Comprehensive morpho-histological observation of digestive system and gut content of wild-grunting toadfish, allenbatrachus grunniens (Linnaeus, 1758)

Abstract

The morphology, histology and histochemistry of the digestive system and gut content of the wild-grunting toadfish (Allenbatrachus grunniens) from the estuary of Pranburi River, Thailand, is investigated. The digestive system of A. grunniens is elongated from the oral cavity to the intestine except for the stomach of a sac-shaped type. The length of the elongated intestine has the intestine coefficient (IC) of 0.52 ± 0.1. The digestive tract is composed of four layers: mucosa, submucosa, muscularis and serosa. The longitudinal folds of the esophagus are lined by the stratified mucosal epithelium which contains several large secretory cells. The gastric rugae in both the cardiac and pyloric regions of the stomach are lined with a simple columnar epithelium. The intestine has numerous intestinal folds lined by simple columnar epithelia. Intestinal goblet cells are organised and inserted among the epithelia. The index of relative importance (IRI) suggests that the main food items are a crab group (73.64%) followed by shrimps (10.43%), fishes (8.02%) and other compositions (7.92%). The IC, morpho-histological features of the digestive system and IRI indicate that A. grunniens is a carnivorous fish.