Histological observation of digestive system of malayan halfbeak, Dermogenys pusilla (Kuhl & van Hasselt, 1823) during juvenile stage from Thailand

Abstract

The histological information a digestive system has never been reported in the Hemiraphids. Here, we first observed a basic histology of digestive system of Dermogenys pusilla, as a representative hemiramphid fish from Family Hemiramphidae. All specimens (n = 20) were collected on October 2016 from Estuary Pranburi River, Thailand. The structural evidence of the digestive system in D. pusilla was divided into the digestive tract and accessory organs (liver and pancreas). The mouth of this fish was a sub-terminal feature, which has elongated shape oral cavity. Epithelial mucosa of the oral cavity was covered with stratified epithelium inserting the mucous secreting cells. The epithelial pharynx was similar to that of oral cavity with infiltration of prominent pharyngeal teeth. Although this hemiramphid fish had no stomach, the long intestine was divided into anterior and posterior intestines. All intestinal regions were lined with a simple columnar epithelium and goblet cells; however, the abundance of the goblet cells in the posterior intestine was greater than the anterior intestine under comparative histological investigation. Several polyhedral hepatocytes of liver tissue in D. pusilla were distinguished by sinusoids that could be distinctly located among hepatocytes, whereas pancreatic parenchyma usually contained clusters of pyramidal cells in the acini. The pancreatic cells also contained large eosinophilic zymogen granules. In the present study, we showed histological characteristics of digestive system of D. pusilla, implying that this fish was a carnivorous fish species.