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Abstract:Parameters related to the seawater, sediment, marine biological, and protected biological resources of Qianliyan national aquatic germplasm reserve were surveyed and evaluated from 2015 to 2018, and the genetic diversity of Apostichopus japonicas (the main protected object) was also studied in 2018. Our results showed that all of the measured parameters met the seawater evaluation standards, but the nitrogen to phosphorus ratios were far higher than the Redfield ratio of 16, indicating that phosphate was relatively deficient compared to nitrogen. Based on the eutrophication evaluation model, the surveyed area was classified as first-grade nutritionally poor. The observed sediment parameters met the Class 1 national sediment quality standards. The marine biodiversity indices were mostly at a high level (H′≥2); however, the diversity of small zooplankton was low in August 2015 (H′=0.93) and the diversity of macrozooplankton was low in May 2016 and May 2018 (H′=0.82, H′=0.22). Comprehensive evaluation showed that the marine ecological environment of the reserve was good and met the functional requirements. The haplotype diversity index of A. japonicas as the main protected object was 0.976, and the nucleotide polymorphisms index was 0.033, indicating that the genetic diversity of A. japonicus was high. The biological resource of A. japonicas was less than the amount when the reserve was built, and the biological resource of Haliotis discus hannai, another main protected object, has been extremely low in the last few years. It is therefore necessary to take strong measures to carry out reserve management and resource restoration work as soon as possible in Qianliyan national aquatic germplasm reserve.

Abstract:To assess the Xiaoshi Island Apostichopus japonicus national aquatic germplasm reserve, parameters related to the water environment, sediment environment, marine ecology, protected biological resources, and genetic diversity of A. japonicus from 2012 to 2018 were examined. The condition of the reserve was evaluated by several indices, including the single factor pollution index (Pi), organic pollution index (A), biodiversity index (H′), haplotype diversity index, and nucleotide diversity index of the mitochondrial DNA D-loop sequence. During 11 cruises, all of the observed parameters met the seawater evaluation standards, except for the dissolved inorganic nitrogen concentrations, which were greater than the established standards in May 2016 (Pi = 1.08) and August 2017 (Pi = 1.31). This indicates that the water was polluted by organic matter (A = 1.001) in August 2017. The observed sediment parameters met the Class 1 national sediment quality standards. The marine biodiversity indices were high (H′ ≥ 2). However, the phytoplankton diversities were low in May 2016 (H′ = 0.45) and August 2017 (H′ = 0.28), and the small zooplankton diversity was low in May 2018 (H′ = 0.77). The biological resources in the reserve area were rich. The number of A. japonicus per unit square area gradually increased from ~2 to 3~5. A. japonicus genetic diversity was high in 2012 (haplotype diversity index = 0.995, nucleotide diversity index = 0.039) and 2018 (haplotype diversity index = 0.993, nucleotide diversity index = 0.037), and there were no significant genetic differences between the groups. Overall, the marine ecological environment and aquatic germplasm resources in the reserve are well-protected. However, it is necessary to prevent future risks associated with dissolved inorganic nitrogen contamination.

Abstract:One of the main problems faced by the aquaculture industry is the discharge of marine aquaculture tailwater. Constructed wetlands may work as a comprehensive water treatment technology, effectively removing pollutants such as nitrogen and phosphorus in aquaculture tail water. For the proper implementation of constructed wetland technology, hydraulic load conditions must be optimized. The treatment effect of vertical flow constructed wetland system on the tail water of Paralichthys olivaceus was studied under three hydraulic loads (V1=0.50 m/d, V2=0.19 m/d, V3=0.10 m/d). The treatment effect of the system for the main pollutants in the aquaculture tailwater was significantly different under three hydraulic loading conditions. When the concentration of chemical oxygen demand (COD) in the influent water was relatively low, the removal rate was also low, with a peak removal rate of only 36.25%. The effect of hydraulic loading on the removal rate of COD was not obvious. When the hydraulic load was 0.50 m/d, the removal rate of total nitrogen (TN) was only 49.50%; however, when the hydraulic load was 0.10 m/d, the TN removal rate was 85.90%. The removal rate of active phosphate (PO43–-P) was less affected by hydraulic load, showing a removal rate of more than 77%. Hydraulic load affects the removal effect of nitrogen and phosphorus in the system; for example, in the downstream unit the removal rate of nitrogen pollutants was more than 80%, whereas in the upstream unit, nitrate nitrogen (NO3–-N) or nitrite nitrogen (NO2–-N) accumulated under high hydraulic loads. The adsorption and conversion of PO43–-P mainly occurred in the upper and middle layers of the downstream unit; the larger the hydraulic load, the closer the adsorption and conversion of PO43–-P was to the rear of the system.

Abstract:In recent years, environmental DNA (eDNA) metabarcoding has been widely used in the field of biological investigation, which includes species detection and biodiversity assessment. eDNA metabarcoding has the potential to rapidly assess species abundances in communities, making it a promising investigation tool in resource conservation and management. Although previous reports concerning eDNA metabarcoding found that the high-throughput sequencing (HTS) reads were related to the biomass in the natural environmental sample, a clear quantitative relationship was not found in this study. In the field and laboratory, the enrichment efficiency of eDNA is difficult to evaluate. Meanwhile, primer bias inevitably occurs in the eDNA amplification process, resulting in uncertainty in the eDNA HTS results, which restricts the application of eDNA metabarcoding for biological resource investigations. Assuming that the eDNA is completely recovered, and there is no primer bias during PCR amplification, an ideal state for deciphering whether there is a linear relationship between the eDNA and HTS reads is created. In this study, under controlled conditions in the laboratory, a sister group was selected (Penaeus vannamei and Penaeus merguiensis) and their DNA samples were mixed in different proportions to simulate eDNA samples enriched from natural waters. In this way, the recovery of the sample and primer bias was at optimal levels. Then, this eDNA template was used to explore the accuracy of eDNA metabarcoding in detecting species biomass. The results showed that when the concentration ratio of the DNA templates of two species was 1:1, the HTS ratio of the two species was 13/24 (P. merguiensis/ P. vannamei). Therefore, even between the closest relatives there is still a slight primer bias (primer migration rate: 1.5%). At the same time, the HTS results from the seven test groups showed an obvious linear relationship between the composition of eDNA in the water and the number of high-throughput sequencing reads, that is, y=0.0716x+0.7043 (r2=0.9824). In summary, this study provides direct evidence to verify the feasibility of eDNA metabarcoding in monitoring aquatic biological resources, and also provides ideas for the subsequent quantitative study of DNA metabarcoding.

Abstract:This study aimed to explore the pathogenic mechanism of the iridescent virus and provide the theory basis for clinical diagnosis and treatment in Epinephelus lanceolatus. The full-length E. lanceolatus interferon-stimulated gene 15 (isg15) was obtained by PCR and rapid amplification of cDNA ends (RACE). The full-length cDNA of isg15 was 910 bp, including an open reading frame (ORF) of 468 bp, which encoded a polypeptide of 155 amino acids. The molecular mass of the deduced amino acid sequence was 17.09 kDa, with an estimated pI of 9.33. Conserved domain analysis revealed that the isg15 protein of E. lanceolatus contained two ubiquitin-like domains, and the C-terminal had a highly conserved motif of "Leu Arg Leu Arg Gly Gly (LRLRGG)". Sequence and phylogenetic analyses showed that the amino acid sequence of isg15 in E. lanceolatus had the closest identity to Epinephelus coioides, with a similarity of approximately 88.24%. In addition, the homologous similarity of the E. lanceolatus isg15 with Scophthalmus maximus and Larimichthys crocea was 61.18% and 60.59%, respectively. Real-time quantitative PCR was used to detect the expression patterns of the isg15 gene in the healthy tissues of E. lanceolatus and the changes in the spleen and kidney at different times after infection with the iridovirus. The results showed that the isg15 gene was mainly expressed in the blood of E. lanceolatus and was highly expressed in various immune-related tissues, such as the liver and kidney. Upon induction with iridovirus, isg15 gene expression was up-regulated in the kidney and spleen, and reached a peak at 72 h, indicating that isg15 may play an important role in the immune response of E. lanceolatus against viral infection. In this study, the analyses and expression patterns of isg15 in E. lanceolatus were studied, which is helpful to further understand the antiviral regulatory mechanism of isg15 in teleosts, and provides a theoretical basis for the disease-resistant molecular breeding of E. lanceolatus.

Abstract:To better understand the effects of pyramiding advantageous genotypes of the growth-related molecular markers in grass carp (Ctenopharyngodon idella), ten molecular markers related to growth traits were selected from our previous studies, located in apoA-I-1 (apoprotein A-I-1), PKL (pyruvate kinase L), CPA1 (carboxypeptidase A1), CS (citrate synthase), Aldo-B (aldolase-B), SLα (somatomammotropin-α), and MYH (myosin heavy chain). The genotype of each marker in forty-eight grass carp was analyzed, and two parents with the most advantageous pyramiding genotypes were selected to create a family. Seven-month-old individuals (n=382) were randomly sampled from the second filial generation. The results showed that the number of advantageous genotypes varied (0~7), and the corresponding number of individuals was 44, 67, 83, 85, 44, 38, 15, and 6. The average weight of the advantageous genotypes was 129.66, 144.45, 151.33, 153.53, 154.77, 160.50, 167.50, and 176.67 g. Correlation analysis showed that the pyramiding number was positively correlated with the growth traits. Further analysis showed that the average number of advantageous genotypes was 2.58, which was improved compared to the average number in the parent group (1.00). These results indicate that the growth traits of grass carp can be improved by aggregating the advantageous genotypes. This study also provides a theoretical basis for gene pyramid breeding in grass carp.

Abstract:Sinibrama taeniatus is a rare and unique small economic fish found in the upper reaches of the Yangtze River, including the Qinjiang, Qingyi, Jialing, and Dadu Rivers. In recent years, due to the Three Gorges Project and overfishing, wild populations of S. taeniatus have decreased sharply. Water temperature is a critical factor for newly hatched larvae, significantly affecting growth, differentiation, and survival. Determination of the optimal water conditions for S. taeniatus growth performance is essential to maximize production. To explore the effects of temperature on the growth and survival of S. taeniatus larvae and juveniles, an experiment was conducted at 16℃, 19℃, 22 ℃, 25℃, 28℃ and 31℃. The entire developmental process was divided into four stages: Larvae feeding, disappearance of the yolk sac, appearance of the scales, and intact scales. The length of each stage (in days) was counted, and the growth parameters such as total length and weight were measured. The results showed that the development process accelerated with increasing water temperature. The time to intact scales in the 28℃ and 31℃ groups was shorter than in the other temperature groups but did not differ from the 25℃ group. At 80 days of development, the body weight of S. taeniatus in the 25℃ and 28℃ groups was significantly heavier, especially in the 28℃ group. With increasing temperatures, the survival rate of S. taeniatus larvae and juveniles initially increased and then decreased. The survival rate was higher at 22℃~28℃, and the composition survival rate was highest at 25℃. The correlation coefficients of the fitting function between total length (L) and the days after hatching (D) were greater than 0.99, indicating that a cubic growth function properly reflects growth at different temperatures. Based on the development process, growth index, and survival rates of S. taeniatus larvae and juveniles, 25℃~28℃ is the optimal temperature range for S. taeniatus production.

Abstract:The innate immune system of the Japanese flounder plays a vital role in resisting the invasion of pathogens. A macrophage is a type of leukocyte found in body tissues, which are part of the innate immune system. Macrophages are crucial to the immune response and play an important role in the clearance and phagocytosis of pathogens and abnormal cells. Macrophages can not be subcultured, so it is necessary to establish an efficient technique for macrophage isolation and culture. In this study, macrophages were isolated from the head kidney of the Japanese flounder, and the obtained cells were purified by differential adherence. Trypan blue staining showed that the cell survival rate was 99.62%. Subsequently, L-15 medium (Gibco), 5% fetal bovine serum, 1% mycillin, 1% nonessential amino acids, and 30% L929 cell culture medium were used to culture the cells at 24℃. We compared the macrophages of Japanese flounder from different culture media and different serum concentrations. The results showed that the L-15 medium (Gibco) and 5% serum culture were the best. Cells cultured under this condition had a higher adherence rate, remaining above 85% after seven days of culture. Microscopic observations and Giemsa staining showed that the adherent cells had similar morphological characteristics to the macrophages, including a round shape and oval cell nuclei that were biased toward the side of the cell. Cells were identified via the macrophage-specific marker mpeg1, and the results showed that the gene was successfully amplified in the isolated cells. In this study, techniques to isolate and culture Japanese flounder macrophages were established, providing a basis to study macrophage functioning and to better understand the innate immunity of teleost fish in vitro.

Abstract:The quality of ovigerous female resources affects the development of the Litopenaeus vannamei industry, and the introduction of different ovigerous female groups from abroad can improve the ovigerous female resources in China. However, it is important to analyze the morphological characteristics of the introduced populations to breed high-propagation and high-growth L. vannamei and obtain high-quality germplasm. Here, cluster analysis, principal component analysis, and discriminant analysis are used to analyze the morphological differences of four imported L. vannamei populations. The coefficient of variation for each trait was less than 15.000%, except body weight. One-way analysis of variance (ANOVA) showed no differences in carapace width / carapace length and abdomen width / abdomen length among the four populations. Cluster analysis showed minimal differences between the PRIMO and SIS groups, and the degree of differentiation between the Ecuador and API groups gradually increased. Four principal components were constructed by principal component analysis, and the cumulative contribution rate was 88.861%. The contribution rate of principal component 1 was 32.606%, principal component 2 was 23.982%, principal component 3 was 17.569%, and principal component 4 was 14.704%. Discriminant analysis established discriminant functions for the four groups, and the discriminant accuracy P1 was 33.3%~67.1%, P2 was 30.8%~69.5%, and the comprehensive discriminant accuracy was 52.1%. The coefficient of difference for each trait ratio of the four ovigerous female populations was less than 1.28, indicating morphological differences among the four L. vannamei populations. However, the morphological differences did not reach sub-species levels.

Abstract:The effects of four socking densities [G1 (100 ind./m3), G2 (200 ind./m3), G3 (300 ind./m3), and G4 (400 ind./m3)] on the growth indices, energy metabolism content, and metabolic enzyme activity of Fenneropenaeus chinensis were studied in a 28-day indoor culture experiment via the cage culture method. The results showed that the weight gain rate, relative growth rate, and specific growth rate of the G2 group were highest and did not differ from G1 (P>0.05). The weight difference coefficient of G3 and G4 increased significantly (P<0.05). The weight gain rate, relative growth rate, specific growth rate, and survival rate were significantly lower than G1 (P<0.05), and the G4 group differed significantly from the G1 group (P<0.01). The G3 and G4 groups significantly increased the levels of hemolymph glucose, lactic acid, and pyruvate (P<0.05) and reduced the triglycerides content (P<0.05). The glucose, lactic acid, pyruvate, and triglyceride contents of G2 did not differ from G1 (P>0.05). The amino acid content also did not vary between densities (P>0.05). This indicates that high-density stress can increase energy demands, and F. chinensis tend to use sugars and lipids as energy sources when experiencing density stress. The activities of hexokinase, pyruvate kinase, 6-phosphate fructokinase, and lactate dehydrogenase in G3 and G4 were significantly increased (P<0.05), suggesting changes in the body's oxidative metabolism pathways and increased catabolism. Succinate dehydrogenation enzyme activity was significantly reduced (P<0.05), indicating a decrease in tricarboxylic acid cycle activity. This provides further evidence that density stress inhibited aerobic metabolism. In summary, growth in the G3 and G4 groups was significantly affected, there was increased use of carbohydrates and lipids, and aerobic metabolism of the tissues was inhibited in F. chinensis. Therefore, 100~200 ind./m3 is recommended as the appropriate density when F. chinensis are 4.5 g.

Abstract:For the establishment of the TaqMan RT-PCR detection method for the shrimp movement disorder nodavirus (MDNV), primers and probes were designed based on the RNA-dependent RNA polymerases (RdRp). The pMD18-MDNV plasmid and RNA standard containing the MDNV target gene were used as templates to optimize the reaction mixtures and program. The optimized reaction with 20.0 μL master mix included the following components: 11.0 μL one-step RT-PCR buffer, 0.8 μL enzyme mixture, 0.3 μmol/L forward primer, 0.3 μmol/L reverse primer, 0.4 μmol/L probe, 1.0 μL template, and 5.2 μL RNA-free H2O. The optimized reaction procedure was as following: incubation at 54.5℃ for 15 min, incubation at 95℃ for 1 min, then 45 thermal cycling amplifications (95℃ for 10 s, 60.3℃ for 30 s). The newly established method was specific for MDNV detection, showing a good linear relationship between the log value (Starting quality, Sq) and number of reaction cycles within the range of 1.4×1010~1.4×101 copies/μL pMD18-MDNV standard plasmid. The method could detect as low as 5.5×101 copies of the RNA standard or 1.4×101 copies of the pMD18-MDNV standard plasmid. Meanwhile, the newly developed assay showed that the coefficient of variation of the Ct value intra-assay and the Ct value inter-assay were less than 1.27% and 1.83%, respectively, indicating a good repeatability and stability. In the samples collected from shrimp farming provinces in China in 2019 using this new method, the positive detection rate of MDNV in Litopenaeus vannamei was 23.5% (16/68). The TaqMan RT-PCR method established in this study was specific, fast, and sensitive in the detection of MDNV. This method could provide technical support for the qualitative and quantitative detection and monitoring of MDNV in shrimp farming practices, as well as effective prevention and control of MDNV.

Abstract:Filter-feeding bivalves have a wide range of food sources, including phytoplankton, organic detritus, and zooplankton, among others. In order to identify the food composition of filter-feeding bivalves, Crassostrea gigas cultured in Sanggou Bay, a typical northern large-scale mariculture bay, were used in the experiment. The eukaryotic composition of the stomach contents of C. gigas and of the ambient seawater column were analyzed using Illumina sequencing technology, in August 2019. Overall, 111,359 reads were optimized, and 239 operational taxonomic units were recognized by amplifying the 18S rDNA V4 loci sequences. The eukaryotes found in the stomach contents of C. gigas belonged to 34 phyla, with the majority belonging to Chlorophyta, Pyrrophyta, Streptophyta, Bacillariophyta, and Protozoa. As for the composition of the ambient seawater, the eukaryotes belonged to 37 phyla and they were mainly classified under Chlorophyta, Chordata, Arthropoda, Dinophyceae, and Bacillariophyta. The analysis showed that phytoplankton is the main food source for C. gigas, although Streptophyta and Protozoa accounted for a non-negligible portion of the total food content—10.43% and 4.11%, respectively. These results provide insights to further understand the feeding ecology of filter-feeding bivalves, as well as their role in material cycles and energy flow in mariculture ecosystems.

Abstract:Intertidal bivalves experience broad fluctuations of abiotic factors including pH, salinity and temperature, which could affect their physiology and biochemistry. They are also exposed to trace metals such as copper (Cu) and cadmium (Cd) that accumulate in their tissues and may negatively affect respiration and cardiac activity. Therefore, understanding the impact of pH and heavy metals on intertidal bivalve physiology is of prime importance especially in the context of global ocean acidification. We determined the interactive effects of low pH (7.7 and 7.3) and the addition of heavy metals (Cu or Cd) on the physiological functions including oxygen consumption rate (OR), filtration rate (FR) and heart rate of a common intertidal bivalve, Ruditapes philippinarum. The experiment was conducted under laboratory conditions with pH 8.2 as the control treatment. Addition of Cu at concentrations of 0.06 and 0.60 mg/L suppressed OR, FR, and heart rate (P<0.05). The clams’ heart rate decreased from 23.8 bpm (beats per minute) to 10.5 bpm after being exposed to 0.06 mg/L Cu for 20 min. No significant effect of Cd (0.03, 0.30 mg/L) was found on OR or FR (P>0.05), however clams incubated in the 0.30 mg/L Cd group had a significantly higher heart rate (39.0 bpm) than the control (25.3 bpm) (P<0.05). Low pH had no effect on OR and FR (P>0.05), but clams´ heart rate in the pH 7.3 treatment decreased at the beginning of incubation and recovered rapidly. Our findings suggest that short-term exposure to Cu, Cd, or low pH, all impact the cardiac activity of clams, and the order of toxicity was Cu>Cd>pH. Heart rate was a more sensitive endpoint than OR and FR. There were no interactive effects of low pH and Cu or Cd on the respiration of clams. Our study provides referential data for studying the response of intertidal bivalves to heavy metal exposure and ocean acidification, which may be helpful in the prevention and biological reparation of potential heavy metal pollution in coastal areas.

Abstract:In this study, the preparation method and primary culture conditions of Chlamys farreri gill cells were optimized. The toxic effects of benzo[a]pyrene (B[α]P) were compared and analyzed by three cell activity detection techniques. The results showed no significant difference in the survival rates of the primary cultured gill cells disinfected with 1% penicillin-streptomycin solution (Pen-Strep) and gentamicin for 10~30 min. There were also no bacterial infections observed in the microscopic examinations after 30 min, and the cells were in good condition. The effect of trypsin digestion time on the harvest of gill cells was significant. Within 15~25 min of digestion, the survival rate of the gill cells was higher, and the best trypsin digestion time was 25 min. With 150~300 g relative centrifugal force, the morphology and survival rate of the gill cells significantly differed, and the survival rate and cell integrity were better at 150 g. There were no changes in survival within 6~12 h after adding fetal bovine serum (FBS, 5%~20%). At 24 h, the survival rates of the 5% and 20% treatment groups decreased significantly, but the 10% and 15% treatment groups were unaffected. The cytotoxicity of B[α]P on the scallop gill cells was detected by three cell activity tests, and the results showed no change in the activity of the gill cells with the trypan blue exclusion assay. The cell counting kit-8 assay showed that the activity of the gill cells was significantly inhibited at the highest concentration (16 μg/mL), while the neutral red assay showed a positive toxicity correlation between the B[α]P concentration and time. These results suggest that the best preparation method for C. farreri gill cells is disinfection for 30 min, trypsin digestion for 25 min, relative centrifugal force at 150 g, and the addition of 10% fetal bovine serum to the primary culture medium. The neutral red assay can be used as a sensitive index to evaluate the toxicity of B[α]P.

Abstract:As a growth cofactor, vitamin B (VB) participates in the body's various physiological and biochemical processes in the form of prosthetic groups or coenzymes. Meanwhile, the vitamin B is an essential nutrient in ensuring the regular operation of most biological activities. In this study, pharmacological experiments, confocal microscopy observation, and biofilms staining with mordant were used to understand the effects of vitamins B on marine biofilm formation and metamorphosis of Mytilus coruscus, which is a marine bivalve. VB7 and VB12 were used to investigate its impact on biofilm formation of Pseudoalteromonas marina, which exhibits an induction activity on the metamorphosis of M. coruscus larvae. The direct induction activity of VB7 and VB12 on larval metamorphosis was also detected. Results showed that the VB7 and VB12 at 0.02 and 0.2 mmol/L could directly and significantly increase the larval metamorphosis, and the concentration of VB7 and VB12 at 0.02 mmol/L had the most potent induction. Moreover, VB7 and VB12 at 0.02 mmol/L can also accelerate the growth of P. marina. The biofilm of P. marina formed at 0.02 mmol/L VB7 or VB12 had significant inducting effects on larval metamorphosis. The biofilm thickness, bacterial density, and extracellular polymeric substances (EPS) such as polysaccharides (especially the colonic acid), proteins, and lipids increased significantly after VB7 or VB12 treatment. In summary, VB7 and VB12 can increase the mussel larval metamorphosis directly. At the same time, they can also induce the production of biofilm EPS and further enhance the mussel larval metamorphosis inducing ability of the biofilm, suggesting that VB7 and VB12 can promote the larval metamorphosis of M. coruscus by changing the biofilm EPS composition. The results of this study provide a new theoretical basis and innovative methods for exploring the molecular mechanism of larval metamorphosis. It also provides a solid theoretical basis for the application of vitamin B in improving the artificial breeding technology of M. coruscus, solving the problems of mussel aquaculture industry and ecological restoration.

Abstract:Dimethyl sulfide (DMS) is an important biological sulfide in the ocean that can alleviate global warming. Dimethylsulfoniopropionate (DMSP) is the DMS precursor and mainly exists in phytoplankton. Filter-feeding bivalves are an important ecological group in coastal ecosystems, and their phytoplankton feeding activities may affect the production of dimethyl sulfide. In this study, four common economic filter- feeding bivalves, the Pacific oyster Crassostrea gigas, blue mussel Mytilus edulis, Zhikong scallop Chlamys farreri, and manila clam Ruditapes philippinarum were selected as experimental subjects, and fed them on the microalgae Isochrysis galbana with higher dimethylsulfoniopropionate (DMSP) contents. Variations of dimethyl sulfide (DMS) and DMSP in the water under static and disturbance conditions were monitored in a laboratory simulation experiment, and the effects of DMS(P) release from bivalve feces were analyzed. The results showed that the bivalves'feeding activities on phytoplankton had no significant effect on the release of DMS (P>0.05) under static conditions, but the concentration of DMSPp was significantly reduced by biodeposition (P<0.05), ~40% of the DMSPp intake was converted to fecal DMSP (DMSPf). DMSPf diffused into the water under disturbance conditions, and increased the concentrations of total suspended DMSP (DMSPt) and DMS. The disturbance experiment of total original water revealed that compared to the control group (0 r/min), the DMS and DMSPt in the treatment group, can increased up to 16.8% and 38.5% respectively. Further disturbance experiment of quantitative fecal found that the DMS and DMSPt concentrations in 1 L of seawater containing 0.08 g of feces increased following disturbance. DMS and DMSPt increased from 7.6 nmol/L and 906.4 nmol/L (static condition) to a maximum of 21.3 nmol/L and 2 505.9 nmol/L (disturbance condition), representing increases of 180% and 174%, respectively. This study contributes to a better understanding of how bivalves' feeding activities influence the marine sulfur cycle, the follow-up research can be extended to the field enclosure experiment and aquaculture area investigation.

Abstract:Comparative studies of the karyotypes of closely related species may aid our understanding of the mechanisms of chromosomal evolution relevant to speciation. It may also help to clarify phylogenetic relationships. In the present study, we analyzed the karyotypes of ten wild immature East Asian common octopus (Octopus sinensis; 5 male and 5 female) from the coastal regions of the East China Sea. O. sinensis were held in seawater containing 0.005% colchicine for 2 h, and then the gill and kidney were collected for chromosome sample preparation via the hot-dropping method. The results showed that the diploid chromosomal number of O. sinensis is 60, and the karyotype formula is 2n = 14m + 26sm + 12st + 8t, NF = 100. No satellite, secondary constriction, or heteromorphic chromosomes of sex were observed. Therefore, we speculate that the sex determination mechanism of O. sinensis is autosomal. This study provides basic data for cytogenetic studies of Octopus and serves as a valuable reference for O. sinensis germplasm identification and conservation.

Abstract:This experiment was conducted to study the effects of Bacillus aerobically fermented soybean meal (FSBM) on the growth performance, serum biochemical indices, and intestinal structure of largemouth bass (Micropterus salmoides). Five isoproteic and isoenergetic diets were formulated. A high fish meal (FM) diet containing 50% white fish meal was used as a control diet (0); FSBM was used to replace 10%, 20%, 30%, and 40% of the FM in the control diet to obtain the other experimental four diets. Largemouth bass [with initial body weight of (19.83±0.33) g] were randomly divided into five groups and reared in an indoor cage system for 75 d. Each group had 3 replicates, and each replicate contained 30 fish. The results showed that the weight gain rates of the 20% and 30% trial groups were significantly higher than that of the control group (P<0.05), but there was no significant difference in feed efficiency and survival rate in all experimental groups (P>0.05). There were no significant differences in either condition factor or hepatosomatic index between all trial groups (P>0.05); but the viscerosomatic index was significantly lower than that of the control group (P<0.05). There was no significant difference in serum albumin in all trial groups (P>0.05); the total protein and globulin of experimental groups were significantly higher than those of the control group (P<0.05); the serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities of the trial groups were significantly higher than those of the control group (P<0.05); In the 30% and 40% FSBM treatments, the intestinal muscular layer appeared thinner and villi integrity dropped. These results indicate that at least 20% of dietary FM protein in the diets of juvenile largemouth bass can be replaced by FSBM without having any adverse effect on growth performance, physical fitness, and intestinal health.

Abstract:The aim of this study was to investigate the effects of fishmeal replacement by soy peptide protein on the growth performance, body composition, digestive enzymes activity, and antioxidant capacity of yellow catfish (Pelteobagrus fulvidraco). The control group (A0) received 30% fishmeal, and the experimental groups received soy peptide protein substitutes at 17%, 33%, and 50% (A17, A33, and A50), and four kinds (A0, A17, A33, and A50) of iso-nitrogen compound feeds were prepared. There were 4 replicates and 30 juvenile yellow catfish per group [average body weight: (3.7±0.6) g], and the experiment ran for 80 days. The results showed that there were no significant differences in the growth performance of A17 and the control group (P>0.05). The weight gain rate of A33 was significantly higher than the control group (P<0.05), but there were no other differences (P>0.05). In A50, the feed coefficient ratio was significantly higher than the other groups (P<0.05), while the weight gain rate, specific growth ratio, and protein efficiency ratio were significantly lower than the other groups (P<0.05). There were no differences in the viscerosomatic and hepatosomatic indexes (P>0.05). Soy peptide protein substitution did not affect the contents of water, ash, or crude protein in yellow catfish (P>0.05). However, when the level of soy peptide protein increased from 33% to 50%, the crude fat content decreased significantly (P<0.05). The activities of intestinal lipase and amylase were significantly higher in the treatment groups (P<0.05), and the activity of gastric amylase in A33 and A50 was significantly higher than the control group (P<0.05). Soy peptide protein substitution did not affect malondialdehyde (MDA) activity in the liver. In conclusion, when fishmeal replacement was less than 33%, the growth performance of yellow catfish increased and there were no adverse effects on the antioxidation capacity of the liver. This is the first study to explore the effects of soy peptide protein replacement on P. fulvidraco growth and provides a reference for feed preparation and soy peptide protein use.

Abstract:The study was designed to investigate the effects of dietary protein levels on the growth, ovarian development, and biochemical composition of the swimming crab Portunus trituberculatus [initial body weight of (10.98±0.28) g]. Four experimental diets, which were isoenergic and islipidic, were formulated to contain different protein levels (30%, 34%, 38%, and 42%, defined as diets 1~4, respecitvely). These diets were fed to pond-reared P. trituberculatus females for a 120-day culture experiment. The results showed that: The dietary protein levels had no significant influence on the growth of pond-reared P. trituberculatus females. Diet 3 had the highest gonadosomatic index (GSI) and total edible yield (TEY). The crude protein contents in the ovary and hepatopancreas increased significantly with the increasing dietary protein (P<0.05). Among the four treatments, diets 1 and 3 had the highest crude protein contents in the muscles (P<0.05). Similarly, an increasing trend was found for the total lipid contents in the ovary with the increasing levels of dietary protein (P<0.05). Diet 1 had the highest total lipid contents in the hepatopancreas and muscles, while the lowest total lipid content was found for diet 2 (P<0.05). The contents of total essential amino acids (∑EAA) and non-essential amino acids (∑NEAA) in the muscles of diets 1 and 3 were significantly higher than those of the other two treatments (P<0.05). These results indicate that the appropriate protein level in the diet of adult P. trituberculatus females is approximately 40.16%. The results show that an appropriate dietary protein level could improve ovarian development and muscle nutrition, which provides a reference for the formulation of a diet for P. trituberculatus inhabiting a pond.

Abstract:Geosmin and 2-methylisoborneol are semi-volatile, off-flavor compounds with similar chemical structures that are produced by certain species of actinomycetes, fungi, and blue-green algae. These off-flavor compounds tend to bio-accumulate within fish, depending on the concentrations in the water, the water temperature, the fat content and mass of the fish, and other abiotic and biotic factors. It is necessary to develop an accurate test of geosmin and 2-methylisoborneol in fish muscle to improve the quality of aquaculture products. A novel qualitative and quantitative determination method for geosmin and 2-methylisoborneol in fish meat was established, using cis-decahydro-1-naphthol as an internal standard and headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry. The method of geosmin and 2-methylisoborneol extraction and quantification in fish meat was investigated, the conditions of headspace solid phase microextraction were optimized, and the adaptability of the method was examined through the measurement of actual samples. In the range of 0.1~10.0 μg/L, the ratio of the peak area of geosmin and 2-methylisoborneol to the peak area of the internal standard was linearly related to the ratio of the mass concentration. The correlation coefficient (r2) was > 0.999, the detection limits were 0.018 μg/kg and 0.023 μg/kg, respectively, the limits of quantification were 0.059 μg/kg and 0.076 μg/kg, the average recovery of the three concentration gradients was 68.67%~80.30% and 62.67%~83.40%, and the relative standard deviations were between 2.35%~6.53% and 3.16%~6.80%. This method is highly sensitive, has good repeatability, and can be used to determine the geosmin and 2-methylisoborneol contents of fish.

Abstract:This study aimed to investigate the quality evaluation method and the key factors leading to the quality deterioration of commercial frozen shrimps. Eleven different frozen shrimp (Litopenaeus vannamei) samples were purchased from two supermarkets in Shanghai, and their quality traits were studied. Sampling was conducted to analyze the effects of supermarket level, product formation, frozen-storage period, and retail location on quality characteristics such as water loss, texture, and color. Electronic tongue technology was used to distinguish its flavor profile. Correlation analysis, factor analysis, and multiple linear regression analysis were combined to establish the quality evaluation model and explore the key influencing factors. The results indicated that with respect to water loss, texture and color, there were certain differences in the frozen shrimps of different commodity types. The correlation analysis showed that thawing loss, centrifugal loss, and cooking loss were significantly and positively correlated with adhesiveness. The centrifugal and cooking losses were significant and positively correlated with a* and b*. The centrifugal loss exhibited a negative correlation with L*. The b* was found to be significant and positively correlated with adhesiveness. Three principal factors were extracted by factor analysis based on eigenvalues greater than one; the cumulative variance contribution rate being 84.05%. The ranking orders of comprehensive scores of the principal components and the sample collection information were consistent. The comprehensive evaluation model established by the factor analysis was F=0.577F1+0.293F2+0.131F3, where F1, F2, and F3 were three main score factors, such that the higher the F, the higher the quality level. Further regression analysis was conducted. The results indicate that the main factors affecting the quality of the frozen shrimps were supermarket level and frozen-storage period, while the secondary factors were product formation and retail location. With respect to the quality parameters of water loss, texture, color, etc., supermarket level and frozen-storage period emerged as the key factors affecting the quality deterioration of frozen shrimps, warranting more focused attention in future studies.

Abstract:In recent years, there has been growing scientific and public interest in the protection of endangered aquatic animals, especially cetaceans. Chinese scientists have carried out numerous studies on marine mammals. However, only a few works have focused on the marine finless porpoise compared with the other two cetacean species/subspecies: Indo-Pacific humpback dolphins and Yangtze finless porpoises. Therefore, it is necessary to conduct systematic studies on marine finless porpoises. In this article, we reviewed the historical records, taxonomy, and studies on marine finless porpoises, particularly aspects such as the ecology, biology, conservation, genetics, acoustics, feeding, and breeding. In addition, further studies and conservation strategies are recommended accordingly, aiming to better understand and protect marine finless porpoise.