Marine bivalve hatchery productivity is continuously challenged by apparition and propagation of new diseases, mainly those related to vibriosis. Disinfectants and antibiotics are frequently overused to prevent pathogen presence, generating a potential negative impact on the environment. Recently, the use of highly diluted compounds with immunostimulant properties in marine organisms has been trailed successfully to activate the self-protection mechanisms of marine bivalves. Despite their potential as immunostimulants, little is known about their way of action. To understand their effect, a comparative transcriptomic analysis was performed with Argopecten ventricosus juveniles. The experimental design consisted of four treatments formulated from pathogenic Vibrio lysates at two dilutions: [(T1) Vibrio parahaemolyticus and Vibrio alginolyticus 1D; (T2) V. parahaemolyticus and V. alginolyticus 7C]; minerals [(T3) PhA+SiT 7C], scorpion venom [(T4) ViT 31C]; and one control (C1) hydro-alcoholic solution (ethanol 1%). The RNA sequencing (RNAseq) analysis showed a higher modulation of differentially expressed genes (DEG) in mantle tissue compared to gill tissue. The scallops that showed a higher number of DEG related to immune response in mantle tissue corresponded to T1 (V. parahaemolyticus and V. alginolyticus lysate) and T3 (Silicea terra®-Phosphoric acid®). The transcriptome analysis allowed understanding some interactions between A. ventricosus juveniles and highly-diluted treatments.

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.

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