Morphological study of the gastrointestinal tract of Larimichthys crocea (Acanthopterygii: Perciformes)

The present study aimed to investigate the macroscopic and histological structure of the gastrointestinal tract (GIT) of Larimichthys crocea (Richardson, 1846). It consists of esophagus, stomach regions, pyloric caeca, intestinal regions, and rectum. Sixteen tubular light yellowish pyloric caeca of similar sizes were observed in all individuals. The digestive wall consists of mucosa, submucosa, muscularis, and adventitia. No major differences appeared in the structure of the tunica, epithelial cell types, connective tissues and musculature glands of L. crocea GIT. The mucosal epithelia in the oesophagus has longitudinal branched folds with frontward and hindmost zones. The gastric tunica mucosa has a characteristic folded structure and can be divided into three regions. The intestinal tunica mucosa is characterized by villi structures and numerous mucus-secreting cells. Mucus-secreting goblet cells were strongly positive to AB at pH 2.5 in the oesophagus (excluding gastro-oesophageal junction) and intestine mucosal regions, which indicates an abundance of carboxylate mucins. The surface epithelia of the gastric mucosa is PAS-positive and AB-negative. SEM examination revealed that cells in the epithelium of the esophagus have an unbroken apical layer and goblet cells. The intestinal coefficient (IC) of L. crocea was 0.80 +/- 0.21, consistent with a carnivorous or omnivorous habit. Our study adds the knowledge of the digestive system of L. crocea and might be useful in the management of L. crocea stocks.