Anatomy and histology of the digestive tract and immunolocalization of Npy (orexigenic peptide) in the fish Cichlasoma dimerus (Cichliformes: Cichlidae).

BRECCIA, ANDRÉS; PALMIERI, MÓNICA; DI YORIO, MARÍA P.; BATTISTA, ARIADNA; VISSIO, PAULA; PEREZ SIRKIN, DANIELA

REVISTA DE BIOLOGíA TROPICAL

REVISTA DE BIOLOGIA TROPICAL

Lugar: Turrialba; Año: 2022 vol. 70 p. 307 - 318

0034-7744

Introduction: The digestive tract of Neotropical cichlids has not been deeply studied, and it is a fundamentaltopic for understanding fish physiology, nutrition, trophic associations, and evolution.Objective: To describe anatomically and histologically the digestive tract of the Neotropical cichlid fishCichlasoma dimerus and to immunolocalize the orexigenic peptide (Npy) along the intestine.Methods: We euthanized 14 adult individuals and fixed the organs in Bouin’s solution; we stained 7 μm thickparaffin sections for general description and with Alcian Blue (pH = 2.5, AB) and Periodic acid-Schiff (PAS)to identify acid or neutral glycoconjugates, respectively. Additionally, we performed immunohistochemistry forNpy in 3 adult individuals. We manually counted PAS- and AB-positive cells, and Npy-immunoreactive cellsper fold.Results: There is a short oesophagus, a sac-like stomach, and a tubular intestine with two loops. The oesophagushas a stratified epithelium with a high density of PAS- and AB-positive goblet cells and striated muscle fibersin the tunica muscularis. The stomach mucosa is formed by simple columnar epithelium. The intestine has asimple columnar epithelium, with brush border and interspersed PAS- and AB-positive goblet cells, and Npyimmunoreactive cells. There is an ileorectal valve in the transition between the posterior intestine and the rectum.This last gut portion has goblet cells and a thicker tunica muscularis.Conclusions: C. dimerus shares features with other Neotropical cichlids, but the goblet cells and gastric glandsdistribution seems to be unique for the species. To our understanding, this is the first work to describe Npyimmunoreactive cells distribution in the intestine of a Neotropical cichlid fish.