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Molecular analysis of the 16S rDNA of the intestinal microbiota of whiteleg shrimp Litopenaeus vannamei was examined to investigate the effect of a Bacillus mix (Bacillus endophyticus YC3-b, Bacillus endophyticus C2-2, Bacillus tequilensisYC5-2) and the commercial probiotic (Alibio(®)) on intestinal bacterial communities and resistance to Vibrio infection. PCR and single strain conformation polymorphism (SSCP) analyses were then performed on DNA extracted directly from guts. Injection of shrimp with V. parahaemolyticus at 2.5 × 10(5) CFU g(-1) per shrimp followed 168 h after inoculation with Bacillus mix or the Alibio probiotic or the positive control. Diversity analyses showed that the bacterial community resulting from the Bacillus mix had the highest diversity and evenness and the bacterial community of the control had the lowest diversity. The bacterial community treated with probiotics mainly consisted of α- and γ-proteobacteria, fusobacteria, sphingobacteria, and flavobacteria, while the control mainly consisted of α-proteobacteria and flavobacteria. Differences were grouped using principal component analyses of PCR-SSCP of the microbiota, according to the time of inoculation. In Vibrio parahaemolyticus-infected shrimp, the Bacillus mix (~33 %) induced a significant increase in survival compared to Alibio (~21 %) and the control (~9 %). We conclude that administration of the Bacillus mix induced modulation of the intestinal microbiota of L. vannamei and increased its resistance to V. parahaemolyticus.

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This study describes the expression of genes that encode digestive enzymes (trypsin, pepsinogen, maltase-glucoamylase, sucrase-isomaltase, alkaline phosphatase and leucine aminopeptidase) using qRT-PCR in 0-to 7-day post-hatching (dph) chame (Dormitator latifrons). Additionally, adults liver and intestine were analysed for enzyme expression.Results showed that transcripts for all enzymes are present in both adult and larvae tissues. In adults, the expression of maltase-glucoamylase and sucrose-isomaltase showed the highest values in the middle intestine, while the liver and anterior and posterior intestine showed low expression levels. Other enzymes showed low expression in all tissues, with the exception of leucine aminopeptidase, which showed high expression in liver. In larvae whole-body samples of D. latifrons, maltase-glucoamylase and sucrose-isomaltase showed the highest expression from 3 to 5 dph, while other enzymes maintained low levels from hatching to 7 dph. The highest expression of disaccharidases such as maltaseglucoamylase and sucrose-isomaltase corresponded to the beginning of exogenous feeding, suggesting that this species exhibits an herbivorous profile. However, the presence of proteolytic enzymes may indicate that D. latifrons is programmed to be able to digest other substrates. This information will contribute to the development of larval feeding protocols to produce chame juveniles in laboratory conditions, as prior larval feeding essays have not been successful, using either live feeds or commercial fish larval diets. K E Y W O R D S chame, digestive enzyme, Dormitator latifrons, gene expression How to cite this article: Morelos-Castro, Román-Reyes JC, Luis-Villaseñor IE, Ramírez-Pérez JS, Rodríguez-Montes de Oca GA. Expression analyses of digestive enzymes during early development and in adults of the chame fish Dormitator latifrons. Aquac Res. 2020;51:265-275. https ://doi.