Morphological and histochemical characterization of the digestive tract of the puffer fish Sphoeroides testudineus (Linnaeus 1758) (Tetraodontiformes: Tetraodontidae)

Abstract

Morphological analysis of the digestive tract of Sphoeroides testudineus showed an esophagus with an anterior and a posterior portion, the abdominal pouch. No stomach was observed between the abdominal pouch and the intestine. The intestine was arranged in three segments and two loops, and the distal portion had the rectum opening into the anus. Histochemical analyses showed that the esophagus secreted acid mucosecretions, and that there was a qualitative increase in goblet cells from the proximal to distal area of the intestine. The rectum showed cells secreting acid and neutral mucus. Given these features, this species presents a morphology which creates a link between its ecology and behavior.

Morphological characterisation of the digestive tract of the catfish Lophiosilurus alexandri Steindachner, 1876 (Siluriformes, Pseudopimelodidae)

“…The digestive tract of fish is a widely studied topic, from the classic works of Al‐Hussaini (); Angelescu and Gneri () to recent works, such as Germano et al. (); Santos, Arantes, Santiago, and Santos (), Santos, Arantes, Pessali, and Santos (); Fagundes, Rotundo, and Mari (); Andrade, Guimarães, Rotundo, and Mari (). These studies provide crucial information for the cultivation and conservation of species (Santos, Arantes, Santiago et al., ; Wilson & Castro, ).…”

Comparative histochemical analysis of intestinal glycoconjugates in the blunthead pufferfish Sphoeroides pachygaster and grey triggerfish Balistes capriscus (Teleostei: Tetraodontiformes)

“…The tetraodontiform digestive system also presents some remarkably distinctive features, such as jawbones with cutting edges instead of true teeth and a stomach modified to inflate the body in pufferfishes (Tetraodontidae) and porcupinefishes (Diodontidae; Wilson & Castro, ). In these species, the stomach has completely lost its digestive function and forms an abdominal pouch that is filled with water in case of danger: the mucosal epithelium is of a stratified squamous type with interspersed muciparous cells, similar to the oesophageal one and the gastric glands are lacking (Fagundes et al ., ). In addition, they have lost the gastric proton pump genes atp4a and atp4b (involved in the production of gastric juice) and have retained a single pepsinogen gene that is not expressed in the stomach but only in the skin for defence purposes (Castro et al ., ).…”

“…In other families, such as triggerfishes (Balistidae) or sunfishes (Molidae) a true functional stomach is retained (Chanet et al ., ; Chiba et al ., ). At the opposite extreme, the intestine of Tetraodontiformes has diverged little from the plesiomorphic teleost condition (Chiba et al ., ; Fagundes et al ., ). In general, the tetraodontiform intestine lacks caeca, is relatively short (except for the Ostraciidae and Molidae) and is differentiated oro‐aborally into a small intestine and rectum (Breder & Clark, ).…”

“…Very little is known about the composition of gastrointestinal mucins in these fishes. In the checkered pufferfish Sphoeroides testudineus (L. 1758) conventional histochemistry [periodic acid–Schiff reagent (PAS), alcian blue (AB) pH 0.5, AB pH 2.5 stains] indicates that goblet cells in both the small intestine and the rectum secrete neutral and acidic glycans (Fagundes et al ., ). Details about glycan composition, demonstrated by in situ techniques such as lectin binding, are apparently lacking, despite several studies describing extensive variation among fishes and the involvement of mucins in several gastrointestinal functions, such as lubrication, protection against mechanical and chemical damage, modulation of food and oxygen absorption, osmotic exchanges and interactions with symbionts and pathogens (Desantis et al ., ; Díaz et al ., ; Domeneghini et al ., ; Pedini et al ., ).…”

“…In general, the tetraodontiform intestine lacks caeca, is relatively short (except for the Ostraciidae and Molidae) and is differentiated oro‐aborally into a small intestine and rectum (Breder & Clark, ). The intestinal epithelium is a high simple columnar type, comprising mainly enterocytes with a high brush border and goblet cells (Chiba et al ., ; Fagundes et al ., ; Mohsin, ; Zhenzhen et al ., ). Very little is known about the composition of gastrointestinal mucins in these fishes.…”