Abstract
The present study aimed to investigate the macroscopic and histological structure of the gastrointestinal tract (GIT) of Larimichthyscrocea (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.
Highlights
Morphological studies help in understanding the relationship between physiological and biochemical functions and molecular mechanisms
The body measurements obtained to L. crocea (n = 12) were: body weight (198.79 ± 20.36 g), total body length
The gastrointestinal tract (GIT) of L. crocea consists of the esophagus, stomach regions, pyloric caeca, intestinal regions, and rectum
Summary
Morphological studies help in understanding the relationship between physiological and biochemical functions and molecular mechanisms. Due to various structural differences in the GIT of fish, nutritional studies have been the focus of most research in the field. The large yellow croaker, Larimichthys crocea (Richardson, 1846), known as drums or croakers in reference to the repetitive drumming echoes they make, belong to Sciaenidae (Ramcharitar et al 2006). This important carnivorous marine fish species is cultivated in many Asian countries, China (Feng and Cao 1979). In aquaculture, studying the anatomical and histological characteristics of the GIT of fish may help to understand the development of pathological conditions, to devise nutritional formulations and promote the management of L. crocea stocks
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