Abstract:Keystone species play an important role in the structure and function of an ecosystem. Changes in keystone species can cause oscillations in community structure and ecological succession, or even result in the dysfunction and collapse of ecosystems. Therefore, understanding long-term changes in keystone species of an ecosystem provides insights into the processes of ecological succession. We built a food-web topological structure for the fish community in Laizhou Bay for each of five years, based on the spring bottom trawl survey data for Laizhou Bay during 1959, 1982, 1993, 2003, and 2015, and then, conducted network analysis to evaluate long-term changes in keystone fish species from 1959 to 2015. The constructed food webs included 21~46 different fish species and 70~296 prey-predator relationships. The structural density of these food webs ranged from 0.155 to 0.300, and interspecific connectivity ranged between 0.140 and 0.182, which matched the ecology of fish communities under natural conditions. The keystone fish species in Laizhou Bay changed from Amblychaeturichthys hexanema, Lateolabrax japonicus, Scomberomorus niphonius, and Lophius litulon in 1959 to Engraulis japonicus, L. litulon, and Larimichthys polyactis in 1982, and then, to Trichiurus lepturus, E. japonicus, and S. niphonius in 1993. After ten years, Liparis tanakae, E. japonicus, and L. litulon became the new keystone fish species, which were replaced by L. tanakae, Hexagrammos otakii, and A. hexanema in 2015. Conclusively, the keystone fish species in Laizhou Bay gradually changed from economically valuable species (e.g., L. japonicas, L. polyactis, and S. niphonius) to those of less economic value (e.g., A. hexanema and L. tanakae). Meanwhile, the diversity of the keystone fish species reduced from different pelagic or groundfishes (e.g., L. japonicus and S. niphonius) to those inhabiting only the bottom. These changes have simplified the topological structure of food webs in Laizhou Bay, which to some extent, has reduced the functional stability of the fish community.

Abstract:This study investigated the development and resorption of the oocyte of Cleisthenes herzensteini in the Yellow Sea, using light microscopy and morphometric methods. Oocyte development was divided into five phases, based on morphological criteria and nutrition accumulation. Oocytes in phase I were small, with little cytoplasm. In phase Ⅱ, oocytes were distinguished by the appearance of yolk nucleus near the cell nucleus. In phase Ⅲ, cortical vacuoles first appeared on the edge of the cytoplasm and then extended to the center, with the occurrences of crystalline yolk and double follicular membrane. Oocytes in phase Ⅳ were full of non-crystalline yolk, with the cell nucleus moving towards the animal pole and the zona radiate becoming thicker. In phase Ⅴ, the cell nucleus of the oocyte dissolved, and the hydrated oocyte was released from the follicular membrane. Ripe ovary that had not ovulated completely was in turn resolved, with the yolk absorbed and the zona radiate ruptured after the spawning season. In addition, this study showed that C. herzensteini was characterized by asynchronous oocyte development and batch spawning, based on histologic observations of the different stages of the ovary and the oocyte size-distribution method. The sizes (major axes) of the oocytes in the stage Ⅳ, Ⅴ, and Ⅵ-Ⅳ¢ ovaries had unimodal distributions, with the three modes at 0.45~0.55 mm, 0.60~0.65 mm, and 0.40~0.50 mm, respectively. Oocyte size distribution was bimodal for stage Ⅴ¢ ovary, the oocytes mainly distributed at both 0.50~0.55 mm and 0.90~0.95 mm, with the percentage of hydrated oocytes and small oocytes increased. The two dominant size groups of oocytes in the stage Ⅴ¢ ovary were well separated with a clear hiatus, and the oocytes in the larger-size group were all hydrated, which was in accordance with the characteristics of batch spawners. In the course of protecting C. herzensteini resources, we should take into account their reproductive characteristics.

Abstract:Enhancement release has been proven effective in natural resources recovery of Chinese shrimp Fenneropenaeus chinensis in the last several decades in China, however, to assess the effectiveness of enhancement release, we still need to develop a high-efficient and easy-operational method to replace those physical-tagging release method with labor intensive, size- and number-limited. In the present study, single (with maternal known) parentage identification using eight simple sequence repeat (SSR) markers genotype fingerprint was used to trace Chinese shrimp released in Bohai Bay in 2013. A total of 884 shrimp spawners were collected from two hatcheries in Tianjin City respectively after enhancement release of shrimp larvae in May 2013. A total of 844 shrimp samples were recaptured around the release location approximately 4 months after the shrimp larvae were released into the natural sea. Genotype data of 8 SSR loci of the 1,726 samples were used for maternal-offspring parentage identification using CEervus 3.0 software. The allele number in each locus ranged from 8 to 68 with an average value of 33.25, which produced the cumulative exclusion probability with one parent known of all these sight loci up to 99%. Among the 844 recaptured shrimp samples, 448 (♂:♀=212:232, gender information was lost for 4 samples) were successfully traced to their 337 maternal parents using a logarithm of odds (LOD) > 3.0 threshold. Among these 337 maternal parents, 253 had a single offspring, 62 had two offspring, 18 had three offspring, 3 had four offspring, and 1 had five offspring. For the first time, a large number of released shrimp were identified from recapture samples, and this study showed that it is possible to trace all released Chinese shrimp without using any type of physical tag in enhancement release activities. This not only means more precise recapture ratio assessment than ever expected, but also this method demonstrates an effective method for large-scale hatchery release as well as for organisms used in hatchery enhancement which are not suitable for physical tagging.

Abstract:The community of macrobenthos was investigated at 32 stations in the southern coastal waters nearby the Shandong Province in August 2006. A total of 182 species were identified, including 92 species of Polychaeta, 29 species of Mollusca, 42 species of Crustacea, 9 species of Echinodermata, and 10 species of minor phyla. Nine of the top ten dominant species (Nephtys oligobranchia, Mediomastus sp., Aricidea fragilis and Sigambra bassi, Leptomya minuta, Paralacydonia paradoxa, Sternaspis scutata, Eudorella pacifica, Lumbrinereis debilis, Prionospio sp.) were polychaetes. The average abundance of the macrobenthos was 2001 ind./m2, and the average biomass was 15.92 g/m2 in the investigated area. The value of Shannon-Wiener index (H¢) of macrobenthos was 2.20~4.59 with an average of 3.92. The value of Margalef’s richness index (d) was 0.99~5.39 with an average of 3.98. The value of Pielou's evenness index (J) was 0.61~0.89 with an average of 0.80. According to the results of CLUSTER analysis, the macrobenthos at the 32 stations could be clustered into two infaunal communities at 36% similarity, which were Mediomastus sp.-N. oligobranchia-Prionospio sp. Community (Community Ⅰ), and N. oligobranchia-A. fragilis-S. bassi Community (Community Ⅱ). The dissimilarity between Community Ⅰand CommunityⅡwas 77.21%. Analysis on Shannon-Wiener index (H¢) showed that all stations were unpolluted except for the 147th station, which suggested that the macrobenthic environment in the investigated area was generally clean. Pearson correlation analysis showed that the abundance and the depth of the water were significantly and negatively correlated (r=–0.38, P<0.05). BIOENV analysis indicated that the most crucial combination of environmental factors for the structure of community was silt + depth + organic carbon (r=0.46). Compared to the results of other previous reports, the average abundance value in our study was the highest. while the average biomass value was the lowest

Abstract:Studies on the abundance and biomass of planktonic ciliates were conducted in the Bohai Bay during spring (May), summer (July) and autumn (September) of 2015. Fifteen stations were investigated in each season. One-liter sample of seawater from the surface layer was collected and fixed in 1% acid Lugol’s iodine solution. Water samples were pre-concentrated using the Utermöhl method and observed using an Olympus IX71 inverted microscope. The dimensions of the ciliates were measured and the cell volume of each species was estimated using appropriate geometric shapes. The carbon/volume ratio used to calculate the biomass was 0.19 pg C/µm3. The classification of tintinnids was based on previous literatures about taxonomy. The abundance and biomass of ciliates and the community structure varied in the three seasons. The average abundance of ciliates in the spring, summer and autumn was (1016± 868) ind./L, (2011±1327) ind./L and (2456±1776) ind./L respectively. The average biomass of ciliates in the spring, summer and autumn was (1.91±2.53) μg·C/L, (5.78±4.45) μg·C/L and (3.11±2.40) μg·C/L respectively. Tintinnids accounted for (26.7±23.3)% of the total ciliate abundance, and the value was the highest in the summer (43.4%±25.1%) and the lowest in the autumn (12.3%±8.1%). Aloricate ciliates and tintinnids exhibited different distribution patterns. The abundance and biomass of aloricate ciliates were higher in the coastal and offshore areas, while tintinnids tended to accumulate in the coastal area. Twenty five tintinnid species were identified that belonged to 8 genera, 15 of which were in genus Tintinnopsis. The most dominant species were Tintinnopsis baltica, Tintinnopsis beroidea and Tintinnidium primitivum in the spring. The most dominant species were Tintinnopsis tocantinensis, Tintinnidium primitivum and Tintinnopsis amoyensis in the summer. The most dominant specie was Tintinnidium primitivum in the autumn. The lorica oral diameter of the tintinnid community was larger in the summer [(35.9±8.2) μm] and autumn [(34.8±5.2) μm] than in the spring [(31.5±2.5) μm]. The Shannon index and Pielou index of the tintinnid community were both higher in the summer than in the spring and autumn. Our study may provide basic data for the future research on both the planktonic ecosystem and the development of the fishery industry.

Abstract:With increasingly serious heavy metal pollution in the aquatic environment, the pollution status in fish has affected the food safety and attracted much attention. It is urgent to know the condition of heavy metal pollution in fish in the Yellow Sea and the Bohai Sea. It is also crucial to know different metal pollutions in one fish species and to identify the prominent type of heavy metal. Here we analyzed the status of heavy metal pollution in fish in the Yellow Sea and the Bohai Sea based on the literature and historical data, and compared the different situations to determine the prior pollution. We analyzed the exceeding standard rate, the detection rate and the limitation standard of heavy metals and found the priority order as Cr, As, Cd, Pb and Hg. The prior pollution in fish in the Yellow Sea and the Bohai Sea were determined using the comprehensive evaluation method with the bio concentration factors (BCF), the toxicity effect, the pollution index and the exceeding standard rate. The score of Cd was the highest, and the order of scores was Cd > Hg > As* > Cr > Pb. Different fish species had different prior heavy metal pollution. Cd was the prior heavy metal in Cynoglossus robustus and Scomberomorus niphonius, and As* was the prior one in Synechogobius hast. Then we conducted the validation experiment with samples including C. robustus, Mugil cephalus, Synechogobius hasta, S. niphonius and Larimichthys polyactis that were collected from eight coastal cities along the Yellow Sea and the Bohai Sea. The results of the validation experiments were consistent with those of the screening method, therefore the screening method should be reliable.

Abstract:Water samples at different depth were collected during 4 cruises nearby the Zhangzidao Island in October 2015 and January, April and July 2016. The spatial-temporal distribution of total particulate matter (TPM), particulate organic matter (POM) and organic content (defined as PCOM, %) in the surface and bottom layers were analyzed. With the results of the regression analysis of POM with Chlorophyll a (Chl-a) and other environmental factors, the potential interaction between the scallop culture and the suspended particulate matter was analyzed, and the major influencing factors of the latter were also discussed. The results were described as follows. Concentration ranges of TPM and POM nearby the Zhangzidao Island were (16.760~97.54) mg/L and (2.20~17.20) mg/L respectively, and their annual averages were (31.65±9.58) and (6.97±2.08) mg/L. The PCOM ranged from 8.69% to 37.09%, with an average of (22.25±4.18)%. The TPM concentration showed a seasonal trend as autumn> spring>summer>winter. The highest TPM concentration was found in the surface layer in autumn. However, the highest and lowest POM concentrations and the organic contents appeared in summer and winter respectively. The concentrations of POM and TPM had a similar pattern of horizontal distribution in most areas. Higher POM concentration was found in the central area compared to the surroundings in spring and summer, and the opposite pattern was found in autumn and winter. The concentrations of POM and TPM in the bottom water were significantly higher (P<0.01) than in the surface water in summer, but there was no difference in the other seasons (P>0.05). In all 4 seasons, there was significantly positive correlation (P<0.01) between POM and Chl-a nearby the Zhangzidao Island. In addition, there was also positive correlation (P<0.01) between POM and Chl-a in the bottom layer in spring and the surface layer in summer. A negative correlation was found between POM and salinity only in the surface water in summer, which indicated that the land sources might affect the concentration of POM in summer.

Abstract:Neon flying squid (Ommastrephes bartramii) is an important commercial fishing target for China in Northwest Pacific. Accurate prediction of fishing grounds can improve the squid production capacity. The present study selected historical catch and fishing effort data of Chinese squid-jigging fishery from 2005 to 2013 as suitability index (SI) sources. SI curves were created through nonlinear regression based on 4 environmental factors, including sea surface temperature (SST), chlorophyll-a concentration (Chl-a), SST gradient (Grad) and the temperature of 100 m water layer (T100) from Argo float dataset. On the premise of given constrained conditions, two habitat suitability index (HSI) models were constructed based on catch and fishing effort. Non-significant explanatory variables in the model were eliminated via the stepwise regressions. By comparing the goodness-of-fit of two models, catch-based model provided higher accuracy than fishing effort-based one. The adjusted correlation coefficients were 0.853 (P<0.001), 0.773 (P<0.001), 0.789 (P<0.001), 0.745 (P<0.001) and 0.724 (P<0.0001) from July to November, respectively. The weight coefficients of SI for environmental factors were in accord with the constraint and seasonally varied. In particular, the SI of T100 played the most important role in the HSI score in the main fishing season (July, August and October) while the SI of SST was the major factor to affect HSI in November. The forecast experiment of HSI model was carried out with environmental factors in 2014. Spatial position of forecasted fishing grounds were consistent with actual ones, and catch in high HSI (>0.7) regions accounted for 49.06% of the total catch, while catch in low HSI (<0.3) regions accounted for only 9.06% of the total catch. These findings indicate that the HSI model is able to predict neon flying squid fishing grounds in Northwest Pacific.

Abstract:X-box binding protein 1-S (Xbp1-S) is a key transcript factor mainly associated with B cell development and differentiation. The 1380 bp full-length cDNA of OnXbp1-S including 1155 bp ORF, 127 bp 5'UTR and 98 bp 3'UTR was cloned with RACE, which encodes 384 amino acids with a molecular weight of 41.32 kDa and a theoretical isoelectric point of 4.36. Homology analysis revealed that the OnXbp1-S gene was homologous to other fish with the most similarity with Notothenia coriiceps. OnXbp1-S expresses in all tested tissues, with the highest mRNA expression in liver, and the highest protein level in thymus and the lowest protein level in muscle. Streptococcus agalactiae stimulation induced the expression of OnXbp1-S with the highest level at 192 h post-infection. In addition, mature B cells have a much higher OnXbp1-S level than naive B cells. Taken together, the results indicated that OnXbp1-S might be involved in the immune response in Nile tilapia against S. agalactiae infection, and play a role in B cell development and differentiation.

Abstract:The deterioration of water quality from the intensive culture system and environmental pollution are common problems in the practical farming of Litopenaeus vannamei. The toxicity from deteriorating water, such as ammonia accumulation, has lethal effect on shrimp and can increase the susceptibility to pathogens, which might cause frequent high mortality in the period of early stage of L. vannamei cultured in the farms. The high heritability of acute ammonia stress in L. vannamei (0.575) indicated its ammonia tolerance could be improved largely by selection. However, the genetic gain of the disease resistance is very slow in shrimp because of the low heritability of disease resistance traits and low selection intensity by the limitation of pathogen infection test. To explore and improve the ability of disease resistance, we performed the WSSV infection test with ammonia-sensitive population (SP) and ammonia-tolerant population (TP) under ammonia stress (10 mg/L), named SPAV and TPAV, the normal ammonia level (<0.01 mg/L), named SPV and TPV, and no ammonia stress without WSSV infection as the control group (<0.01 mg/L), named SPC and TPC. The results showed that SP started to die at 5 h after WSSV infection, which was significantly earlier than that of TP (about 16 h). The mortality rate of SPAV increased rapidly after 60 h and reached 100% at 137 h, which was significantly higher than SPV (70.42%), TPAV (42.67%), and TPV (18.99%). The cumulative mortality rate of SPV was 73.67% at 144 h, which was significantly lower than SPAV, but significantly higher than TPAV (46.15%), TPV (18.99%) and SPC (34.79%). The cumulative mortality rate of TPAV at 144 h was significantly higher than TPV and TPC, but there was no significant difference between TPV and TPC. These results indicated that ammonia stress increases the susceptibility to pathogens, and that the population with high ammonia tolerance have high WSSV disease resistance, which will provide new ideas to improve the disease resistance and reduce mortality.

Abstract:Genetic parameters of breeding object traits are important to design breeding scheme and evaluate selection response before performing a selective breeding program. In this study, a total of 15000 individuals from 100 families of Litopenaeus vannamei at the juvenile stage were desalinated and reared at a low salinity of 5 to explore the survival rate and the heritability. The results showed that the range of the survival rate at the desalination stage and culture stage were 19.33%–100.00% and 11.9%–99.2%, and the average survival rate were 66.7% and 67.5%, respectively. The range of the overall survival rate at the juvenile stage was 6.67%–90.67% with the average survival rate 46.91%. There were significant differences on the survival rate between families at two stages (P<0.01). There was significant and moderate positive correlation on the survival rate of families between two stages (r=0.61, P<0.01). The heritabilities of survival for two stages were estimated by the model of the additive genetic effect (A) and the model combining A and the common environmental effect (C). Based on the A model, the heritability of survival for the desalination stage, culture stage and combination of two stages were 0.09, 0.10 and 0.14, respectively, which were significantly different from zero (z﹥2.58). Based on the A+C model, heritability of survival were 0.06, 0.05 and 0.07, respectively, which were not significantly different from zero (z<1.96). The genetic correlation on the survival rate of families between two stages for the A and A+C models were 0.41±0.09 and 0.48±0.09, respectively. The additive genetic effect was partially confounded with the common environmental effect because the proportion of half-sib families to full-sib families was only 47% when each family were cultured in a separate cage. Therefore, the heritability estimates based on the A model were overestimated, and the heritability estimates based on the A+C model was underestimated. The results implied that the adaptability of low salinity for Pacific white shrimp can be improved through a selective breeding program.

Abstract:A full-length cDNA sequence of F-ATPase β subunit gene from Portunus trituberculatus (ptF-ATPaseβ) was cloned by rapid amplification of cDNA ends (RACE). The sequence of ptF-ATPaseβ was 1965 bp, containing a 571 bp 5' UTR, 341 bp 3' UTR, and a 1053 bp open reading frame (ORF) that encodes 350 amino acids polypeptides. The isoelectric point (pI) was 4.86 and the molecular mass was 37.9 kDa. The amino acid sequence analysis demonstrated that ptF-ATPaseβ has an F1-ATPaseβ domain, an AAA domain, and an ATP-synt-ab-C domain. Homology and phylogenetic analysis revealed that the amino acid sequence of ptF-ATPaseβ shared a high similarity (89%) with Penaeus monodon and Litopenaeus vannamei. ptF-ATPaseβ mRNA level was detected in all tested tissues including the hepatopancreas, muscle, heart, gill, stomach, intestine, testis, and ovary. The ptF-ATPaseβ had the highest level in the hepatopancreas and heart, and the lowest expression in the intestine. With the increase of inbreeding coefficient, ptF-ATPaseβ expression decreased significantly in the hepatopancreas and heart (P<0.05). The ATP synthase activity in the heart began to fall from F6 generation and was significantly lower than F0 generation (P<0.05), but there was no significant change in the hepatopancreas. The results illustrate that inbreeding gradually reduces the expression of ptF-ATPaseβ and the ATP synthase activity in P. trituberculatus.

Abstract:Microsatellite has become an important molecular marker for genetic diversity analysis and marker-assisted breeding as its unique advantages, such as high stability and repeatability, strong specificity and codominance. To understand the distribution and frequency of microsatellite of P. yessoensis genome, the current study analyzed the microsatellite sequences of P. yessoensis genome by establishing and sequencing a RAD library. The sequences were assembled, and SSRs were detected by bioinformatics method. The total length of the DNA sequences of P. yessoensis genome is 92,551,435 bp and 3,618 contigs from all filtered 259,535 contigs containing SSR sequences. The 3460 potential SSR loci were identified with the number of repeat motif from 2 to 6 using appropriate amplifying primers. A total of 1587 trinucleotide SSRs (45.87%) were the most common motif, and ATA (11.41% of whole trinucleotide motifs) was the richest motif. The dinucleotide and the tetranucleotide types ranked the second and the third with a proportion of 37.05%(1282) and 14.48%(501), respectively, while the pentanucleotide type accounted for 2.02%(70), and the hexanucleotide type was the least amount with a proportion of 0.58%(20). Interestingly, the abundance of microsatellites of the same repeat type decreased with the increase of copy number, and the abundance of microsatellites of the same copy number decreased with the increase of the repeat unit length. The variation of length distribution frequency, copy numbers and the abundance of the microsatellite suggested that the mutation rate of shorter repeats was larger than that of the longer repeats. These results provide basic information of microsatellite of P. yessoensis, which would be useful to study the genome and population genetics of P. yessoensis.

Abstract:Pacific oyster (Crassostrea gigas) is an euryhaline and eurythermal shellfish with the advantages of rapid growth and hardiness. Its breeding scale and production is the largest in the aquaculture, which has contributed to the economic growth and the improvement of the people's living standard in China. The annual output of aquaculture in China is 4.57 million tons in 2015, and the market demand for high quality oysters is ascending. Therefore, it is of great significance to improve nutritional quality and create new strain of oyster. In order to discover different physiological metabolisms between selfing lines and reciprocal crosses of C. gigas with various glycogen content, the filtration rate, oxygen consumption rate and ammonia excretion rate were studied under certain temperature (20℃) and salinity (32). In terms of the filtering rate, the highest one and the lowest one were selfing group AA and selfing group BB, respectively, which were significantly different (P<0.05). There was no significant difference between reciprocal group AB and reciprocal group BA. The heterosis value of the reciprocal cross was 8.44%. In the oxygen consumption rate, the highest one and lowest one were selfing group BB and reciprocal group AB, respectively. There was significant difference between AA and BB (P<0.05). The heterosis value of the reciprocal cross was –43.87%. The oxygen consumption rate was negatively correlated with the glycogen content with the correlation coefficient –0.884 that was significantly different (P<0.01). There was no significant difference for the ammonia excretion rate with 0.04 mg NH3-N/(g·h) among all groups. In summary, the major differences among groups were water filtration rate and oxygen consumption rate. This study could provide important physiological metabolic germplasm reference for the breeding of high glycogen content line of C. gigas.

Abstract:Integrins are heterodimeric cell surface receptors that consist of α and β subunits to regulate cell adhesion, migration, proliferation, apoptosis and phagocytosis. The present study identified the β-integrin gene from Solen grandis (SgβInt) and analyzed the characterization of its encoded protein. The phylogenetic tree was constructed by the neighbor-joining method and the three-dimensional structure was predicted with SWISS-MODEL. The full-length cDNA of SgβInt was 1168 bp, containing a 61 bp 5´UTR, 18 bp 3´UTR and an open reading frame (ORF) of 1089 bp that encodes a polypeptide of 362 amino acids with an estimated molecular mass of 30.0 kDa. The encoded protein of SgβInt shared significant similarities with that in Capra hircus and Mus musculus. The phylogenetic tree indicated that SgβInt had a close genetic relationship with Crassostrea gigas to form a mollusk branch. The three-dimensional structure of SgβInt consisted of one α-helice and nine β-sheets as a member of integrin superfamily. SgβInt expressed in all tested tissues, including mantle, gill, hemocyte, gonad, muscle and hepatopancreas, with the highest expression in gill which was 487.5 times higher than gonad. SgβInt was induced by all the three pathogen associated molecular patterns (PAMPs) including LPS, PGN and glucan with the peak level at 3 and 48 h post LPS and glucan stimulation, respectively. SgβInt expression reached the maximal level at 6 h post PGN stimulation with 53.5-fold induction. All the results revealed that SgβInt might regulate the immune response of S. grandis to microorganism. This study shed new light on the research of β-integrin in mollusk and immune defense mechanism of S. grandis.

Abstract:The current study cloned the full-length cDNA of C-type lectin (Sb-Lec1) using RACE (Rapid amplification of cDNA ends) method from Scapharca broughtonii with 700 bp that includes a 5′ UTR of 29 bp and 3′ UTR of 167 bp. The 504 bp open reading frame (ORF) encodes a polypeptide of 167 amino acids, including a signal peptide of 23 amino acids, one carbohydrate-recognition domain (CRD) motif of 129 amino acids and 6 cysteines involved in the formation of disulfide bond. The predicted protein molecular weight is 19.11 kDa, with a theory isoelectric point of 4.74. Multiple sequences alignment and phylogeny analysis showed that the identity of Sb-Lec1 gene shared with Crassostrea gigas, Mytilus galloprovincialis, and Argopecten irradians was 38%~40%, 34%~35%, and 38%~39%, respectively. The amino acids of CRD motif had many similarities with other species such as 4 conserved Cys. Phylogenetic analysis revealed two main branches including all C-type lectin of molluscs and the C-type lectin of vertebrate, and that the deduced polypeptide of Sb-Lec1 had the characteristics of the C-type lectin family. Quantitative real-time PCR (qRT-PCR) was used to assess the mRNA expression in all tested tissues, including hemocytes, foot, adductor muscle, mantle, gill, and hepatopancreas. The highest and lowest Sb-Lec1 mRNA were in hepatopancreas and adductor muscle, respectively. Vibrio anguillarum challange induced Sb-Lec1 mRNA expression in all tested tissues (P<0.05). These results showed that Sb-Lec1 gene may play an important role in immune defense.

Abstract:Vibrio anguillarum, an etiological agent of fish septicemia, has caused great economic losses in many marine and fresh water fish. Vaccination is an effective and safe approach to control fish septicemia. The pathogenicity V. anguillarum serotype O3 in cultured marine fish of China promotes us to evaluate the immunogenicity and protective efficacy of three V. anguillarum serotype O3 inactivated vaccine. Three V. anguillarum serotype O3 strains (SMP1, SMP3, and SMP4) were rejuvenated in flounder Paralichthys olivaceus and then were determined for lethal dose 50% (LD50) in Trichogaster trichopterus which had been acclimated to 10 salinity. The result showed that LD50 of SMP1, SMP3 and SMP4 were 105.1 CFU/ml, 104.7 CFU/ml and 105.4 CFU/ml, respectively. Three inactivated vaccine were obtained by incubation of V. anguillarum with 0.2% formaldehyde for 36 h at 28℃. Each vaccine was used to vaccinate flounder P. olivaceus via intraperitoneal injection with a dosage of 108 CFU/ml. Specific serum antibody titers against V. anguillarum cells were detected evidently (P<0.05) at 7 d post vaccination, and the highest titers of 1:1280(SMP1), 1:640 (SMP3) and 1:905 (SMP4) were detected at 4 weeks post vaccination (P<0.05). Meanwhile, the relative percent survival rates (RPS) were 94.4% (SMP1), 100% (SMP3) and 73.7% (SMP4). These results indicated that V. anguillarum serotype O3 inactivated vaccines were able to induce immune response in fish and provide effective protection against V. anguillarum infection, and SMP3 is the best candidate for vaccine development and application.

Abstract:Excessive sulfur dioxide (as residual SO2) residue is currently one of the main factors affecting the quality and safety of shrimp and its products. In the study, the effects of processing methods such as boiling, steaming, microwave oven baking, frying and air drying on SO2 residue in sea shrimp were studied. The findings were described as follows. Using appropriate cooking methods, such as boiling, steaming, microwave oven baking and frying could remove SO2 residue to certain extents. Different kinds of cooking mode had different eliminating effects on SO2 residue in shrimp, and the order of eliminating effect was that boiling > steaming > microwave oven baking > frying. The SO2 residue in shrimp meat increased first and then decreased in the process of air drying, with the higher temperature, there was better eliminating effect. Under the conditions of air drying at 20℃, 40℃, 60℃ and 80℃, the residual rate of SO2 in dried peeled meat were 132.00%, 146.70%, 78.25% and 48.90% respectively, when the moisture content was in accordance with the standard of dried peeled shrimp. The air drying methods at normal temperature in most dried peeled shrimp production went against the elimination of SO2. Shell peeling treatment could effectively reduce SO2 residue in shrimp during the production of dried peeled shrimp and roasted shrimp. The results will provide scientific basis for the control of SO2 residue in the shrimp, and help the consumers and producers of shrimp industry reduce the risk of SO2 residue by proper processing methods.