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Abstract:Accurate knowledge of species distributions and population dynamics is the basis for fishery resource assessments. However, it is difficult to monitor certain species with small populations or complex life histories. Recently, as a new monitoring technology, environmental DNA (eDNA) has been widely used in species monitoring, biodiversity assessments, and biomass assessments. In this study, eDNA technology was employed to understand the distribution of Chinese shrimp during its winter migration. In December 2019, we collected water samples from three water layers in the south-central Yellow Sea to test the eDNA of Chinese shrimp Fenneropenaeus chinensis. In addition, laboratory experiments were carried out on the surficial sediments of the seabed. First, it was found that the eDNA of Chinese shrimp exhibited a specific vertical distribution in the natural water, which was characterized by a high concentration in the bottom layer and low concentration in the surface layer. This distribution is related to the life habits of Chinese shrimp. Second, the surficial sediments would re-suspend and release eDNA to the surrounding areas under the action of external forces, causing a large impact on the water. In this study, the surficial sediments were divided into three experimental groups. The maximum amounts of eDNA released by the three experimental groups were 1624.06, 3453.34, and 1143.24 copies/L, the effects of which lasted for approximately a week. It is hoped that this study will assist with the eDNA sampling design in the future.

Abstract:This study analyzed the carbon and nitrogen stable isotopes from 36 species of marine fishes in the Yellow Sea and northern East China Sea in 2011~2014. The feeding characters were determined by calculating the benthos proportion (Bp) with the δ13C data, and the trophic levels (TLs) were calculated using the δ15N data. The results showed that the trophic levels of the fishes ranged from 2.75 to 4.34 (mean 3.47). Four of the 36 species were completely plankton-feeding, and eight of them were benthos-feeding. The number of mixed feeding and complete benthos-feeding species was 12. Most of the fish species (91.67%) belonged to the middle (TL=3.5~4) and low (TL<3.5) trophic levels. However, the number of high trophic level (TL>4) species was only 3, and all were mixed feeding. In contrast to the TL research results of 1986, 1992, and 2004, the authors of this paper found that the trophic levels of some species had changed slightly in recent years. For example, the TL of Scomberomorus niphonius had decreased to varying degrees, while that of Setipinna taty had increased to a certain extent. The feeding character results were compared to those of 2004, 2009, and 2011. It showed that the feeding character of some fishes, such as Argyrosomus argentatus, had changed significantly. That of others, such as Larimichthys polyactis, had not changed significantly.

Abstract:In order to better understand the temporal and spatial variation in characteristics of phytoplankton community structure and their relationship with environmental factors in Sanggou Bay, four seasonal cruises were carried out at 21 sites in April (spring), July (summer) and November (autumn) 2017 and in January 2018 (winter). Analysis identified 51 species from 31 phytoplankton genera in the surveyed area. Among these, 43 species were from 24 genera of diatoms, 4 species from 3 genera of dinoflagellates, 2 species from 2 genera of Chlorophyta, and 1 species of Cyanophyta. Seasonal analysis showed that there were 22 species in spring, 20 species in summer, 23 species in autumn, and 20 species in winter. The dominance index showed that diatoms comprised the dominant species, and that Paralia sulcata was the dominant species throughout the year, with percentages ranging between 18.6% and 84.9%. The abundance of phytoplankton cells ranged from 0.16×103 cells/L to 12.2×103 cells/L (winter > spring > autumn > summer). The species diversity index (Shannon-Wiener index) varied from 0.69 to 1.35 (autumn > summer > winter > spring). The species evenness index J (Pielou) ranged from 0.42 to 0.70. Phosphate is the main limiting nutrient for phytoplankton growth in Sanggou Bay. The results reveal the spatial and temporal variation characteristics of phytoplankton community in a typical large-scale mariculture bay and provide the basic data for in depth understanding of the structure and function of the mariculture ecosystem.

Abstract:To study the population dynamics and conservation strategies of the Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis), Vortex (v.10.3.7.0) was used to analyze the population viability. Taking 1999 as the starting point, a retrospective analysis revealed that the extinction probability of finless porpoise was most likely to be 0.0754 and was not higher than 0.5629. The mean extinction time was most likely to be 93.5 years and not less than 87.9 years. Taking 2017 as the starting point, through the analysis of the current situation, it was found that the extinction probability of the Yangtze finless porpoise population was 0.3551~0.6985, and the average extinction time was 83.5~88.0 years. In certain situations, the proportion of newborn male Yangtze finless porpoise was 0.55, 0.50, and 0.45, respectively. The results showed that masculinization increased the probability of extinction from 0.6985 to 0.9157, and feminization brought it down to 0.3664. At the same time, comparison of the data found that a 10% decrease in the proportion of newborn males and a 10% increase in the breeding rate of adult females had the same effect. The above results suggested that the extinction risk of the finless porpoise population in the Yangtze River was relatively high. Focusing on the protection and restoration of high-quality habitats, especially those related to parents–children, is important for the protection of the Yangtze finless porpoise.

Abstract:Using data from the spring fishing port samples and bottom trawl surveys in the Beibu Gulf, the biological characteristics and inter-annual changes of Saurida tumbil were investigated. The population structure of S. tumbil in the Beibu Gulf had a miniaturization trend - the average standard length (SL) and body weight (BW) decreased from 2008 to 2018, with ranges of 15.8~16.9 cm and 48.8~77.5 g, respectively. There were also temporal variations in SL and BW; the average values decreased by 6.5% and 34.5% from 2008 to 2018, respectively. The range of the allometric parameter b was 3.03~3.42, indicating that S. tumbil had positive allometric growth (b>3) in the Beibu Gulf in spring. Analysis of the inter-annual change in length at 50% maturity (L50) in females showed that the S. tumbil population maturated before the L50, decreasing 12.6% from 2008 (19.0 cm) to 2018 (16.6 cm). Compared to 2011 (18.6 cm), the 2015 female L50 reduced by 3.8% (17.9 cm). Fatness also declined from 2008 to 2018 (range: 1.09~1.29), as evidenced by consistent downward trends in the fatness samples from both fishing methods. However, fatness had an overall increasing trend with increasing SL.

Abstract:Sex determination and differentiation in fish are not only influenced by genetic factors, but also controlled by environmental factors. Previous studies have shown that cortisol plays an important role in the feedback of environmental stress in fish. Fish hsd11b1l and hsd11b2 can regulate the concentration of cortisol. In this study, we cloned full-length cDNA of hsd11b1l and hsd11b2, and analyzed their sequence characteristics in Chinese tongue sole (Cynoglossus semilaevis). We then detected their spatiotemporal expression characteristics and expression patterns after temperature stress. The full-length cDNA of hsd11b1l was 1650 bp with 864 bp open reading frame encoding a predicted 287 amino acid protein. While the full-length of hsd11b2 was 4526 bp with 1209 bp open reading frame encoding 402 amino acid protein. The qPCR showed that the highest expression of hsd11b1l was within the liver and the expression level in the ovary was two-fold higher than that in testis. In particular, the expression level of hsd11b1l in the ovary was higher than in testis at the stages of 6 mpf and 3 ypf. The hsd11b2 was expressed mainly in the testis and expression level peaked in testis at 6 mpf. Conversely, expression of hsd11b2 was hardly detected in any stages of ovary development. In addition, we analyzed the expression patterns of hsd11b1l and hsd11b2 after high-temperature (28℃) treatment. The expression levels of hsd11b1l and hsd11b2 was significantly reduced in the gonads of males (P<0.05) after the high-temperature treatment for 2 months. For the acute high-temperature treatment (48 h), the expression of hsd11b1l significantly decreased in the gonads of both females and males (P<0.05), and the expression of hsd11b2 was only significantly down-regulated in the male testis (P<0.05). In this study, the expression patterns of hsd11b1l and hsd11b2 genes in the developmental stages of gonads affected by high temperature stress lays a foundation for understanding the relationship between temperature and sexual differentiation in Chinese tongue sole.

Abstract:The effects of five different feeding frequencies on the growth performance, physiological index, and hepatic heat shock protein 70 (hsp70) gene expression levels of juvenile Thamnaconus septentrionalis [body weight of (6.47±0.56) g] were studied. The experiment design included 5 feeding frequencies, namely 1, 2, 3, 4, and 5 times/d (referred to as F1, F2, F3, F4, and F5 respectively), and each treatment group was designed with 3 parallels, and each tank was cultured 30 fish. The experimental period was 30 days and water temperature range was 17℃~26℃, the salinity was 30~31, the pH was 6.8~7.6, and the dissolved oxygen was ≥ 5 mg/L. Results showed that under different feeding frequency conditions, the growth, body composition, digestive enzymes, and antioxidant enzyme activities of the juvenile T. septentrionalis were affected. With the increase in feeding frequency, the feeding and growth of T. septentrionalis showed an upward trend. The F5 group had the largest value, with a feeding rate of 3.95%, a weight gain rate of 347.19%, a specific growth rate of 5.07%/d. The weight gain rate of the F5 group exceeded twice the value of the F1 group. The condition factor of the F1 group was 1.79, which was significantly lower than that of the other four groups (P<0.05). The hepatosomatic index gradually increased, and the F4 and F5 groups exhibiting significantly higher values than the other three groups (P<0.05). With an increase in the feeding frequency, the crude protein content of the experimental fish showed a trend of first increasing and then decreasing: F2 showed the highest crude protein content of 59.82%, and the crude lipid content showed a gradually increasing trend: F5 was the highest with a crude lipid content of 31.23%. Trypsin activity showed a trend of first decreasing and then increasing with the increase in feeding frequency. The F3 group had the lowest activity of 37.48 U/μg prot; lipase activity gradually increased, and the F5 group showed the highest activity of 2.67 U/g prot; amylase activity was not affected by the feeding frequency (P>0.05). Catalase activity, superoxide dismutase activity, and the content of malondialdehyde were the highest in the F5 group, at 14.71 U/mg prot, 250.32 U/mg prot, and 2.73 nmol/mg, respectively. The relative expression levels of the hsp70 gene in the liver was not affected by the feeding frequency (P>0.05). Based the findings of this study and the comprehensive consideration of the growth performance and physiological indices of Thamnaconus septentrionalis, the optimal feeding frequency for this species was determined to be 3 times/d.

Abstract:To reveal the molecular genetic mechanisms of body mass and morphological traits in turbot (Scophthalmus maximus) and scan molecular markers and candidate genes, which can be used to improve the target traits, a genome-wide association study (GWAS) was carried out using specific-locus amplified fragment technology (restriction site-associated DNA, 2b-RAD). First, body mass (BM), body length (BL), body width (BW), and caudal peduncle width (CPW) of 441 individuals were measured at about 473 days of growth period in a turbot breeding population. Second, all individuals were genotyped using 2b-RAD, and 23,988 SNPs were obtained after strict quality control. Using a multivariate linear mixed model (mvLMM) for GWAS of traits of BM-BL and BL-BW-CPW, 9 and 2 pleiotropic QTNs were detected for each phenotypic combination, respectively. However, a single-trait linear mixed model (LMM) based on the FaST-LMM algorithm was used for the association analysis of each trait, and the results showed that 4 QTNs were detected in the BM trait, 1 QTN was associated with BL and BW traits, respectively, and no significant locus was found in the CPW trait. A comparison between results of mvLMM and LMM found that mvLMM could detect more QTNs than LMM in GWAS, and the pleiotropic QTNs detected by mvLMM were more biologically meaningful. This study applied mvLMM and LMM to the joint GWAS of body mass and morphological traits in turbot, 17 significant QTNs were detected both using mvLMM and LMM, and 4 of them were detected repeatedly. Furthermore, 12 candidate genes were found by searching the nearest gene of each detected QTN on the whole turbot genome. All of them might be important candidate markers and functional genes, which could influence turbot body mass and morphology. Our study also provided the theory and a reference for marker-assisted selection of body mass and morphological traits in turbot.

Abstract:The genetic resources available for the commercially important pelagic yellowtail kingfish (Seriola lalandi) are relative sparse. 2b-RAD simplified genome sequencing technology was applied to screen single nucleotide polymorphisms (SNPs) in yellowtail kingfish, and a total of 26,665 SNPs were obtained. A genome-wide association study was carried out to detect body weight- and total length-associated SNPs in 119 individuals from the yellowtail kingfish population in the Yellow Sea. The results showed that 17 SNPs associated with body weight and with potential genome-wide significance were found. Genes in the candidate regions with 1 Mb windows were screened, and 17 candidate genes were obtained. A total of 12 SNPs associated with total length and with potential genome-wide significance were identified, and 12 candidate genes were found. For these candidate genes, KEGG pathway analysis showed that they are mainly involved in the metabolic regulation pathway of growth and development in other vertebrates, which may be important candidate SNP loci and functional genes closely related to the growth traits of yellowtail kingfish. The present results could provide genetic information for the sustainable utilization of germplasm resources and genetic breeding of yellowtail kingfish in the in the future.

Abstract:We observed, measured, anatomized, and photographed the external shape, meristic and metric characters, digestive system, and reproductive system of Anarrhichthys ocellatus. The results are as follows: the body type of the A. ocellatus is anguilliform, the skin color is black or rubricans without any mackerel scales, and there are a number of dollar spot-like eyes on the head, back, and dorsal fin. The number of spots on the dorsal fin, pectoral fin and anal fin were 232~267, 15~22, and 189~220, respectively. A. ocellatus has no ventral fin, and the tail fin is linked to the dorsal fin and pectoral fin and cannot be distinguished. There are two incomplete lateral lines on each side, the upper is 18–25 and the lower is 76~85. The female lateral line is distinct. However, that of the male is not. A. ocellatus also has no pyloric caeca, and the number of upward gill rakers, downward gill rakers, and vertebrae are 49~70, 55~73, and 232~271, respectively. Besides, the magnitude of variation in the total length/standard length is small, with little difference between females and males. The values of the head length/proboscis length, head length/eye diameter, and standard length/intestine length not only vary largely, but present poor linear correlation, with great differences between females and males. Therefore, the females and males can be distinguished. The relationship between weight and length: W = 0.0337Sl2.4798 (R2 = 0.9992), for females, W = 0.0326Sl2.486 (R2 = 0.9990); and for males, W = 0.0359Sl2.4672 (R2 = 0.9995). The digestive system consists of the digestive tract and digestive glands, and the oropharyngeal cavity is large; A. ocellatus has jaw teeth, without cavities and plow teeth, the pharyngeal teeth are well-developed, the stomach is “I”-shaped and large. The intestines are wide and short, and the ratio of intestine length/total length is 0.45. The related traits and characteristics show that the A. ocellatus is carnivorous and hermaphroditic. The ovaries (Ⅲ~Ⅳ) are elliptical, pink, and left right symmetrical. The testes (Ⅲ~Ⅳ) are “Y”-shaped and pink.

Abstract:Recently, with the increase of global plastic production, microplastic accumulation in aquatic environments is increasing. This seriously endangers the living environment and aquatic organism health. Furthermore, it endangers human health through the food chain. Microplastic detection in aquatic products is fundamental to understanding microplastics. Using digestive compounds to extract and separate microplastic from aquatic organisms is an effective means. It is particularly important to choose the correct digestive compounds and conditions. In the present experiment, zebrafish was used as an aquatic model, and polystyrene was used as the raw material. Zebrafish and microplastics were mixed in proportion. The microplastics were separated and extracted using different digestive compounds. Initially, 10% KOH, 30% H2O2, 69% HNO3, and trypsin were selected based on digestibility, recovery rate, Raman spectroscopic analysis, and scanning electron microscopy. The results showed that 30% H2O2 has the lowest digestibility and can change its chemical structure. Trypsin has the lowest recovery rate. Scanning electron microscopy and stereoscopic microscopy showed that 69% HNO3 changed the microplastics color and corroded the surface. Therefore, 10% KOH solution was selected as the optimal digestive compound. Then, the optimal digestion conditions of KOH solution were determined using single factor and Box-Behnken design tests. The results showed that the optimum digestion conditions were: concentration – 4%, temperature – 47℃, time – 20 h, with 97.38% digestibility. The digestive compounds and conditions screened in this study could significantly improve zebrafish digestion efficiency. The results provided a new method for the digestion of aquatic products and further detection and analysis of microplastics in aquatic products.

Abstract:Apparent digestibility coefficients (ADCs) of dry matter, crude protein, crude lipid, gross energy, phosphorus and amino acids in white fish meal, Peruvian red fish meal, meat and bone meal, corn gluten meal, soybean meal, peanut meal, cottonseed meal, and rapeseed meal were determined for juvenile tiger puffer (Takifugu rubripes) with initial mean body weight of 37.90 g. A reference diet and test diets that consisted of a 70 : 30 mixture of the reference diet to test ingredient were used with 0.1% Y2O3 as an external indicator. White fish meal, Peruvian red fish meal and soybean meal had higher ADCs of dry matter, dry matter ADCs ranged in 43.35%~70.54% among ingredients tested. Protein ADCs of feed ingredients ranged in 50.91%~92.78%, meat and bone meal had significantly lower ADCs of protein compared with that of white fish meal, Peruvian red fish meal, soybean meal, peanut meal, rapeseed meal and distillers dried grains with solubles (DDGS) (P<0.05). Amino acid ADCs generally reflected protein digestibility. ADCs of lipid were relatively high in the ingredients tested. Energy ADCs of feed ingredients ranged in 30.58%~90.01%, white fish meal, Peruvian red fish meal, soybean meal and peanut meal had significantly higher ADCs of energy (76.26%~90.01%). Phosphorus ADCs of feed ingredients ranged in 9.13%~68.14%, white fish meal, Peruvian red fish meal had significantly higher ADCs of phosphorus among ingredients tested. In conclusion, ADCs of dry matter, crude protein, crude lipid, gross energy, phosphorus and amino acids in white fish meal, Peruvian red fish meal were higher, while ADCs of dry matter, crude protein, crude lipid, gross energy, phosphorus and amino acids in meat and bone meal and DDGS were lower compared with that other tested ingredient for tiger puffer. Soybean meal and peanut meal had higher ADCs of protein and essential amino acids in plant protein ingredients. Resultant digestibility data may provide useful information to commercial tiger puffer feed industry.

Abstract:Learning and information transfer are two important parts of fish cognitive processes. This study aimed to compare the time and behavioral parameters of juvenile seabass (Dicentrarchus labrax) with or without experienced individuals under a specific environmental condition. The experimental device was “L”-shaped and consisted of three 60 cm×60 cm test compartments made of PVC material. The two adjacent compartments were connected by a cylinder channel with an inner diameter of 12 cm (i.e., first channel and second channel). The experiment comprised two trials: The first tested the time and behavior of an alone fish (AF) to complete the task, and the second tested the time and behavior of inexperienced fish (SF) in the presence of experienced fish to complete the task and the correlation of behavioral parameters between pairs of fish. The results showed that the time for the AF and SF to pass through the second channel was significantly lower than that through the first channel (P<0.05), regardless of the presence of experienced fish. Over the entire experiment, no significant difference was observed between the times taken for AF and SF to pass through the second channel (P>0.05), but less time was taken in the second trial. The pairs of fish showed similar motion trends within 10 min after they first met and kept the relative movement distance within one total length. There were significant correlations between the pairs of fish in terms of the distance moved, velocity, acceleration, turn angle, and activity. These results suggested that inexperienced fishes’ behavior might be influenced by an experienced individual, and that inexperienced fish might obtain more complex information in the process of exploring their environment.

Abstract:A rapid reduction in the dissolved oxygen concentration of water is an important factor contributing to disease in shrimps. In this study, we examined differential gene expression in the shrimp Palaemon carincauda under conditions of hypoxic stress. We obtained 10.62 Gb of high-quality sequencing data, from which 155113 transcripts and 118953 unigenes were assembled. Among the unigenes, 37580 were annotated and 33659 were found to be homologous to genes in the Nr protein database. We also annotated 11275 unigenes using the KEGG database, which were further classified into 223 metabolic pathways. We detected 1392 genes that were differentially expressed in shrimps exposed to hypoxic stress, among which 311 and 1081 were up- and down-regulated, respectively, and 784 were annotated. The enrichment of differentially expressed genes in antioxidant activity, cell connection, protein-binding transcription factor activity, multicellular biological processes, replication, and reproductive processes indicated that exposure to hypoxia activated a series of physiological responses in shrimps associated with adaptation to low levels of dissolved oxygen. Among the genes up-regulated under hypoxic stress was hypoxic induction factor 1 (HIF1), which is comprised the two subunits HIF1α and HIF1β. RT-PCR analysis revealed that during the latter stages of hypoxic stress, there was a notable up-regulated expression of HIF1α and HIF1β in the hepatopancreas and gills of P. carincauda. These observations indicated that P. carincauda cells induced hypoxic induction factor production in a hypoxic environment, thereby inducing an increase in blood oxygen supply. We also detected an enrichment of differentially expressed genes in the glycolysis/glucose generation pathway, arginine and proline metabolism, and pyruvate metabolism in response to hypoxic stress, which indicated an upregulation of anaerobic metabolic processes such as glycolysis, and increased metabolism of certain carbohydrates and amino acids. In addition, we detected numerous differentially expressed genes associated with the pathways involving lysozymes, phagocytosis, peroxisomes, and endocytosis in P. carincauda exposed to hypoxia, thereby indicating that HIFs might reduce mitochondrial oxygen consumption by inhibiting mitochondrial biosynthesis and activating mitochondrial autophagy.

Abstract:Melanosis is a prominent problem in the transportation and storage of Antarctic krill. In order to explore the similarities and differences in the process of melanosis between Antarctic krill and common sea shrimps, Euphausia superba and Trachypenaeus curvirostris were selected as research objects. A sensory evaluation of the melanosis process of the two shrimps during storage at (2±1)℃ were observed. The phenoloxidase (PO) was extracted and purified from the two species, the biochemical properties of which were further examined and compared. The results showed that the black spot formation was more serious in Antarctic krill under cold conditions at 24 h, and large areas of black spots were concentrated in the cephalothorax, abdominal shell, and tail of Antarctic krill. For T. curvirostris, slight black spots were observed in the cephalothorax and tail after 72 h, and then gradually spread to the whole body. The crude PO solutions of the two shrimp species were purified using ammonium sulfate and filtered through Sephadex G-100 gel. The purification fold of the PO solutions of T. curvirostris and E. superba reached 17.22 and 19.67, respectively. The optimum PO temperature was 30℃ for E. superba and 40℃ for T. curvirostris, respectively. The PO activity of Antarctic krill was higher at low temperatures and that of sea catch shrimp was higher at high temperatures. The optimum pH was between 6.0 and 7.0 for both species. Sodium metabisulfite, sodium bisulfite, 4-HR, L-cysteine, and ascorbic acid can all effectively inhibit the PO activity of the two shrimp species. Among these chemical reagents, 4-HR showed the best inhibitory effect on PO activity. The findings in this paper may provide a basis for the quality control during cold chain logistics of Antarctic krill, and also provide a reference for effectively suppressing melanosis in shrimps after death.

Abstract:The restoration of oyster reefs is a hot issue and has being attracting the attention of researchers worldwide. Crassostrea gigas and C. ariakensis are two important species that build up oyster reefs; however, the population dynamics of these two species in low-salinity estuaries are not the same. We used experimental ecology methods to study the effects of acute lowered salinity (10 and 20, with natural seawater about 29 as a control) on the variations in the physiological metabolism of C. gigas and C. ariakensis. The results showed that acute lowered-salinity incubation significantly affected the oxygen consumption rate, ammonia excretion rate, and feces production rate of these two oysters (P < 0.05), but the responses of these two species were also different. The highest oxygen consumption rate, ammonia excretion rate, feeding rate and feces production rate of C. gigas were found in the control group, which indicated that a decrease in salinity impacted the metabolism of this species. However, C. ariakensis showed better metabolic parameters at salinity 20 than that in the other two groups. To normalize the metabolic rate of oysters with a broad range of wet weights, a regression equation for the metabolic rate to wet weight was established: Y=aWb. The wet weight (20 g) was used for the comparison after normalization. At salinity 20, the respiration rate of C. ariakensis was strong, and the respiration energy accounted for 16.1% of the total energy consumption, while C. gigas showed a stronger oxygen consumption rate in natural seawater (respiratory energy accounted for 7.8% of the total energy consumption), and a lower oxygen consumption rate at salinity 10 (respiratory energy accounted for 0.7% of the total energy consumption). Our results indicated that the acute lowered-salinity incubation had a more significant influence on C. gigas than C. ariakensis, and a low-level reduction in salinity can even promote the energy metabolism of C. ariakensis. From the perspective of energy metabolism, this study explored the response of C. gigas and C. ariakensis to acute reductions in salinities, and provided references for oyster reef restoration, selective breeding, and aquaculture.

Abstract:The freshwater mussel Anodonta woodiana is a freshwater bivalve with important economic and ecological values, e.g., as a food source or for pearl cultivation, water purification, and aquatic biological monitoring. In order to understand the morphological change, organ development, and growth rate characteristics of A. woodiana during its early life stages, relevant studies were conducted on 1~30-day-old juveniles. From the 1 to 30-day stages, the leading and trailing edges of the hinge for the juveniles were raised upward. The umbo was contracted relatively inward. The anterior grew rapidly and extended outwards, but the posterior grew toward the ventral edge. The ventral edge grew toward the ventral edge. The most obvious feature in the one-day-old juveniles was the appearance of a mobile foot. The visceral mass was more obvious in 4-day-old juveniles. At 10 days old, the gills were clearly visible, and the anterior and posterior adductors were formed. The intestine and heart were obviously visible in 15-day-old juveniles. The incurrent and excurrent siphons had been formed in 20-day-old juveniles. For the 25-day-old juveniles, the organs were fully developed. The shell length, height, and age grew exponentially, and the shell length and height grew at a positive allometry. These results can provide theoretical guidance for the artificial breeding of A. woodiana, its germplasm resource protection and population restoration, and the effective development and utilization of this bivalve as a special indicator for aquatic pollution biomonitoring.

Abstract:To explore the molecular mechanism of denitrification by Bacillus subtilis and screen out candidate genes and small RNA (sRNA) related to the response of B. subtilis to ammonia nitrogen. Transcriptome sequencing and sRNA analysis were performed on B. subtilis in both an ammonia-rich environment and a control group. The relative expression changes in differentially expressed genes were analyzed using real-time PCR. The results showed that each sequencing sample yielded approximately 1.40 × 107 reads on average. There were 3918 differentially expressed genes in the control and treatment groups as per DESeq2 analysis, which enriched 176 signaling pathways in the KEGG database, including eight signaling pathways (bacterial two-component system pathway, arginine biosynthesis, purine metabolism, and so on) adapted to the ammonia-rich environment. We found that epsA, tasA, SinR, glnR, glnA, tnrA, and ureABC genes may be involved in the response of B. subtilis to ammonia nitrogen in water. Sixty-two annotated strains of B. subtilis sRNA were obtained. The prediction and analysis results of sRNA target genes revealed that there are 3960 potential target genes involved in carbohydrate transport and metabolism, amino acid transport and metabolism, and transcription processes. Among them, the target genes corresponding to sRNA2073 and sRNA2182 were sinR and tnrA, respectively. Real-time PCR analysis showed that the relative expression changes of argH, codY, argG, glnA and glnR were consistent with transcriptome sequencing. These results provide reference data for further exploring the molecular mechanism of nitrogen removal by B. subtilis in wastewater.

Abstract:Zeylanicobdella arugamensis is an important ectoparasitic leech that can infest more than 30 species of marine fish. Diseases associated with Z. arugamensis are prevalent in China and many countries of Southeast Asia, and frequently cause the death of cultured marine fishes. In order to continually and steadily provide sufficient live leeches and cocoons for the research of the prevention and treatment of Z. arugamensis, this study established a propagation method for Z. arugamensis through in vivo infestation experiments, and proved that two ornamental fish species, spinecheek anemonefish (Premnas biaculeatus) and tomato anemonefish (Amphiprion frenatus), were suitable for use as fish hosts. The parasite descendants generated by the in vivo propagation method are still very transmittable after nine generations. This study also used micrography to observe cocoons and the life cycle of propagated fish leeches. The results showed that the average cocoon size of Z. arugamensis was (0.66±0.06) mm, and there was only one fertilized egg in each cocoon. The life cycle of Z. arugamensis can be divided into two stages: The cocoon hatching stage and the juvenile development stage. Under a seawater temperature of 26℃ and salinity of 30, Z. arugamensis can complete its life cycle in as short as 20 days. The cocoons of Z. arugamensis developed into juvenile leeches in nine days, with a hatching rate as high as 83.8%. The juvenile leeches subsequently infected the host fish, grew to mature adults, and produced new cocoons in 11 days. This article confirmed for the first time that P. biaculeatus and A. frenatus were both susceptible hosts for Z. arugamensis. This study not only established an in vivo propagation method for Z. arugamensis, but also provided technical support for research on the pathogen, pathology, pathogenic mechanism, detection, and prevention of leech diseases related to Z. arugamensis.

Abstract:To evaluate the quality characteristics of red swamp crayfish, Procambarus clarkii, crayfish from pond and paddy field cultures were used to compare the muscle, amino acid, and fatty acid compositions between the two culture models. The results showed that there was no significant difference in crude protein and crude fat between the two culture models (P>0.05). The muscle moisture content of crayfish in the pond culture was significantly higher than that in the paddy field culture (P>0.05), while the total ash content was significantly lower than that in the paddy field culture (P<0.05). Seventeen amino acids, including seven essential amino acids and four flavor amino acids, were detected in the muscle and hepatopancreas of the crayfish in the two culture models. There was no significant difference in the muscle WEAA/WTAA values between the two culture models (P>0.05), while the hepatopancreatine WEAA/WTAA values in the pond culture model were significantly higher than those in the paddy field model (P<0.05). According to the amino acid and chemistry score, the first limiting amino acids in the muscle and hepatopancreas were sulfur-containing amino acid (methionine and cysteine), while the second limiting amino acid in the muscle was valine and that in the hepatopancreas was leucine. In addition, 20 and 24 fatty acids were detected in the muscle and hepatopancreas of crayfish, respectively. Palmitic acid (C16:0) was the highest saturated fatty acid in the muscle and hepatopancreas, and oleic acid (C18:1n9c) was the highest monounsaturated fatty acid. The muscle and hepatopancreas of crayfish in the pond and paddy field models have higher edible and nutritional values.

Abstract:The primary nutrients in kelp (Saccharina japonica) products cultivated under standardized and traditional long-line modes in the waters of Sanggou Bay, Shandong Province, were analyzed and compared. The results showed there was no significant difference in the moisture content of the kelp produced by the two methods, and in both cases, the moisture content was higher than 88%. The cultivation method did not significantly affect the total protein content of the kelp, but the soluble protein level was significantly different between the two methods. The fat content was low in all the kelp samples, and the difference between the products of the two cultivation methods was not significant. The essential amino acid content (except lysine) of kelp from the standardized cultivation method was higher than that from the traditional method. The amino acids responsible for flavor were higher in kelp produced by the standardized method than in kelp produced by traditional cultivation. Glutamic acid content in kelp from standardized production was high (1.75%) in comparison to other amino acids (1.27%). The fatty acid content of kelp from both cultivation modes was lower than 1%. The average levels of zinc, magnesium, sodium, and potassium in kelp from standardized cultivation were higher than traditionally produced kelp. Additionally, the soluble sugar content of kelp from standardized cultivation was significantly higher than that from traditional cultivation. The alginate content was 22.66% and 21.27% in the standardized cultivation and traditional cultivation modes, respectively. The results showed that the protein, amino acid, fatty acid, mineral elements, soluble sugar, and alginate contents in kelp produced by standardized cultivation were all higher than in kelp grown the traditional way. Therefore, the nutrient value and quality of kelp products were significantly better, when produced by standardized cultivation. The value of kelp products for food and industrial raw materials was also higher. Therefore, the standardized kelp cultivation method in Sanggou Bay has significant advantages.

Abstract:The seagrass bed ecosystem is one of the most productive ecosystems on earth with important ecological functions and ecological service values. In August 2016, the seagrass resources and ecological characteristics were investigated and analyzed in Shuangdao Bay sea area of Weihai city, Shandong Province. Seagrass beds of Zostera marina and Phyllospadix iwatensis covering approximately 442.19 hm2 were discovered. Z. marina was distributed over 434.46 hm2, which is approximately 98.3% of the total seagrass area. These Z. marina plants mostly grow in the eastern part of Shuangdao Bay and in the farming ponds of Stichopus japonicus. The average shoot density and biomass of Z. marina were (174.2±9.2) shoots/m2 and (337.7±17.5) g DW/m2, respectively. The distribution area of P. iwatensis was 7.73 hm2 and was approximately equivalent to 1.7% of the total seagrass area. These P. iwatensis plants mostly grow on rocky coasts and displayed an obvious band-like distribution. The average shoot density and biomass of P. iwatensis were (889.1±17.1) shoots/m2 and (605.9±18.1) g DW/m2, respectively. The average water depth of seagrass beds was about 1.6 m and the farming ponds growing Z. marina had a hard substrate with an average particle size of (4.3± 0.2) mm. The investigation showed that the seagrass habitats are being seriously threatened by human activities, such as pollution discharge from the land, culling, and fishing. Suggestions for the protection of the seagrass beds in Shuangdao Bay have been proposed to provide supplementary data on China’s seagrass resources and their conservation.

Abstract:In the atmosphere, amines play potentially important roles in climate change, which is a hot spot of the current international research. The ocean is an important source of amines in the atmosphere; however, the mechanism of the formation of amines in the environment has not been elucidated due to the difficulty of detecting amines in seawater. This article outlines the concentration characteristics of amine precursors in marine organisms and their impact on amines in the marine environment; summarizes the concentration characteristics of amines in sediments, seawater, and the atmosphere; analyzes the formation pathway of amines in marine atmospheric particles; and identifies the difficulties in the detection of amines in seawater and the related problems that need urgent attention. This study provides insights into the transport and transformation of amines in the marine environment and the resulting climatic effects on the marine atmosphere.