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The invasive golden apple snail Pomacea canaliculata has a strong reproductive capacity and has rapidly spread in Asian countries. Current control methods include physical, chemical, and biological approaches, but there has been limited research on the control of P. canaliculata in its different life stages. This study assessed the effectiveness of using giant river prawns Macrobrachium rosenbergii in controlling juveniles of P. canaliculata through a controlled indoor experiment. The density, size, and dispersal range of recently hatched juvenile snails were significantly lower among those kept with prawns than those kept without prawns, indicating a control effect of M. rosenbergii at least on P. canaliculata juveniles. Furthermore, the study speculates on the potential application of M. rosenbergii in the context of a rice–prawn symbiotic system of ecological farming to control invasive P. canaliculata. In terms of effectiveness and safety, its application might lead to a win-win situation for both rice-farm profits and the ecological benefits of invasive species control. [ABSTRACT FROM AUTHOR]

Abstract Acute hepatopancreatic necrosis disease (AHPND) is an emerging disease in shrimp aquaculture which directly caused by binary photorhabdus insect-related (Pir) toxins PirABvp from Vibrio parahaemolyticus. To delineating the evolutionary origin and structure variation of PirAB, the protein sequence of PirABvp resembles from bacteria and insects were retrieved from the public database. The evolutionary relationship of PirABvp and resembles were analyzed phylogenetically. I-TASSER server was used to predict the protein-structure of PirA/B in investigated species. The cell-free supernatant obtained from the broth of V. parahaemolyticus and crude and heterologously expressed PirABvp proteins were respectively administrated to shrimp (Litopenaeus vannamei), crab (Eriocheir sinensis), European seabass (Dicentrarchus labrax), bloodworm (Nereis succinea) and mosquito (Aedes albopictus) to confirm the host range of toxin. Results showed that majority of PirAB located in a genomic island with low GC content. Phylogenetic analysis of PirB from bacteria and insects divided them into three lineages, namely Marine, Soli and Insect lineage respectively, with the majority belonging to Soli lineage. Overall, resembles of PirABvp were structurally similar to the PirABvp, but harbored three highly variable regions in receptor binding region and ligand binding sites, respectively. Shrimps bioassayed with cell-free supernatant of V. parahaemolyticus , crude and heterologously expressed PirABvp proteins resulted in 76.5%, 68.7% and 86.6% mortality, respectively. However, almost no mortality was found in crab, bloodworm, mosquito and European seabass. In summary, results indicated that PirBvp and its homologs have significant sequence divergence and remarkable variability in the receptor binding sites, which might explain why PirABvp are shrimp-specific toxins. Homology analysis of proteins revealed that there were three evolutionary directions for PirAB and the emergence of PirABvp was an ancient event that not associated with the aquaculture practices of shrimp. This study enhanced our understanding of the evolution of pirAB , which provided new insights into the origins of AHPND. However, why only shrimp is highly susceptible to PirABvp remains mysteries and need to solve in the future research. Highlights • The emergence of PirABvp was an ancient event that not associated with the aquaculture practices of shrimp. • PirB has species-specific receptor binding sites, which might affect its pathogenicity against the different host. • PirABvp has no adverse effects on other three animals and seems to be shrimp-specific toxins. [ABSTRACT FROM AUTHOR]

Partial or complete replacement of fish meal (FM) with fermented soybean meal (FSM) was examined in Macrobrachium nipponense over an 8-week growth trial. Growth and immune characteristics were evaluated. Fermented soybean meal replaced 0 (FM, control), 25% (R25), 50% (R50), 75% (R75), or 100% of the FM (R100) in five isocaloric and isonitrogenous diets. Each diet was fed to juvenile prawns (mean weight, 0.103 ± 0.0009 g) twice daily to apparent satiation in five replicates. Weight gain and specific growth rate of M. nipponense were significantly higher in prawns fed the R25 diet than that of prawns fed the FM diet. No significant differences were observed among the other treatments. Total hemocyte count and hemolymph phagocytic activity decreased as the proportion of FSM increased. Total antioxidant activity competence and malondialdehyde level in the hepatopancreas were highest in prawns fed the R100 diet. mRNA levels of the antioxidant genes Cu–Zn superoxide dismutase and catalase, heat shock cognate protein 70, and heat shock protein 90 were significantly differentially regulated in the prawn hepatopancreas. In addition, percent mortality increased after challenge with live Aeromonas hydrophila . Percent mortality of prawns fed the R100 diet was significantly higher than that of prawns fed the FM and R25 diets. These findings demonstrate that (1) M. nipponense growth performance was not affected by including a high proportion of FSM in the diet, and the best growth performance was obtained when 25% of the FM was replaced with FSM; (2) nonspecific immunity was impaired when all of the FM was replaced with FSM. [ABSTRACT FROM AUTHOR]

Feeding frequency is important for the improvement of growth performance and immunity of aquatic animals. In this study, the effect of feeding frequency on growth, body composition, antioxidant status and mRNA expression of immunodependent genes before or after ammonia-N stress was examined in Macrobrachium nipponense . Prawns were randomly assigned to one of five feeding frequencies (1, 2, 3, 4 and 6 times/day) following the same ration size over an 8-week growth trial. After the feeding trial, prawns were challenged by ammonia-N. The weight gain of prawns fed with 3–6 times/day was significantly higher than that of prawns fed with 1 time/day. The best feed conversion ratio was obtained from prawns fed with 3–6 times/day. Body crude lipid with feeding frequency of 3, 4 or 6 times/day was quite lower than that with 1 time/day. High feeding frequency (6 times/day) induced significantly elevated hepatopancreas super oxide dismutase and catalase activities. The malondialdehyde level in prawns fed with 6 times/day was also significantly increased, which was higher than that of prawns fed with other feeding frequency. mRNA expression of toll like receptor 3 and myeloid differentiation primary response protein MyD88 was promoted by feeding frequency from 3 to 4 time/day but inhibited by high or low feeding frequency. Similar mRNA expression variation trends of the two genes were observed in prawns after ammonia-N stress. After ammonia-N challenge, the highest cumulative mortality was observed in prawns fed with 6 times/day, which was significantly higher than that of prawns fed with 2–4 times/day. These findings demonstrate that (1) too high feeding frequency induced oxidative stress and malondialdehyde accumulation, negatively affecting the health status of prawns and reduced its resistance to ammonia-N stress; (2) the optimal feeding frequency to improve growth and immune response of this species at juvenile stage is 3–4 times/day; (3) considering costs of labour, a feeding frequency of 3 times/day is recommended for this prawn. [ABSTRACT FROM AUTHOR]

Selenium (Se) is an essential nutrient for crustaceans. The dietary selenium requirement of juvenile oriental river prawn Macrobrachium nipponense was evaluated. Yeast-selenium was added to basal semi-purified diet at six levels to make diets with the concentration of 0.11, 0.31, 0.47, 0.59, 0.88 and 1.17 mg Se kg − 1 . These diets were fed to juvenile prawns (initial weight 0.133 ± 0.003 g) in quintuplicate for 8 weeks. Our results indicated that the growth performance of prawn was significantly affected by dietary selenium. Prawns fed the 0.47 and 0.59 mg Se kg − 1 diets achieved the highest weight gain rate (WGR), whereas the deficiency (0.11 mg kg − 1 ) and excess (1.17 mg kg − 1 ) of Selenium inhibited their growth. Whole-body and muscle Se concentrations generally increased with the level of dietary Se. The highest concentrations in body and muscle were observed in the prawns fed the 1.17 mg kg − 1 diet, which were significantly higher than those of prawns using 0.11, 0.31, 0.47 and 0.59 mg kg − 1 diets. Selenium also affects the activity of antioxidant enzymes. The activities of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) were significantly higher in prawns fed with 0.31, 0.47 and 0.59 mg Se kg − 1 than other groups, whereas the maleic dialdehyde (MDA) content had the opposite pattern from GSH-Px activity. Significantly elevated glutathione reductase (GR) activity and reduced glutathione (GSH) content were found in prawns fed the 0.31, 0.47, 0.59 and 0.88 mg kg − 1 diets. The prawns fed with 0.31–0.88 mg Se kg − 1 exhibited the highest total antioxidant competence (T-AOC activity), which was significantly higher than 1.17 mg kg − 1 group. Furthermore, selenium is involved in prawn immune competence. Serum phenoloxidase (PO) and lysozyme activities in prawns fed the 0.31, 0.47, 0.59 and 0.88 mg Se kg − 1 diets were significantly higher than those fed the 0.11 and 1.17 mg Se kg − 1 diets. The minimum dietary selenium requirements for maximal growth and antioxidant ability of juvenile oriental river prawn were evaluated as 0.58–0.68 mg kg − 1 diet based on WGR and GSH-Px activity in the hepatopancreas, and 1.07 mg Se kg − 1 diet was required to maximize whole body selenium content. Statement of relevance In this study, we evaluated the minimum dietary selenium requirement for juvenile oriental river prawn Macrobrachium nipponense . Dietary selenium deficiency and excess significantly reduced growth, antioxidant ability and immunity of prawn. Our results illustrate that supplementing appropriate amount of dietary selenium is necessary in prawn culturing. The minimum dietary selenium level for maximal growth and antioxidant ability of juvenile M. nipponense is recommended as 0.58–0.68 mg kg − 1 diet based on the analyses of WGR and GSH-Px activity, and 1.07 mg Se kg − 1 diet is required to maximize whole body selenium content. This research will facilitate to the development of practical diet for prawn. [ABSTRACT FROM AUTHOR]

To investigate the potential alleviative effect of taurine supplementation on growth and oxidant stress in freshwater prawn Macrobrachium nipponense (De Haan) exposed to dietary lead, pelleted feeds were prepared with two concentrations of lead (0 and 10 mg/kg diet) and two levels of taurine (0 and 15 g/kg diet). Healthy prawns were randomly distributed between the four treatment groups, with three tanks per group and 50 prawns per tank. Dietary lead decreased weight gain and the activities of superoxide dismutase, catalase and glutathione peroxidase; increased malondialdehyde content; altered hepatopancreas morphology; and decreased the expression of heat shock protein 90 (HSP90; p <.05). A significant interactive effect was found between dietary lead and taurine on the malondialdehyde level, and taurine supplementation significantly decreased the malondialdehyde level under lead stress (p <.05). No significant effect on growth, hepatopancreas morphology and HSP90 expression was observed with taurine supplementation under lead stress. Overall, dietary lead affected growth, induced oxidative stress and impaired hepatopancreas morphology of the prawns, and dietary taurine significantly alleviated oxidative stress through a decreased malondialdehyde level, whereas the capacity of taurine to alleviate the decreased growth rate, hepatopancreas damage and low HSP90 expression under lead stress was limited. [ABSTRACT FROM AUTHOR]

Arachidonic acid (ARA) is involved in the growth and regulation of immunity in fish. Little research has focused on ARA in crustaceans. This study was an 8-week feeding experiment investigating the effects of dietary ARA on growth, antioxidative indices, and immune characteristics of the juvenile oriental river prawn ( Macrobrachium nipponense ). An ARA-enriched oil was supplemented into the basal diet to formulate six isonitrogenous and isoenergetic diets containing 0.02% (the control group), 0.28%, 0.54%, 0.86%, 1.22%, and 1.54% ARA dry weight. Diets were fed to juvenile prawns (mean weight: 0.104 ± 0.002 g) twice daily to apparent satiation in three replicates. Weight gain and specific growth rate of M . nipponense significantly increased with increasing dietary levels of ARA from 0.02% to 0.86% and thereafter declined. Hepatopancreas super oxide dismutase and catalase activities significantly increased with supplementation with ARA, particularly in prawns fed 1.22% and 1.54% ARA. The malondialdehyde level in prawns fed 1.54% ARA also significantly increased, and was higher than that of prawns fed ARA from 0.02% to 0.86%. Serum lysozyme activity was significantly greater in prawns fed 0.86% ARA compared with the other groups. mRNA expression of toll-like receptor signaling pathway-related genes was promoted by a dietary ARA level from 0.54% to 0.86% but inhibited with the higher ARA levels (1.22–1.54%). The mortality percentage increased after challenge with live Aeromonas hydrophila . The mortality percentage of prawns fed 1.54% ARA was significantly higher than that of prawns fed 0.28–1.22% ARA. The results suggest that the optimal dietary ARA requirement for juvenile M . nipponense is 0.82% (dry weight) based on second-order regression analysis of weight gain vs . dietary ARA level, and that 0.86% ARA could significantly enhance non-specific immunity of M . nipponense ; however, too high a level of ARA will affect the health status of this prawn. [ABSTRACT FROM AUTHOR]