Effects of substrate on burrowing behavior,feeding physiology,and energy budget of undulated surf clam Paphia undulata

Substrate is an important abiotic factor for burrowing shellfish,as it not only provides them with shelter,but also impose significant effect on their physiological metabolism.However,the physiological responses of burrowing clams within various substrates get less attention due to difficulty in carrying out physiological tests in buried conditions.Consequently,this study investigated the burrowing behavior,feeding physiology and energy budget of Paphia undulata,which is an important aquaculture bivalve species in south China.The clams were exposed to mud and sand substrates with variable physical properties in the laboratory,to determine the suitable substrate conditions for this species.The results showed that the percentage of burrowing clams,digging index,burrowing time,burrowing depth and scope for growth(SFG)were higher in mud substrates with≥40%water content.Likewise,burrowing percentage,digging index,and burrowing depths were higher in substrates with≤40%sand content.Moreover,the burrowing depth had significant effect on the feeding physiology and SFG of P.undulata as clams burrowed at 6.3±1.8 cm had higher clearance rates and SFG as compared to other buried depths.This study further revealed that low water content in the sediment inhibited physiological performances of P.undulata by impairing feeding or absorption,hence reducing the SFG.In conclusion,mud substrate with≥40%water content or with≤40%sand content is suitable for proper burrowing and growth of P.undulata.Our findings therefore provide fundamental knowledge that will be applicable in the improvement of bottom aquaculture and conservation of P.undulata.

Gap junction gene innexin3 being highly expressed in the nervous system and embryonic stage of the mud crab Scylla paramamosain

Innexin proteins are a class of transmembrane proteins existing in invertebrates and they have diverse biological functions. The innexin protein Sp-inx2 has been demonstrated to play roles in immune response and promotion of cell apoptosis in the mud crab Scylla paramamosain . One novel innexin gene, named as Sp-inx3 was characterized from S. paramamosin in this study, with an open reading frame of 1 101 bp encoding 367 amino acid residues. Multiple sequence alignment revealed that the Sp-inx3 is highly homologous with innexin3 of Cancer boredis and Homorus americanus . Quantitative real-time PCR (qPCR) and the western blotting results revealed that Sp-inx3 gene was expressed predominantly in the eyestalk, brain, and thoracic ganglion mass in both female and male crabs. The immunohistochemistry assay (IHC) also showed the widespread and intense immunoreactivity of Sp-inx3 in the brain and thoracic ganglion mass. Sp-inx3 mRNA transcription profi les exhibited signifi cantly higher expression from the embryo1 to embryo4 period and low level of expression at the prehatching period and zoea I larva period of S . paramamosain . These results indicate that the Sp-inx3 may play an important role in the nervous system and early embryonic development of S . paramamosain.

Phylogenetically diverse,acetaldehyde-degrading bacterial community in the deep sea water of the West Pacific Ocean

As a major aldehyde pollutant widely existing in industry and our daily life, acetaldehyde is more and more harmful to human health. As characteristic habitat niche, bacteria from deep sea environments are abundant and distinctive in heredity, physiology and ecological functions. Thus, the development of acetaldehyde-degrading bacteria from deep sea provides a new method to harness acetaldehyde pollutant. Firstly, in this study,acetaldehyde-degrading bacteria in the deep sea water of the West Pacific Ocean were enriched in situ and in the laboratory respectively, and then the diversity of uncultured bacteria was studied by using 16 S r RNA genes. Then acetaldehyde-degrading strains were isolated from two samples, including enrichment in situ and enrichment in laboratory samples of deep sea water from the West Pacific Ocean using acetaldehyde as the sole carbon source,and then the ability of acetaldehyde degradation was detected. Our results showed that the main uncultured bacteria of two samples with different enrichment approaches were similar, including Proteobacteria,Actinobacteria, Firmicutes, Cyanobacteria, but the structure of bacterial community were significant different.Four subgroups, α, γ, δ and ε, were found in Proteobacteria group. The γ-Proteobacteria was dominant(63.5%clones in laboratory enriched sample, 75% clones in situ enriched sample). The species belonged to γ-Proteobacteria and their proportion was nearly identical between the two enrichment samples, and Vibrio was the predominant genus(45% in laboratory enriched sample, 48.5% in situ enriched sample), followed by Halomonas(9% in situ enriched sample) and Streptococcus(6% in laboratory enriched sample). A total of 12 acetaldehyde-degrading strains were isolated from the two samples, which belonged to Vibrio, Halomonas,Pseudoalteromonas, Pseudomonas and Bacillus of γ-Proteobacteria. Strains ACH-L-5, ACH-L-8 and ACH-S-12,belonging to Vibrio and Halomonas, have strong ability of acetaldehyde degradation, which could tolerate 1.5 g/L acetaldehyde and degrade 350 mg/L acetaldehyde within 24 hours. Our results indicated that bacteria of γ-Proteobacteria may play an important role in carbon cycle of deep sea environments, especial the bacteria belonging to Vibrio and Halomonas and these strains was suggested for their potentials in government of aldehyde pollutants.

Identification of a chitinase from the hepatopancreas of Chinese black sleeper(Bostrychus sinensis)

Chinese black sleeper(Bostrychus sinensis)is a fish that lives both in seawater and freshwater,feeds on crustaceans,aquatic insects and occasionally shellfish.The existence of digestive enzyme in viscera to act on chitinous exoskeleton of the prey is of interest.In this study,a chitinase was purified to homogeneity using ammonium sulfate precipitation,DEAE-Sephacel ion exchange,Sephacryl S-200 HR and Superdex 200 gel filtration columns.The purified protein presents a molecular mass of 58 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis(SDS-PAGE)and results in a single band on native PAGE.According to peptide mass fingerprinting,two peptides containing a total of 20 amino acid residues,were 95%identical to a chitinase from yellow perch(Perca flavescens)and 100%identical to the chitinase from greater amberjack(Seriola dumerili).The purified chitinase showed optimum activity at pH 6.0,and was stable at acidic conditions and temperature below 55℃.The enzymatic activity was quite stable in the presence of NaCl,even at 1 mol/L.The chitinase was capable of degrading chitosan into low molecular mass chitooligosaccharides(COS)with sizes in a range of 200-700 Da,and the circular dichroism profile of the COS greatly differed from native chitosan.Full-length cDNA encoding the present chitinase was cloned and the transcript levels of chitinase in various tissues were determined by quantitative real-time PCR.The results showed that the transcript level of chitinase was highest in esophagus and hepatopancreas.

Anaerobic metabolism and thermal tolerance:The importance of opine pathways on survival of a gastropod after cardiac dysfunction

Organisms on rocky shores are frequently exposed to high temperatures,which cause impairment of cardiac function and retard cellular oxygen delivery.However,some gastropods can survive at several degrees Celsius higher than their Arrhenius break temperature of cardiac function(ABT),indicating the importance of anaerobic metabolism for their thermal tolerance.We measured the global molecular responses to heat stress in limpet Cellana toreuma using 454 GS-FLX to investigate the variations of genes involved in anaerobic metabolism at high temperatures.Next,the gene expression levels of 4 anaerobic enzymes and activity of alanopine dehydrogenase(AlDH),which is involved in opine pathway,were measured in response to elevated temperature.A total of 19 heat shock proteins(HSPs)were determined using real-time PCR at different temperatures.At high temperatures,the extensive upregulation of HSP genes was an effective but energetically expensive form of protection to prevent thermal damage.The upregulation of hypoxia-inducible factor 1 alpha mRNA indicated the condition of cellular hypoxia and the high gene expression and enzyme activity of AlDH suggested that opine pathway was the main anaerobic pathway.These results implied that anaerobic metabolism was enhanced to provide energy in the face of thermal stress.Our findings highlight the ecological significance of the anaerobic metabolism of gastropods to thermal adaptation.For predicting the ecological impact of global warming on the distribution of gastropods,the role of anaerobic pathways should be evaluated.