Abstract:Climate change affects the distribution of fish species and thus alters the pattern of fish abundance. However, effects of climate change on China coastal fisheries have not been studied yet. Estuaries play an important role in the function of marine ecosystem, hence they are key habitats for many fishery species and form ideal fishing grounds. Here we investigated the impacts of climate change on fish abundance by estimating the distribution of dominant and important species in the Yangtze River estuary. The analysis was performed using the dynamic bioclimate envelope mode, and the distribution data of fishery species were based on the survey during 2012-2013 in the Yangtze River estuary. Three climate change scenarios (RCP2.6, RCP6.0 and RCP8.5) were evaluated combined with the projection data from the Geophysical Fluid Dynamics Laboratory. The water temperature in the Yangtze River estuary was estimated. Without human activities, the increment of fish abundance, particularly the demersal fish abundance, increased over time in all three climate change scenarios. The increment and the distribution followed the order RCP8.5>RCP6.0>RCP2.6. The distribution of fish abundance increment in RCP8.5 was wider than those in the other two scenarios. It is expected that the fish abundance increment will be mainly in the north of the Yangtze River estuary in 2020 and 2030, and in 2050 the increment may migrate to the southern part, and there will be less increment in the offshore water body of the Yangtze River estuary. The center of fish abundance increment will be mainly located in the coastal area of the Chongming Island. These results suggest that the climate change greatly contributes to the fish abundance distribution in the Yangtze River estuary, and that the effects of climate change on fish abundance distribution vary in different scenarios. Therefore, climate change should be considered in the future adaptive fishery management in the coastal waters.

Abstract:As a result of the scaled stock enhancement of tongue sole, Cynoglossus semilaevis, since 2006 in China, millions of juveniles were released into the Bohai Sea and the Yellow Sea annually. However, it is difficult to evaluate the effectiveness of this operation because of a lack in efficient marking techniques. Here we tested the potential of alizarin complexone (ALC) as a marking material on tongue sole otolith. ALC solutions with 5 concentrations ranging from 0 to 200 mg/L in undiluted seawater were prepared. One hundred tongue sole juveniles of two sizes (70 d and 170 d post hatching) were randomly assigned into the 5 groups of ALC solutions and in each group the subjects were immersed into the solution for 12 hours, 24 hours, and 36 hours. Duplication was performed for each group. The results showed strong markings with ALC on otoliths of tongue soles. The optimal concentrations of ALC were 100 mg/L for 36-h marking and 150 mg/L for 24-h marking, which ensured both sound survival rate and strong marking signals. The marking quality (MQ) was assessed with scores from 0 to 3, and a score > 2 was regarded acceptable for adequate mark identification. The marking signals on the otolith were enhanced as the solution concentration increased, which however also increased the mortality rate. The marked juveniles (170 d) were cultured in indoor tanks for 4 months to determine how long the ALC marking could last. The marking signals were still clear at the end of the culture, and there was no difference in the growth between marked and unmarked subjects with the same size. These results indicated that ALC could form lasting signals on otoliths of tongue soles, and thus may be a useful tool in the evaluation of stock enhancement and the identification of tongue sole populations.

Abstract:Species identification plays a key role in the protection of biodiversity. However, there have been great challenges in traditional morphological identification because of its innate limitations and the lack of experienced techniques. Recently thanks to the development of molecular biology, DNA-based identification is becoming a more accurate alternative method. The cytochrome oxidase I (COI) barcode is a short piece of DNA from a standard region of the mitochondrial genome, which can be used to identify and classify different species and has been proved to be highly effective in many species including fish. The advantage of COI is that it is long enough to identify variations among species yet short enough to be sequenced quickly at low cost. In this study, we analyzed DNA barcoding of Engraulidae species in order to explore the feasibility of DNA microarray technology in species identification. Oligonucleotide probes were designed based on the COI sequences of mitochondrial obtained from 101 individuals of 30 fish species in 11 genera. Forty-six specific probes obtained from 24 species were selected with online software Oligo Array 2.1, among which the probes potentially forming hairpin, stem-loop, or homo-dimers were identified with Oligonucleotide Properties Calculator and excluded. The remaining probes were virtually hybridized with the target sequences in Oligo Heat Map (OHM), and subsequently a total of 26 probes from 16 species bound to the target sequences specifically. The DNA microarray technology identified 14 species, accounting for 46.7% of the total with 100% accuracy. Therefore, DNA microarray based on COI sequences should have practical values in the identification of Engraulidae fish species. Nevertheless, this technique needs further improvement and the key step would be screening and optimization of high quality molecular probes.

Abstract:Larval development of pacific cod (Gadus macrocephalus Tilesius) (0–80 dph) was observed using microscope. The experimental conditions included water temperature 2–12℃, salinity 28–32, pH 7.8–8.2, and illumination intensity 800–1200 lx. Under the micro aeration hydrostatic conditions, it was observed that on 0–5 dph (day post hatching), the yolk-sac larvae supported by complete endogenous nutrition. Specifically, on 1 dph, the pigmentation became darker and rainbow pigment appeared in the eyeball; on 5 dph, the digestive tract was cleared except for the liver; on 6 dph: the larvae started feeding, and there were small particles in the digestive tract; on 9 dph: the yolk sac was absorbed by most of the larvae and they began to feed on exogenous nutrition, in addition the rotifera in the alimentary canal and the blood circulation became visible; on 12 dph, yellow pigment became obvious in the heads of larvae; on 15 dph, colors of melanin and yellow pigment were intense, and the blubber of larvae started to form; on 17 dph, the rainbow pigment was visible in the eyes; on 20 dph, the development of eye was completed, the blood circulation could be seen in abdominal arteries, and pigment was found in the tail. During 30-50 dph, the fin ray began to develope. On 30 dph, the tail fin began to develop; on 40 dph, the larvae started feeding artemia, and the first, second, and third dorsal fins came into view; on 50 dph, the coccyx curled up, and the anal and dorsal fins were apparently visible. During 60–80 dph, the pigment cells and fin ray were further developed, and the gallbladder could be clearly observed. On 60 dph, gills were covered in red; on 70 dph, silver scales appeared on the abdomen; on 80 dph, the caps of gills were greatly developed and pelvic fins could be seen. Our observation described the developmental process of pacific cod and may provide useful data for the future large-scale artificial breeding.

Abstract:A study was conducted to investigate the effects of the dietary protein level on the growth, ammonia-nitrogen excretion, and amino acid accumulation in the muscle of juvenile turbot (Scophthatmus maximus L.) in a recirculating aquaculture system. One hundred and forty-four healthy juveniles with initial body weight of (145.08±0.56) g were randomly divided into four groups each of which had three replicates of 12 fish. Groups Ⅰ–Ⅳ were fed with diets containing 41%, 46%, 50%, and 55% protein respectively. The fishmeal content was the only variable in the diet. The results were shown as follows: (1) As the protein level went up, the weight gain rate (WGR) increased first rapidly and then slowly, while feed conversion rate (FCR) showed a reversed trend. The WGRs of Groups Ⅲ and Ⅳ were significantly higher than that of Groups Ⅰ and Ⅱ by 18.48%–65.95%, and compared to Group Ⅰ the FCRs of Groups Ⅲ and Ⅳ were lower by 25.64% and 28.21% respectively (P<0.01). (2) Ammonia excretion rate (AER) of juveniles cyclically varied between day and night, and there were two peaks appearing 6–8 h post feeding. There was a positive correlation between AER and the dietary protein level. The AER of Group Ⅳ was significantly higher than that of other groups by 17.95%–35.07% (6 h post feeding in the morning, P<0.01) and 14.25%–31.27% (8 h post feeding in the evening, P<0.05). The AER of juveniles increased sharply when the dietary protein level was above 50%. (3) The content of 17 amino acids in muscle was higher than 65 mg/100mg in each group, and it rose along with the increase in the dietary protein level (P>0.05). The contents of total amino acids, essential amino acids, and flavor amino acids in the muscle of Groups Ⅲ, Ⅳ were not significantly higher than those of other groups (P>0.05). There was no difference in the amino acid composition between groups (P>0.05). The results indicated that the growth performance of juveniles might not be improved when the dietary protein level was above 50% at which level the AER was markedly increased, and that the content and composition of amino acids in the muscle might not be altered by the dietary protein level. Therefore, the optimal protein level of juvenile turbots may be 45%–50%.

Abstract:Five hundred and forty Cyprinus carpio var. Jian with initial body weight of (26.77±1.56) g were randomly divided into 6 groups, and every group had three replicates each of which had 30 fish. Six diets were formulated with Schizochytrium at the concentrations of 0, 0.40%, 0.80%, 1.20%, 1.60% and 2.00%. An 8-week feeding trial was conducted to determine the effects of diary Schizochytrium on growth performance, serum nonspecific immunity indices, and disease resistance of C. carpio Jian. The results showed that weight gain rate and specific growth rate significantly increased in the 0.80% group (P<0.05). The highest condition factor was observed in the 1.20% group (P<0.05). The survival rate showed no significant difference between the six groups (P>0.05). The antioxidant and nonspecific immune activities were apparently altered by Schizochytrium (P<0.05). As the concentration of Schizochytrium increased, the contents of catalase, total superoxide dismutase, and glutathione were first elevated and then reduced, and the maximum of each was observed in the 1.20%, 0.80%, and 1.20% groups respectively (P<0.05). The malondialdehyde content dropped first and then increased with the lowest value observed in the 0.8% group. The nonspecific immune capacity in the 0.80% group was significantly higher than in other groups (P<0.05). The activity of lysozyme was raised and then reduced along with the increase in the Schizochytrium level, and the maximum was observed in the 1.20% group (P<0.05). The nitric oxide content rose along with the rise of Schizochytrium level, and was significantly higher than the control group (P<0.05). The Aspartate aminotransferase/aspartate aminotransferase (GOT/GPT) ratio reached the minimum in the 0.80% group. Also in the 0.80% group, the respiratory burst activity of blood cells was elevated significantly and the accumulated mortality rate was the lowest (P<0.0.5). In conclusion, we recommended that the optimal Schizochytrium level for C. carpio Jian should be 0.80%–1.20%.

Abstract:The tongue sole C. semilaevis is a flatfish with high economic value and is extensively exploited in northern China. However, broodstock nutrition of this species is still based on a diet of fresh feeds, which has an important sanitary risk, and contributes to the deterioration of water quality. Therefore, a 90 days feeding trial was conducted to investigate the effect of dietary Antarctic krill meal in broodstock diets on reproductive performance and antioxidant function of male tongue sole Cynoglossus semilaevis. Three diets were formulated to contain respectively 0, 10%, 20% Antarctic krill meals. Three-year-old tongue sole C. semilaevis were stocked in concrete tanks (25 m3) and acclimated to laboratory conditions for 7 days. Then they were randomly divided into three groups, each group had three polyethylene tanks (diameter: 230 cm, high: 100 cm), and they were fed to apparent satiation twice per day for 12 weeks. Results showed that, the hepatosomatic index, sex index, sperm concentration and testosterone contents had no significant differences on each experimental groups (P>0.05). The superoxide dismutase (SOD) activities in semen and eggs had no significant differences between K-10 and K-20 group (P>0.05), but were significantly higher than that of the control group (P<0.05); The malondialdehyde (MDA) content in semen, serum and liver had no significant differences between K-10 and K-20 group (P>0.05), but were significantly lower than that of the control group (P<0.05). In conclusion, the present study suggested that dietary Antarctic krill meal had no significant effect on reproductive performance (P>0.05), but can significant improve antioxidant function for male C. semilaevis (P<0.05).

Abstract:Grass carp ovary cell lines (GCO) was used in the study of Grass Carp Hemorrhage and has been established by Chinese Academy of Sciences Institute of Aquatic Animal in 1970s. GCO has been cultured for more than 300 generations and plays an important role in fish virology research in China. In this study, we performed morphological observation, drawing of the growth curves, cell cycle analysis, chromosomal analysis, cytopathic effect assay (CPE), TCID50 assay, cell apoptosis detection, and electron microscopic observation to demonstrate the characteristics of GCO and the cell proliferation of spring viremia of carp virus (SVCV). It was observed that GCO cell line mainly consisted of epithelial-like cells. GCO grew at temperatures between 15℃ and 28℃, and the optimum was 25℃. The growth rate of GCO cells increased proportionally with the foetal bovine serum (FBS) concentration (5% to 20%), and the optimum concentration of FBS was 10%. There were 48 chromosomes in GCO cells. Four known fish cell lines were tested to determine the susceptibility of SVCV, and the results demonstrated that GCO was susceptible to SVCV. Moreover, GCO displayed higher sensitivity to SVCV and increased viral production than the control cell line, epithelioma papulosum cyprini (EPC), fathead minnow (FHM), and chinook salmon embryo (CHSE-214) cell lines. These results suggested that GCO cell line could be a useful diagnostic tool in SVCV isolation and diagnosis, and could serve as a suitable biological system in the pathogenicity study of SVCV. One advantage of this cell line is that it grows in a wide temperature range (15℃ to 28℃), and thus can be used in isolating both warm-water and cold-water fish viruses. These characteristics of the GCO make it a potential tool in the future study of other fish viruses.

Abstract:In this study, the nutritional components and meat qualities of Ctenopharyngodon idellus, Liza haematocheila, and Centropristis striata were analyzed and compared. The results showed that the weight ratio of head to body of L. haematocheila was 17.09%, which was significantly higher than that of C. striata and C. idellus. The content of soluble and insoluble collagen in C. striata muscle was higher than that of the two other species, which were 0.22 mg/ml and 2.12 mg/ml respectively. The contents of flavor amino acid in C. striata, L. haematocheila, and C. idellus were 44.37%, 32.80%, and 24.50% respectively. As for the total content of six essential amino acids, C. idellus showed the lowest value of 53.31%, the value for L. haematocheila was 57.14%, and C. striata showed the highest value of 62.64%. The fatty acid analysis indicated that the saturated fatty acid (SFA) of L. haematocheila was up to 41.26%, which was significantly higher than that of the other two (P<0.05). The level of poly-unsaturated fatty acids (PUFA) in the muscle of C. striata was the highest (34.58%, P<0.05). The EPA concentration in the muscle of L. haematocheila was 8.27%, and it was not significantly different from that of C. striata. The DHA concentration in the muscle of C. striata was 13.51%, which was significantly higher than that of C. idellus (3.84%) and L. haematocheila (3.02%). The activity of SOD in the muscles of the three species was significantly different, and it was the highest in L. haematocheila and the lowest in C. striata. The content of MDA in the muscle of C. striata was 19.98 nmol/mg that was higher than that in C. idellus and L. haematocheila (P<0.05). In conclusion, the muscle of L. haematocheila had strong antioxidant capability, and this characteristic may contribute to the long-term preservation and food processing quality.

Abstract:Fenneropenaeus chinensis is one of the prominent aquaculture shrimp species in China. To better understand its reproductive biology, here we investigated the sexual differentiation and development of the shrimp. The morphological changes of the female thelycum and the male petasma were observed. The larvae of F. chinensis collected from Yellow Sea Fisheries Research Institute (YSFRI) in Aprils of 2012 and 2013 were cultured in a circulating water system. The adult F. chinensis were purchased from aquatic produce market. The samples were fixed in Bouin’s solution for 16–24 h after being anesthetized with seawater saturated with Mg2SO4, and then stored in 70% ethanol at 4℃ for observation of external sexual development. The images were taken by Olympus CX22 LEDRFS1 microscope. It was found that the sexual differentiation of female shrimp started at 16 days post-larva (PL16). A subsidence appeared in the conuli on the ventral plate between the fourth and fifth pairs of pereopods in female shrimp, but no subsidence in the conuli was found in male shrimp. The valves that were components of thelycum appeared at the base of the fourth (anterior valve) and fifth pairs of pereopods (posterior valve) at PL54. At PL112, the form of anterior valve appeared to be similar to “epsilon type”. At PL124, the thelycum began to develop. Compared to the development of thelycum, the growth of petasma of male shrimps was late. The initial differentiation of endopodite on the first pair of pleopods was found at PL54, indicating the formation of male external genitalia. At PL106, petasma appeared to be similar to that of adults. The cannelure became obvious and periphery up folded, but the endopodite on the first pair of pleopods in female remained a willow-leaf shape.

Abstract:The effects of culturing in stages on the growth of shrimp Litopenaeus vannamei and the water quality were investigated from April to July in 2015. Experiments were conducted in 6 shrimp culturing ponds (2650 m2, 53 m×50 m each). The shrimp was first cultured in 2 ponds with a density of about 300×104 ind/hm2 for early cultivation. The subjects were stocked at 3 culturing time points, 36, 48 and 83 days, and were referred to as T1, T2, and C groups respectively. After early cultivation, the shrimp in the T1 and T2 groups were divided into two ponds with a suitable density (60×104 ind/hm2). The survival rate, the growth of shrimp, and the water quality were evaluated during the experimental period. The growth increment of weight and length during the first week was significantly boosted and the specific growth rate (SGR) for T1 and T2 reached 9.36 %/d and 6.36 %/d respectively. The T1 group showed the highest SGR and food consumption during the experiment, and the feed conversion ratio (FCR) was higher in T1 (1.053) than in T2 (0.822). In most of the divided culturing periods, the T2 group maintained a higher SGR. Compared to the T1 and T2 groups, the C group had lower concentrations of NH4+-N and NO2--N, a higher level of total particle matter (TPM), and a lower content of Chl-a. The T2 group had the highest Chl-a content. These results indicated that the shrimp might achieve rapid growth later if divided into different ponds after a proper cultivation period (48 days). The organic matter accumulation in the pond decreased in the early cultivation, which helped improve the water quality of the pond. However, the water quality may worsen when the feed consumption in the pond reached a certain level in unit time. In conclusion, divided culturing in the different ponds could improve both the growth of shrimp and the water quality.

Abstract:Intraspecific hybridization was investigated using two stocks of the Scapharca broughtonii, China population (C) and Korea population (K). The fertilization rate, larval survival rate, growth, and heterosis were compared between two reciprocal hybrid crosses C♀ × K♂ (CK) and K♀ × C♂ (KC) and two parental groups C♀ × C♂ (CC) and K♀ × K♂ (KK). The fertilization rate of the parental groups was higher than that of the reciprocal hybrid crosses, but the hatchability results indicated that there was no significant difference between the two reciprocal hybrid crosses and the two parental groups. The shell lengths of the KK and KC groups were larger than those of the CC and CK groups in larval, juvenile, and adult stages. The CC and CK groups, however, showed higher survival rate in juvenile and adult stages. The heterosis of the KC cross in terms of the shell length and the survival rate was obvious, but the CK cross did not show positive heterosis in any aspect during the entire experiment. The difference in heterosis between the two reciprocal hybrid crosses might be related to the maternal effects, heredity, and environment.

Abstract:Meretrix meretrix is of high commercial value and widely distributed in the coastal area of China. Deterioration of pond environment has caused huge economic loss in pond aquaculture of M. meretrix in recent years. To better understand this process, here we explored the physiological metabolisms of M. meretrix under different salinities and pH. Effects of different salinities (16, 18, 20, 22, and 24) and pH (6.7, 7.7, 8.7, 9.7, and 10.7) on the filtration rate and ingestion rate of M. meretrix were tested under static conditions. Both the filtration rate and the ingestion rate rose as the salinity increased from 16 to 20, and they dropped in the range of 20 to 24. The control group with salinity 20 had the highest filtration rate (1.51 L/g·h) and ingestion rate (6.65 mgPOM/g·h), which were significantly higher than the groups with salinity 16, 18, 22, and 24 (P<0.05). Therefore, salinity 20 was most likely the optimum for the growth of M. meretrix. The filtration rate and ingestion rate increased along with the pH rising from 6.7 to 8.7, but then decreased in the range of 8.7–10.7. Both the filtration rate and the ingestion rate reached the maximum at pH 8.7, which were 1.04 L/g·h and 11.91 mgPOM/g·h respectively, and these values were significantly higher than those in the groups with pH 6.7, 9.7, and 10.7 (P<0.05). Noticeably, there was no difference in the two groups between pH 7.7 and pH 8.7 (P>0.05). So we deduced that the optimum range of pH was 7.7 to 8.7. Our study may provide important information that can help improve the pond aquaculture of M. meretrix.

Abstract:In vitro whole-bionic digestion model has been an effective approach to study the bioaccessibility of contaminants in food. Due to the high exposure of cadmium (Cd), samples of Chlamys noblis were pretreated with in vitro bionic digestion for the bioaccessibility of Cd. The releasing mechanism of Cd in C. noblis was investigated in a simulated gastrointestinal tract environment where the chyme was obtained at 37℃ through digestion with enzymes and inorganic substances in saliva, stomach, and intestine. The samples of C. noblis were treated with four digestion juices separately, including saliva, gastric juice, duodenal juice, and bile. It was found that the dissolution equilibrium time of Cd in the digestion juices followed the order: saliva < gastric juice < bile < duodenal juice. In the bionic experiments, Cd dissolution quantity showed the pattern: gastric juice > bile ≈ duodenal juice > saliva. There was a linear correlation between the logarithm of concentration (lnC) and its corresponding dissolved time (t) in duodenal juice (R2=0.9530) and in bile (R2=0.8891), however, no correlation was found in saliva or gastric juice. pH may be the key factor of Cd dissolution in the bionic digestion with saliva and gastric juice, and digestive enzymes played the essential role in the digestion with duodenal juice, bile, and in vitro whole-bionic digestion. There was no significant difference when the sample-to-fluid ratio changed from 1:10 to 1:120 (g/ml), implying that this ratio might only slightly affect the bioaccessibility. The releasing ratio of Cd in C. noblis was 70% and the maximum bioaccessibility in C. noblis chyme was also 70%.

Abstract:In this study we investigated the potential alteration of carbon sequestration capability of artificial reef eco-system caused by the additives peanut straw and Argopecten irradias shell. After the intensity test four types of reefs with different proportions of additives were selected for experiments, and the effects of additives on carbon fixation by various fouling organisms adhering to the reefs were analyzed. It was found that Ostrea plicatula Gmelin was the dominant species of fouling organisms, and that additives did not apparently affect the fouling organisms. Peanut straw and A. irradias shell did not improve the carbon sequestration of O. plicatula Gmelin (P>0.05). The calculation of carbon sequestration in the reefs with addition of shell showed that the minimum carbon content per unit reef was 104.13 kg and 2.60 kg per hollow stere, and that the maximum content per unit reef was 260.32 kg and 6.51 kg per hollow stere. As for reefs with straw, the minimum content per unit reef was 296.28 kg and 7.41 kg per hollow stere; the maximum content per unit reef was 740.70 kg and 18.52 kg per hollow stere. The total carbon fixed by experimental reefs was up to 2802.87 kg. In this experiment each unit included 250 reefs. Assuming all the reefs within the marine area of about 66.67 hm2 contain additives, we calculated that reefs with 10% substitution of A. irradias shell could fix 52040.00 kg carbon, and that reefs with 25% substitution of peanut straw could fix 370350.00 kg carbon. Our results suggested that sequestration of reefs could be an effective method to improve carbon sinking. The effects of crop straws and shell as additives of artificial reefs need to be further investigated in the future.

Abstract:Chemical and biological methods were employed to determine specific activities of several enzymes including trypsin, pepsin, alkaline phosphatase (AKP), lipase, and alanine aminotransferase (ALT) at different stages of fertilized eggs and 0–10 days old larvae of golden cuttlefish Sepia esculenta. The results showed that the soluble protein content was elevated in the early embryonic and larval stages, but was depressed from the mid to late embryonic stages. The protein content was the highest in the blastula and gastrulae stage(Ⅱ) (81.50 mg/g), and the lowest in the newly-hatched larvae (Ⅶ) (4.24 mg/g). During the development, the specific activities of trypsin, pepsin, and ALT in five enzymes all followed the up-down-up pattern. Activities of all three enzymes were detectable but very low in embryonic developmental stages, suggesting their maternal originality. Moreover, the enzymatic activities were significantly increased in newly-hatched larvae, which were 0.51 U/g, 1.68 U/mg and 37.84 U/g respectively. The enzymatic activities in 5 days old larvae (Ⅷ) dropped significantly compared to the level before hatching, and rose slowly in 10 days old larvae (Ⅸ). The activities of both AKP and lipase were generally elevated, starting from very low during the embryonic stages to significantly higher after hatching. These results implied the gradual maturation of organs and the improvement of digestion capability.

Abstract:The rapid development of abalone aquaculture has been accompanied by serious problems such as massive mortality that has caused huge economic losses. Therefore, it is an urgent mission to perform the immunological studies, to analyze the causes of death, and to find an effective disease prevention method. In this study, 100 16-month old abalone were randomly sampled as experimental materials, all of which were from green egg full-sib family 3♀ × 10♂ of Haliotis discus hannai. We divided the samples according to their sexes and egg colors, and then measured their growth traits (the total weight, the shell length, and the shell width) and activities of five enzymes including superoxide dismutase (SOD), alkaline phosphatase (AKP), acid phosphatase (ACP), catalase from Micrococcus lysodeikticus (CAT), and lysozyme (LZM). The single-factor analysis of variance was performed in this study. We found that there was no significant difference in the growth between individuals with different egg colors (P>0.05), and that green egg samples displayed a better growth performance. As for immune enzyme activities, there was no difference in SOD and CAT between the four egg color groups. The activities of AKP, ACP, and LZM in the green egg samples were significantly different from those in the brown and brownish red egg samples (P<0.05), but they were not different from those of breen egg samples. The enzyme activities in different egg color samples followed the order green>breen>brown> brownish red. Our results will provide guidelines for the egg color breeding of highly productive and resistant strain of H. discus hannai.

Abstract:Dried distiller's grains with solubles (DDGS) is the primary corn co-product of dry-grind fuel ethanol plants. It consists of distiller's grains combined with condensed solubles from yeast fermentation, and typically contains about 27% crude proteins, 7% starch, 42% neutral detergent fibers, and 0.6% phosphorus. DDGS has gained increasing interest as a potential feed ingredient for aquaculture animals due to the low cost and enrichment in proteins, vitamins, and minerals. This research was carried out to investigate the effects of DDGS level on the growth performance, body composition, and immune enzyme activities of sea cucumber Apostichopus japonicas. Five isonitrogenous and isocaloric diets were formulated that contained 0, 10%, 20%, 30%, and 40% DDGS, designated as DDGS0 (control), DDGS10, DDGS20, DDGS30, and DDGS40 groups respectively. Three replicates of sea cucumber weighing (9.69±0.28) g were fed in one dietary group till apparent satiety two times every day for 56 days. The weight gain (WG) and the specific growth rate (SGR) were decreased along with the increase in DDGS level but there was no significant difference between experimental groups (P>0.05). The body wall index (BI), the intestine index (II), the intestine length ratio (ILR), and the composition of body wall were not affected by the addition of dietary DDGS (P>0.05). The activities of lysozyme (LZM) and acid phosphatase (ACP) in coelomic fluid were higher in the DDGS20 and DDGS40 groups than in the control group (P<0.05). The activities of phenol oxidase (PO) in coelomic fluid were raised along with the increase in the level of DDGS, and were significantly higher than that of the DDGS0 group (P<0.05). The activity of alkaline phosphatase (AKP) was not affected by dietary DDGS (P>0.05). These results indicated that corn DDGS could be a potential dietary ingredient and could be used at a concentration of 20% to 40% to improve the growth and immunity of sea cucumbers.

Abstract:The cDNA and gene of phospholipase A2 (Re-PLA2-1) of Rhopilema esculentum were cloned using RACE, and the mRNA expression was monitored at different developmental stages with quantitative real-time PCR analysis. The full-length cDNA of Re-PLA2-1 was 824 bp, containing a 5’-untranslated region (5’-UTR) of 48 bp, an open reading frame (ORF) of 504 bp, and a 3’- untranslated region (3’-UTR) of 272 bp. SMART analysis showed that Re-PLA2-1 was a secreted protein, including a putative signal peptide consisting of 19 amino acid residues and a domain of phospholipase A2. The deduced amino acid sequence of Re-PLA2-1 was highly similar to those of PLA2s from Conus magus, Nematostella vectensis, Crassostrea gigas and so on, and they could form a cluster of pfam09056 GⅨ PLA2 revealed by the multiple sequence alignment and phylogenetic analysis. They shared the essential features of pfam09056 PLA2s family, including a calcium-binding site, the catalytic active sites, and a PLA2 domain, which perfectly corresponds to the conserved disulfide-bonded cysteine residues involved in the formation of the internal disulfide. The size of Re-PLA2-1 gene was 2671 bp that included four exons and three introns. Quantitative real-time PCR analysis revealed that the expression of Re-PLA2-1 mRNA occurred in all four developmental stages. The expression was the highest in strobila and the lowest in ephyra. These results contributed to further understanding the biological function of PLA2 in R. esculentum.

Abstract:It has been revealed that wild juvenile Eriocheir sinensis (WC) are advantageous in culture performance compared to pond-reared juvenile crabs (PR), however, their differences in the disease resistance, immunity, and the early culture performance remained unclear. In this study we addressed these questions by conducting the culture experiment, the pathogen challenge test, and the analysis of non-specific immune indices. The early culture performance included the first molt interval, survival rate, and weight gain rate. The mortality during the pathogen challenge test and immune indices of WC and PR populations were also examined. Our results were described as follows: (1) Both male and female WC showed significantly lower first molt interval and weight gain rate (WGR) than PRs, but there was no significant difference in the survival rate and the specific growth rate (SGR) between the two groups (P>0.05). (2) Within 12–96 hours in the pathogen challenge test, the cumulative mortality of WC was lower than that of PR, and after 96 hours the cumulative mortality of WC and PR were 28.3% and 50.0% respectively. (3) In terms of the non-specific immune indices in hepatopancreas, the alkaline phosphatase (ALP) activities of both male and female individuals were significantly lower in the WC population than in the PR population. For males, total antioxidant capacity (T-AOC) and nitric oxide (NO) were higher in WC, and for females, malondialdehyde (MDA) was lower in WC. (4) In terms of the non-specific immune indices in hemolymph, WC had significantly higher NO and lower acid phosphatase (ACP) than PR in both sexes. Moreover, for female, WCs had higher T-AOC, hemocyanin (Hc), and glutathione reductase (GR) than PR, but lower ALP, γ-glutamyl transferase (γ-GT), and glutathione peroxidase (GSH-Px). In conclusion, the pond-reared juveniles showed better culture performance during the early culture stage, while wild juveniles had stronger immune ability and lower mortality than the pond-reared juveniles. Each type of the crab seeds may have advantages in certain aspects, and the mechanisms underlying the differences need to be investigated in future studies.

Abstract:This study investigated the effects of inbreeding on the reproductive performance of swimming crab Portunus trituberculatus, by comparing reproductive traits, including fecundity, egg production, fecundity per unit body weight, egg production per unit body weight, hatchability and metamorphosis rate, in full-sib families of six generations (F1m to F6m). The results showed that the range of inbreeding depression coefficients were –2.789% ~ –6.620%, –1.188% ~ –5.938% and –1.859% ~ –7.222% for fecundity per unit body weight, egg production per unit body weight and hatching rate, respectively, and there was no significant inbreeding depression in these three traits (P > 0.05). As inbreeding level increased, metamorphosis rate from zoea Ⅰ to juvenile crab Ⅱ presented a downward trend.

Abstract:Due to the deteriorating marine environment and the repetitive red tides, harmful pollutions with shellfish toxins have caused increasing concerns. Diarhettic shellfish poisons (DSP) are one type of the most dangerous shellfish toxins. To develop an effective method of collecting DSP from sea water, we evaluated the adsorption efficiency of HP20 resin for four common diarhettic shellfish poisons including okadaic acid (OA), dinophysistoxin-1 (DTX-1), dinophysistoxin-2 (DTX-2), and gymnodimine (GYM) in the seawater column, based on the solid phase adsorbent and toxin tracking (SPATT) technology. The distribution of DSPs in the seawater column and their levels in shellfish were measured. We selected five sampling sites in an oyster farming area, collected samples of both the seawater and oysters on a weekly basis, and studied the correlation between the contents of DSPs in the seawater and those in oysters. During a 7-day sampling period, HP-20 resin accumulated showed high adsorption ratios for the four DSPs, which were 98.9%, 103.3%, 93.5%, and 76.6% for OA, DTX-1, DTX-2, and GYM respectively. The DSPs were detected throughout the entire study period except for DTX-2. The concentrations of OA, DTX-1, and GYM were 20.451–422.35 µg/kg, 15.954–368.678 µg/kg, and 20.452–282.231 µg/kg respectively. During the monitoring period, the contents of the three DSPs in the seawater varied temporally and showed a uniform pattern of distribution. The levels of DSPs in oysters were raised along with the increase of DSPs in the seawater with a latent appearance of peak values. These results suggested that our method should be efficient in the simultaneous temporal and spatial monitoring of DSPs in aquatic environments and in shellfish samples. This method may also be applied in DSP early warning system.

Abstract:In this study we performed a series of experiments in order to find an effective control of dinoflagellate in microalgal community of the water environment. Scrippsiella trochoidea, Cyclotella striata, Chlorella pyrenoidosa, and Scenedesmus quadricauda were used as representative microalgal species in this study. Strain A3 was added into either monoculture or mix-culture systems of the four microalgaes at a concentration of 107 CFU/ml, and the morphology and cell density of the microalgae were analyzed every 48 hours for 10 days. Treated with A3, S. trochoidea in the monoculture system lost the motion activity on Day 1, then they inflated and finally lysed on Day 5. The cell density of S. trochoidea was 7.07×102 cells/ml on Day 10, which was significantly lower than that of the control group (P<0.05). Morphology of C. pyrenoidosa was not affected by Strain A3. The cell density of C. pyrenoidosa was 2.58×107 cells/ml on Day 10, and it was higher than that of the control group (P<0.05). Morphology of S. quadricauda was also unaffected by Strain A3. There was no significant difference in the cell density of S. quadricauda between the experimental group and the control group (P>0.05). C. striata lysed due to the effects of A3 on Day 8, and the cell density of C. striata in the control group and the experimental group were 4.38×105 cells/ml and 1.78×105 cells/ml, respectively. The lytic effect of Strain A3 on four microalgal species in the mix-culture systems was similar to that in the monoculture systems. These results suggested that Strain A3 might have strong lytic effect on S. trochoidea in the mix-culture systems. However, Strain A3 did not inhibit the growth of S. quadricauda and C. pyrenoidosa, and had weaker lytic effect on C. striata. Therefore, the algicidal activity of Strain A3 was highly specific to S. trochoidea, and hence could be used to develop probiotics against dinoflagellate blooms in aquaculture ponds.