Single or combined effects of dietary arabinoxylan-oligosaccharide and inulin on growth performance,gut microbiota,and immune response in Pacific white shrimp Litopenaeus vannamei

The single and synergistic effects of dietary arabinoxylan-oligosaccharide(AXOS)and inulin at different doses(2,4,and 8 mg/g diet)on survival,growth performance,gut microbiota,and immune response in Pacific white shrimp Litopenaeus vannamei were assessed.Singular application of either inulin or AXOS at doses of 4 mg/g diet showed the most stimulatory effects on the growth rate and gene expression levels of chitinase,cathepsin L,chymotrypsin,and extracellular signal-regulated kinase(ERK)in each single prebiotic feeding trial.Compared with single prebiotic treatments,simultaneous application of AXOS and inulin at 4 mg/g diet enhanced remarkably the growth parameters of shrimp and the expression of related genes(chitinase,cathepsin L,chymotrypsin,ERK,myeloid differentiation factor 88,and phenoloxidase)after 8-week feeding(P<0.05).Additionally,gut microbiota analysis indicated the dietary supplementation with combined prebiotics increased significantly the bacterial community richness and relative abundance of Bacillus Pseudomonas Bacteriovorax,and Lactobacillus,and reduced the abundance of Vibrio Rhodococcus,and Photobacterium in the digestive tract of L vannamei.Compared with the single prebiotic treatment and the control,combined prebiotics supplementation boosted notably the survival rate and expression levels of immune-related genes in shrimp infected with Vibrio alginolyticus or white spot syndrome virus.Therefore,simultaneous application of AXOS and inulin shall have a great potential of dietary supplement in the culture of L.vannamei.

Behavioral responses to ocean acidifi cation in marine invertebrates:new insights and future directions

Ocean acidification(OA)affects marine biodiversity and alters the structure and function of marine populations,communities,and ecosystems.Recently,effects of OA on the behavioral responses of marine animals have been given with much attention.While many of previous studies focuses on marine fish.Evidence suggests that marine invertebrate behaviors were also be affected.In this review,we discussed the effects of CO2-driven OA on the most common behaviors studied in marine invertebrates,including settlement and habitat selection,feeding,anti-predatory,and swimming behaviors,and explored the related mechanisms behind behaviors.This review summarizes how OA affects marine invertebrate behavior,and provides new insights and highlights novel areas for future research.

The Effect of Bioturbation Activity of the Ark Clam Scapharca subcrenata on the Fluxes of Nutrient Exchange at the Sediment–Water Interface

Filter-feeding shellfish are common benthos and significantly affect the biogeochemical cycle in the shallow coastal ecosystems.Ark clam Scapharca subcrenata is one of the widely cultured bivalve species in many coastal areas owing to its tremendous economic value.However,there is little information regarding the effects of the bioturbation of S.subcrenata on the fluxes of nutrient exchange in the sediment-water interface(SWI).In this regard,S.subcrenata was sampled during October 2016 to determine the effects of its bioturbation activity on the nutrient exchange flux of the SWI.The results showed that the biological activity of S.subcrenata could increase the diffusion depth and the rate of the nutrients exchange in the sediments.The bioturbation of S.subcrenata could allow the nutrients to permeate into the surface sediments at 6-10cm and increase the release rate of nutrients at the SWI.The releasing fluxes of DIN and PO43−-P in the culture area were found to be around three times higher than that in the non-cultured region.The culture of S.subcrenata has been proved to be an important contributor to nutrient exchange across the SWI in the farming area of Haizhou Bay.Nutrients exchange in the SWI contributes a part of 86%DIN,71%PO43−-P and 18%SiO32−-Si for the aquaculture farm.

Influence of salinity on the early development and biochemical dynamics of a marine fish, Inimicusjaponicus

Fertilised eggs of the devil stringer(I nimicus japonicus) were incubated at different salinity levels(21, 25, 29, 33, and 37), and then the hatching performances, morphological parameters, and biochemical composition(protein, lipid and carbohydrate) of the larvae were assayed to determine the influence of salinity on the early development of I. japonicus. The tested salinity levels did not af fect the times of hatching or mouth opening for yolk-sac larvae. However, the salinity significantly influenced the hatching and survival rates of open-mouthed larvae, as well as the morphology of yolk-sac larvae. The data indicated that 30.5 to 37.3 and 24.4 to 29.8 were suitable salinity ranges for the survival of embryos and larvae of I. japonicus, respectively. Larvae incubated at a salinity level of 29 had the greatest full lengths, and decreasing yolk volume was positively correlated with the environmental salinity. With increasing salinity, the individual dry weights of newly hatched larvae or open-mouthed larvae decreased significantly. Newly hatched larvae incubated at a salinity level of 29 had the greatest metabolic substrate contents and gross energy levels, while the openmouthed larvae's greatest values occurred at a salinity level of 25. Larvae incubated in the salinity range of 33 to 37 had the lowest nutritional reserves and energy values. Thus, the I. japonicus yolk-sac larvae acclimated more readily to the lower salinity level than the embryos, and higher salinity levels negatively influenced larval growth and development. In conclusion, the environmental salinity level should be maintained at 29–33 during embryogenesis and at 25–29 during early larval development for this species. Our results can be used to provide optimum aquaculture conditions for the early larval development of I. japonicus.

Performance of feeding Artemia with bioflocs derived from two types of fish solid waste

The production of bioflocs with the solid waste from recirculating aquaculture systems(RAS)and feeding Artemia results in additional nutrient retention and lowers waste discharged from RAS.The solid waste from the drumfilters of two RAS,which stocked European eel(Anguilla anguilla)and Nile tilapia(Oreochromis niloticus),was used as substrate to produce bioflocs in suspended growth reactors,referred to as E-flocs and T-flocs,respectively.Mono-diets consisting of 100%E-flocs and 100%T-flocs were added to culture Artemia,referred as E-Artemia and T-Artemia,respectively,in a laboratory scale test.The efficiency of this feeding regime was investigated.A significant difference was observed in terms of crude protein content(35.59±0.2%)for E-flocs,(29.29±0.95)%for T-flocs,(70.01±0.92)%for E-Artemia and(65.63±0.89)%for T-Artemia.134 out of the total operational taxonomic units(OTUs)were present in E-flocs and T-flocs from the analysis of high-throughput sequencing data.Most of the shared OTUs belonged to cyanobacteria.C18:1n7 of T-flocs was higher than that of E-flocs(P<0.05).C18:2n6 of E-flocs was significantly higher than that of T-flocs(P<0.05).No significant difference was observed in the other fatty acid compositions(P>0.05).The survival rate of E-Artemia was(22±0.02)%,significantly higher than that of T-Artemia(16%±0.02%)(P<0.05).No significant difference was observed between the average body weight of E-Artemia(2.38±0.40 mg)and E-Artemia(2.91±0.21)(P>0.05).The EPA of Artemia fed with E-flocs was(3.00±0.46)%,significantly higher than that of T-Artemia(1.57±0.19%)(P<0.05).This study offers a method for reusing the aquaculture waste,which will be helpful to achieve a zero-pollution discharge for aquaculture systems.

microRNA expression profile of fish erythrocytes

MicroRNAs(miRNAs)are short noncoding sequences that can regulate the expression of target genes.Erythrocytes,also called red blood cells(RBCs),are the largest proportion of cells in blood.Erythrocytes deliver oxygen in the body of vertebrates and contribute to the body’s immune function.Illumina sequencing technology was used to analyze pooled RNA samples isolated from erythrocytes,in order to characterize their gene expression profile and increase the range of miRNAs identified in Nile tilapia erythrocytes.This study identified conserved(n=309)and novel(n=194)miRNAs.Quantitative reverse-transcription polymerase chain reaction and next-generation sequencing results indicated that miR-451 was the most abundant in RBCs,followed by let-7a-1,miR-2188 and miR-144.Moreover,the tissue expression mode of these highly expressed miRNAs was characterized.Results show that miR-451,miR-2188,and miR-144 were all highly expressed in RBCs but were low abundance in other tissues.miR-1 and miR-10b were also abundantly expressed in muscle,while miR-122 was abundantly expressed in the liver.let-7a-1,miR-10b,and miR-1 were significantly higher in the testis than in the ovary.The tissue distribution of miRNAs implies that these noncoding sequences have a potential role in regulating tissue differentiation or maintaining tissue characteristics.The results of a dual-luciferase reporter assay indicated that miR-144 and miR-10b inhibited the expression of the meningioma expressed antigen 5 gene in vitro.This study contributes to the Nile tilapia miRNA database and reveals the profile of erythrocyte miRNA expression.