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Abstract:To determine the distribution of fish resources in the Hongchaojiang Reservoir and its correlation with environmental factors, the fish resources available in the Hongchaojiang Reservoir were evaluated in April 2018 using an echo detector (EY60, 200 kHz). According to the results, there was no significant difference in fish density between day and night in the Hongchaojiang Reservoir (P>0.05); however, the mean target strength was greater in the daytime than in the nighttime (P<0.05). The mean target strength in the day and at night was (–43.30±0.32) dB and (–44.50±0.26) dB, respectively, because small fish between –60 dB and –54 dB (–60 to –57 dB and –57 to –54 dB increased by 9.25% and 4.76%, respectively) increased during nighttime, while fish between –54 and –48 dB increased during the daytime (–54 to –51 dB and –51 to –48 dB increased by 7.42% and 5.27%, respectively). Fish distribution in the Hongchaojiang Reservoir displayed significant spatial variation (P<0.05). Fish density was characterized by higher density upstream than downstream, and higher density in the Reservoir branch than in the Reservoir center. Average fish density was 109.52 ind./1000 m3 and the maximum density was observed in the upstream S3 site, with a density of 330.21 ind./1000 m3, while the minimum density was observed in the downstream S8 site, with a density of 21.50 ind./1000 m3. Correlation analysis revealed that fish density distribution was positively correlated with total phosphorus (TP), permanganate index (CODMn), and chlorophyll a, and negatively correlated with water depth (P<0.05). Fish target strength exhibited a significant negative correlation with water temperature, turbidity, TP and CODMn (P<0.05). The results suggest that abiotic factors such as chlorophyll a and TP drive the spatial distribution of fish in the Hongchaojiang Reservoir. In addition, the results also reflect the influence of biological factors (fish bait, escape from predators, etc.) on fish distribution. The results of the study provide insights that could enhance our understanding of the distribution of fishery resources in the Hongchaojiang Reservoir.

Abstract:Anthropogenic activities and environmental contamination have degraded the marine germ plasm resources as well as the environmental quality of their habitats in China. Therefore, China actively promotes the establishment of aquatic germ plasm resource protection areas. However, studies focused on the environmental quality of the germ plasm resource protection areas remain limited. In this study, based on survey data for environmental factors such as nutrients, heavy metals, and petroleum hydrocarbons obtained in May and August 2018, we evaluated the ecological environment quality of a Solen grandis national germ plasm resource protection area in Haizhou Bay using the comprehensive quality index. In addition, the eutrophication index and the organic pollution index were used to analyze the water environment quality of the protection area. According to the survey findings, all monitored factors satisfied the classⅠseawater quality national standard, excluding inorganic nitrogen concentrations at some stations. In 2018, the comprehensive quality index of this Solen grandis national germ plasm resource protection area in Haizhou Bay was 0.31~0.39, and the water quality in the area was slightly clean. The N/P ratios were higher than the Redfield ratio and the phosphate concentrations in seawater were much lower than the amounts required for normal phytoplankton growth and development, which implied that phosphorus was a major nutrient limiting biological productivity in the area. The eutrophication index was in the 0.05~0.27 range, which indicated that the nutritional level of the seawater in the protection area was poor. The organic pollution index was in the –0.24~0.81 range, which indicated favorable water quality in the protection area. These evaluation results suggest that the seawater environment quality in the Solen grandis national germ plasm resource protection area in Haizhou Bay has been maintained appropriately when compared with the historical survey data from 2008~2013.

Abstract:In the Quzhou area, there are five important reservoirs: Huangtankou (S1), Tongshanyuan (S2), Shizikou (S3), Huayuanlong (S4), and Jincanglong (S5). To ascertain the eutrophication level and the main driving factors in reservoirs in the Quzhou area, we analyzed the water quality in 2018 to determine the relationship between eutrophication and environmental factors. The comprehensive trophic level index (TLI) method showed that reservoirs S1, S2, and S3 were mesotrophic, S4 was lightly eutrophic, and S5 was highly eutrophic, which concurred with the relative chlorophyll a (Chl-a) concentrations. To improve the comprehensive development and utilization of the reservoirs, industry, such as aquaculture, was developed in Quzhou. Results showed that eutrophication in aquacultural areas was significantly higher than that in breeding and releasing areas. Furthermore, we analyzed how water quality was affected by aquaculture using a cluster analysis. Results showed that effectively managed aquaculture may not be the main contributing factor for eutrophication. Based on the N/P ratio, we found nitrogen limitation occurred in S5, whereas phosphorous limitation occurred in the other reservoirs. Therefore, we should focus on controlling phosphorous and nitrogen. The regression equation among Chl-a, TLI, and the correlated environmental factors was expressed using multiple linear stepwise regression as follows: Chl-a = 19.793 CODMn–32.065 TP–33.004, TLI = 1.062 CODMn +18.468 TP–0.06 SD + 0.450 T + 1.765 TN + 33.886, where TP, SD, T, and TN stand for total phosphorous, transparency, temperature, and total nitrogen respectively. Combined with a correlation and principal component analysis (PCA), it was concluded that CODMn, TP, SD, T, and TN were the main factors influencing reservoir eutrophication in the Quzhou area, among which nitrogen and phosphorous and organic compounds were the impact factors, and water temperature was the main cause of seasonal change. However, pH and DO were a consequence of eutrophication, and could be indicators of the eutrophication level. pH and DO increased with increasing eutrophication, but in highly eutrophic water, algal overgrowth can cause a rapid decrease in DO in the water.

Abstract:To improve the removal efficiency of nitrogen pollutants by the biological aerated filter (BAF) system in a recirculating aquaculture system (RAS) and reduce the accumulation of nitrates and the amount of aeration, a type of iron-based composite biological filler was introduced into the BAF system. The environment of aerobic, anoxic, and anaerobic cycling, in turn, was built with intermittent aeration in this BAF system. The surface morphology characteristics of the fillers were investigated using a scanning electron microscope. The treatment performance of nitrogen pollutants under different proportions of the two substances in the composite filler and different aeration operation modes were investigated. Then, single-factor tests were used to optimize the important operating parameters (including temperature, hydraulic loading rate, and influent ammonia nitrogen load) of the BAF with the iron-based composite biological filler. The results showed that the denitrification efficiency improved by approximately 10%, the accumulation of nitrous nitrogen was reduced by 25%, and 50% of the amount of aeration was saved after adding iron-based packing in the BAF system.The BAF system with the iron-based composite biological filler exhibited the best removal performance under the following operating conditions: Intermittent aeration time of 12 h, composite proportion of the polypropylene carbonate gel hydrophilic filler and sponge iron in the composite filler of 3∶1, the temperature of 30℃, hydraulic loading rate of 1.2 m3/(m2·d), and the influent ammonia nitrogen load of 1 mg/L. The introduction of the biological sponge iron composite filler and intermittent aeration could improve the removal efficiency of nitrogen pollutants in the BAF system. It significantly reduced the accumulation of nitrite nitrogen and reduced the power consumption of the operation. The results of this study will be useful in understanding how aerobic and anaerobic environments promote nitrogen transformation. This study also optimized the operating parameters for the actual application of the BAF system with the iron-based composite biological filler in RAS.

Abstract:Antimicrobial susceptibility testing (AST) is of great significance to the assessment of environmental health of fisheries, clinical applications, epidemiological research, etc. Here, the merits of an automated microbial-growth electrical-sensor-based AST method are compared with the standard broth microdilution (BMD) method, using Vibrio parahaemolyticus (VP) as a microorganism model, and tetracycline, kanamycin, enrofloxacin, and penicillin V as antibiotics model. Results show that the essential agreement of the minimal inhibitory concentration (MIC) obtained with the two methods is 100%, for both standard and isolated VP strains. The MICs obtained with the automated microbial-growth electrical-sensor-based AST method are no lower than those obtained with the BMD method, indicating that the senor is more sensitive than visual detection in identifying critical values. In addition, a dynamic sensorgram of the automated microbial-growth electrical-sensor-based AST provides more detailed information on the antibiotic activity at different growth stages. Because of the outstanding merits of sensitivity, efficiency, and user-friendly operation, microbial-growth electrical-sensor-based AST is a promising method that can be applied widely in the future.

Abstract:Heat shock protein 70 (HSP70) is closely related to the stress resistance and anti-stress ability of organisms, where it plays a crucial role. In the present study, a 735 bp core cDNA sequence of the hsp70 gene isolated from the liver tissue of Pelteobagrus fulvidraco ♀×P. vachelli ♂ was amplified using reverse transcription polymerase chain reaction (RT-PCR), and the bioinformatics was analyzed. The relative mRNA expression of the hsp70 gene in different tissues was tested using quantitative real-time PCR (qPCR), which revealed that hsp70 mRNA was found in all tested tissues, including liver, gill, brain, and muscle, and hsp70 mRNA expression levels in liver tissue were significantly different from that in brain, gill, and muscle tissue (P<0.05). At 20℃ (control), 25℃, 28℃, and 31℃, the hsp70 gene expression in liver, gill, brain, muscle tissue generally increased with increasing temperature. The hsp70 gene expression level in gill tissue at 28℃ and 31℃ was significantly higher than that in other tissues (P<0.05), which indicated that gill tissue was sensitive to heat stress in the hybrid. It was suggested that this may be an organism protection strategy for gill tissue, which is important for respiratory metabolism under extreme changes in temperature.

Abstract:This study examined the effects of salinity stress on the antioxidant system of the liver, kidney, and gill and the serum cortisol levels of Luciobarbus capito. Four NaCl salinity groups (3, 6, 9, and 12 g/L) and a freshwater control group were set up in this experiment. Further, we detected the activities of acid phosphatase (ACP), alkaline phosphatase (AKP), glutathione peroxidase (GSH-Px), and the content of malondialdehyde (MDA) in the liver, kidney, and gill, as well as the serum cortisol level at seven salinity exposure time points (3 h, 6 h, 12 h, 24 h, 48 h, 96 h, and 7 d). The results indicated that under salinity stress, the antioxidant enzyme activity, MDA content in the liver, kidney, and gill, and serum cortisol levels were increased and then decreased as the stress exposure time increased, after which they tended to be stable. They reached the maximum value within 24 h after exposure of L. capito to salinity and reduced within 48 h and stabilized within 96 h~7 d. Antioxidant enzyme activities, MDA content in the liver, kidney, and gill; and serum cortisol levels were proportional to salinity. Further, ACP, AKP activity, and MDA content were higher in the kidney than in the liver and gill under salinity stress. ACP activity was approximately 1.27~1.96 U/g prot in the liver, 1.42~2.15 U/g prot in the kidney, and 0.98~1.96 U/g prot in the gill; AKP activity in these three tissues was approximately 0.31~0.86, 1.01~1.87, and 0.13~0.84 king unit/g prot, respectively, and MDA content was 17.02~55.98 nmol/mg prot, 13.05~57.27 nmol/mg prot, and 8.33~53.93 nmol/mg prot, respectively. However, GSH-Px activity in the three tissues was 44.41~114.77, 16.52~67.59, and 9.07~48.00 active unit, respectively, indicating that it was significantly higher in the liver than in the kidney and gill. In addition, serum cortisol level was 197.00~355.50 ng/L under salinity stress. Overall, L. capito can become normal through self-regulation under 12 g/L salinity, indicating that they have strong adaptability to saline environment.

Abstract:The present study aimed to assess the effect of Bacillus licheniformis on the growth, intestinal digestive enzymes activity, non-specific immunity and resistance against Aeromonas salraonicida in the fat greenling (Hexagrammos otakii). A total of 270 H. otakii with an average initial body weight of (22.0±2.0) g/tail were randomly allocated to three groups (the control group and two experimental groups with different B. licheniformis levels) with three parallels per group and 30 fish per parallel. Fish in the control group were fed a basal diet consisting of albumen, and the ones in the two experimental groups were fed basal diets supplemented with 5×107 (0.5%) or 1×108 CFU/g (1.0%) B. licheniformis, respectively. After 50 days, fish were infected with A. salraonicida, and the cumulative mortality rate was determined within 14 days. The specific growth rate was found to be significantly higher in fish fed diets containing B. licheniformis when compared with the control group (P<0.05). Furthermore, the activities of SOD, CAT, and T-AOC in the serum of H. otakii in the experimental groups were significantly increased compared with the control group (P<0.05). Conversely, the MDA levels in the experimental groups were decreased compared with the control group (P<0.05). The GSH-Px activity in the 1.0% B. licheniformis group was lower than that in the control group, but the activity in the 0.5% B. licheniformis group was higher than that in the control group. The activities of GS, MDH, and HK in the serum of fish in the experimental groups were increased compared with the control group (P<0.05). Compared with the control group, AST and ALT activities in the serum of fish in the experimental groups were decreased (P<0.05) and CHE and ADA activities were higher than those in the control group (P<0.05). The activities of trypsin, amylase and lipase in the intestines of fish in the experimental groups were increased to different degrees, with the highest activity observed in the 1.0% B. licheniformis group (P<0.05). The bacterial challenge test revealed that the 14 day cumulative mortality rate in the 1.0% B. licheniformis group was only 35.55% (P<0.05). The results obtained in the present study revealed that B. licheniformis can increase growth, activities of intestinal digestive enzymes, and non-specific immunity, as well as enhance resistance against A. salraonicida in H. otakii.

Abstract:The effects of protein content and stocking density on growth performance, nitrogen excretion, and related physiological and biochemical indexes of juvenile fish were studied using juvenile tiger puffers (Takifugu rubripes) with an average initial body weight of 15.60 g. A two-factor, three-level (2×3) design was used, with three different protein levels (38.87%, 45.55%, and 51.00% dry matter) and stocking densities of 1.53 kg/m3 (20 fish in a tank of 0.196 m3 volume), 2.30 kg/m3 (30 fish per tank), and 3.06 kg/m3 (40 fish per tank). The feeding trial was conducted in an indoor flow-through system. Each diet was fed to triplicate tanks for 8 weeks. The results showed that, at a certain stocking density, low dietary protein resulted in lower weight gain compared with the medium and high dietary protein levels (P<0.05). Neither dietary protein content nor stocking density significantly affected body proximate composition of experimental fish. At a certain dietary protein level, high stocking density increased total protein and total cholesterol contents in serum compared with medium stocking density (P<0.05). The total protein in serum was higher in the low-protein group than in the medium-protein group (P<0.05). The activity of alkaline phosphatase in serum was significantly higher in the low-protein group than in the high-protein group (P<0.05). No significant interaction was observed between the effects of dietary protein content and stocking density on growth performance and nitrogen excretion. Ammonia nitrogen excretion in the high-stocking-density group was higher than that in the low-stocking-density group at 3 hours after still-water feeding (P<0.05). Results of this study suggest that 45.55% dietary protein was sufficient to maintain normal growth in tiger puffers. Dietary protein content and stocking density had no significant interaction in the effects on growth performance and ammonia nitrogen excretion.

Abstract:From July 2017 to June 2018, a total of 295 naked carp Gymnocypris przewalskii, which were used for comparative study of reproductive characteristics, were collected from Erhai, Dahu, and the estuaries of Heima River, Quanji River, Shaliu River, and Buha River in Qinghai Lake. With the exception of the Quanji estuary, spawning stock, sex ratios (female to male, SR) in all locations showed more female than male individuals (i.e., SR>1). The biological minimum size (BMS) of naked carp differed among spawning stocks, and all males reached sexual maturity at a smaller size compared with the females. The smallest BMS of female and male individuals, whose age, total length, and body weight, respectively was 5 y, 157 mm, and 42.5 g, and 4 y, 124 mm, and 24.5 g, was found in the Buha and Shaliu estuary stocks. The gonadosomatic index (GSI) of female naked carp was significantly higher than that of the males for each spawning stock (P<0.05). The GSI of Shaliu estuary female fish (19.67±1.36)% was significantly higher than that of Erhai (10.28±1.36)% and Dahu (13.35±1.24)% fish (P<0.05). However, the GSI of male fish did not differ significantly among the six stocks (P>0.05). Mean total fecundity (Ft) and relative fecundity (Fr) varied from (3338.18±324.25) eggs/female and (21.88±2.10) eggs/g Wb (from Heima estuary) to (10699.40±613.91) eggs/female and (82.68±4.63) eggs/g Wb (from Shaliu estuary), and significant differences were observed in both Ft and Fr between these two stocks (P<0.05). According to these results, the reproductive characteristics of naked carp in Qinghai Lake show a differentiation trend, with differentiation among different spawning populations already visible. The present study can provide potential data for a more accurate fish stocking and fisheries management plan, including stock optimization, enhancement, and release schedules, for naked carp.

Abstract:In the present study, the gastric evacuation rates, hepatic and intestinal digestive enzyme activities, and serum glucose and cortisol concentrations in “Yunlong” groupers (Epinephelus moara ♀ × E. lanceolatus ♂: body weight (680.35±39.84) g) were evaluated to illustrate the characteristics of gastric evacuation and digestive enzyme activity. In addition, the degree of fitting of the gastric emptying curve was analyzed using a linear model, square root model, and cubic root model. The gastric evacuation rates of “Yunlong” groupers exhibited a typical curve digestive pattern (slow-fast-slow) during the gastric evacuation process. All the three mathematical models could fit the gastric evacuation data of “Yunlong” groupers; however, the cubic model obtained the optimal result. According to the cubic model, 80% (appetite basic recovery) and 100% (complete recovery of appetite) gastric emptying occurred at feeding after 9.5 hours and 14.8 hours in “Yunlong” groupers, respectively. The hepatic and intestinal digestive enzyme (amylase, chymotrypsin, and lipase) activities increased significantly from 0 to 6 h, and then decreased from 9 to 24 h during the gastric evacuation process in “Yunlong” groupers. The concentrations of serum glucose and cortisol corresponded with digestive enzyme activities during gastric emptying in “Yunlong” groupers. In addition, serum cortisol and glucose concentrations and digestive enzyme activity increased slowly from 0 h to 3 h, then increased significantly from 3 h to 6 h (P<0.05), with the highest values obtained at 6 h, and then decreased significantly until gastric evacuation was completed (P<0.05). In addition, the gastric evacuation rate was positively correlated with digestive enzyme activity during gastric evacuation in “Yunlong” groupers. In conclusion, the results reveal that the optimal interval feeding recommended is at 10 h and twice per day, based on the gastric evacuation rate and feeding digestion characteristics of “Yunlong” groupers in captivity.

Abstract:Otolith microchemistry are widely applied in the field of fish migration ecology. However, the extraction of otoliths always results in damage to tissue and the death of the fish. Therefore, it is of great importance to discover an alternative material as a nonlethal substitute for otoliths for effective microchemical “fingerprint” analysis. Consequently, the similarities of microchemical characteristics between the pectoral fin ray and otolith of Coilia nasus were compared in this study. The ratio of Sr/Ca and classification of Sr concentration mapping results in the otolith matched the typical patterns of anadromous, freshwater, and land-locked ecotypes well. Of note, the results of the pectoral fin rays showed that C. nasus taihuensis and C. brachygnathus had consistently low Sr/Ca ratios [(1.38±0.52)~ (2.04±0.74) and (1.40±0.32)~(1.81±0.66), respectively], which coincided with the first stage of C. nasus [(2.06±0.64)~(2.26±0.29), i.e., freshwater phase], which reflected the characteristics of the freshwater habitat “fingerprints.” Furthermore, the C. nasus pectoral fin ray, like the otolith, could be divided into three distinct phases from the core to the edge, corresponding to the bluish, greenish, and bluish “fingerprint” changes in the results of mapping analysis. The present study strongly suggested that pectoral fin rays are a nonlethal and low-damage substitute for otoliths to investigate the migratory habit and conduct life history research using microchemical “fingerprint” analysis. In addition, considering the advantages of sample collection and pre-treatment, pectoral fin rays could play a role in the future as an alternative material for accurate assessment of Coilia resources and the effectiveness of artificial fish release using microchemical marking approaches.

Abstract:The Large-scale family-based selective breeding can effectively increase genetic gain in shrimp, but tagging individuals for tracking pedigree is time-consuming, labor-intensive, and would cause inaccurate kinship. Molecular markers are effective in solving this problem. In this study, we developed 37 SNP markers derived from transcriptome sequences and performed analysis on genetic diversity, family clustering, and parentage for 22 families of Litopenaeus vannamei. The results provided examples for the application of SNP markers in selective breeding of shrimp. The results showed that the average expected heterozygosity (He) and observed heterozygosity (Ho) for 37 SNP loci were 0.38 and 0.34, respectively. Further, the average polymorphism information content (PIC) was 0.30, which means moderate polymorphism (0.25

Abstract:Exopalaemon carinicauda is a widely-distributed species. Its wide temperature and salinity tolerances, fast growth, and strong adaptability have enabled it to become a characteristic breeding species in coastal areas of China. In China, there are around 100 million acres of saline-alkali water with breeding potential. Saline-alkali water has a high-pH, high-carbonate alkalinity, and complex ion composition, which hinders the full development and utilization of resources. Due to its strong environmental adaptability, E. carinicauda has been successfully cultivated in coastal saline-alkali waters in recent years. It is urgent to improve its germplasm for saline-alkali aquaculture production of this species. In this study, quantitative genetics principles and intra-sibling correlation methods were used to estimate the heritability and heredity-related parameters of saline-alkali stress in 50-day-old E. carinicauda. Fifty full-sib families (including 42 half-sib families) were constructed by directional mating. The survival time under saline-alkali stress was analyzed with a general linear model (GLM) using SPSS software, and the genetic correlation with and heritability of saline-alkali tolerance were estimated. The results showed that the heritability of saline-alkali tolerance was 0.18~0.60, and the estimated value was not significant. The genetic correlation and phenotypic correlation between saline-alkali tolerance and body length were –0.401 and 0.127, respectively. The genetic and phenotypic correlations between saline-alkali tolerance and body weight were –0.196 and 0.033, respectively. The results of this study showed that selective breeding has great potential to improve the saline-alkali tolerance of E. carinicauda, and taking the saline-alkali tolerance as the breeding index would not significantly affect the body length and weight of E. carinicauda.

Abstract:To explore the effect of the beta-N-acetylglucosaminidase (NAGase) gene on the high pH tolerance of Fenneropenaeus chinensis, the single nucleotide polymorphism (SNP) of FcNAGase and its correlation with the high pH tolerance of F. chinensis were determined by direct sequencing and real-time fluorescent quantitative PCR. The results showed that 29 potential SNP loci were detected on the FcNAGase gene by direct sequencing, the distribution frequency was 1.13/100 bp, in which the mutation frequency of introns was 0.35/100 bp, and that of exons was 0.78/100 bp. Fourteen SNP loci were detected in the high pH tolerance population of F. chinensis using fluorescence quantitative PCR. The observed heterozygosity (Ho) ranged from 0.2581 to 0.9390, the expected heterozygosity (He) ranged from 0.0595 to 0.4490, and the polymorphism information content (PIC) ranged from 0.0574 to 0.3731. The chi-square test result revealed that two SNP loci were related to high pH tolerance traits (P<0.05), namely P12 (P=0.036) and P27 (P=0.018). The results of this experiment provided basic data and methods for molecular marker assisted breeding of F. chinensis.

Abstract:In this study, the 14-3-3 gene of the swimming crab (Portunus trituberculatus) was cloned using the Rapid Amplification of cDNA Ends (RACE) method. The full length was 2510 bp and the ORF was 741 bp, encoding 247 amino acids and with a predicted molecular weight of 27.98 kDa. Sequence alignment analysis showed that the Pt14-3-3 gene has the highest homology with the 14-3-3 gene of Eriocheir sinensis (100%). Phylogenetic tree analysis indicated that the Pt14-3-3 amino acid sequence of P. trituberculatus was closely clustered into one with Eriocheir sinensis. Tissue expression analysis showed that the Pt14-3-3 gene was expressed in hepatopancreas, muscle, gill, heart, eyestalk, and hemolymph, and the expression level was highest in hepatopancreas. After low salt stress, the expression levels of the Pt14-3-3 gene in sputum and hepatopancreas were significantly upregulated at 48 h and 12 h, respectively, and reached the maximum, which was 1.34 times (P<0.05) and 7.54 times (P<0.05), respectively. After artificial infection with Vibrio parahaemolyticus and WSSV, the Pt14-3-3 gene was upregulated in the hepatopancreas and blood cells and the lowest was up to 17.52 times (P<0.05). The results of this study indicated that the Pt14-3-3 gene plays an important role in low salt adaptation and immune response of the Portunus trituberculatus.

Abstract:Chitinase plays an important role in the molting, digestion, and pathogen defense of Portunus trituberculatus. However, little is known about the P. trituberculatus chitinase genes. To understand the P. trituberculatus chitinase gene family, we investigated its chitinase gene 1 (PtCht1). PtCht1 has a total cDNA of 2220 bp and encodes for 583 amino acids. We found that PtCht1 exhibited the basic structure and contained the conserved sequence of the chitinase GH18 family genes of crustaceans. The phylogenetic tree showed that Cht1 of P. trituberculatus was clustered with Cht1 of other species such as Scylla serrata, with 92.80% homology. Therefore, we concluded that PtCht1 is a Group1 gene of the crustacean GH18 family. Further, it is the first P. trituberculatus gene in this classification. Additionally, the results of whole tissue expression analysis showed that PtCht1 was highly expressed in the hepatopancreas, and the expression level in the hepatopancreas during the inter-molt was significantly higher than in the pre-molt and post-molt (P < 0.05). After low salinity stress treatment, the expression level of PtCht1 gene in hepatopancreas rapidly rose to the peak at 3 h (2.72-fold); in the gill, except for 12 h, the expression level of PtCht1 gene was significantly up-regulated (P < 0.05), up to 9.96-fold. Our results show that the PtCht1 gene can participate in the digestion of foods containing chitin and plays a significant role in the regulation of osmotic pressure. Thus, our study is a landmark study in Group1 gene research of the chitinase GH18 family of P. trituberculatus. To conclude, the gene function studies of PtCht1 provide new clues for analyzing the effect of salinity on the growth of P. trituberculatus.

Abstract:In spring (April) of 2017, Oratosquilla oratoria samples were collected three times near the coast of Haiyang and Yantai. Twelve morphological parameters were measured by traditional morphological method of linear measurement. Fifteen proportional trait indexes were calculated and compared by multiple statistical methods such as Independent-Sample t-test, CD test, principal component analysis, and discriminant analysis. The t-test and CD test results showed that the samples from Haiyang (Haiyang stock) had a longer and thinner body shape than those from Yantai (Yantai stock). The carapace, tail, and raptorial claw of the Yantai stock, whereas the abdomen of the Haiyang stock constituted larger proportion of the total length of the organism. Although there were significant differences in the length of the carapace, thoracic somite, tail, and the propodus between the two stocks (P<0.01), they did not reach the level of subspecies (CD<1.28), characterized by morphological differences between different geographic groups within the same species. According to the principal component analysis, the female stock constructed three principal components with a cumulative contribution rate of 87.571%. The male stock also constructed three principal components with a cumulative contribution rate of 83.156%. The difference in the transverse body shape factor between Haiyang and Yantai stocks was clear. The discriminant function of stocks was established by discriminant analysis and the comprehensive discriminant accuracy was 74%. These results showed that O. oratoria shrimps were species with sexual dimorphism. The difference in adult morphology is more evident, particularly in males between Yantai and Haiyang stocks.

Abstract:To evaluate the genetic diversity of the sea cucumber (Apostichopus japonicus) populations, thirteen simple sequence repeat (SSR) loci were used to amplify eight different geographical populations of sea cucumbers collected from China, Korea and Russia. The results showed that the average observed heterozygosity (Ho) and average expected heterozygosity (He) of 13 microsatellite loci were 0.47 and 0.80, respectively. The polymorphism index content (PIC) of the 13 loci ranged from 0.465 (AJ06) to 0.909 (AJ09). Except for AJ06, the loci were moderately polymorphic (0.250.5). The number of alleles (A) ranged from 10 (AJ06) to 34 (AJ07), with an average of 19.4. The total number of effective alleles was 83.8. The number of effective alleles (Ne) ranged from 1.7 (AJ06) to 11.8 (AJ09), and the average number was 6.5. The results of genetic diversity analysis showed that the PIC ranged from 0.6392 (SK-MP-B) to 0.7122 (QD), indicating that all populations had high genetic diversity. The construction of DNA fingerprints could distinguish all eight populations. The eight populations of sea cucumbers were allocated to three free-mating groups using Structure software, which were consistent with those generated using UPGMA cluster analysis. UPGMA cluster analysis showed that the Qingdao, Yantai, and Mokpo black populations were clustered into one group, whereas the Russian, Posco yellow, Kunsan black, and Posco black populations were clustered into another group. The Posco red population was located in the exception group and was located on a separate branch. Cluster analysis showed that the genetic structure and differentiation of the populations of sea cucumbers were not only related to the geographic location but was also related to body color. The results provided the foundation for the genetic identification and genetic resource conservation of the sea cucumber.

Abstract:To study the effect of sanguinarine on intestinal microbiota diversity in Trionyx sinensis, 480 individuals [initial weight (31.75±7.20) g] were randomly selected and divided into four groups. Three experimental diets RS2, RS3, and RS4 were formulated with 50, 100, and 150 mg/kg sanguinarine, respectively, and no sanguinarine was included in the control group. At the end of the experiment, the total DNA of the midgut tissue was extracted and the 16S rRNA V3-4 region was sequenced. The results showed that the total number of operational taxonomic units (OTU) in experimental groups was significantly higher than that in the control group, and the complexity and richness of intestinal flora was also significantly higher than that of the control group. Analysis of the structure and composition of the intestinal flora revealed that RS1 and RS2 were closer in structure, whereas RS1 was farther away from RS3 and RS4. Proteobacteria and Chlamydiae were the dominant phyla, and Helicobacter was the dominant genus. Helicobacter abundance in experimental groups was significantly lower than that in the control group, whereas the abundance of Acinetobacter, Lactobacillus, and Bifidobacterium were all significantly higher than that in the control. Therefore, the study demonstrated that adding an appropriate amount of sanguinarine (100~150 mg/kg) in the feed could effectively promote intestinal flora diversity and richness, and improve the community structure of T. sinensis intestinal flora.

Abstract:This study investigates the response of heart rates to cadmium-related stress and its early warning capacity among juveniles of “standardized” Anodonta woodiana, a unique bioindicator used in the “Freshwater Mussel Watch” project. Heart rates of early juvenile mussels at several typical growth stages, from heartbeat-clearly-observed to shells-no-longer-transparent, i.e., EJ1 [25 days old; shell length (1.5±0.1) mm], EJ2 [55 days old; shell length (10.5±0.6) mm], EJ3 [70 days old; shell length (20.4± 0.9) mm], and EJ4 [85 days old; shell length (30.0±2.0) mm], were studied under non-lethal/non-injury conditions. The response of heart rates to different concentrations of Cd2+ (0.0025, 0.005, 0.025, 0.1, and 0.5 mg/L) in EJ4 were examined. The results show that heart rates of early juveniles generally differed little between ante meridiem and post meridiem (P>0.05) states. Heart rates were linearly and negatively correlated with age and shell length (P<0.05). Heart rates were linearly and negatively correlated with exposure time in the exposure groups of 0.0025 and 0.5 mg/L Cd2+ (P<0.05). However, heart rates were linearly and negatively correlated with Cd2+ concentrations in all exposure groups (P<0.05). These results indicate that a new early warning/monitoring system for Cd2+ contamination may be developed using responses characteristic of “standardized” A. woodiana to Cd2+ concentrations.

Abstract:Heat stress affects Pyropia haitanensis yield and quality, and is the main factor restricting the development of the Pyropia industry. Previous studies found that the genes related to the ubiquitin proteasome system (UPS) of P. haitanensis were significantly up-regulated under heat stress; however, its molecular function in response to high temperatures is unknown. Therefore, in this study, the function of the cullin E3 ligase gene (PhCUL1) was studied using molecular biology and genetics. The results showed that the full-length cDNA of PhCUL1 was 2,500 bp, including an open reading frame (ORF) of 2,481 bp. This gene has a Cullin domain (407~618 aa) and a Cullin Nedd8 domain (754~821 aa). The Cullin Nedd8 domain is a protein fusion site that confers PhCUL1 with E3 ligase activity. Phylogenetic analysis showed that PhCUL1 was clustered with P. umbilicalis. qRT-PCR results showed that the PhCUL1 gene was significantly induced by high temperature. In addition, a transgenic expression system of Chlamydomonas reinhardtii was constructed to verify the function of the PhCUL1 gene. Transgenic C. reinhardtii plants overexpressing PhCUL1 exhibited obvious tolerance to heat stress. The relative PhCUL1 expression in C. reinhardtii exhibited upregulation within 6 hours. These results indicated that PhCUL1 plays a crucial role in response to heat stress in P. haitanensis and its specific regulatory mechanism needs further study. This study provided a better understanding of the mechanisms of UPS in P. haitanensis in response to high temperature and a theoretical basis for the selection of new varieties with high temperature resistance.

Abstract:Marine biodiversity and its sustainable use are threatened by climate change and human activities, and research on this topic has drawn increasing interest worldwide. We used bibliometrics and knowledge mapping analysis to review information related to marine biodiversity indexed in the ISI Web of Science Core Collection database. We created descriptive statistics of the number of articles published annually, the journal frequency, and the country distributions. Then, the author, institution cooperation network, and keyword-based knowledge mapping and burst analysis were used to explore hotspots of marine biodiversity research. The descriptive statistics suggest that the number of studies has increased in recent decades, and scientific research influence and international attention are very high. Authors and institutions have formed frequent and stable cooperative networks. Author cooperation has formed core authorships, such as Miloslavich P., Danovaro R., and Mouillot D. Institutional cooperation has enabled extensive collaborations among James Cook University, the University of Tasmania, and the University of British Columbia. Ecology, biodiversity conservation, marine freshwater biology, and environmental sciences are the main disciplines of marine biodiversity. Burst analysis showed that current marine biodiversity research has five study frontiers: (1) the impacts of human activities and climate change on marine biodiversity, (2) the protection and sustainable utilization of marine biodiversity, (3) the establishment and management of marine protected areas beyond national jurisdictions, and the protection of ecologically or biologically significant marine areas, (4) the observation and evaluation of marine biodiversity and ecosystem change, and (5) marine genetic diversity and geographic variations in diversity.

Abstract:China is one of the largest producers of cultivated mollusks and the production has increased steadily over the last 30 years. The aquaculture industry growing specific kinds of cultured mollusks in some localities or regions might suffer huge losses owing to infectious diseases. Mass mortalities of bivalves and small abalone (Haliotis diversicolor supertexta) associated with herpesviruses have frequently occurred since the 1990s, resulting in huge economic and social damages to related families and communities. Herpesvirus now represents the most destructive pathogen faced by mollusk aquaculture in China. Significant losses, which resulted from the epidemics associated with herpesvirus infection, have attracted enormous attentions in related sectors, including the scientific community. Epidemiological and etiological investigations showed that the herpesviruses infecting bivalves and abalone were Ostreid herpesvirus 1 (OsHV-1) and Haliotid herpesvirus 1 (HaHV-1). The outbreak of herpesvirus infection in mollusks not only happened in China but also in many other countries and regions around the world. Pacific oysters such as Crassostrea gigas were the most seriously affected bivalves. The significant loss associated with infectious diseases has attracted huge attentions from producers and researchers in the mollusk aquaculture sector around the world. To mitigate production loss associated with herpesvirus infection in mollusk aquaculture, researchers have investigated the characteristics of OsHV-1 and HaHV-1 viruses, their geographical distribution, susceptible hosts, epidemiological characteristics, and disease diagnosis and have tried to find ways to prevent and control them, including the use of disease resistance breeding. Large investments in scientific research has made OsHV-1 and HaHV-1 the most well studied viruses of mollusks. They also represented the only two mollusk viruses with clear classification status. In this study, we summarized the recent progress related to OsHV-1 and HaHV-1, with an emphasis on the occurrence, spread, damage, and disease control practices in China.