The freshwater prawn Macrobrachium acanthurus represents a valuable resource for fishermen's communities in Mexico, although the information of its culture conditions and nutrition is still scarce. Prebiotics are defined as non-digestible components that are metabolized by specific health-promoting bacteria in the host's digestive system, improving the health status and growth performance of cultured aquatic organisms. Fructooligosaccharides (FOS) and mannan oligosaccharides (MOS) are among the most used prebiotics in aquaculture. The present work aimed to determine the effects of dietary FOS and MOS in the growth performance, immune responses, and sexual maturity of juvenile freshwater prawn Macrobrachium acanthurus. Juveniles (0.06 ± 0.001 g) were fed with diets supplemented with a 3 g kg-1 diet of commercial FOS and MOS for 80 days. At the end of the feeding trial, the following indices were calculated: weight gain, specific growth rate, and feed conversion efficiency, as well as superoxide dismutase and lysozyme activities in hepatopancreas tissue. The growth performance, survival, juveniles' protein contents did no show significant differences among the groups. No differences were detected in superoxide dismutase and lysozyme activities among experimental groups. Around day 60 of the feeding trial, the females fed with the prebiotics maturated, and by the end of the trial, several of them were carrying eggs. It seems that prebiotics might have a role in sexual maturation, but further research is necessary to establish if prebiotics influences the early maturation of M. acanthurus.

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The effect of sodium propionate (SP) added to balanced diets was determined for Atractosteus tropicus juveniles on growth, survival, digestive enzyme activity, and expression of genes associated with the immune system. Five treatments (0, 0.5, 1.0, 1.5, and 2.0%) were evaluated in triplicate during a 61-day feeding trial. 180 organisms (3.65 ± 0.12 g) were distributed in 15 tanks of 70 L. The juveniles were fed five times daily with 6% in relation to the biomass of the organisms. Juveniles fed with 0.5% of SP showed higher final weight, absolute weight gain (AWG), and specific growth rate (SGR). Fish fed with 1.5 and 2.0% SP showed highest survival rate (91.6%). Control group (0%) showed greater activity of lipases and trypsin. The highest activity of alkaline proteases and chymotrypsin was found in treatments with 0 and 0.5% SP, while addition of 1.5% of SP promoted highest activity of acid proteases, and highest relative gene expression of ocln, muc2, and nod2. The inclusion of SP in the diet of A. tropicus juveniles may benefit the activity of digestive enzymes, as well as the expression of genes related to the function of intestinal barrier and therefore increasing the survival of organisms.