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The black tiger shrimp, Penaeus monodon, is the most economically important penaeid shrimp in Bangladesh for both culture and capture fishery. The culture of these penaeid shrimps is always risky due to different diseases and environmental stressors. This study aimed to assess the relative expression of the Penaeus monodon Rab7 gene in the post larvae (PL) of the P. monodon cultured under different salinity conditions. We challenged the PL of the P. monodon in aquariums with two different salinity and dissolved oxygen conditions during a 7-day test. The relative expression of Rab7 was upregulated during the experimental period of 36 hours. Average differences in the relative expression of Rab7 were 0.3-folds and 0.5-folds, and 0.4-folds and 0.6-folds after 18 and 36 hours of rearing in 2 and 54 ppt salinity treated shrimp PL, respectively, when ß-actin was used as an internal control. On the other hand, when elongation factor 1 alpha (EF1a) was used for normalization, the average relative expression of Rab7's fold differences were 0.2-folds and 0.5-folds, and 0.3-folds and 0.6-folds after 18 and 36 hours of rearing in 2 and 54 ppt salinity treated shrimp PL, respectively. Therefore, our results suggested that the relative expression of the Rab7 was positively correlated with an increased level of salinity and challenge duration. The significant increase in the expression level of Rab7 in the PL of P. monodon exposed to high salinity stress (54 ppt) conditions indicated its functional role in osmotic stress in shrimps. However, further studies are necessary to elucidate the mechanisms of how Rab7 is upregulated in shrimp cells after applying different levels of salinity using a larger sample group. [ABSTRACT FROM AUTHOR]

Abstract Background Probiotics are widely used to promote host health. Compared to mammals and terrestrial invertebrates, little is known the role of probiotics in aquatic invertebrates. In this study, eighteen tanks with eight hundred of shrimp post-larvae individuals each were randomly grouped into three groups, one is shrimps administered with E. faecium as probiotic (Tre) and others are shrimps without probiotic-treatment (CK1: blank control, CK2: medium control). We investigated the correlations between a kind of commercial Enterococcus faecium (E. faecium) powder and microbiota composition with function potentials in shrimp post-larvae gut. Results We sequenced the 16S rRNA gene (V4) of gut samples to assess diversity and composition of the shrimp gut microbiome and used differential abundance and Tax4Fun2 analyses to identify the differences of taxonomy and predicted function between different treatment groups. The ingested probiotic bacteria (E. faecium) were tracked in gut microbiota of Tre and the shrimps here showed the best growth performance especially in survival ratio (SR). The distribution of SR across samples was similar to that in PCoA plot based on Bray-Curits and two subgroups generated (SL: SR

Background: Probiotics are widely used to promote host health. Compared to mammals and terrestrial invertebrates, little is known the role of probiotics in aquatic invertebrates. In this study, eighteen tanks with eight hundred of shrimp post-larvae individuals each were randomly grouped into three groups, one is shrimps administered with E. faecium as probiotic (Tre) and others are shrimps without probiotic-treatment (CK1: blank control, CK2: medium control). We investigated the correlations between a kind of commercial Enterococcus faecium (E. faecium) powder and microbiota composition with function potentials in shrimp post-larvae gut. Results: We sequenced the 16S rRNA gene (V4) of gut samples to assess diversity and composition of the shrimp gut microbiome and used differential abundance and Tax4Fun2 analyses to identify the differences of taxonomy and predicted function between different treatment groups. The ingested probiotic bacteria (E. faecium) were tracked in gut microbiota of Tre and the shrimps here showed the best growth performance especially in survival ratio (SR). The distribution of SR across samples was similar to that in PCoA plot based on Bray-Curits and two subgroups generated (SL: SR < 70%, SH: SR ≥ 70%). The gut microbiota structure and predicted function were correlated with both treatment and SR, and SR was a far more important factor driving taxonomic and functional differences than treatment. Both Tre and SH showed a low and uneven community species and shorted phylogenetic distance. We detected a shift in composition profile at phylum and genus level and further identified ten OTUs as relevant taxa that both closely associated with treatment and SR. The partial least squares path model further supported the important role of relevant taxa related to shrimp survival ratio. Conclusions: Overall, we found gut microbiota correlated to both shrimp survival and ingested probiotic bacteria (E. faecium). These correlations should not be dismissed without merit and will uncover a promising strategy for developing novel probiotics through certain consortium of gut microbiota. [ABSTRACT FROM AUTHOR]

In Bangladesh, shrimp post-larvae (PL) are mainly produced in hatcheries. From 2000s shrimp PL are reared in nurseries containing small earthen ponds by relatively poor people for a few days before stocking into the shrimp farms. This study assesses the physical and chemical parameters of five such nurseries at Satkhira district, Bangladesh using scientific instruments and semi-structured questionnaire. The nursing process involved stocking of PL (4151.8 ± 1581.35 PL/m2) in small earthen ponds (<18m2 area/pond) and raring for up to 10 days with feeding. Most of the physico-chemical parameters were within the suitable range recommended for shrimp culture. The survival rate of PL ranged from 80% to 90%. The nursing system was profitable as the average Benefit-Cost Ratio (BCR) was 1.19. The establishment and operation of these nurseries do not require any expensive equipment or complex technology and can be run by less educated and poor people. However, constraints like lack of credit and continuous water supply are hindering the scaling up of these nurseries in size and number. By providing means to overcome the constraints these nurseries can be an excellent income generating source for the poor entrepreneurs as well as contribute in increasing shrimp production in Bangladesh. [ABSTRACT FROM AUTHOR]

Mangrove leaf litter is a potential source of nutrients for shrimp post larvae. To introduce mangrove trees in shrimp farms it is necessary to identify the combination of trees which is most beneficial for shrimp. The present study evaluated the effects of mixed leaf litter of four mangrove species (Avicennia officinalis (Ao), Sonneratia apetala (Sa), S. caseolaris (Sc) and Heritiera fomes (Hf) on shrimp post larvae performance and water and soil quality. Leaf litter with and without supplemental feed was applied to shrimp culture tanks according to a 4 × 2 factorial design and followed by testing a subset of treatments in mesocosm pond conditions. Shrimp post larvae of 15-days old (PL 15) with an average weight of 0.01 g were used for both experiments, each with a 4-week duration without water exchange. Under controlled conditions in the tanks, leaf litter and feed resulted in 22 to 32% higher weight gain of PL shrimp than combined weight gain realized when receiving only leaf litter or only feed, indicating synergism. Based on this, the pond experiment was designed with combined application of leaf litter and feed. The pond experiment resulted in higher shrimp weight gain than realized in the tanks. In tanks, the highest average individual weight gain of PL was observed for the leaf litter mixture SaAoHf (0.23 g)followed by SaScHf (0.21 g), ScAoHf (0.21 g) andSaScAoHf (0.20 g). Paralleling the results of the tank experiment, SaAoHf leaf litter also gave the highest average individual weight gain (1.2 g) of PL shrimpin the ponds but other leaf litter treatments followed by SaScAoHf (0.95 g), ScAoHf (0.84 g) and SaScHf (0.69 g) leaf litter. The different mixtures of mangrove leaf litter also resulted in significant differences in biological oxygen demand (BOD 5), phytoplankton and zooplankton concentrations in pond water and organic carbon in soil. Both phytoplankton (P < 0.01, Pearson correlation r = 0.910)and zooplankton (P < 0.05, r = 0.535) abundance was positively correlated to shrimp weight gain. The low feed conversion ratio (FCR) in the treatments combining leaf litter and supplemental feed as compared to treatments using only feed indicated extra food benefits for shrimp PL from decomposing leaf litter. Overall, mixed mangrove leaf litter had a positive effect on shrimp performance and this effect was highest for SaAoHf leaf litter. • Mixed mangrove leaf litter combined with feed creates synergy in shrimp culture ponds. • Shrimp post larvae grow better on mangrove leaf litter in mesocosm ponds than in tanks. • The contribution of mangrove leaf litter to shrimp production depends on the mix of tree species. • Shrimp production correlates positively with phytoplankton and zooplankton in mesocosm ponds. [ABSTRACT FROM AUTHOR]