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Schizochytrium mangrovei PQ6 contains many important polyunsaturated fatty acids, such as docosahexaenoic acid (DHA, C22: 6-3), eicosahexaenoic acid (EPA, C20: 5-3) and docosapentaenoic acid (DPA, C22: 5-6). These fatty acids are essential for survival and growth of many marine fish larvae. In this paper, fresh biomass of S. mangrovei PQ6 was used for culturing rotifer Brachionus plicatilis. In the first formula (L1), rotifers were fed on baker's yeast; in second formula (L2), rotifers were fed on mixed two microalgae, Nannochloropsis oculata and Chaetoceros gracilis; in the third formula (L3), rotifers were fed on S. mangrovei PQ6 biomass. The results indicated that S. mangrovei PQ6 biomass can replace baker's yeast and autotrophic microalgae in feeding rotifers. Total lipid, total fatty acid and polyunsaturated fatty acid contents of rotifers fed on formula 3 (S. mangrovei PQ6) were higher than those within others. High polyunsaturated fatty acid (C ≥ 20) in omega-3 and 6 groups; DHA and DPA contents of rotifers fed on S. mangrovei PQ6 were the highest, accounting for 39.81% of total fatty acid; 41.95% and 8.24% polyunsaturated fatty acids, corresponding to 20.52; 12.15 and 2.4 mg/g of dried weight, respectively. The survival rate of black sleeper's larvae was highest when they were fed on rotifers grown on L3 formula (51.20 ± 0.89%), followed by L2 formula (48.70 ± 2.67%) and the lowest with L1 formula (43.44 ± 1.54%) (P < 0.05). However, among three formulas, no significant difference was found in the growth of black sleeper's larvae (P > 0.05). These results suggest that biomass of S. mangrovei PQ6 can replace traditional feed like autotrophic microalgae or baker's yeast for biomass culture of the Brachionus plicatilis rotifer for rearing black sleeper's larvae to enhance seed quality to meet demands of market. [ABSTRACT FROM AUTHOR]

Our previous studies suggested that 17α,20β-dihydroxy-4-pregnen-3-one (DHP), an oocyte maturation inducing progestin, also acts as a sex pheromone in Chinese black sleeper Bostrichthys sinensis , a fish species that inhabits intertidal zones and mates and spawns inside a muddy burrow. The electro-olfactogram response to DHP increased during the breeding season. In the present study, we cloned the cDNAs of the nine progestin receptors ( pgr , paqr5 , 6 , 7 ( a , b ), 8 , 9 , pgrmc1 , 2 ) from B. sinensis , analyzed their tissue distribution, and determined the expression in the olfactory rosette during the reproductive cycle in female and male fish. The deduced amino acid sequences of the nine progestin receptors share high sequence identities with those of other fish species and relatively lower homology with their mammalian counterparts, and phylogenetic analyses classified the nine B. sinensis progestin receptors into their respective progestin receptor groups. Tissue distribution of B. sinensis progestin receptors showed differential expression patterns, but all these nine genes were expressed in the olfactory rosette. Interestingly, paqr 5 mRNA was found in the intermediate and basal parts of the olfactory epithelium but not in the central core using in situ hybridization, and its expression level was the highest in the olfactory rosette among the tissues examined. These results suggested Paqr5 may have an important role for transmitting progestin signaling in the olfactory system. The expression levels of paqr7a and paqr7b , pgr and pgrmc2 mRNA peaked around the mid meiotic stage, and that of paqr8 peaked at late meiotic stage in the olfactory rosette in males, while the olfactory expression of paqr5 decreased gradually as spermatogenesis progressed. In contrast, the expression of the progestin receptors did not change significantly during the development of the ovary in the olfactory rosette in females, except that of pgr . Interestingly, the changes of paqr8 expression in the olfactory rosette in males mirrored the changes of plasma DHP levels in females during the reproductive cycle, suggesting the Paqr8 may also be important for deciphering progestin signaling released by female. To our knowledge, this is the first time to demonstrate the presence of all known progestin receptors in a teleost olfactory rosette, and to show different expressions between the males and females during the reproductive cycle. This study provides the first evidence on changes of all purported progestin receptors during a reproductive cycle in teleost olfactory rosette, and suggests that distinct olfactory sensitivities to DHP may be due to the changes and compositions of each progestin receptor in B. sinensis . [ABSTRACT FROM AUTHOR]

Abstract: In this study, the gene encoding serum transferrin (STF) in the Chinese black sleeper (Bostrichthys sinensis) was cloned and sequenced. The full BsSTF cDNA is 2324bp in length with an open reading frame (ORF) of 2067bp encoding 688 amino acids and has 47.1%–65.7% identity with other fish homologues. The BsSTF genomic DNA is composed of 17 exons and 16 introns and is well conserved with respect to other vertebrate species in the number of exons and in the position of introns. The expression of the BsSTF mRNA was examined in all tissues tested including liver, blood, muscle, spleen, stomach, skin, intestine, brain, head kidney, fin, gill and gonad, with the highest expression levels found in the liver. Temporal transcriptional changes of BsSTF during embryonic development of the Chinese black sleeper were detected, and the results showed a substantial decrease in the early stages, from the cleavage stage to the blastula stage, reaching minimum levels at the blastula stage and increasing gradually until the pre-hatching stage, indicating that BsSTF is likely an important factor in early embryonic development. After infection with Vibrio harveyi, BsSTF expression was found to increase mainly in the liver and stomach, acting as a positive acute protein, suggesting that BsSTF is involved in the immune response. [Copyright &y& Elsevier]

Ovarian, testicular and seminal vesicle extracts of mature Chinese black sleeper ( Bostrichthys sinensis Lacepede), synthetic steroids 17α-progesterone (17α-P), 17α,20β-dihydroxy-4-pregnen-3one (17α,20β-P) and prostaglandins PGE2 and PGF2α were used in an attempt to attract broodfish and to induce spawning. Furthermore, 17α-P, PGE2 and PGF2α levels were determined in extracts, and PGE2 and PGF2α levels were determined in holding and spawning waters. The results showed that ovarian extracts attracted more males than females to enter artificial nests, while testicular and seminal vesicle extracts attracted more females than males. The highest percentage of spawned nests were found when 17α,20β-P and PGE2 were administered to the nests, while the largest egg numbers and the mean highest fertilization rate were observed when PGE2 was added. In ovarian extract, 17α-P level was higher than levels in testicular or seminal vesicle extracts. The PGE2 levels were significantly ( P<0.05) higher than PGF2α in the ovarian, testicular and seminal vesicle extracts. The PGE2 and PGF2α levels in spawning waters were higher than those in holding waters. The PGE2 levels were greatly significantly ( P<0.01) higher than PGF2α in spawning and in holding waters. The results suggest that the sex organs of B. sinensis contain 17α-P, 17α, 20β-P, PGE2 and PGF2α and that 17α-P, 17α,20β-P and PGE2 may act as sex pheromones in this species, attracting both male and female conspesifics to spawning sites and inducing spawning. Among the compounds tested, PGE2 was the most effective sex pheromone for induction of spawning in B. sinensis. [ABSTRACT FROM AUTHOR]

Bostrichthys sinensis inhabits brackish water, living in the crevices of the river mouths of Shang Xi andGuangdong, China. In its natural habitat, it may encounter aerial exposure frequently during low tides, and it usually remains quiescent in the absence of water. Upon aerial exposure in the laboratory, the ammonia excretion rate decreased to one-fourth that of the submerged control. Although all the enzymes of the ornithine-urea cycle were detected in the liver of this fish, the activity of hepatic carbamoyl phosphate synthetase was too low for the cycle to be functioning. Indeed, ammonia accumulated in the tissues and was not converted to urea. Results indicate that ammonia produced through amino acid catabolism was detoxified to glutamine during the first 24 h of aerial exposure. The excess amount of glutamine stored in the muscle during this period couldaccount approximately for the reduction in ammonia equivalent excreted. There was indeed a significant increase in the activity of glutamine synthetase from the liver of specimens exposed to terrestrial conditions. In contrast to the production of alanine, formation of glutamine is energetically expensive. Since B. sinensis remained relatively inactive on land, the reduction in energy demand for muscular activity might provide it with the opportunity to exploit glutamine formation as a means to detoxify ammonia. After 72 h of aerial exposure, B. sinensis reduced internal ammonia production, possibly through reductions in proteolysis and amino acid catabolism, to avoid excessive accumulation of ammonia. [ABSTRACT FROM AUTHOR]

Dissolved oxygen (DO) content is crucial for the development and health of aquatic animals. DO content is closely related to the antioxidant response of aquatic animals, while the interplay between DO content and the gut microbiota of aquatic animals is unclear. Thus, the objective of this study was to compare the changes in gut microbiota in Bostrichthys sinensis under normoxic (CT group) and hypoxic (Y group) conditions. Superoxide dismutase and catalase activities were similar in the CT and Y groups. The diversity and richness of the community decreased significantly in the Y group, concurrent with an altered composition in the gut microbiota. A dissimilarity test demonstrated that the structure of the gut microbiota was strictly separate between the CT and Y groups. The relative abundance of Gammaproteobacteria increased significantly while the relative abundance of Deltaproteobacteria decreased significantly in the Y group compared to the CT group. A significant increase in the relative abundance of Proteus was observed in the Y group, whereas the relative abundance of Desulfovibrio declined sharply. A network analysis revealed that average connectivity and sub-module numbers decreased in the Y group, suggesting that the complexity, efficiency, and robustness of the gut microbiota network in B. sinensis declined distinctly under the hypoxic condition. Clostridia was the main component serving as a module hub in the CT and Y group networks. Furthermore, most of the shared operational taxonomic units (OTUs) belonged to Clostridia. These results suggested that Clostridia both occupied an important position in the two networks of the B. sinensis gut microbiota, however the niche of Clostridia was notably altered based on its interactions with other species under the hypoxic condition. The interactions between Clostridia and other OTUs in the Y group network converted, indicating that a hypoxic condition could affect the function of Clostridia in the network. The homeostasis of the B. sinensis gut microbiota was disrupted under the hypoxic condition due to deterioration in the network structure resulting from a decrease in the number of module hubs and average connectivity. Microbial metabolism could be affected by the hypoxic conditions, and the abundant microbial functional pathways had advantage to the survival of B. sinensis. This study revealed the effects of DO on the composition of gut microbiota in B. sinensis and further illustrated the importance of interspecific interactions and species roles for evaluating the development and health of B. sinensis using an ecological network analysis of the gut microbiota. • Antioxidant response of B. sinensis were not changed in long-term low dissolved oxygen condition. • The diversity and richness of intestinal bacteria could be changed in B. sinensis under hypoxic condition. • Although Clostridia both occupied an important position in the two networks, the niche of Clostridia was notably altered. • Microbial functional pathways could be impacted by environmental factors to adapt living environment. [ABSTRACT FROM AUTHOR]