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Abstract:

Abstract:Habitat restoration is a crucial measure for conserving fishery resources and maintaining sustainable production. The habitat of juvenile in the Yangtze Estuary has been seriously degraded. In this study, the density, size composition, and growth characteristics of juvenile in artificial floating wetland (AFW) habitats were continuously monitored from May to November. The objective was to assess if juvenile select and use the AFW habitats, which will provide important information for future habitat restoration efforts in the Yangtze Estuary. The results show that the three-dimensional AFW habitats supported and a variety of aquatic organisms that lived symbiotically. Juvenile inhabited in the AFW habitat from June to October, and the highest density was 466.6 ind/m². However, the density decreased significantly with time (<0.05). There were differences in the size composition of larvae across months. Larvae with body weight <0.2 g were abundant in June and July, accounting for 98.1% and 66.0% of the total, respectively. Larvae weighing 0.2 g to 1.0 g were abundant in August, accounting for 84.7%. Larvae weighing 1.4 g to 1.8 g were abundant in September, accounting for 74.0%. The exponential value (2.3673; =0.9669) was 2.3673, indicating isometric growth (i.e., carapace length growing faster than body weight). The AFW provides an alternative habitat for juvenile , which meets the habitat requirements of hiding and feeding in the early development stages.

Abstract:There are large differences in morphology and living habits of Japanese flounder () in the early stages of metamorphic development. These differences make an ideal model of metamorphosis in fish. The thyroid hormone (TH) plays a decisive role in the development of metamorphosis. The physiological role of TH is to regulate the transcription of target genes via the thyroid hormone receptors (TRs) and thyroid hormone response elements (TRE)-AGGT(C/A)A. In this study, was used to investigate a new method for finding the target genes regulated by TH. We expressed and purified the p3×Flag-TRαA and p3×Flag-TRβ fusion proteins to identify the target genes downstream of TH by using a cyclic amplification and selection of target (CAST) method. We found 11 potential TRαA target genes and 12 potential TRβ target genes. TRαA and TRβ share 4 identical potential target genes, which are ), aminoacyl tRNA synthetase complex interacting multifunctional protein 1 (). The expression of these genes was tested in different adult tissues and different metamorphosis development stages of in the NC (normal control), TH (thyroid hormone), and TU (thiourea) groups by real-time quantitative PCR. The expression of these genes was highest in the adult brain tissue (<0.05). The expression of these genes during early metamorphic development was highest at 17 dph (days post hatching) and lowest at 28 dph and 32 dph. The expression of these genes in the TH group was lower than in the NC group (<0.05). The difference between the NC group and the TH group at 17 dph was the largest (<0.05), while NC and TH groups had the smallest expression differences at 28 dph and 32 dph (>0.05). Compared to the TH group, the expression in the TU group increased slightly in each period (, and are target genes directly regulated by TH and that the expression of these genes is inhibited by TH. This study successfully identified an effective method to locate the target genes of TH. TH can inhibit the transcription of the target genes during metamorphosis. These results provide basic information for improving the thyroid hormone regulation network. However, further research is required to determine how TH inhibits the expression of these genes.

Abstract:Cytochrome c oxidase (COX) is the terminal enzyme of the mitochondrial electron transport chain, and COX6A is one of the nuclear-encoded subunits. To gain insights into the potential function of ) and the related miRNAs, genes, as well as the expression patterns in different tissues and in response to salinity changes were accomplished. In addition, miRNAs which target to cox6a gene was analyzed. The results showed that two , were identified in the spotted sea bass genome. The phylogenetic relationships confirmed their annotations. Multiple sequence alignment suggested that the C-terminal amino acid sequences of COX6A are relatively conserved. The higher expression level of mRNA was detected in the hypophysis, brain, liver, and kidney, while was highly expressed in the heart and kidney. We obtained four candidate microRNAs (miR-30e-5p, miR-223, miR-200a-3p, and miR-155-5p) which target ). Quantitative reverse transcription-PCR (qRT-PCR) results showed that , miR-30e-5p, miR-223, and miR-200a-3p expressed differentially during the low and high salinity environments, while the expression of miR-155-5p only changed significantly in response to the high salinity treatment, indicating that , and the four miRNAs are involved in osmoregulation in the spotted sea bass. During the acute salinity transfer experiment, the expression of miR-30e-5p, miR-223, and miR-200a-3p was negatively correlated with was the strongest, which suggested that miR-30e-5p, miR-223, and miR-200a-3p may be involved in the regulation of gene expression. This study also provides a valuable reference for the comprehensive analysis of the molecular mechanisms of osmotic regulation in fish.

Abstract:is a commercially important sea urchin species in China and Japan. The chromosomes are difficult to prepare, so the karyotype of is unknown. Egg membrane or fertilization membrane removal is a key step in the preparation of the echinoderm chromosome. To identify the optimal method of egg membrane and fertilization membrane removal, four reagents[triazole solution (2 g/L), dithiothreitol solution (3×10^-3 mol/L), p-aminobenzoic acid solution (3×10^-3 mol/L), and hydrochloric acid solution (pH 4.75)] were used to treat the eggs and embryos for 10 min, 20 min, 30 min, 40 min, 50 min, and 60 min post-fertilization at the 2-cell, 4-cell, 8-cell, and 16-cell stages, respectively. The chromosomes of the blastocyst embryos whose membranes were removed were prepared by conventional air-drying, and the karyotypes were analyzed. The results showed that all four reagents could remove the egg membrane or fertilization membrane. The eggs treated with 2 g/L of triazole for 30 min had an 85.50% membrane removal, 97.25% fertilization rate, and 1.75% deformity rate, indicating that this was the best method. Sixty-one metaphase cells with well-dispersed and well-preserved chromosomes were successfully prepared from the early blastocysts by the optimal membrane removal method. Karyotype analysis showed that the diploid chromosome number of was 42, and the karyotype was composed of 10 pairs of metacentric chromosomes, 10 pairs of submetacentric chromosomes, one pair of subtelocentric chromosomes, and 84 chromosome arms. Thus, the karyotypic formula is 2n=42=20m+ 20sm+2st and NF=84. The chromosome number is the same as that in previous reports for this species and in other sea urchins, such as . The karyotype is the same as . In conclusion, this study compared the membrane removal efficiencies of four reagents, and the results showed that treating with 2 g/L triazole solution for 30 min was the optimal method. We also obtained the karyotype of . The results provide a technical reference for the preparation of sea urchin chromosomes and chromosome manipulation breeding.

Abstract:Cyclin-dependent kinases (CDKs) are members of the serine/threonine protein kinase family and key regulators of the cell cycle transitions in eucaryon. CDK1, also known as Cdc2 or p34cdc2, is the first documented CDK and is vital for mitosis and meiosis. CDK1 functions as a catalytic subunit by binding with its regulatory subunit cyclin B to form a complex at the transition from G2 to M phase. The gene has been described in several species, but investigations in mollusks are lacking. To study the function of the gene in juveniles of selected (red clams) and natural (yellow clams) populations of gene via rapid amplification of cDNA ends (RACE). The cDNA is 1623 bp long and contains a 353 bp 5' untranslated region (UTR), a 370 bp 3' UTR, and a 900 bp open reading frame (ORF) encoding 299 amino acids. The predicted amino acid sequence of exhibited serval conserved characteristics, including a STKc-CDK1-euk domain, specific sequences of the CDK family DLKPQN and G/V-T/S-X-X-Y/F-X-A-P-E, the cyclin B binding site PSTAIRE, and ATP-coupled-sites GXGXXG and K33. Sequence alignments revealed that kinases from other species. The tissue distribution analyses showed that is expressed in all of the tested tissues. The highest expression was in the gonad, followed by the mantle, suggesting that plays an important role in the cells with active division in the gonad and mantle. In different aquaculture conditions experiments, the red clams grew faster than the yellow clams under high and low light and under high and low algal concentrations. The expression profiles of under different aquaculture conditions were consistent with the growth results that expression level was also higher in the red clams. Therefore, we speculate that is closely related to early juvenile growth and that the light and algal concentrations also play important roles (inappropriate conditions may inhibit juvenile growth). The red clams may possess better growth and development characteristics than the yellow clams. The results of this study contribute to a better understanding of the mechanisms of growth and provide basic information for breeding new varieties of .

Abstract:‘Huangguan No. 1’ female and male gametophyte clones were cultured in sterilized seawater with different concentrations of nitrogen (N) and phosphorus (P). The effects of different iron ion (Fe³⁺) concentrations on the growth and development of the gametophytes were studied via observation of the morphological changes, the maximum fluorescence yield of photosystem II (), and calculation of the gametogenesis rate (including the oogonium formation rate, ovulation rate, and seedling formation rate). The results showed that 3.60 μmol/L of Fe³⁺ was the most effective at promoting vegetative growth in gametophytes in seawater with N and P concentrations of 0.825 mmol/L and 0.0336 mmol/L, respectively. Under different N and P concentration conditions, the maximum fluorescence yield of kelp gametophyte could be increased when the Fe³⁺ concentration was 3.60-17.80 μmol/L, and there was no significant difference between each concentration group (>0.05). Under different nitrogen and phosphorus concentrations, the oogonium formation rate, ovulation rate, and seedling formation rate were significantly improved at Fe³⁺ concentrations of 3.60 μmol/L, 8.90 μmol/L, and 17.80 μmol/L. So the iron could increase the developmental process. When the nutrient concentration of N and P reached 0.275 mmol/L and 0.0112 mmol/L, 0.36-17.80 μmol/L Fe³⁺ could promote the gametophyte from vegetative growth to reproductive growth. At Fe³⁺ concentrations of 3.60-17.80 μmol/L, the gametophyte development indicators did not differ (>0.05) among different nitrogen and phosphorus groups. Even if the N and P concentrations reach 0.825 mmol/L and 0.0336 mmol/L, all of the gametes remained in vegetative growth without development under the iron-free conditions. If iron was sufficiently available, most of the gametes (65%) remained in vegetative growth under low nitrogen and phosphorus conditions. A small proportion of gametophytes (35%) entered the developmental state, but the development lagged behind the other N and P concentration groups in the experiment. These results indicated that iron, nitrogen, and phosphorus have synergistic effects on the growth and development of gametophytes and that iron is the key factor in the transition from vegetative growth to gametogenesis. Under appropriate concentrations of nitrogen (0.275 mmol/L) and phosphorus (0.0112 mmol/L), additional Fe³⁺ (3.60 μmol/L) had the greatest effect on the transition process. This study provided a theoretical basis for iron, nitrogen, and phosphorus use during the culture process of gametophytes seedlings and promotes the development of its seedling industry.

Abstract:This study aimed to investigate the effects of different photoperiods on the growth, feeding, and muscle nutrient quality of =450, body length:(13.50±0.52) cm, body weight:(46.04±0.61 g)] were evenly distributed into five different photoperiods (0L:24D, 8L:16D, 12L:12D, 16L:8D, and 24L:0D, "L" and "D" imply light dark and the numbers refer to the number of hour.) and cultured for 60 d. The daily growth index of in the 8L:16D group was significantly higher than the other groups (<0.05). The feed conversion efficiency of the 8L:16D group was higher than the 0L:24D and 24L:0D groups, which increased by 58.28% and 121.98%, respectively (<0.05). The crude lipid contents of the 8L:16D and 0L:24D groups were lower than the 16L:8D group, decreasing by 19.70% and 21.67%, respectively (<0.05). Compared to the 0L:24D and 24L:0D groups, the collagen content of the 8L:16D group increased by 82.04% and 92.98%, respectively (<0.05). Seventeen amino acids were detected in all of the groups, and the total amino acid contents in the muscle of the 8L:16D and 12L:12D groups were higher than the 0L:24D group, which increased by 11.60% and 9.16%, respectively (>0.05). Total content of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) was highest in the 8L:16D group (14.21%) and lowest in the 0L:24D group (12.30%). The photoperiods differentially affected the growth, feeding, and nutritional quality of the juveniles and the results suggest that the 8L:16D and 12L:12D photoperiods are most suitable.

Abstract:This study aimed to explore the effects of different feeding modes on the growth, digestive enzymes, body composition, and aquaculture water quality of in pond polyculture. Three experimental groups were fed chilled feed (Diet 1 group), an artificial diet (Diet 3 group), or a 1:1 mixture of the chilled feed and artificial diet (Diet 2 group). Each experimental group contained 3 replicates, and the experimental period was 45 days. The body weight of and the water quality factors were measured and analyzed every 5 days. At the end of the experiment, samples were collected to analyze the digestive enzymes and body composition. The results are as follows:(1) After 30 days, the body weight of in Diet 2 group was significantly higher than in the Diet 1 and Diet 3 groups (<0.05), but the Diet 1 and Diet 3 groups did not differ significantly (>0.05). The weight gain rate and specific growth rate gradually decreased throughout the experiment. (2) The protein level in the feed gradually decreased from Diet 1 group to Diet 3 group, while the protease activity of gradually decreased and the amylase activity gradually increased. There were no differences in the lipase activity among the experimental groups (>0.05). (3) Diet 2 group had the highest contents of crude protein, followed by Diet 1 group, and then Diet 3 group. The crude protein contents in Diet 2 group were significantly higher than Diet 3 group (>0.05). The water contents in Diet 2 group were significantly lower than in the Diet 1 and Diet 3 groups (<0.05). There were no significant differences in the crude fat or ash contents (>0.05). (4) As the experiment progressed, chemical oxygen demand (COD), ammonia nitrogen, nitrite, nitrate, inorganic nitrogen, and inorganic phosphorus levels in the aquaculture water increased. At the end of the experiment, the water quality indicators were in the order of Diet 1 group > Diet 2 group > Diet 3 group. Together, these results suggest that mixed feeding (chilled feed + artificial diet) was beneficial to the growth, digestion, and protein accumulation of but polluted the aquaculture water to some extent. Thus, the development of an environment-friendly artificial diet is still preferred.

Abstract:Carbon and nitrogen stable isotope technology is an important tool for delineating the nutritional positions and structure of ecosystem food webs. Muscles are commonly used to determine stable isotopes, but changes in the muscle lipid contents affect the results. To investigate this effect, this study selected 45 samples of from the offshore waters of southern Zhejiang and divided them into two groups, 3.5< C:N ≤ 4.0 (group 1) and C:N >4.0 (group 2). Changes in the carbon-nitrogen stable isotope ratios before and after lipid removal and the best lipid correction model were selected from multiple regression models. Pearson correlation analysis revealed significant positive correlations of δ¹³C (stable isotope of carbon), δ¹⁵N (stable isotope of nitrogen), and C:N before and after lipid removal in group 1 (P<0.05). δ¹⁵N before and after lipid removal in group 2 was significantly positively correlated (<0.05), but C:N and Δδ¹³C were positively correlated (<0.05). According to AIC (Akaike information criterion), the linear model has the best fitting degree for the samples with C:N in the range of 3.5 to 4.0, and the fitting equation is Δδ¹³C=1.30×(C:N)-3.69. The nonlinear model has the highest fitting degree for samples with C:N more than 4.0, and the fitting equation is Δδ¹³C=-5.71+5.12×ln(C:N). This study found that the lipid contents significantly affect the determination of carbon stable isotopes. Pretreatment by lipid removal is required for isotopic analysis, especially for muscle samples with high lipid contents. The lipid normalization model simplifies sample processing and has wide-ranging applicability. It is important to select the correct model for different species in diverse locations with varying fat contents.

Abstract:The jumbo flying squid () is a short-lived cephalopod species widely distributing in the eastern Pacific Ocean. Presently, international squid-jigging fishing vessels from China, Japan, Peru, and Chile target this species. China mainland started to exploit in 2001 and now has the largest squid fishery in the world. The oceanic waters off Peru are abundant and important fishing grounds. China has hundreds of fishing vessels operating in these waters, outside of the exclusive economic zones of Peru. The habitat is strongly affected by climatic and environmental variability at different spatial and temporal scales. In this study, two critical environmental variables[the sea surface temperature (SST) and sea surface height anomaly (SSHA) from 1950 to 2015] that affect the abundance and distribution of were used to calculate the habitat suitability index in the waters off Peru. We also evaluated the effects of El Niño and La Niña events on habitat suitability. The integrated HSI values were calculated by the Arithmetic Mean Method. The El Niño and La Niña years from 1950 to 2015 were defined by the 5-month running mean of the SST anomalies in the Niño 3.4 region (5°N-5°S, 120°-170°W) and measured by SSTs above or below a threshold of +0.5℃/-0.5℃ for 5 consecutive months. The intensity of each anomalous event was identified from the National Oceanic and Atmospheric Administration (NOAA). The results suggest that strong El Niño events, compared to weak and moderate El Niño events, are associated with warmer SST and higher sea surface height (SSH). These changes led to smaller suitable areas of SST and SSHA, thereby decreasing the suitable habitat range. During weak La Niña events, SST was warmer and SSH was higher, but during moderate and strong La Niña events, SST was colder and SSH was lower. The range of suitable habitats during strong La Niña events was significantly wider than that during moderate and weak La Niña events. Moreover, as the intensity of El Niño increased, the latitudinal gravity centers of the suitable habitat shifted southward, and as the intensity of La Niña increased, the latitudinal gravity centers of the suitable habitat shifted northward. Our findings suggest that there are significant differences in the environmental conditions of the squid fishing ground during El Niño and La Niña events. These differences directly affect the range of suitable habitats and spatial distribution of .

Abstract:Haizhou Bay is a traditional fishing ground in China. Due to overfishing and environmental pollution, large- and medium-sized economic fish resources in this area have declined. Prior research has focused on fish species with high economic value or emerging dominant prey species such as while overlooking non-dominant species such as those in the genus. This group contains numerous small benthic species commonly found in the Haizhou Bay fishing ground, which perform important ecological functions. Fishery resource conservation should be ecosystem-based, so it is necessary to investigate changes in all of the fish resources. Therefore, this study focused on three non-dominant prey species within , to investigate the growth parameters changes under environmental stress. Using data from 18 bottom trawl surveys in the Haizhou Bay from 2011 to 2019, the von Bertalanffy growth function (VBGF) was estimated via electronic length-frequency analysis (ELEFAN) with the TropFishR package in R. The number of samples was relatively small, so bootstrap resampling was employed to improve the robustness of our estimates. The results show that from 2011 to 2019, the three species experienced a population decline and miniaturization. The infinite length of decreased from 21.60 cm to 13.96 cm, while the growth parameter decreased from 19.72 cm to 19.35 cm, and the growth parameter C. richardsoni decreased from 18.74 cm to 14.91cm, and the growth parameter K decreased from 0.45 to 0.43. All three species showed a decreasing trend in infinite length or an declining trend in the growth parameter species as the r-strategists responded to the local environment stressors (e.g., overfishing and environmental pollution). However, shortened infinite body length and increased growth rates manifest one another and may be related to differences in the specific environmental stressors the three species experienced. This study provides important data on the growth and population development of and provides a reference for future assessments and fisheries restoration efforts in Haizhou Bay.

Abstract:The gut bacterial diversity of Japanese seabass () reared in nearshore net pens at Zhoushan were analyzed by high-throughput sequencing on an Illumina MiSeq platform. The Japanese seabass were fed raw fish, and the giant croaker were fed formulated feed. The bacterial composition of the formulated feed and the seawater in the net pens were also analyzed. A total of 886 operational taxonomic units (OTUs), belonging to 8 phyla and 40 genera, were identified from the fish guts, formulated feed, and seawater. A total of 550 OTUs, belonging to 5 phyla and 15 genera, were identified from the guts of the Japanese seabass and giant croaker. At the phylum level, Firmicutes dominated in the fish gut, while at the genus level, Bacillus dominated in giant croaker. Similarities in the bacterial communities were higher between guts of different fish species than between fish gut and the seawater in the net pen. This suggests that gut bacterial communities of Japanese seabass and giant croaker are independent of the seawater in the net pens. There were more common OTUs between the giant croaker gut and the formulated feed than between the giant croaker gut and the seawater, suggesting a greater impact of the feed on the intestinal bacterial community.