Administration of Three Autochthonous Bacillus subtilis Strains Induce Early Appearance of Gastric Glands and Vestiges of Pylorus in Piaractus mesopotamicus Larvae

Abstract

Autochthonous microorganisms as probiotics are a novel alternative to antibiotics. The genus Bacillus is highly used by its ability to survive on adverse conditions. Piaractus mesopotamicus, a native fish, is the most produced specie in Argentinian aquaculture. The low level of knowledge, high stress conditions and demand of animals led to a deficit in the number of larvae and fry. The aim of this study was to evaluate the probiotic effect of previously selected autochthonous Bacillus on biometrical parameters of P. mesopotamicus larvae when administered together in a combined suspension in different doses and stages. Results showed that the bacterial administration did not cause significant effects on the variables evaluated. However, the dose containing 6 × 107 CFU L-1 of each strain showed the highest average values of P. mesopotamicus biological parameters, regardless the stage of administration. Histological evaluations of animals administered with this dose did not showed adverse effects and indicated the capability of this dose, administered in a particularly period of time, to stimulate the early appearance of gastric glands, vestiges of what would be the pylorus and a higher development of liver. Thus, we proposed the safe use of this dose in a combined probiotic mixture to be studied in further assays.

Autochthonous probiotic mixture improves biometrical parameters of larvae of Piaractus mesopotamicus (Caracidae, Characiforme, Teleostei)

“…In opposition to our findings, AZIMIRAD et al (2016) reported significant increments in both, total microorganisms and LAB counts, accompanied by significant increments in weight gain when administering Pediococcus acidilactici and fructooligo saccharide to angelfish (Pterophyllum scalare). Increment in the number of sporulated microorganisms after its administration to aquatic animals was previously described by our group (GUIDOLI et al, 2016a). Also, JAMALI et al (2015) andCHAI et al (2016) demonstrated that shrimps administered with higher doses of Bacillus strains presented higher counts of sporulated microorganisms in their guts.…”

“…Bacterial strains were isolated from Piaractus mesopotamicus, selected by their in-vitro expression of beneficial properties, genetically identified, registered in culture collections, tested in vivo individually and protected by patent aims (CONICET & UNNE, 2013;GUIDOLI et al, 2015GUIDOLI et al, , 2016aGUIDOLI et al, and 2016b. Lactic acid bacteria (LAB) and Bacillus cells were grown at 37°C in LAPTg (1% yeast extract, 1.5% peptone, 1% tryptone, 1% glucose, 0.1% Tween 80; pH 7.2) and Nutrient Broth (Britania © ), respectively.…”

“…Bacterial cells were obtained by centrifugation, and re-suspended in saline solution at the desired concentrations. The multi-strain suspension (MIX) contains the eight strains combined in previously determined concentrations (GUIDOLI et al, 2016a and2016b) (Table 1). …”

“…The results of these tests allowed us to select the most efficient doses of each microorganism for the formulation of a multi strain probiotic product for future assays (GUIDOLI et al, 2015(GUIDOLI et al, , 2016a(GUIDOLI et al, and 2016b.…”