The ontogeny of acidic digestive tract in larval turbot Scophthalmus maximus based on H+/K+-ATPase and pepsinogen

Acidic digestion is an important digestive process of marine fish.In fish stomach,two enzymes are involved in the secretion of hydrochloric acid(HCl)and proteomic digestion:H^(+)/K^(+)-ATPase and pepsinogen.However,the starting of digestive function in fish is still unclear.To reveal the details of acidic digestion of turbot Scophthalmus maximus in early development,a 40 day of turbot larvae culture was conducted.The H^(+)/K^(+)-ATPase gene from the turbot S.maximus(smH^(+)/K^(+)-ATPase)was identified and characterized.Based on our previous discription on pepsinogen of turbot S.maximus,we combined pepsinogen and H^(+)/K^(+)-ATPase and analyzed the mechanism of acidic digestion in turbot.Results show that the spatial and temporal expression profiles of H^(+)/K^(+)-ATPase agreed with pepsinogen A and C in turbot,indicating a synergetic action between H^(+)/K^(+)-ATPase and pepsinogen during the acidic digestion process.In addition,the turbot juveniles showed a faster growth after the expressions of H^(+)/K^(+)-ATPase gene and pepsinogen gene,demonstrating that pepsin had a higher digestive efficiency,for which a compound diet should be provided to the fish from Day 22 onward.This study provided a reference for biology research and aquaculture of turbot and other marine fishes.

Laboratory simulation of dissolved oxygen reduction and ammonia nitrogen generation in the decay stage of harmful algae bloom

To evaluate how the decay of bloom-forming algae affect the coastal dissolved oxygen,a laboratory simulation was conducted in terms of three typical harmful algae,Alexandrium catenella,Prorocentrum donghaiense,and Skeletonema costatum.Algae of same biomass(55μg/mL)were conducted in lightproof columns,and the cell density,dissolved oxygen(DO),and ammonia nitrogen of different layers were monitored at certain time series.Results show that the decomposition of algae significantly decreased the DO,and increased the ammonia nitrogen in all layers;and significant deference between different species was observed.The A.catenella treatment showed the lowest DO(average concentration of 3.4 mg/L)and the highest ammonia nitrogen(average concentration of 0.98 mg/L)at the end of test,followed by P.donghaiense;and the S.costatum showed relatively high DO and low ammonia nitrogen due to slow decay rate.Results indicate that decomposition of harmful bloom algae,especially dinoflagellate,would cause significantly DO depletion and toxic ammonia nitrogen increase,which will detrimentally affect both pelagic and benthic ecosystem.

Changes of melatonin and its receptors in synchronizing turbot(Scophthalmus maximus)seasonal reproduction and maturation rhythm

In most fish,reproduction is seasonal or periodic under the suitable conditions.In turbot(Scophthalmus maximus)farms,one of the most economically important marine flatfish species,changes in daylength could cause changes in the spawning time.In this study,to characterize the regulation of reproductive physiology following light signals,three melatonin receptors(Mtnr)investigated in turbot were named sm Mtnr1,sm Mtnr2,and sm Mtnr1 c.Distinct expression profiles demonstrated that Mtnr m RNAs were concentrated in the brain(as detected in the hypothalamus(Hy)and mesencephalon(Me)),gonad and eye.The most abundant Mtnr1 and Mtnr2 m RNA expression levels were detected in the central nervous system at the beginning of the breeding season,suggesting that Mtnr1 and Mtnr2 may play vital roles in the regulation of turbot gonadal development.In addition,the melatonin profiles gradually increased and reached to the highest level at the spawning stage,indicating that melatonin is a potent hormone in the regulation of fish oocyte growth and maturation.The results of this study suggested that melatonin is the primary factor that transduces the light signal and regulates the physiological functions of turbot seasonal reproduction.Moreover,the results of this study may establish a foundation for further research seeking to identify fish melatonin receptors involved in the gonadal development and gamete maturation.

Nutrient depletion is the main limiting factor in the crude oil bioaugmentation process

The biodegradation was considered as the prime mechanism of crude oil degradation.To validate the efficacy and survival of the crude oil-degrading strain in a bioremediation process,the enhanced green fluorescent protein gene(egfp)was introduced into Acinetobacter sp.HC8-3 S.In this study,an oil-contaminated sediment microcosm was conducted to investigate the temporal dynamics of the physicochemical characterization and microbial community in response to bacterium amendment.The introduced strains were able to survive,flourish and degrade crude oil quickly in the early stage of the bioremediation.However,the high abundance cannot be maintained due to the ammonium(NH 4^(+)-N)and phosphorus(PO 4^3--P)contents decreased rapidly after 15 days of remediation.The sediment microbial community changed considerably and reached relatively stable after nutrient depletion.Therefore,the addition of crude oil and degrading cells did not show a long-time impact on the original microbial communities,and sufficient nitrogen and phosphorus nutrients ensures the survive and activity of degrader.Our studies expand the understanding of the crude oil degradative processes,which will help to develop more rational bioremediation strategies.

The parasitic dinoflagellate Hematodinium infects marine crustaceans

Hematodinium is a type of parasitic dinoflagellate that infects marine crustaceans globally.The parasite lives mainly in the hemolymph or hemocoels of affected hosts,and results in mortalities due to malfunction or loss of functions of major organs.In recent years,the parasite had developed into an emerging epidemic pathogen not only affecting wild populations of economically valuable marine crustaceans in western countries but also the sustainable yield of aquaculture of major crabs in China.The epidemics of the parasitic diseases expanded recently in the coastal waters of China,and caused frequent outbreaks in aquaculture of major crab species,especially Portunus trituberculatus and Scylla paramamosain.In addition,the pathogen infected two species of co-cultured shrimps and multiple cohabitating wild crabs,implying it is a significant threat to the sustainable culture of commercially valuable marine crustaceans.In particular,the polyculture system that is widely used along the coast of China may facilitate the spread and transmission of the pathogen.Thus,to provide a better understanding of the biological and ecological characteristics of the parasitic dinoflagellate and highlight important directions for future research,we have reviewed the current knowledge on the taxonomy,life cycle,pathogenesis,transmission and epidemiology of Hematodinium spp.Moreover,ecological countermeasures have been proposed for the prevention and control of the emerging infectious disease.