Abstract:In order to study the relationships between the resistance coefficients and lateral force coefficients of the square-shaped artificial reef with hexagonal openings and between the angle of attack and the opening ratio, we designed four model opening ratios (γ_ty = 0.06, 0.14, 0.25, 0.39) The resistance and lateral force of the rectangular open artificial reef at four kinds of attack angles (θ = 0°, 15°, 30°, 45°) were measured, and the resistance coefficient and lateral force coefficient were calculated. Hexagonal open square reef model resistance F_x (30°) > F_x (45°) > F_x (15°) > F_x (0°), and lateral force F_y (30°) > F_y (15°) > F_y (45°) > F_y (0°) were obtained; the reef model resistance F_x (30°) was 1.28-1.72 times that of F_x (0°), and the lateral force F_y (30°) was F_y (0°) 2.8 to 11.1 times. The angle of attack can have a greater impact on the resistance and lateral forces of the reef model. With 4 kinds of opening ratios and 4 kinds of attack angles, the resistance coefficient C_D ranged from 0.98 to 1.53. Resistance coefficient C_D (30°) > C_D (15°) > C_D (45°) > C_D (0°). The reef model resistance coefficient C_D (30°) can be up to 1.26 times compared to C_D (0°). At 4 kinds of opening ratios and 4 kinds of angles of attack, the lateral force coefficient C_L ranged from 0.001 to 0.21. The lateral force coefficient C_L (30°) > C_L (15°) > C_L (45°) > C_L (0°). The maximum lateral force coefficient C_L (30°) of the reef model can reach 3.5 times compared with C_L (0°). When θ = 30°, the effect of lateral force on artificial reefs cannot be ignored.

Abstract:Nuclear factor kappa B (NF-κB) plays an important role in regulating immune response and inflammation. In order to obtain the NF-κB promoter reporter gene and further study the mechanism of the immune response in primitive vertebrates, based on the CDS sequence of the NF-κB gene previously cloned from Lampetra morii, we obtained the L. morii NF-κB promoter sequence by using the 5′upstream promoter characteristic sequence of the NF-κB from L. japonica, which is highly homologous to L. morii, as a template to design primers. The cloned NF-κB promoter sequence from L. morii was 3 169 bp, which was submitted to NCBI Genbank to obtain accession number MN368861. The sequence is predicted by AliBaba2.1 software to include CREB (cgtgacttca), Oct-1 (aatatgaatt), GATA-1 (gaacctatct), AP-1 (ggttgagtca), NF-kappa B (ctttcctgtt), IRF-1 (tttcctgttc), Sp-1 (tgtgaggggt), c-Jun (acgtgacttc), c-Fos (ggttgagtca) and many other transcription factor binding sites, and contains TATA box transcription core elements. The MethPrimer software predicts that there are CpG islands with a CG content greater than 50% and a length of 196 bp at the 1 207-1 402 bp sequence. pGL3-NF-κB-pro recombinant plasmid was constructed by double digestion technology and transfected into human embryonal kidney (HEK293T) cell and epithelioma papulosum cyprinid (EPC) cell. The results of double luciferase reporter gene system assay showed that the fragment sequence had promoter activity in both mammalian cell lines and fish cell lines, while the promoter activity increased significantly after Toll-like receptors (TLR) ligands LPS stimulation in HEK293T cell. In this study, the NF-κB reporter gene of L. morii was successfully constructed, and its activity was confirmed in different cell lines. The results showed that NF-κB is involved in the immune response of TLR signaling pathway after LPS stimulation in L. morii. The construction of the NF-κB reporter gene of L. morii laid a foundation for exploring the signaling mechanism of the primitive vertebrate immune system.

Abstract:To gain a better understanding of the role in gonadal development of StAR in Pelodiscus sinensis, we cloned StAR cDNA full length of 2 377 bp, containing an open reading frame (ORF) for 300 amino acid residues. The predicted StAR of P. sinensis was maximally identical with turtle StAR protein. qRT -PCR result revealed that StAR mRNA was checked in seven different tissues of the turtle, among which the maximum level was detected in testis. The StAR mRNA had been expressed at embryonic 16th stage. In the study, the male turtle was treated by letrozole, and the results showed that the level of StAR mRNA expression increased rapidly compared to the control firstly, and then the expression levels decreased. The recombinant plasmid was constructed and the StAR polyclonal antibody was obtained by immunizing mice. Western blot analysis showed that the expression of StAR in different tissues was consistent with qRT-PCR result. Immunohistochemical results showed that StAR protein was expressed in ovarian stromal cells. Therefore, the StAR gene might play an important role in gonadal differentiation, steroid hormone synthesis and spermatogenesis in P. sinensis.

Abstract:Fishing intensity is one of the important parameters in the field of fishery resources management and assessment. The traditional calculation method cannot satisfy the needs of real-time, large-scale, fast statistical spatial-temporal distribution. This paper proposes to divide the operation stages of fishing vessel production trip based on VMS data; combined with the operating characteristics of stow net fishing vessels, to use the threshold division and density clustering algorithm to extract the net position, and to calculate the fishing duration of each trip; the geographical grid is divided and accumulated within its range. The average fishing duration per square kilometer (h/km²) of each grid was used as the quantitative basis for the fishing intensity of the stow net, and the spatial distribution of fishing intensity was visualized. In this research, the Beidou VMS position data of the stow net fishing vessels belonging to Zhejiang Province in 2017 were taken as the research object. A total of 733 effective operating trips and 6021 net positions were extracted, and the total fishing time was 736 761.78 h. Geographic grids of 0.1° × 0.1° are divided in the range of 121.6°-126.5°E and 27.6°-33.9°N. The stow nets in the first half of 2017 were relatively scattered, and the average fishing intensity of each grid was 11.26 h/km²; relatively concentrated in the second half of the year, with an average fishing intensity of 12.83 h/km²; with the annual average of 14.76 h/km². Among them, in the range of 125.4°-126.1°E and 31.2°-32.1°N there exists the highest fishing intensity, with an average of 28.51 h/km². The net position extraction, fishing duration and spatial distribution of fishing intensity designed in this paper may provide new research ideas for analyzing the operation status of fishing stow nets and the quantification of fishing intensity.

Abstract:In order to support the development of genomics and cytogenetics of Collichthys lucidus, in the present study, the genome size of C. lucidus was determined by using flow cytometry, and the relative length, the relative area and the integrated optical density (IOD) of 24 pairs of chromosomes were determined using PI staining and microscopic image analysis software, and the physical length of chromosomes was estimated based on the values of IOD. The results showed that male and female's genome sizes were respectively estimated at (786.52±1.95) Mb and (802.91±2.19) Mb. Female genome was significantly larger than male genome (by about 16.39 Mb). The genome of female comprised 24 pairs of telocentric chromosomes, the karyotype formula is 2n=48=48t, NF=48, with the physical length ranging from (22.17±0.72) Mb to (46.30±1.06) Mb. The genome of male comprised 46 telocentric chromosomes and one metacentric chromosome, the karyotype formula is 2n=47=46t+1m, NF=48. The male specific metacentric chromosome was Y chromosome, with an estimated physical length of (62.95±2.89) Mb. Physical lengths of chromosomes are correlated linearly with the relative area and the relative lengths. In conclusion, new parameters of chromosomes present in this paper will facilitate to chromosome identification and pairing of C. lucidus, which will serve as reference data for the assembly of the Y chromosome and the evolution of chromosome in Sciaenidae.

Abstract:Fish obtain energy and nutrients through feeding activities, and appetite is an important factor affecting fish feeding. Appetite regulation is a complex network in which the brain integrates the body's energy and feeding signals to regulate fish feeding behavior through appetite regulators, including orexigenic peptides and anorexigenic peptides. As a new endocrine factor, apelin plays a wide range of biological roles in vivo. Among them, the role of apelin in the regulation of food intake is attracting the attention of researchers. This paper reviews the tissue distribution of apelin, the effects of starvation and nutrients on apelin expression, the effects of apelin treatment on animal feeding, especially fish feeding, its possible mechanisms and signaling pathways, so as to provide references for promoting fish feeding and aquaculture.

Abstract:This research was conducted to explore the morphological characteristics and difference of Saurogobio dabryi in different river sections of Jialing River. A total of 120 samples collected from upstream, midstream and downstream of Jialing River were analyzed, using the multivariate morphometric method and the landmark-based geometric morphometric method. The morphometric analysis illustrated that there were significant differences among populations of S. dabryi in different river sections. The morphological variations of the three populations were mainly observed on the head, fin and caudal peduncle. The body of S. dabryi in the upstream group was the most slender. Besides that, the fork length, length between pectoral fin and ventral fin, trunk length, the inter-orbital width, dorsal fin coxal length, head depth and beard length in this group were the largest. The midstream group of S. dabryi had the longest pectoral fin, ventral fin and caudal fin, the strongest caudal peduncle, the largest of the width of caudal stalk, the depth of caudal stalk, the longest head, the widest body and the largest length between pectoral fin and rhynchodaeum. For S. dabryi in the downstream, the length between anus and anal fin and head width of the lower reaches were the largest. However, the scatter diagram of relative warp scores analysis showed that S. dabryi population from different river sections of Jialing River cannot be distinguished. The variation coefficient of morphometric characters showed that the phenotypic differences of S. dabryi in the three river sections were intraspecific. We speculated that the morphological variations of S. dabryi in Jialing River should be the result of adaptive evolution to the diverse environments in Jialing River, such as the flow rate, water temperatures, and food types.

Abstract:The community stability is essential to better understand the community structure and ecosystem functioning, and the robustness can elucidate the degree of community stability. Using the fish data of bottom trawl samplings from 2015 to 2018 in the Pearl River Estuary, we established the annual ecological "snapshots" of networks based on the feeding relationship between the fish species. Four characters of the four annual networks were summarized as follows: ① all the networks belonged to the complex networks as the values of P(k) fitted the power-law distribution, indicating the high resistance of the networks to random disturbances (such as fishing and environmental change). The resistance was also a sign for the drastic environmental variations of estuaries habitat; ② the species richness varied significantly in 2015 and 2018, and the densities of networks(D)ranged between 0.03 and 0.10 and had been descending annually since 2015, indicating the degrading of network robustness regardless of species richness; ③ the networks were characterized by the common random networks, such as low average path length (all APL was 1) and low clustering coefficient (C ranged between 0.01 and 0.06), indicating that the networks had the high rates of energy flow and comparatively even distribution of fish species relations. This paper provided clues for the quantitative research on fish community structure and stability in the key habitats of the coastal waters.

Abstract:While the importance of spatial scale in ecology is well established, few studies have investigated the impact of spatial scale on hotspot analysis of biological resources. In this study, in order to analyze the impact of spatial scale on hotspot analysis of Antarctic krill (Euphausia superba) density distribution around Antarctica, the krill density data from 1926 to 2016 by 10-year period was interpolated into ten spatial scales, i.e., 10′×10′, 20′×20′, 30′×30′, 40′×40′, 50′×50′, 1°×1°, 2°×2°, 3°×3°, 4°×4°, and 5°×5°, respectively, and linear, logarithmic, exponential, power-law, and polynomial functions were used to calculate the relationship between the global krill density, krill density in hotspot (coldspot) areas and the spatial scale, and the variations in centroid and hotspot (coldspot) areas at different spatial scales were also analyzed. The results showed that there was a significant scaling relationship between the maximum, skewness, kurtosis, Coefficient of Variation (CV) of global krill density and the spatial scale. Significant scaling relationship between the maximum, skewness, kurtosis, third quartile (Q3), and CV of the krill density in hotspot area and the spatial scale was found. A significant scaling relationship was also found between the maximum, mean, standard deviance (SD), skewness, kurtosis, Q3, CV and spatial scale for the coldspot area. The size of the hotspot (coldspot) area increased with the increasing of the spatial scale, and the offset of centroid indicated the locations of the hotspot (coldspot) areas were greatly affected by the spatial scale. Significant shift of centroid for hotspot (coldspot) areas occurred when the spatial scale was greater than 1°×1°. Therefore, it is not recommended to use spatial scale that is greater than 1° × 1° to identify the local spatial pattern for hotspot analysis of krill density.

Abstract:Previously naturally sex-reversed XY females were found in several Oreochromis niloticus populations, while it is unclear whether the naturally sex-reversed XY females could be used for breeding of YY supermale. CQ and WC O. niloticus populations were introduced. The genetic sexes of CQ and WC are controlled strictly and not strictly by LG23 chromosome, respectively. YY supermales were obtained by crossing CQ XY male fish with WC XY female fish, and whether the F₁ YY male could be used for sex control was tested. The body weight, gonadal somatic index (GSI), serum hormone level and gonadal gene expression patterns in XY and YY individuals of F₁ generation were analyzed. A quarter of YY supermales were obtained in the F₁ generation of the progeny of CQ XY male and WC XY females. F₁ YY supermales were all male and fertile. F₁ YY supermales were crossed with WC XX female, WC XY female (dam), F₁ XX female and CQ XX female, and their offspring were almost all male. Two female fish were found in the progeny of the F₁ YY male and F₁ XX female, and the male ratio is 98%. At 180 days after hatching, there were no significant differences in body weight, GSI and serum hormone levels between F₁ XY and YY hybrids. Testicular gene expression analysis showed that the expression levels of AmhX/AmhY in YY were significantly higher than those of XY fish, while the expression levels of Dmrt1 and Cyp11b2 were not significantly different between XY and YY individuals. The physiological indexes of YY fish are highly similar to those of XY fish. Naturally sex-reversed XY female O. niloticus can be used for breeding YY supermale fish, which can be used for tilapia sex control.

Abstract:Replacement of fish meal in aquafeed has been recognized asa key to sustainable development of aquaculture industry due to the fast expansion of aquaculture industry in the last 40 years. Various plant ingredients, including cottonseed meal, were tested as fish meal substitute in fish feed, however, complete replacement of fish meal with plant ingredients in carnivorous fish feed remains a problem. Cottonseed protein concentrate (CPC) is a novel cottonseed protein ingredient with high protein content and low free gossypol, however, knowledge about CPC as a fish meal substitute in carnivorous fish feed is scarce. In this study, a 10-week feeding trial was conducted to evaluate the potential of replacing fish meal with CPC in black sea bass (Centropristis striata) diet. A single factor experiment including four fish meal levels was done. A control diet (C) was formulated to contain 35% fish meal. In the other three diets, 40% (R40), 60% (R60) and 80% (R80) of the fish meal in diet C were replaced with CPC, respectively. Each diet treatment was triplicated. Initial body weight of black sea bass was (29.5±0.5) g. During the trial, fish were fed with the test diets twice daily. The results showed that the replacement of fish meal with CPC did not significantly affect feed intake, growth, feed utilization efficiency, body composition and wastes of nitrogen, phosphorus and carbon. However, the ratio of fish meal consumption to fish production (RCP) declined with the decrease of dietary fish meal level. According to a multiple dimension analysis based on growth, feed cost, feed utilization efficiency, environment impact and RCP, the farming benefits of black sea bass fed diet R80 was different from those fed diets R40 and R60. This study reveals that fish meal content in black sea bass diet could be reduced to 7% by CPC inclusion.

Abstract:Agouti-related protein (AGRP) and neuropeptide Y (NPY) are important factors involved in the regulation of feeding in both mammals and fish. In this study, the full-length cDNA sequences of AGRP and NPY genes of Megalobrama amblycephala were cloned by RACE technology for the first time, to investigate the expression patterns of AGRP and NPY in different tissues and different physiological conditions of fasting and refeeding in M. amblycephala by Quantitative Real-time PCR technology. Four hundred and eighty juvenile blunt snout breams with an average body weight of (5.30±0.01) g were randomly divided into 4 groups with 3 replicates in each group, i.e. the control group (the daily feeding experiment diet at 3% of the weight), the F/refeeding group (fasted from 1 d to 14 d, refed from 15 d to 28 d and the daily feeding experiment diet at 3% of the weight), the F/excessive refeeding group (fasted from 1 d to 14 d, refed from 15 d to 28 d and the daily feeding experiment diet at 8% of the weight), the fasted group (fasted for 28 d). The results showed as follows: ① The results of histological analysis showed that the epithelium columnar cells of intestine in the fasted group displayed obviously leukocyte infiltration in the submucosa. ② The full length cDNA of M. amblycephala AGRP and NPY are respectively 770 bp and 557 bp, consisting of a 5′ untranslated region of 77 bp and 101 bp, a 3′ untranslated region of 315 bp and 120 bp, and an open reading frame of 378 bp and 336 bp, encoding 125 amino acid and 111 amino acids. Based on similarity comparison, AGRP is relatively conservative and has the highest similarity to AGRP in Cyprinus carpio, and the phylogenetic tree analysis indicated that AGRP and NPY of M. amblycephala is associated with AGRP and NPY in other fishes, respectively. ③ Quantitative Real-time PCR analysis showed that AGRP and NPY were both expressed in all tested tissues with highest expression in brain and then liver and intestine. ④ There were significantly differences in AGRP and NPY mRNA of fish during fasting and refeeding. The expression of AGRP mRNA in the brain firstly increased and then decreased after refeeding, at 28 d, AGRP mRNA expression levels of brain tissue in F/refeeding group were higher than those in other groups, but AGRP mRNA expression levels of intestine tissue in F/excessive refeeding group were higher than those in other groups. Meanwhile, the expression of NPY mRNA showed a trend from decline to rise in the brain and intestine tissues, NPY mRNA expression of brain and intestine tissue in fasting group was higher than that of other three groups. In conclusion, this study showed that AGRP and NPY are involved in feeding regulation in M. amblycephala and have different expression patterns in brain and intestinal tissues.

Abstract:To explore the seasonal variation of commercial farmed scallop Patinopecten yessoensis, primary characteristics, ATP-related compounds and ATPase of scallop in spring (April), summer (July), autumn (October) and winter (January) were analyzed. The thermal stability changes of striated muscle and smooth muscle were analyzed by Mf-Ca²⁺ATPase to explore the seasonal changes of thermal stability of adductor muscle. The results showed that P. yessoensis was the fullest in spring. The condition index of gonad was as high as 6.96%, and only 1.79%-2.95% in other seasons. There was no significant seasonal difference in protein, fat and ATP contents in adductor muscle. The adductor muscle was rich in protein which accounted for 75%-80% of the dry basis. The fat content was very low, only 0.63%-1.00%. It was worth noting that the total sugar content of the adductor muscle in spring and summer was significantly higher than that in autumn and winter, 11.14% and 13.84%, respectively, and the lowest in winter is only 2.67%. ATP content in striated muscle was higher than that in smooth muscle in all seasons, 4.3-5.0 μmol/g, and 1.2-1.6 μmol/g, respectively. There was no significant difference in ATP and related compounds between striated muscle and smooth muscle in different seasons. In addition, striated muscle has similar thermal stability to smooth muscle. The Mf-Ca²⁺ATPase of striated muscle and smooth muscle did not change significantly after 30 min heating at 30 °C and 35 °C. It decreased at 40 °C, and changed obviously at 45 °C. The protein was almost completely inactivated within 10 min heating at 50 °C. Mf in adductor muscle had the fastest inactivation in spring, while the inactivation rate of striated muscle was slightly higher than that of smooth muscle, yet with little difference in winter, autumn and summer. Because of difference of thermal degeneration rates in Mf, it was presumed that there were two types of myosins with different stability in adductor muscle of P. yessoensis, which needs further analysis and elucidation.

Abstract:Takifugu, belonging to Tetraodontidae in Tetraodontiformes, is the typical adaptive radiation species, and there were about twenty Takifugu species along the coast of China. In this study, phylogeny and population genetics of Takifugu species were analyzed based on population scale for the first time. Using mitochondrial genome, we obtained 1, 488 SNPs and 4 INDELs in 124 individuals of 10 Takifugu species. The phylogeny and population genetics analysis showed that T. poechilonotus and T. alboplumbeus could be synonymous, and the sister group of these two species was located at the base of phylogeny tree. Besides, we found that the relationships between T. rubripes and T. fasciatus, T. flavidus and T. bimaculatus were close. In addition, we detected 4 T. bimaculatus individuals which possibly were the hybrid progenies with T. flavidus, and 2 hybrid suspect T. oblongus individuals. For genetic diversity, we found that T. alboplumbeus has the lowest diversity. Moreover, we identified 595 species Species-specific SNPs in 10 Takifugu species. The Ka/Ks analysis showed that cox1 had the lowest Ka/Ks, and the Ka/Ks of nd6 was 1.19, which indicated that nd6 possibly has undergone positive selection. Besides, the ATP synthetase might be under selection in the process of adapting to fresh water of T. ocalletus and T. fasciatus. This study showed that the phylogenetic relationship of Takifugu was complicated. Although the natural hybridization between species was common in the wild, this study can provide reliable molecular markers for the rapid identification of Takifugu species, and provide a solid foundation for the study of the Takifugu phylogeny in the future.

Abstract:The study of the cold-adapted characteristics of Euphausia superb carboxypeptidase and its mechanism of responding to low temperature in the catalytic reaction process was of certain significance to the fundamental research of enzymatic molecular transformation and practical production and application. This paper studied the cold-adaptation of carboxypeptidase from E. superb and discussed its cold-adaptation mechanism, in an attempt to provide support for basic research on molecular modification and broaden its commercial application. The cold-adaptation of carboxypeptidase from E. superb was initially examined by comparing its thermodynamic activation parameters with its counterparts from bovine. Then the cold-adaptation mechanism was discussed with the full gene and predicted structure based on bioinformatics. The results showed the catalytic efficiency K_cat/K_m and affinity to substrate of E. superb carboxypeptidase were higher than its counterparts of bovine at 4 °C and 30 °C respectively and revealed its cold-adaptation behavior. The amino acid sequence of E. superb carboxypeptidase was highly homologous with many species, such as Astacus astacus, as seen in the result of sequence alignment. The active site and Zn binding site were also proved to have conservativeness. Its cold-adaptation may be attributed to the following attributes. The proportions of certain residues were critical in cold-adaptation behavior, such as a higher proportion of Asp and lower proportions of Pro, Arg and Phe compared with its warm-counterparts. It could probably diminish the number of intra-molecular interaction resulting in improved structural flexibility. Furthermore, higher proportion of loose random coils and reduced steric hindrance might be also the key factors promoting its cold-adaptation. The carboxypeptidase from E. superb was prone to have cold-adaptation behavior. The special molecular cold-adaptation strategies to low temperature were revealed as, but not limited to, different proportions of certain residues, more loose random coils and reduced steric hindrance, all of which promoted the catalytic reaction.