respectively. The crude fat content was 14.64%, 17.16%, and 5.11%, respectively. Finally, the collagen content was 0.4986%, 0.4583%, and 0.5626%, respectively. The results showed that the flesh of Atlantic salmon, triploid rainbow trout, and golden trout has high protein, low fat, and low collagen. There were no significant differences in terms of the drip loss, >0.05). The hardness and chewiness of the three species were in the order of:Atlantic salmon < triploid rainbow trout < golden trout. Whilst the pH value showed the opposite results (<0.05). There were no significant differences in terms of the ash, thaw loss, cooking loss, resilience, springiness, and value between the Atlantic salmon and triploid rainbow trout (>0.05). However, the ash, cooking loss, and resilience of the Atlantic salmon and triploid rainbow trout were less than those of the golden trout ( value were higher than those of the golden trout (<0.05). The essential amino acids/total amino acids (EAA/TAA) value in the flesh of the Atlantic salmon, triploid rainbow trout, and golden trout was 42.28%, 41.84%, and 41.63%, respectively. The essential amino acids/non-essential amino acids (EAA/NEAA) value was 73.25%, 71.94%, and 71.32%, respectively. Additionally, both of these were in accordance with the FAO/WHO evaluation standards. Moreover, 22 fatty acids were detected, of which most were unsaturated. The total DHA and EPA content was 6.70%, 6.91%, and 8.95%, respectively, showing that triploid rainbow trout and golden trout are superior to Atlantic salmon in terms of the fatty acid composition. In general, these results showed that Atlantic salmon and triploid rainbow trout have a similar flesh quality and are superior to golden trout. In addition, this study provides basic scientific data for the flesh quality of these fish.

Abstract:Anesthetics have been used in aquaculture to minimize the stress and damage of during harvesting, grading, transportation, spawning induction, and handling. In this study, the effects of several anesthetics, including magnesium sulphate, magnesium chloride, ethanol, eugenol, MS-222, manganese(II) chloride, lidocaine, procaine hydrochloride, ethylene glycol phenyl ether, L-menthol, benzocaine, and 2-trichloromethyl-2-propanol, on adult were tested at a temperature of (18±0.3)℃. The body weight range of adult octopuses was 138-151 g. Six concentration gradients were designed for each reagent. The results showed that magnesium sulfate, eugenol, MS-222, manganese(II) chloride, lidocaine, procaine hydrochloride, ethylene glycol phenyl ether, l-menthol, benzocaine, and 2-trichloromethyl-2-propanol had no anesthetic effects on . In solutions of 0.2-0.6 mL/L ethylene glycol phenyl ether, 0.05 g/L and 0.06 g/L L-menthol, 0.5 g/L benzocaine, 40 μL/L eugenol, and 50-500 mg/L MS-222, presented convulsions, rigidity, and ink-jets, which indicate toxic effects. Moreover, solutions of 2 mL/L ethanol and 2 g/L magnesium chloride had no anesthetic effects on . In solutions of 4-40 mL/L ethanol and 4-40 g/L magnesium chloride, was found to show anesthetic responses, such as gradually turning white in color, a decreased respiratory rate, weak swimming vitality, decreased wrist movement, and lack of response to external stimuli. Based on the different body color changes, swimming dynamic strengths, breathing rates, wrist activity strengths, sucker suction strengths, wrist responses to stimuli, and whether an upside-down individual can return to normal, the level of anesthesia was divided into five periods, whilst the recovery process was divided into four periods. Individuals in 15-35 g/L magnesium chloride and 10-40 mL/L ethanol can achieve phase 4 anesthesia, this stage is most suitable for the observations and measurements of . Individuals in phase 5 can recover quickly after being transferred into normal environment without an anesthetic. As the concentration of ethanol solution increased from 4 mL/L to 35 mL/L, the anesthesia time decreased from 128 to 8 minutes, while the recovery time increased from 5 to 26 minutes, indicating a positive correlation between anesthesia time and concentration of ethanol, and a negative correlation between recovery time and concentration of ethanol. At 40 mL/L, the anesthesia time increased due to the stress reaction of . As the concentration of magnesium chloride solution increased from 3 g/L to 35 g/L, the anesthesia time presented a gradually decreasing trend from 176 to 13 minutes, and the recovery time presented a gradually increasing trend from 6 to 116 minutes, indicating results similar to those of ethanol. Individuals in 40 mL/L of ethanol and 35 g/L of magnesium chloride could reach phase 5 anesthesia, which is characterized by a lack of breathing. in these conditions would die if not transferred in a timely manner, thus high concentrations of ethanol and magnesium chloride are lethal to . The anesthesia and recovery times for 10 mL/L of ethanol and 20g/L of magnesium chloride were the shortest, which were 26 and 40 minutes, respectively. The present study demonstrated that ethanol and magnesium chloride solutions are effective anesthetic agents for .

Abstract:Mollusks, used for analyses of genetic characteristics along the coast of Liaoning Province, are generally of enormous economic value. To study the genetic diversity and genetic differentiation of natural species, which remain unaffected by fishing and aquaculture, the trochid was used in this study. Along the coast of Liaoning Province, five populations of were sampled for the analyses of genomic SNPs and genetic characteristics using Genotyping-By-Sequencing (GBS). With a total of 1315987 SNPs detected, the observed heterozygosity values were calculated to be 0.0851-0.1161, which were generally less than the expected heterozygosity values (0.1424-0.1627), suggesting heterozygote deficiency and risk of population degradation. The loss of genetic diversity in the C4-ZH population may be due to the invasion of other species. Moderate genetic differentiation was found among the five populations. The C5-JZ population was found to have a higher genetic differentiation and lower gene flow. Three specific SNP markers were identified for the C5-JZ population. These results will contribute to the knowledge of the genetic characteristics of natural species along the coast of Liaoning Province and help to protect the coastal ecosystem.

Abstract:To explore the spawning preferences of yellow catfish () for artificial fish nests during the breeding period, preferences for different nest colors and materials were determined under different water temperatures in June to July 2018. The experimental spawning fish nests were hemispherical (25 cm in diameter and 12 cm deep). Gravel palm and plastic fish nests (4-6 pieces) were placed in the same specification. Additionally, 6-layer nylon fishing nets (30 cm×40 cm) and palm pieces of fish nests (30 cm×40 cm) were folded. In the cement tank (290 cm×120 cm×100 cm), the egg-laying preference experiment was carried out under two temperature intervals (24-26℃ and 28-32℃). The ratio of males to females in the experimental compartment was 1:1. The body length and weight of females was (167.8±19.0) mm and (99.9±21.7) g, respectively, whilst for males the body length and weight was (235.1±18.8) mm and (188.5±38.1) g, respectively. The results showed that the average number of eggs in the hemispherical brown palm (no stone) fish nest, under a water temperature of 24-26℃, was 628.49 grains/m² and the average egg attachment rate per unit area was 2.77%. The average egg attachment in the hemispherical palm (no stones) fish nest, under a water temperature of 28-32℃, was 225.48 grains/m² and the average egg attachment rate per unit area was 1.40%. After analyzing the experimental results, it was concluded that 24-26℃ is the optimal water temperature range for yellow catfish spawning. The analysis also showed that yellow catfish have a significant preference for spawning in brown fish nests (<0.05), compared to gray, pink, yellow, and green nests. Furthermore, the sticking effect of eggs on the hemispherical palm (no stone) fish nest was significant (<0.05). The diminishing preference order for other fish nests was:hemispherical palm (with stones) > flat palmettos > hanging palms > hemispherical plastics > cement pool. For sticking eggs, the top preference is the brown hemispherical palm fish nest under the water temperature environment of 24-26℃. The results of this study have important significance for guiding the artificial reproduction of yellow catfish, spawning field repair, and resource proliferation of sticky egg fish.

Abstract:A field survey of the fishes in Jiangsu reach of the Huaihe River was performed from 2016 to 2018, during which the fish community structure and diversity were analyzed. In total, 56 species were collected, belonging to 42 genera, 14 families, and 7 orders. Cypriniformes had the largest number of species, accounting for 66.07% of the total species captured. and were the first dominant species in winter, summer, autumn, and spring, respectively. The catch per unit effort (CPUE) using gill and cage nets was (1190.15±220.28) and (74.87±12.96) g/(net·d), respectively. The ranges of the Shannon-wiener index () values were 2.88-3.85, 2.75-4.74, and 0.74-0.81, respectively. Abundance-biomass curves (ABC) of the fish community indicated that the community was seriously disturbed during spring, and moderately disturbed during the other seasons. Cluster analysis showed that similarities were low (below 57.02%) in different seasons and sections. Similarity percentage analysis (SIMPER) verified this conclusion, showing that the average similarities between the fish community structures in Xuyi and Jinhu were only 41.85% and 36.23%, respectively, while the average dissimilarity was up to 71.21%.

Abstract:To understand the community structure of zooplankton offshore of northwest Hainan Island and explore the relevant environmental factors affecting their distribution, we conducted seasonal investigations in sites offshore of northwest Hainan Island in November 2016 and February, May, and August 2017. A redundancy analysis model was used to analyze the relationship between the community structure and environmental factors. Nonmetric multidimensional scaling ordination analysis was applied to test the differences between the communities. Furthermore, ANOSIM similarity testing was used to analyze the differences among the communities. A total of 215 species, belonging to 113 genus and 7 phyla, were identified, among which 134 species were present in autumn and 94 in summer. The number of identified species was relatively close between winter (113 species) and spring (111 species). The seasonal differences in the average abundance of zooplankton was significant, being highest in winter (152.43 ind/m³) and lowest in spring (64.76 ind/m³). The seasonal differences in the average biomass of zooplankton was also significant, being highest in winter (263.68 mg/m³) and lowest in spring (59.13 mg/m³). The RDA showed that the water depth, phytoplankton abundance, transparency, surface temperature, surface dissolved oxygen, and surface total nitrogen have significant correlations with the community structure of zooplankton. Among these environmental factors, the water depth was the key factor, which affected the variation in the zooplankton community structure according to the seasons. Tropical warm water species were the dominant groups in spring and summer, while offshore warm water species were dominant in autumn and winter, suggesting an ecological differentiation among ecological groups. This was mainly caused by the flow direction of the current in Beibu Bay. Compared with the same latitude (waters of Cheng Mai and Dongzhai Harbor) and a lower latitude (Sanya Bay and waters of Wanning), higher amounts of zooplankton species were found offshore of northwest Hainan Island. When compared with Beibu Bay and the coastal waters of the northern South China Sea, the number of zooplankton species in this study was lower. However, the changing tendencies of dominant groups, ecological communities, and seasonal variation characteristics were consistent among these areas.

Abstract:To date, microbial endocrinology has revealed that many microorganisms have evolved specific mechanisms to sense and respond to stress hormones. Catecholamine stress hormones have been demonstrated to stimulate bacterial growth and virulence-related gene expression. In bacteria, the QseBC two-component system is widely used in signal transduction mechanisms, which have an important impact on bacterial virulence. In this signaling system, the sensor histidine kinase QseC is a bacterial receptor for the host epinephrine (Epi)/norepinephrine (NE), which activates virulence genes in response to interkingdom cross-signaling. In NJ-35, NE exhibited the strongest growth stimulation and enhanced virulence. However, it remains poorly understood whether the QseBC two-component system is involved in the recognition and response process of NJ-35 to NE. To determine whether QseC recognizes NE and regulates bacterial virulence, in this study, we constructed a ) and a complement strain ( toxicity under NE induction. Our data provide evidence that the growth-promoting effect of NE on Δ was significantly higher than that of the wild-type strain NJ-35, and the biofilm formation ability of Δ was remarkably decreased compared to that of the wild-type strain and complement strain was completely deficient in the promotion of the biofilm formation activity by NE, revealing that QseC was necessary for NE to regulate the biofilm formation of was strikingly increased (<0.01), but still lower than that of the wild strain NJ-35 and complement strain + caused by NE, showing that except for QseC, NE could regulate the hemolytic activity of NJ-35 through another non-QseC pathway. Furthermore, NE can dramatically increase the mortality of the wild-type strain NJ-35 against tilapia, while the deletion of the gene inhibited the enhanced-virulence by NE. However, there were no significant differences in the motility, lipase activity, or protease activity between the wild type strain and mutant △ gene inhibited the NE-stimulated growth and virulence of NJ-35, indicating that QseC could regulate the pathogenicity of by recognizing and responding to NE. It is crucial for our study to comprehensively understand the pathogenesis of and the mechanisms behind the interactions between pathogens and their hosts. This study provides the theoretical foundations for new technologies for prevention and control strategies against bacterial diseases.

Abstract:To further understand the effects of light on the brood size of was statistically analyzed under different light intensities which were normal light (12L:12D) and complete dark. The results show that the egg-holding rate of the normal light group was (95.8±3.6)%, which was significantly higher than that of the dark group at 0 (<0.05), indicating that an appropriate light intensity had a promoting effect on the brood size of The effects of different biological diets on the survival rate and development period of larvae were also analyzed, finding that the larvae survival rate was (38.3±2.3)% and the zoea larvae developed into post-larvae after 25-29 d in a mixed diet group ( Daday). In a single diet group (), the larvae survival rate was (26.8±4.9)% and the zoea larvae developed into post-larvae after 37-41 d. The survival rate and development time of larvae in a mixed diet group were significantly higher and shorter, respectively, than those of a single diet group (Moina mongolica Daday was more beneficial to larva survival and development of alone. In addition, the present study also described nine zoea stages of in detail. This study is significant for enriching the reproductive biology theory and conducting artificial propagation of .