Abstract:Based on the continuous research on artificial propagation of Japanese eel Anguilla japonica, the effects of different initial diets on the survival of eel larvae were investigated, and the motion characteristics and feeding behavior of larvae were observed and recorded. The results showed that the shark eggs, krill extract-based diet and shark eggs, jellyfish-based diet and exclusively microalgae had positive effects on larval survival; However, the shark eggs, artemia-based diet and artemia, krill extract-based diet, rotifers and kelp, seaweed homogenate, jellyfish and fermented shark flesh reduced larval survival. The larvae touched the diets repetitiously, and then opened the lower jaw widely and bit, which confirmed that the way for eel larvae to ingest diets was biting after touching.

Abstract:To control seafood quality and regulate oyster aquaculture in Qinzhou Harbor, Beibu Gulf, the oysters (Crassostrea rivularis) were collected from three stations in the region in 2015, and analyzed by atomic fluorescence spectrophotometer and atomic absorption spectrometer. Overall, the content of heavy metals in Crassostrea rivularis exhibited Zn>Cu>Cd>Cr>As>Pb>Hg, and contents of Zn and Cu had the average of 532.03 and 126.96 mg/kg, respectively. Referring to aquatic products standard of NY 5073-2006, we found, with the exception of Crassostrea rivularis collected at the 2nd station of July, the level of Cu from 89% samples exceeded the limit. While referring to aquatic products standard of GB 2762-2012, only the level of samples from the 3rd station of July went beyond the limit. Contents of Pb and Hg were low, with an average of 0.02 and 0.009 mg/kg, respectively. The dietary intakes of heavy metals in Qinzhou Harbor's Crassostrea rivularis were lower than the recommended values of Joint FAO Expert Committee on Food Additives (JECFA), thus the oysters in this region are safe for edibility.

Abstract:In this paper, a crossing-experiment of intraspecific hybridization in Pyropia yezoensis was done for breeding improved strains. The male parent was the red mutation strain (TM-18), which was characterized by red blade, fast growing, high contents of photosynthetic pigments and with resistance to high temperature, and the female parent was the green mutation strain (OMO-1), which was characterized by green blade, slow growing, low contents of photosynthetic pigments and poor resistance to high temperature. An improved strain (TW-9) was finally selected from the recombinant F₁ blades. TW-9 strain showed some different characters from the parental strains. The result showed that at normal temperature (18 ℃) and high temperature (24 and 25 ℃) for 13 days of post-culture, the survival rates of conchospores in TW-9 strain were 1.0, 1.1, and 1.1 times those of TM-18 strain, and were 1.1, 4.7, and 7.2 times those of OMO-1 strain, respectively. At 18 ℃, the abnormal rates of conchospore germlings had no significant difference between different strains, but at 24 and 25 ℃, as compared with TM-18 and OMO-1 strains, the abnormal rates of conchospore germlings in TW-9 strain reduced by 20.3% and 29.5%, and by 78.4% and 69.5%, respectively. When the conchospore germlings (40-day-old, at 18 ℃) were cultured at 18, 24 and 25 ℃ for another 10 days, the absolute growth rates of TW-9 strain were 0.9, 1.5 and 0.8 times those of TM-18 strain, and were 1.4, 1.5 and 28 times those of OMO-1 strain, respectively. In addition, after being cultured at 24 ℃ for 25 days or at 25 ℃ for 10 days, OMO-1 strain blades decayed badly to complete disintegration. However, the blades of TM-18 and TW-9 strains were curl slightly when being cultured at 24 ℃ for 25 days, and TM-18 blades were decay badly to complete disintegration at 25 ℃ for 15 days, while TW-9 blades were only decay slightly at 25 ℃ for 30 days. After being cultured at 18 and 24 ℃ for another 15 days, the phycobiliprotein contents of TW-9 strain were 61.5 and 77.8 mg/g which was almost the same to the TM-18 strain, and were 1.4 and 1.4 times those of OMO-1 strain, respectively. After being cultured at 18 ℃ for 55 days, the blades thickness of TW-9 strain was 25.6 μm, which was reduced by 13.5% and 17.7% compared with those of TM-18 and OMO-1 strains, respectively. Besides, there was no significant difference in quantity of conchospores released between the three strains. These results indicated that TW-9 strain has similar characteristics to TM-18 strain, such as fast growing, high contents of photosynthetic pigments and great quantity of conchospores released, as well as thinner blade and better high-temperature resistance, and its color is close to the wild-type, which could meet the demands for productive cultivation. Therefore, TW-9 strain is expected to become a superior new strain of P. yezoensis.

Abstract:This experiment was conducted to evaluate the effects of intraperitoneal glucose injection on serum indices, hepatic glycolysis and gluconeogenic key enzyme expression levels of intraperitoneal glucose injection of large yellow croaker (Larimichthys crocea). Fish [n=270, mean weight=(100±5) g] were randomly assigned to three groups, a control group that was injected with sterile 0.9% normal saline, the low dosage group that was injected with glucose (300 mg/kg wet weight, LG) and the high dosage group with glucose (1500 mg/kg wet weight, HG). The results showed that ①the plasma glucose level reached a peak at 3 h after both dose glucose injections, and returned to base level at the time of 24 h after injection of low dosage glucose, and it was still higher than base level after 24 h after high dosage glucose relatively. ②The trend of relative expression of HK gene after both dose glucose injections was increased first, then decreased, and reached the peak at 9 h. The relative expression of GK gene trend was to rise first and then remained unchanged and finally fell after both dose glucose injections, and it reached the peak at 9 h, but it was decreased at 4 h after high dosage glucose. The relative expression of PFK gene presented the trend of first increasing and then decreasing, and it reached the highest at 9 h after high dosage glucose. ③The trend of relative expression of PEPCK gene decreased first and then increased, and it reached the minimum at 2 h after high dosage glucose. ④It was significantly higher at 6 h than at any other time point, after high dosage glucose. These results indicate that the plasma glucose level of large yellow croaker increased, and maintained for a long time. The absence of inhibition in the expression of the gluconeogenic enzyme of G6Pase, FBPase concurrent with increased postprandia expression of GK led to postprandial hyperglycaemia in large yellow croaker.

Abstract:To study the effects of soybean antigenic proteins on growth, physiology and biochemistry in obscure puffer (Takifugu fasciatus), the fish with initial weight (39.84±3.09) g were randomly allocated to 8 groups, fed with 8 isonitrogenous and isoenergetic diets which were the practical diets containing high level fish meal (FMH), low level fish meal (FML), fermented soybean meal partially replacing fish meal in FML(FMLF), soybean meal partially replacing fish meal in FML (FMLS) and the semi-purified diets with different levels (0%, 5%, 8% and 12.5%) of soybean antigenic proteins respectively (AP0, AP5, AP8 and AP12.5) for two months. The results showed that the growth performance of FMLF were significantly higher than that of FML, while that in FMLS was not significantly different with FML. The growth of purified diets was increased, followed by decreasing tendency with the level of soybean antigenic protein. The nutritional composition of the muscle was affected by practical feed and semi-purified feed with varying degrees The malondialdehyde (MDA) and total antioxidant capacity (T-AOC) in liver and MDA in serum of soybean meal replacing group were significantly higher than those of FML, but the fermented soybean meal replacing group had no significant difference with the FML. The soybean antigenic proteins level of 8% of purified diets had the peak value in antioxidant capacity that were significantly higher than all the other groups. The glutamic oxaloacetic transaminase (AST) of FMLS in serum was significantly higher than the FML and AST of the FMLF had no significant difference with the FML, while the AST and glutamic-pyruvic transaminase (ALT) of purified diets were fluctuated with the level of soybean antigenic protein. Above results indicated that fish meal partially substituted by fermented soybean meal could promote the growth of obscure puffer compared to soybean meal partially replacing fish meal. Soybean antigenic protein was an important factor affecting the effects of fish meal replacement with soybean meal. The influence of soybean antigenic protein on growth, oxidation resistance and biochemical indexes varied with its content, existence state, alone or in combination with other anti-nutritional factors in diet.

Abstract:As a key enzyme in the antioxidant systems of living organisms, catalase plays an important role in eliminating hydrogen peroxide against oxidative stress. The open reading frame (ORF) of catalase (GenBank Accession No. KKF14425.1) was cloned from large yellow croaker (Larimichthys crocea), which comprised 1584 bp, encoding a peptide of 527 amino acids (aa) in length, with a predicted molecular mass of 59.98 kDa and a theoretical isoelectric point of 8.37. Several highly conserved motifs, including the proximal active site signature "FDRERIPERVVHAKGA", the proximal heme-ligand signature sequence "RLFSYPDTH", the three catalytic amino acid residues of His⁷⁵, Asn¹⁴⁸ and Tyr³⁵⁸ and NADPH binding site were identified in the deduced amino acid sequence of CAT from large yellow croaker. Sequence comparison strongly suggested that this sequence was a member of CAT family and highly homologous with other known CAT of fish, especialy with Rachycentron canadum and Oplegnathus fasciatus (94%) of Sciaenidae, and they also gathered into the same branch in the phylogenetic tree. Constitutive CAT mRNA expression was detected in seven tissues of large yellow croaker with different magnitudes, which was high in liver and low in muscle, suggesting its diverse role in physiology with respect to the tissue type. The mRNA of HSP70 in liver after infection by Vibrio anguillarum was detected based on RT-PCR analysis. The transcriptions of CAT were upregulated, the maximum level appeared at 12 h post-injection with 7.48-fold and dropped back to the original level at 72 h post-injection, which showed a slight rise in the group of PBS injection. The results indicated that CAT in L. crocea can function as a potent antioxidant enzyme in large yellow croaker and may play a role in postimmune responses with respect to its peroxidase activity.

Abstract:A 3×3 factorial experiment was designed to determine the interactive effects of dietary protein and starch levels on growth performance of grouper (Epinephelus coioides). Nine diets were formulated to contain three levels of crude protein (P) (38%, 45% and 52%) and three levels of starch (S) (10%, 20% and 30%). Fish were fed the diets twice daily over a 56-day study period. Fish fed 38% crude protein and 10% starch diet (38P/10S diet) had significantly lower weight gain rate than those fed other diets, and fish receiving 52P/10S diet achieved highest weight gain rate among the test diets, but comparable to fish receiving diets 45P/20S, 45P/30S and 52P/20S. Increasing dietary crude protein and starch levels led to increased feed efficiency, whole-body protein and lipid liver glycogen content and liver lipid contents, and reduced daily feeding rate and whole-body moisture content. Increasing dietary protein level decreased protein efficiency ratio, but increasing dietary starch level increased hepatosomatic index, protein efficiency ratio and viscerasomatic index. Dietary protein and starch levels did not affect whole-body ash content. Hepatic lipase, lipoprotein lipase, fatty acid synthetase, glutamic-oxalacetic and glutamic-pyruvic transaminase activities increased with the increase in dietary protein or starch level. Increasing dietary protein level resulted in lowered liver glucose-6-phosphatase activity, and elevated liver malic enzyme activity, but did not affect liver activities of glucokinase, pyruvate kinase, phosphofructokinase, phosphoenolpyruvate carboxykinase and glucose-6-phosphate dehydrogenase. Increasing dietary starch level led to increased liver activities of glucokinase, pyruvate kinase, phosphofructokinase, glucose-6-phosphate dehydrogenase and malic enzyme, but reduced activities of phosphoenolpyruvate carboxylase kinase and glucose-6-phosphatase. These results indicate that the growth and liver metabolism of grouper were affected by both dietary protein and starch levels, in which the enzyme activity related to glucose metabolism responds to dietary starch level more sensitively than dietary protein level. The diet containing 45% protein and 20% starch is suitable for the optimal growth of this fish species.

Abstract:Peritrophin was one type of proteins which was the important structural component of peritrophic membrane (PM) lining the midgut in invertebrate. It was first separated from insect, and played an important role in protecting insects from invasion by microorganisms. Recently, many peritrophin-like genes were identified from tissues not only intestine in crustacean, which implied that the role of peritrophin-like proteins might be diverse. In this study, two cDNA sequences encoding peritrophin-like protein named as LvPT1 and LvPT2 were found and cloned from Litopenaeus vannamei. Their deduced amino acid sequences exhibited high similarity to each other and most other shrimp peritrophins which have been reported. Tissue expression analysis by Real-time PCR revealed that LvPT1 and LvPT2 were mainly expressed in shrimp ovary, similar with shrimp ovarian peritrophins (SOPs). Semi-quantitative RT-PCR was used for analyzing the expression of LvPT2 during the early development of L. vannamei. The results showed that LvPT2 expression was the highest in fertilized eggs, and decreased significantly in developing process. There was no obvious expression of LvPT2 in nauplius hatched out from the hatching membrane. Therefore, we presumed that LvPT1 and LvPT2 might be the same kind of peritrophin to play the similar role with other shrimp SOPs, in participating in the formation and protection of fertilized egg, and protecting shrimp embryo against pathogen infection.

Abstract:To evaluate the effects of dietary α-linolenic acid (LNA, 18:3n-3)/ linoleic acid (LA, 18:2n-6) ratios on growth performance and LC-PUFA biosynthesis in common carp, we designed five iso-nitrogenous and iso-energetic diets for eight weeks of feeding trial. The control diet (D1) was only supplemented with fish oil as lipid source, while the mix of peanut oil and perilla oil with varying LNA/LA ratios of 0.02, 0.46, 1.09 and 1.53 was used as lipid source for the experimental groups [D2, D3, D4 and D5, VO (vegetable oil) diets], respectively. The results showed that, there were no differences among control group and VO groups in WGR, SGR and FCR. Compared with the control group, the hepatic LC-PUFA levels were significantly low in VO groups, whereas, the hepatic Δ6 fad-a and elovl5-a mRNA expression levels were significantly improved by VO diets. Among the four VO groups, the WGR and SGR were significantly affected by dietary LNA/LA ratios, with higher growth in D4 and D2 groups. Additionally, the hepatic LC-PUFA levels, Δ6 fad-a and elovl5-a mRNA expression levels were higher in the fish fed higher ALA/LA ratios diets. In particular, the highest hepatic LC-PUFA levels were observed in D4 groups, and consistent with this, hepatic Δ6 fad-a and elovl5-a mRNA with the highest level were also showed in D4 groups. The results indicate that VO diets have a negative effect on the hepatic LC-PUFA levels in common carp. However, the optimal balance LNA/LA supplement (1.09∶1) have been successful in raising the efficiency of LC-PUFA production by improving the hepatic Δ6 fad-a and elovl5-a mRNA expression, and decreasing the negative impact of VO diets on tissue LC-PUFA concentration in this fish species.

Abstract:In this study, we used rapid amplification cDNA ends (RACE) methods to obtain the full-length cDNA of Myostatin gene in Onchidium struma. The bioinformatic analysis and expression pattern of MSTN mRNA in different tissues detected by Real-time fluorescent quantitative PCR (qRT-PCR) were performed. The full length of MSTN cDNA sequence consists of 2667 base pairs (bp), comprising a 374 bp 5′ untranslated region (UTR), a 643 bp 3′UTR, and a1650 bp open reading frame (ORF) which encodes 549 amino acids. The MSTN protein was predicted to contain 8776 atoms and its formula is C₂₇₇₄H₄₃₃₁N₇₈₃O₈₆₂S₂₆, with a calculated relative molecular weight of 63.27 kD and pI of 6.02. The result of signal peptide prediction shows that the N-terminal has a signal peptide of 21 amino acids length. The common features were found in MSTN of O. struma, including a conservative hydrolytic site (RSRR) and 9 cysteine residues. The phylogeny analysis shows that the relationship between O. struma and Aplysia californica was the closest. According to RT-PCR results, MSTN gene was expressed in various tissues with the highest expression in the hepatopancreas and lowest in foot; expression in muscle is lower than that in internal organs, and expression in muscle of abdominal skin is higher than other parts. Our results suggest that MSTN gene may play an important role in muscle growth and development in O. struma, and may provide useful information for further studies on evolution of marine invertebrates from sea to wetland.

Abstract:In order to research the effect of Bacillus cereus on the growth rate and intestinal microflora of Litopenaeus vannamei, Bacillus cereus (number PC465) was added to basic feed with concentration of viable bacteria of 10⁸ CFU/g. Shrimps living in 8 pools with the similar light and position were divided into two groups, and the experimental group was fed the immune feed everyday while the blank control group were fed basic feed. Shrimps were fed with a complete breeding cycle (95days) in the farm. Sampled at Day 45, 52, 59, 66, 73, the method of high throughput sequencing of 16S rDNA gene's V4 region was used to determine diversity and composition of bacterial communities in each of these samples. Experiment showed: (1) The growth rate of the experimental group was average 15.2% higher than the blank control group. (2) The intestinal microflora of L.vannamei contained high proportion of Proteobacteria and Bacteroidetes, while Firmicutes, Verrucomicrobia, Planctomycetes, Actinobacteria were at lower rate. (3) In intestinal microflora of the blank control group' shrimps, the average proportion of Proteobacteria (68.30%) was higher than the experimental group (57.94%), while Bacteroidetes was lower than the control group. Proteobacteria was mainly composed of Vibrio, Anaerospora and Rhodovulum. The blank control group' average proportion of Vibrio was 5.40%, while the experimental group was 1.94%. Bacteroidete was mainly of Lutimonas and Tenacibaculum. The blank control group' average proportion of Lutimonas was 5.56%, while the experimental group was 8.12%. The results of the study suggest that dietary with Bacillus cereus can change the intestinal microflora of L. vannamei and enhance its growth.

Abstract:Biomineralization is the process by which mineral crystals are deposited in an organized fashion in the matrix (either cellular or extracellular) of living organisms and the deposition of precise arrays of inorganic crystals in many organisms involves controlled nucleation at interfaces between the crystals and substrate macromolecules. Mollusc shells are used as a model for studying "organic-matrix-mediated" biomineralization, in which crystals are nucleated and grow in a pre-formed structural framework composed of proteins and polysaccharides. Acidic matrix macromolecules glycosaminoglycans were also associated with biological crystal growth and keratan sulfate widespread in animal tissues had a potential role in the process of biomineralization. Sulfotransferase plays a vital role in catalyzing the transfer of sulfonic acid groups in the processes of glycosaminoglycan synthesis, and glycosaminoglycans keratan sulfate with copious amounts of negatively charged sulfonic acid groups participate in the nucleation process of biomineralization. In this study, we cloned the sulfotransferase gene PmCHST1a (Pinctada martensii carbohydrate sulfotransferase 1a) which participated in the synthesis of keratan sulfate and explored the function of sulfotransferase and keratan sulfate in the biomineralization. The full length sequence of PmCHST1a gene was obtained using the RACE technology, and we detected its expression pattern by real-time PCR. RNAi technique was used to study the potential functions of PmCHST1a in nacre formation, and we detected the effects to the synthesis of glycosaminoglycans keratan sulfate at the same time. The results showed that PmCHST1a, whose full length was 1 385 bp, encoded a protein of 366 amino acids. PmCHST1a carried with a typical Sulfotransferase-3 domain (Sulfotransfer-3 domain), a signal peptide and a transmembrane domain which made the protein located in the Golgi apparatus. The results of real-time PCR showed that PmCHST1a was highly expressed in the central zone of mantle. After the RNA interference experiments, the expression of PmCHST1a significantly decreased in the central zone of P. martensii, in union with the significant reduction of the concentration of glycosaminoglycans keratan sulfate in the extrapallial fluid. And the shell nacre crystallized irregularly compared with two control groups. These results showed that PmCHST1a may affect the formation of nacre through affecting the concentration of glycosaminoglycans keratan sulfate in the extrapallial fluid. This study provided the fundamental basis for further research of sulfotransferase and glycosaminoglycans in the formation of nacre.

Abstract:With the rapid development of aquaculture in recent years, the incidence of aquatic animal diseases, especially fatty liver disease, and its prevalence tended to increase and gradually became a stumbling block of aquaculture industry. Due to lack of effective model to study the pathogenesis, we intend to establish a fatty liver model of zebrafish induced by high-fat diet. In this study, normal diet and 16% high fat diet were fed to 1-month-old zebrafish, respectively. After 14, 30 and 90 days feeding, liver was taken as sample to conduct HE staining, transmission electron microscopy (SEM) and masson staining, and qRT-PCR was used to detect liver tissue genes expression level related to lipogenesis and lipolysis such as DGAT, PPARγ, FAS, SREBP1, CIDE, HSL, ATGL, and through Methanol-chloroform extraction we also detected the liver tissue contents of triglyceride. The result has shown, on the 30 th day, hepatic steatosis has occurred, the lipogenesis genes expression and the contents of triglyceride were significantly increased in high fat diet group. On the 90 th day, high fat diet group of zebrafish liver transmission electron microscopy (sem) and masson staining tissue biopsy showed zebrafish liver fibrosis and liver damage, and liver lipid synthesis genes and triglycerides contents decreased significantly. In conclusion, our high fat diet is able to induce hepatic injury, after 30 d feeding, zebrafish got hepatic steatosis and after 90 d feeding, liver fibrosis happened. Its fat synthetic gene expression level and contents of triglyceride in liver rose first and then fell, which has proven that the fat accumulation induced hepatic injury. The construction of the model remedied the defects of previously-built zebrafish high-fat model and this model will provide a support to study the mechanism of fish nutritional fatty liver disease.

Abstract:The abnormity of flatfish is very common in seeding breeding in aquaculture, and the morphological characteristics and distribution of chromatophores, as well as skin color changes during early life history(0-72 d)of Verasper variegatus were continuously observed and photographed, in order to offer reference for research and practice later. Results showed that the whole period of early development of spotted halibut lasted about 50 days in spawning water at 12-19.5 ℃, and there was a rapid growing period after 20 days old.The larval melanophores occurred first and had the most contents, then xanthophores occurred, and iridophoress occurred finally. The larval cytochrome of fry body were distributed symmetrically before metamorphosis, with an increase of the melanophores density firstly and a decrease of the density followed, and the maximal density of melanophores were 1390 cells/mm²at 9 days old. When metamorphosis occurred, the cytochrome and skin color of fry became asymmetrical. On ocular side, larval melanophores of fry body disappeared and were replaced by adult ones, and skin color was saturated and black, and the density of melanophores was stable, about 150 cells/mm². However, on blind side, larval melanophores disappeared and no adult ones appeared, and skin color was white. In our study, albinism often occurred at metamorphosis (35 days old), and adult melanophores of ocular side were blocked, and could not pass the metamorphosis period, and became albino.

Abstract:In order to characterize the bacterial community structure and diversity in rearing water of healthy Litopenaeus vannamei larvae during hatchery period, the genomic DNA of aquatic microbiota from larval stages of nauplius 5 (N5), zoea 2 (Z2), mysis 1 (M1) and postlarvae 1 (P1) was amplified with 16S rDNA V4 primers and sequenced by a high-throughput Illumina MiSeq platform. The results showed that the bacterial Shannon diversity index increased at P1 stage after declining gradually from stages N5 to M1, the Pielou evenness index at N5 stage was a little higher than those of the following three stages, which were approximated closely. During the entire larviculture period, the phylum Proteobacteria was overwhelmingly dominated in rearing water with high abundance up to 50.0%-88.0%, especially, the family Rhodobacteraceae of which had high abundances of 24.2%, 61.6%, 43.3%, and 51.8% at stages N5, Z2, M1, and P1, respectively. Bacteroidetes thrived in various stages with abundance higher than 9.7%, and the family Saprospiraceae of this phylum existed significantly (5.3%-16.9%) in the latter three phases. Actinobacteria presented also dominantly in rearing water except for the N5 stage, and the family Microbacteriaceae with abundances of 5.6%, 37.6% and 10.8% for Z2, M1, and P1 stages, respectively. The phylum Verrucomicrobia dominated only at P1 stage (5.3%). In the larviculture water, the core microbiota at genus level consisted of Loktanella, Marivita, Donghicola, Sulfitobacter, and two unclassified candidates. Thus the microbiota in larval rearing water harbored a high diversity and presented dynamic succession, which differed obviously between N5 stage and the latter three stages. Overall, the main environmental factors in larviculture water varied slightly and exhibited no significant effect on abundance of dominant OTUs (operational taxonomic units). In conclusion, the bacterial community in rearing water of healthy L. vannamei larvae shifts in composition and abundance with larval development and diet feeding. And the core microbiota with potential functions play an important role in maintaining homeostasis in the larviculture system, which could serve as candidates for autochthonous probiotics, as well as healthy indicator for shrimp larviculture.

Abstract:With the development of intensive aquaculture and deterioration of aquacultural environment, it is necessary to select new strains of high resistance to adverse environmental elements and diseases. Salinity is an important abiotic factor in aquaculture, affecting physiological activities in aquatic organisms. In order to select new Penaeus monodon families of low salinity resistance, salinity 0, 0.5 and 1 were used to evaluate the low-salinity-resistant ability of 11 P. monodon families. The results of acute stress experiment showed that the salinity 1 didn't have a serious impact on the survival of P. monodon. All the 11 families were able to adapt to the salinity 1, so 1 salinity stress experiment cannot be used as reference standard of assessment of low salinity tolerance. Salinity 0 and salinity 0.5 had a strong influence on the survival of P. monodon, and all the families eventually died out completely and the survival of different families at the median lethal time were significant different from each other. And results of salinity 0 stress experiment and salinity 0.5 stress experiment had a certain consistency, so salinity 0 and salinity 0.5 can be used as a reference standard to evaluate the low salinity tolerance of P. monodon. According to results of salinity stress experiments, the low-salinity-resistant ability of family J(♀61619×♂61548), family I(♀61173×♂61615), family H(♀61116×♂61625) and family K(♀61689×♂61504) was much stronger than other families, and the low-salinity-resistant ability of family G(♀61685×♂61569), family C(♀61109×♂61537), and family A(♀61119×♂61583) was the weakest. And compared with Thailand strain and Indonesian strain of P. monodon, the African strain has a stronger resistance to low salinity. This study provides four candidate families for low salinity tolerant families selection of P. monodon and has the potential to be the theoretical basis for breeding of P. monodon.

Abstract:In order to study the structure of mussels' foot and the characteristics of byssal thread formation (byssus secretion mechanism), the byssal secretion rate of of three mussels (Mytilus edulis, Septifer virgatus and Modiolus modiolus) were compared under different salinity (20, 22, 24, 26, 28 and 30).The histological structure and byssal secretion process of three mussels were discribed. In this study, the relationship between histological structure and byssal thread formation mechanism of three mussels were discussed.The results are as follows. ① three mussels began to secrete new byssal thread in 2 h after cutting off the old byssuses, three kinds of mussels showed significant differences in the ability of byssal thread formation within 24 h. The number of byssus was at the average of (28.45±6.14) for M. modiolus, and M. edulis and S. virgatus were (15.43±2.9) and (6.87±1.67), respectively; ② salinity caused apparent influences on byssal secretion of three mussels; M. edulis could secrete byssal thread under salinity from 20 to 30 and the byssal number was the highest in 22; S. virgatus stopped secreting byssal thread when salinity is higher than 28; ③ The histologic sections presented that there were microvillus covering the mussels foot and groove in the segmental venter which covered with fine cilia; the internal was composed of the glands, muscles and cavities. The glands were mucous glands, collagen glands, phenol glands, enzyme glands. The differences of the muscle distribution and the size of cavity of three mussel foot resulted in the density distinction of foot. Studies suggested that M. modiolus showed stronger ability of environmental adaptation than S. virgatus and M. edulis because of faster secretion of byssuses.

Abstract:As the coldest water spawning species among the loliginids, Patagonian longfin squid (Doryteuthis gahi) plays an important ecological role in the Southwestern Atlantic Ocean ecosystem. However, the information on reproductive biology of this species is very limited. So the reproductive characteristics of D. gahi in the southwest Atlantic Ocean, including the sexual structures, gonad development and reproductive investment were studied based on the biological measurement and statistical analysis. The results indicated that the overall sex ratio of females to males was about 1.79∶1 and the ratio was not significantly away from the hypothesis of 1∶1. The size-frequency was unimodal for both sexes in dorsal mantle length and body mass, and no significant difference of growth between females and males was determined according to the length-weight relationship analysis. In females, the gonadosomatic index (GSI) ranged from 0.11 to 6.44, and the nidamental gland index (NGI) ranged from 10.74 to 36.51. There was significant correspondence between these two indices. In males, the GSI ranged from 0.29 to 5.75, and the spermatohporic complex index (SCI) ranged from 0.06 to 1.21. However, there was no statistical correlation between these two indices. The condition (defined as the residuals from the body weight-dorsal mantle length relationships) of females decreased with maturity, while the reproductive investment (defined as the residuals from the reproductive system weight-dorsal mantle length relationships) increased with sexual maturation onwards. In contrast to females, the condition of males increased with maturity, while the reproductive investment decreased during the course of sexual maturation. Though a slightly negative relationship was found between the condition and reproductive investment for both sexes, the condition was not significantly correlated with the reproductive investment. These findings implied that sourcing energy for reproduction in D. gahi might be mainly on exogenous, and the reproductive strategy was more inclined to the intermittent spawning strategy.