Abstract:In this study we investigated the expression patterns of Hsp90α and Hsp90β of Paralichthys olivaceus after the temperature treatment and Vibrio anguillarum infection. qRT-PCR was used to detect the expression of Hsp90 in different tissues of P. olivaceus during a series of growth stages (1-, 8-, 12-, and 24-month old). The results showed that Hsp90α and Hsp90β were expressed in 13 tissues including liver, spleen, head kidney, kidney, heart, muscle, dorsal skin, stomach, intestine, gill, pelvic fin, brain, and blood at all growth stages. The expression level of Hsp90β was overall higher than that of Hsp90α. Expression of Hsp90α was significantly higher at 8-month than at other growth stages in the liver, gills, dorsal skin, dorsal muscle, and pelvic. As the level of Hsp90β varied at different growth stages, it was observed to be higher in the liver and intestine. After a treatment at 5–32℃ for 1 h, the expression of Hsp90α in the liver and spleen was rapidly increased, whereas the expression of Hsp90β did not changed evidently. After a continuous treatment at 10℃ and 28℃ for 8 h, the expression of both Hsp90α and Hsp90β in the liver and spleen declined after an initial increase. Expression of Hsp90α varied in a wider range than Hsp90β. Within 72 h after the infection with V. anguillarum, expression of Hsp90α and Hsp90β in the spleen first rose and then decreased, and expression of Hsp90β had a larger variation range. These results indicated that Hsp90α and Hsp90β might have distinct expression patterns in different tissues at various growth stages. Hsp90α may be apt to respond to high temperature, while Hsp90β could be more sensitive to pathogen infection. These data will provide the basic data for better understanding of the functions of Hsp90 in P. olivaceus.

Abstract:The family Gobiidae is one of the largest fish families consisting of more than 200 genera and 2000 species. This family was found in near shore seawater, brackish water, and freshwater in the temperate and tropical areas all over the world. In this study we applied microsatellite DNA (short sequence repeat, SSR) to characterize the genetic structure of Gobiidae. We analyzed 153 SSR sequences amplified in our laboratory and 535 SSR sequences downloaded and screened from GenBank. The 686 sequences originated from 19 different species of Gobiidae. The total length of these sequences was about 295062 bp, in which 473 microsatellite repeat loci were found by using the bio-software Tandem Repeats Finder. The length of the repeat sequences was 33370 bp. We found that 361 dinucleotide repeat sequences accounted for the majority (76.32%) of the 473 repeat loci. Moreover, the AC repeat sequences were the most common (94.18) in the dinucleotide repeat sequences, whereas AT and GC repeat sequences were not observed. The number of the trinucleotide repeat sequences was 35 (7.4%), including 12 ACT repeat sequences that were the majority (34.29%). There were 68 tetranuleotide repeat sequences including 31 CTAT that was the dominant (14.38%). The numbers of both petranucleotide and hexanucleotide repeat sequences were 2 (0.42%) and 7 (1.48%) respectively. Intriguingly repeats of single nucleotide sequences were absent. Our results about the distribution of microsatellite contributed to a better understanding of the genomic structure of goby fish, and might provide important information for the development and application of goby fish microsatellite markers.

Abstract:In this study we compared the elimination rates of enrofloxacin in 3 major aquacultured flatfish, turbot (Scophthalmus maximus), olive flounder (Paralichthys olivaceus) and tongue sole (Cynoglossus semilaevis), in 20℃ seawater after the oral drug administration. Healthy turbot, olive flounder and tongue sole weighing 300-400 g were selected and orally administered with enrofloxacin for 3 consecutive days. Plasma and various tissues, such as liver, gill, muscle and kidney, were sampled on 1, 3, 6, 10, 15, 20, 25, 30, 35, and 40 days post drug administration, and the enrofloxacin concentration in these tissues were determined using reversed-phase high performance liquid chromatography (HPLC). The elimination curves of enrofloxacin for 3 flatfish species were plotted as concentration versus time, and the half-lives of the drug were calculated. It was found that in all 3 species the concentration of enrofloxacin residue was higher in kidney than in other tissues. Elimination of enrofloxacin in kidney of olive flounder was the fastest among the 3 flatfish species, followed by turbot and then tongue sole. Half-lives in the 3 species were 3.75, 6.54 and 7.37 days respectively. As for drug elimination in plasma, enrofloxacin was removed slower than its metabolite ciprofloxacin. Overall, elimination of enrofloxacin was the fastest in olive flounder followed by turbot, and it was the slowest in tongue sole. In China, the maximum residue limit (MRL) of enrofloxacin in seafood was 50 μg/kg, therefore the withdrawal periods of enrofloxacin for farmed turbot, olive flounder and tongue sole should be at least 44, 33 and 47 days respectively.

Abstract:In this trial, five isonitrogenous and isolipidic diets were formulated with different carbohydrate sources at 20%, including glucose, sucrose, dextrin, corn starch, and gelatinized corn starch. The Trachinotus ovatus with initial weight of (31.24±0.58) g were fed with each diet for 8 weeks. Then the effects of different carbohydrate sources on a variety of biological activities were compared so to determine the optimal carbohydrate sources. The results suggested that the carbohydrate sources with higher molecular weight significantly increased the weight gain (WG) and the specific growth rate (SGR) (P<0.05). The group fed with gelatinized corn starch showed the highest WG (335.35%) and SGR (2.62%/d). The vicerosomatic index (VSI), hepatosomatic index (HSI), liver glycogen content, and muscle glycogen content of the five carbohydrate groups were significantly different (P<0.05), and those of the glucose group were the highest. Carbohydrate sources also affected the levels of plasma glucose, total cholesterol, and triglycercide (P<0.05). No significant difference was observed in hepatic hexokinase (HK) activity (P>0.05). Activities of glucokinase (GK), pyruvate kinase (PK) and phosphofructokinase (PFK) reached the highest in the glucose group (P<0.05). These results suggested that macromolecules (starch) are better for the growth of T. ovatus than glucose, sucrose, and dextrin, thus gelatinized corn starch should be the optimal carbohydrate source. Furthermore, carbohydrate sources may also have effects on the glycogen synthesis, glycolipid transformation and glycolysis.

Abstract:To investigate how temperature affects activities of digestive enzymes and serum biochemical indices of Pampus argenteus juveniles, in this study we tested their biochemical indices in experimental temperature groups (22℃ and 32℃), and the control group (27℃). P. argenteus juveniles were randomly assigned to three replicates in each group and reared for 48 h. In the 22℃ group, the activities of pepsin and trypsin in the gut showed no significant change (P>0.05). However, the amylase activity was decreased whereas the lipase activity was increased (P<0.05). In the 32℃ group, activities of lipase, pepsin, and trypsin were significantly enhanced (P<0.05), but amylase activity was first increased followed by a decline (P<0.05). In the 22℃ group, the contents of glucose (GLU) , lactic acid (LD) , and cortisol (COR) were raised (P<0.05); the levels of triglyceride (TG) and creatinine (CREA) showed a decrease-increase- decrease pattern (P<0.05); the content of total serum protein (TP) dropped first and then went up (P<0.05). In the 32℃ group, levels of TP and TG were decreased; no significant changes were observed in the GLU level (P>0.05); LD decreased first and then increased, whereas COR altered in an opposite way (P<0.05); the content of CREA was elevated. There were also significant differences in gut and serum between different experimental temperature groups at the same time point. These results indicated that the acute temperature stress might jeopardize the digestive and excretory systems of P. argenteus juveniles, therefore it should be avoided in the process of industrial aquaculture to improve the living condition of P. argenteus juveniles.

Abstract:Common malformations were observed in artificially cultured Epinephelus akaara. The malformations could be divided into two categories: the spinal deformity and gill jaw deformity. To compare the nutritional values of the two types of deformed fish and normal ones, conventional nutrient determination methods were applied to analyze the body indices and muscle nutrient component and quality. The results were shown as follows:(1) The total length and muscle rate of spinal deformed fish were (21.97±1.50) cm and (71.12±1.45)% respectively. Those of gill and jaw deformed fish were (22.43±0.12) cm and (71.28±0.39)%. The values of both were significantly different from those of normal fish (25.70±0.75) cm and (78.58±0.20)%. (2) The difference in muscle crude protein and crude ash between the three types was small and insignificant, whereas the crude fat content of spinal deformed (3.55±0.06)%, there was a significant difference between the normal fish (2.71±0.07)% and gill jaw deformed (2.48±0.01)%. (3) The amino acid content and essential amino acid index of spinal deformed [(17.55±0.65%) and 83.04] and gill jaw deformed[ (15.89±0.11)% and 73.82] were lower than those of normal fish [(19.86±0.52)% and 89.25]. (4) In terms of meat quality, cohesion, elasticity, adhesiveness, and chewiness were compared between the three groups, and the order was normal fish > spinal deformed fish > fish gill and jaw deformed fish. Comprehensive analysis suggested that nutritional values of the two types of deformed fish were lower than that of normal fish, and it was the lowest in the gill and jaw deformed. In addition, we also tested the levels of elements such as Cu, Zn, Fe, Mn, Ca, and P in spines and gill and jaw bones of the three types of fish. We found that there was no significant difference in these elements in the spine, except for Fe and Mn. This indicated that the change in Fe and Mn content might be the cause of spinal deformity in cultured E. akaara.

Abstract:It has been clear that the dietary arachidonic acid (ARA) is essential in the growth of juvenile Japanese seabass (Lateolabrax japonicas), and the requirement of ARA could vary at different growth stages. A 12-week feeding experiment was conducted to investigate the optimal level of ARA in diet of Japanese seabass [mean initial weight (207.16±0.72) g)]. Six isonitrogenous and isoenergetic diets were formulated with graded levels of dietary ARA, 0.05%, 0.22%, 0.37%, 0.60%, 1.38% and 2.32%, respectively. Triplicate groups of 20 fish were fed to apparent satiation twice daily. The water temperature ranged from 23 to 30.5℃, the salinity from 26 to 31 and the dissolved oxygen content was approximately 6.5 mg/L during the experimental period. The results showed that no significant differences in survival rate (93.33%-98.33%) were found among dietary treatments (P>0.05). With the increase of dietary ARA levels, the specific growth rate (SGR) and feed efficiency (FE) increased at first, and then kept steady after reaching their peaks at the 0.37% dietary ARA level (P<0.05). No significant differences were found in hepatosomatic index (HSI), viscerasomatic indexes (VSI) and condition factor (CF) among dietary treatments (P>0.05). The body composition analysis showed that the whole-body protein content first increased and, then decreased with increasing dietary ARA, while the whole-body lipid content followed the opposite pattern. With the increase of dietary ARA levels, the activities of superoxide dismutase (SOD) in serum and liver significantly increased at first and then showed a declining tendency (P<0.05), but the malondialdehyde (MDA) contents in serum and liver had a converse trend with SOD (P<0.05). The activities of glutamic-oxaloacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) in serum observably decreased when the dietary ARA level increased from 0.05% to 0.37%, and then increased when the dietary ARA level increased from 0.37% to 2.32% (P<0.05). The broken-line model analysis based on SGR and FE indicated that the optimal level of dietary ARA for Japanese seabass of (207.16±0.72) g of the diet was 0.37%.

Abstract:The aim of this study was to determine if algal products rich in DHA or EPA are able to completely replace fish oil in microdiets for marine fish juveniles, Japanese flounder Paralichthys olivaceus. To address the problem, an 11-d feeding experiment was carried out on 18-day old juveniles. The experimental subjects were fed with five groups of isolipidic and isoenergetic microdiets that were control group with fish oil (FO), 50% replacement group by mixed Schizochytrium sp., Nannochloropsis sp. and olive oil (M50), 100% replacement group (M100), 100% replacement group by Schizochytrium sp. and olive oil (S100), and 100% replacement group by Nannochloropsis sp. and olive oil (N100). The results showed that there were no significant effects of fish oil replacement with microalgae on growth. The groups containing Schizochytrium sp. (M50, M100 and S100) had higher survival rates than FO and N100 groups. No changes in the major fatty acid compositions of juveniles were observed with the replacement of fish oil by microalgae. In addition, Pearson correlation analysis showed that the percentage content of C14:0, C16:1n-7, C18:2n-6, C20:0, C18:3n-3, C22:0, C20:4n-3, EPA, C22:5n-6 and DHA in juveniles were significantly and positively correlative to those in diets (P<0.05). The same correlations were also observed for total saturated, monounsaturated and n-3 polyunsaturated fatty acids, and DHA/EPA ratio. In conclusion, fish oil replacement with microalgae as lipid sources can fully satisfy the growth and development in juvenile flounder, and fatty acids in microalgae can be effectively digested and absorbed. Furthermore, the addition of microalgae in diets enhanced the DHA content and DHA/EPA ratio in juveniles, and hence improved the survival. Therefore, the fish oil replacement with microalgae in the culture of Japanese flounder juveniles is feasible. This study will be helpful and suggestive for screening new lipid sources to replace strained fish oil resource.

Abstract:In this study, 10 typical types of Scomberomorus niphonius gillnets used in the Bohai Sea and the Yellow Sea area were identified and investigated. Based on the analysis of the main parameters of the 10 net types mentioned above, we selected nets with 4 different mesh sizes (110 mm, 115 mm, 120 mm, and 125 mm) to perform a comparative experiment on the fishing boat “Luchangyu-64068” operated in the central and southern Yellow Sea from 10 April to 15 May in 2013. The highest number and weight of fish were caught with net of mesh size 120 mm, and the CPUE was 0.1696 ind/webbing/day and 373.78 g/webbing/day respectively. The fishing efficiency of 120 mm mesh size was also the highest among the 4 studied sizes. Further optimization of main parameters of big-mesh gillnets for S. niphonius were conducted on fishing vessels “Luchangyu-64068” and “Lulaizhouyu-66287” in the central and southern Yellow Sea, offshore of Yantai, Weihai and Laizhou Bay, from 12 April to 27 May in 2015. Using the net of 120 mm mesh size on “Luchangyu-64068”, we caught S. niphonius with the mean fork length of 764.18 mm and mean body weight of 3623.27 g. Among them the longest was 1000 mm; the shortest was 490 mm; the heaviest individual weighed 7500 g, and the lightest was 850 g. The CPUE was 0.1379 ind/webbing/day and 517.65 g/webbing/day. “Lulaizhouyu-66287” employed net of 122 mm mesh size, and the mean fork length and mean body weight of fish caught was 780.47 mm and 4065.17 g respectively. The longest was 910 mm; the shortest was 600 mm; the heaviest individual was 7400 g; the lightest was 2000 g. The CPUE was 0.0778 ind/webbing/day and 283.35 g/webbing/day. Because nets of 120 mm mesh size showed higher fishing efficiency than that of 122 mm, it should be more suitable for catching the spring cohort of S. niphonius. The main parameters of a net of 120 mm mesh size were as follows: 33.00 m×18.54 m in the principal dimension of fishing gear, 500 mesh×175 mesh, 120 mm in mesh size, PA monofilament (Φ=0.48 mm) as the netting material, T-direction hanging ratio 0.55, static buoyancy distribution 267.9 g/m, and buoyancy to sinker-weight ratio 1.768∶1. Due to the replacement of the upper hanging line and float line by decreasing the mesh size of cork line selvedge strip, less net material was need to maintain the major structure and performance of the net. The proper mesh size of cork line selvedge strip should be equal to mesh size of main netting multiplied by T-direction hanging ratio of main netting.

Abstract:In this study we evaluated the contents of major nutrients including amino acids and fatty acids of two krill meals, Antarctic krill meal and hydrolyzed krill meal, and analyzed the muscle samples of five species of flatfishes, Verasper Variegates, Platichthys stellatus, Platichthys biocoloratus, Verasper moseri, and Scophthalmus maximus. The nutritional values of the two krill meals were tested with the essential amino acid index, score of ratio coefficient of amino acid, and relativity of essential amino acids, and the levels of fluorine in the two krill meals were also measured. Sixteen kinds of amino acids were found in muscles of five flatfishes, including seven essential amino acids and four flavor amino acids. The amino acid composition of muscles of the five flatfishes complied the standards of Food and Agriculture Organization of the United Nations/World Health Organization (FAO/WHO). The contents of crude proteins in Antarctic krill meal and hydrolyzed krill meal were 60.84% and 68.60% respectively, which satisfied the standards of the first class products index and the superfine products index. After hydrolysis, the content of crude proteins was significantly increased (P<0.05), whereas the content of crude lipids dropped (P<0.05). The content of ash was unaltered (P>0.05). These results suggested that there was a good balance in the amino acid composition of the two krill meals, and that the relativity of essential amino acids was similar to the fish meal. In addition, the content of fluorine in the hydrolyzed krill meal was significantly lower than that in the Antarctic krill meal (P<0.05). In conclusion, Antarctic krill meal and hydrolyzed krill meal had high nutritional values and potentially could be largely employed in aquaculture feeds.

Abstract:Chinese shrimp (Fenneropenaeus chinensis) is an ecologically and economically important shrimp species. During the culture, F. chinensis were exposed to a series of stressors that adversely affect biological activities including growth rate. Ammonia, a product of protein degradation and bacterial activity, is a strong stressor in shrimp aquaculture. Glutamate dehydrogenase (GDH) is an abundant and ubiquitous mitochondrial enzyme that catalyzes reversible amination of glutamate. cDNA of GDH from F. chinensis (FcGDH) was cloned by rapid amplification of cDNA ends (RACE). The FcGDH cDNA was 1779 bp in size, and it included a 1659-bp open reading frame (ORF) that encoded a 522 amino-acid polypeptide of which the isoelectric point (pI) was 6.54 and the molecular mass was 61.3 kDa. Homology analysis revealed that the amino acid sequence of FcGDH was highly conserved with its homologs in other arthropod. The similarities between FcGDH and GDHs of Litopenaeus vannamei and Eriocheir sinensis were 98% and 89% respectively. Phylogenetic analysis showed that FcGDH was in the same branch with that of L. vannamei and then in the same branches with those of E. sinensis, Drosophila melanogaster, and Aedes aegypti in order. The tissue expression analysis showed that FcGDH was detected in all tested tissues including muscle, gill, hepatopancreas, stomach, intestine, lymph, and hemocytes. The highest expression of FcGDH was in the muscle that was an amino acid pool and the major tissue for protein deposition. After exposure to ambient ammonia, the expression of FcGDH gene was up-regulated significantly in muscles compared to the control group (P<0.01). The expression level of FcGDH in hepatopancreas was down-regulated significantly at 3 h (P<0.05), and was then stabilized up to 24 h. The expression of FcGDH was increased significantly after 48 h and reached the maximum at 72 h compared to the control group (P<0.01). These results implied that FcGDH might play an important role in the process of ammonia detoxification.

Abstract:Shrimp production has been a well-developed pillar of the aquaculture industry in China. Fenneropenaeus chinensis, one of highly valuable shrimp species, was mainly raised in the Bohai Sea and the Yellow Sea in North China. Antimicrobials are most frequently applied during intensive aquacultures to prevent or cope with disease outbreaks. However, antimicrobials may also have toxic effects on cultured animals such as immunosuppression. To better understand the mechanisms, we measured activities of superoxide dismutase (SOD), alkaline phosphatase (AKP), lysozyme (LZM), and phenoloxidase (PO) in serum upon the treatment with sulfamethazine (SM2) at different concentrations. It was found that SM2 significantly enhanced SOD activity at 50 mg/kg, whereas inhibited SOD at 150 mg/kg. At 100 mg/kg, SM2 first boosted SOD activity in the first 2 days and then suppressed it from Day 3 of treatment compared to the control group. Treated with 50 mg/kg SM2, the activity of AKP was inhibited from Day 2 of treatment till Day 2 after the treatment, followed by a recovery to the control level. When the SM2 concentration was 100 mg/kg, the AKP activity was elevated to a peak value on Day 5 of the treatment and then dropped back to the control level. In the treatment with 150 mg/kg SM2, AKP activity altered in the same pattern as the medium concentration group. SM2 had inhibitive effects on LZM at 50, 100, and 150 mg/kg. In spite of the concentrations of SM2, the PO activity showed the same trend that it rose to a higher level than the control followed by a decrease. The non-specific immunity was inhibited by SM2 at 150 mg/kg. Therefore, the dosage of antibiotics should be carefully evaluated to ensure healthy aquaculture of shrimp.

Abstract:In this study we aimed to develop an economical, visual-friendly, and portable test to detect yellow head virus (YHV) in field. Based on sequence of nonstructural protein N of YHV, a padlock probe (PLP), detection probe, and universal primers were designed. Subsequently the hyper-branched rolling circle amplification (HRCA) assay and the corresponding test strip were developed. The reaction time and temperature were optimized. Padlock probes were linked to the target sequence by T4 DNA ligase at 37℃ for 30 min, and reacted by Bst DNA polymerase large fragments at 61℃ for 30 min. The test strip was then made using the detection probe. The serials diluted reference materials were used to examine the sensitivity of the YHV HRCA test strip, and the result was compared with that of the conventional reverse transcription polymerase chain reaction (RT-PCR). Three primary shrimp viruses including white spot syndrome virus, infectious hypodermal and hematopoietic necrosis virus, and taura syndrome virus were used for the specificity test of the YHV HRCA test strip. Furthermore, the efficiency of the test strip was verified with 80 patches of 4 shrimp species collected in China and abroad, and the results were also compared with RT-PCR. The test results showed that the detection limit of the HRCA test strip was close to 10 copies/μl, which was 100-fold higher than RT-PCR. It was also shown that the test strip had a satisfying specificity for YHV, and there were no cross-reaction with white spot syndrome virus, infectious hypodermal and hematopoietic necrosis virus, or taura syndrome virus. The overall YHV test results using the HRCA test strip were identical with RT-PCR, but the former was more convenient, sensitive, and easier to interpret in the field.

Abstract:The dynamic changes and diversity of archaeal communities in two kinds of ponds (M1: the pond with sanded walls and netted bottom; M2: the traditional pond with soil) for the polyculture of Portunus trituberculatus-Exopalaemon carinicauda in different seasons were investigated. The study was conducted with a combination of cloning/sequencing and terminal restriction fragment length polymorphism (T-RFLP) analysis based on archaeal 16S ribosomal RNA. Physicochemical characters of the sea water were monitored at the same time to examine the relationship between environmental factors and archaeal communities. The results showed that the archaeal communities in both M1 and M2 were composed of Crenarchaeota and Euryarchaeota. Halobacteriales and thermoplasamatales in Euryarchaeota were the majority accounting for nearly half of the entire sample. Halobacteriales was more abundant than thermoplasamatales, however, it was the marked alteration in the relative abundance of thermoplasamatales that primarily led to the archaeal community shift. The structure of archaeal community in aquaculture water changed dramatically during the culture. The archaeal communities of M1 and M2 were similar at the beginning of the culture, but changed significantly over time. Principal component analysis showed that the variation in M2 was larger than in M1, which indicated the lower stability of archaeal community in the former. Redundancy analysis indicated that 84.2% of the archaeal community in M1 could be explained by the 9 factors measured in this study, while that M2 was also determined by other factors and only 35.7% was explained. The improvement of pond sediment could reduce the extent of changes in the archaeal community. Correlation analysis showed that the higher the diversity index was, the smaller the influence of environment on the distribution of archaea. In general, the distribution of archaea in pond water changed over seasons, and was greatly affected by temperature, dissolved oxygen, total nitrogen, and total phosphorus

Abstract:Sea cucumber (Apostichopus japonicus) has become one of the major aquacultural species in China. Genetic improved seeds of sea cucumber play a key role in the ever-increasing profit. Information on the genetic parameters of papillae number, the important economic trait of sea cucumber, however, has been lacking. To investigate the repeatability, required measure times, and the most probable producing ability (MPPA) of sea cucumber, we applied quantitative genetic methods to determine the repeatability coefficients of papillae number of four sea cucumber populations in the age of 12–17 month, including Korean self-propagated population (KK), Duoci self-propagated population (DD), Shandong self-propagated population (SS), and Three-way cross population (DK). Based on the estimates, we also calculated and compared the required measure times, MPPA, and correlation efficient between MPPA and body weight of the four populations. We found that the repeatability coefficients of papillae number were low in all four populations. The repeatability coefficients of the four population followed the order: DD(0.29)>DK(0.28)>SS(0.20)>KK(0.19). For population DD and DK, the papillae number needed to be measured for 5 times to reach a relative accuracy above 80%, while for SS and KK populations 8 measure times were required. The MPPA for papillae number followed the order: DD(41.3)>DK(40.8)> KK(39.8)> SS(39.1), with the significant difference between DD and SS only (P<0.05). The phenotype correlation between MPPA and body weight in each population was significantly positive. Therefore, repeatability and MPPA could be used as criteria in population selection for papillae number. Our results suggested that DD and DK populations might have higher papillae numbers, higher potential for selection, and less measure times needed than the other two populations, hence they could be the key populations for papillae number selection.

Abstract:In this study, we investigated the composition and function of free amino acids (FAAs) in the gill of Portunus trituberculatus under different salinities. In a 5-day experiment, the contents of FAAs were measured under a series of salinities. We found that in seawater-adapted P. trituberculatus, the concentration of taurine (2.54 mg/g) was the highest, followed by alanine (0.65 mg/g), glutamate (0.64 mg/g), arginine (0.58 mg/g), glycine (0.48 mg/g) and proline (0.25 mg/g). The level of total free amino acids (TOFAA) in the gill increased significantly with the rise in salinity (P<0.05). When salinity was 10, 20, 33, 40, and 50, the concentration of TOFAA in the gill was 5.32 mg/g, 7.26 mg/g, 6.34 mg/g, 7.25 mg/g, and 7.90 mg/g respectively. Non-essential amino acids (NEAA) increased significantly as the salinity was elevated from 10 to 50. Essential amino acids (EAA) was not affected by external salinity change (P>0.05). NEAA includes glutamate (Glu), alanine (Ala), glycine (Gly), aspartic acid (Asp), serine (Ser), cysteine (Cys), tyrosine (Tyr), proline (Pro), and Tauine (Tau), and the rest are EAA. TAA include aspartic acid (Asp), glutamate (Glu), glycine (Gly), and alanine (Ala). The concentrations of free Gly, Glu, Ala, Pro in the gill of P. trituberculatus were raised sharply (P<0.05) with the increase in salinity, whereas the concentration of free Arg decreased (P<0.05). The results suggested that FAAs, especially individual Gly, Glu, Ala, and Arg, could play an important role in salinity adaption. During adaptation, the FAAs pool (mainly NEAA) in the gill may be directly associated to osmoregulation. Change in the FAAs pool in the gill after acclimatization suggested that mainly NEAA might be involved in intracellular osmoregulation. It was also demonstrated that the salinity change mainly affected the NEAA content in the gill.

Abstract:Here we studied the properties of flora in the gut content and attachments of sea cucumber (Apostichopus japonicus) as well as in the sediments of pond where sea cucumber were cultured. 16S rDNA PCR denaturing gradient gel electrophoresis (PCR-DGGE) was employed as the major method. The DGGE band numbers were 30.00±1.00, 15.33±1.70, and 21.67±2.62 for gut content, attachments, and pond sediments respectively. This indicated that the gut content had the highest diversity of bacterial species. UPGMA cluster analysis showed that flora from three gut content samples could be categorized into one branch with a similarity value of 0.785, and that flora from attachments and pond sediment samples were clustered into another branch with a similarity value of 0.532. Twenty specific DGGE bands from the three kinds of samples were cut and sequenced. The results showed that Synechococcus sp., Desulfobacterium, Desulfosarcina sp., Polaribacter, Algibacter sp. were the dominant bacterial species in the gut content; Robiginitalea sp., Silicibacter sp. were dominant in attachments; and Proteobacterium, Cytophaga, Desulfosarcina sp. were dominant in the sediment. The specific bacteria in the gut content could be candidates of probiotics in the sea cucumber culture.

Abstract:Apostichopus japonicus that usually habits in the temperate zone, is one of the important aquaculture species at northern China coast. Dissolved oxygen, known as the oxygen content in water, is necessary for the survival of aquatic organisms and directly affects the enzyme activity, metabolism, and growth of aquatic organisms. Therefore, low dissolved oxygen during the hot weather is very harmful for sea cucumber aquaculture and has become an urgent issue. Here we investigated the effects of hypoxic stress on antioxidant capacity of A. japonicus. The experimental group was exposed to hypoxia [(2.0±0.2) mg/L] for 8 h, followed by reoxygenation [(7.0±0.2) mg/L] for 2.5 h. Then tissues from the muscle, respiratory tree, and digestive tract were collected at different time points. Levels of lactic acid, malondialdehyde (MDA), and activities of the antioxidant enzyme system in different tissues and time points were analyzed. It was found that during the exposure to hypoxia, the lactic acid content and activities of total antioxidant capacity (T-AOC), catalase (CAT) and glutathione-S-transferase (GST) were significantly higher compared with the control group (P<0.05), whereas the activity of superoxide dismutase (SOD) became lower (P<0.05) with the extension of hypoxic exposure. The level of MDA in the muscle tissue was significantly lower than in the control group (P<0.05), however, was higher in the respiratory tree and digestive tract. All of the oxidative stress indices gradually returned to normal levels during reoxygenation. These results indicated that as the aerobic metabolism was inhibited during hypoxia, the anaerobic metabolism was increased to maintain the energy supply. The elevated T-AOC, CAT and GST activities and declined SOD activity caused by hypoxia might be an antioxidant strategy to adapt to the hypoxic environment. Our study may provide useful information for the control of hypoxic conditions in sea cucumber aquaculture.

Abstract:DNA methylation plays important roles in many biological processes such as gene expression regulation and genomic imprinting. Up to date, studies have mostly focused on the status of DNA methylation in different tissues of aquatic animals. Stress-inducing alteration in DNA methylation in shellfish remains elusive. Japanese scallop Patinopecten yessoensis, an economically valuable bivalve species, are only cultured in northern areas of Shandong Province and Liaoning Province in China due to their specific temperature requirement. In the present study, methylation-sensitive amplification polymorphism (MSAP) was employed to investigate the profiles of genome-wide DNA methylation of P. yessoensis after acute temperature stress. P. yessoensis was challenged at 17℃ and 24℃ for 9 hours and 24 hours respectively. Then DNA in the gill was extracted with traditional phenol/chloroform method. Next, each DNA sample was digested by the combination of EcoRⅠ HpaⅡ, EcoRⅠ, and MspⅠ, followed by the connection to adapters with T4 ligase. Nine pairs of E/HM primers were selected to study the change in genome-wide DNA methylation. Totally 314–337 amplified sites were obtained in all subjects, of which 79–94 were methylated sites, accounting for 23.45%–28.51% of all sites. The total methylation rates of all experimental groups, except for that of 24℃/24 hours, were insignificantly lower than the control level. Moreover, the reduction in methylation was positively correlated with the temperature difference and exposure time. These data implied that the level and pattern of DNA methylation could be altered by acute temperature stress. Our findings provided insight into gene screening for important traits and better understand of epigenetic dynamic in bivalves.

Abstract:Flavor is an important example of sensory evaluation of food quality. Flavor of marine algae could be affected by various factors such as the strain, aquaculture area, and the harvest time. Pyropia haitanensis is one of the important cultivated algae in China; however, few studies have been done on what affects its flavor. In this study, we selected two strains of P. haitanensis, Shenfu 2 and Zhedong 1, cultured in Dongtou and Xiangshan Counties of Zhejiang Province in China. The subjects were harvested for 4 or 5 batches, and the volatile components were analyzed by head space solid-phase micro extraction and gas chromatography coupled with mass spectrometry, as well as multivariate data analysis. Totally 115 volatile components were detected in the two strains living in different culture areas, of which the major species were hydrocarbons, aldehydes, and ketones, specifically 8-heptadecene, pentadecane, 1-heptadecene, nonanal, and octanal. Principal Component Analysis (PCA) showed a clear difference in the volatile components between two strains cultured in two areas. The strain-specific differences were shown in 8-heptadecene, 1-heptadecene, nonanal, 2-ethenyl-6-methyl pyrazine, and octanal; the area-specific differences were signified in 8-heptadecene, nonanal, 2-ethenyl-6-methyl pyrazine, 1-heptadecene, and styrene. In addition, the volatile components at different harvest time were closely correlated to the water quality. Therefore, it is important to select appropriate areas for P. haitanensis culture.

Abstract:Oyster (Crassostrea gigas) is popular seafood with delicious taste and rich nutrients. The produce of oyster in China was as large as 4,352,000 tons in 2014. In this study we investigated the effects of high pressure processing (HPP) and cold storage on microbial inactivation, the total volatile basic nitrogen (TVB-N), and the pH of oysters. Tastes of oysters after HPP and heat processing were compared. It was found that there was an over 2-lg reduction in the total number of bacterial colonies after 300 MPa processing for 15 min. Similar results were observed under conditions such as 400 MPa for 10 min or 15 min, and 500 MPa for 5 min, 10 min or 15 min. Particularly when treated at 500 MPa for 10 min, no colony in oysters could be detected. The results above indicated that HPP treatment could effectively suppress the microorganisms in oysters. The shelf life of raw-eaten oysters could be extended to 15 days when stored at 4℃ after HPP treatments such as 300 MPa for 15 min, 400 MPa for 10 min, and 500 MPa for 5 min. TVB-N was also effectively inhibited by HPP treatments. The TVB-N level remained <10 mg/100 g in 20 days when stored at 4℃ after HPP at 300 MPa for 15 min. Oysters treated with HPP had significantly higher pH value and hardness compared to the untreated (P<0.05), and the springiness was also increased. The electric nose test detected no significant difference in taste between HPP-treated and the untreated oysters. However, the taste of heat-treated oysters was apparently different from those of HPP-treated and the untreated. These results indicated that HPP treatment might be an effective non-thermal processing technology. HPP with proper conditions could efficiently extend the shelf life of raw-eaten oysters and improve their quality.

Abstract:Toxins produced by harmful algae has been a global food safety issue in aquaculture industry. Unlike conventional phytoplankton and shellfish monitoring techniques, solid phase adsorption toxin tracking (SPATT) simulates the contamination of filter feeding bivalves and employed passive sampling of adsorption substrates. Combined with appropriate assays such as HPLC-MS/MS and ELISA that purify and analyze algal toxins, SPATT gives early warning of harmful algal blooms and the subsequent contamination of shellfish. In this review we discussed the progress and prognosis on studies of SPATT. We elaborated the advantage of SPATT in detecting marine toxins including diarrhetic shellfish poisoning, paralytic shellfish poisoning, amnesic shellfish poisoning, ciguatoxins, cyanotoxins, and homoanatoxins. We also summarized the function of different absorbent resins such as HP-20, SP-70, SP700, SP850, SP825L, XAD4, and L-493. SPATT is an inexpensive and convenient tool for fast detection of algal toxins.