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

Histological information of digestive system of fish in Family Hemiraphidae has never been reported. Although the malayan halfbeak Dermogenys pusilla is a carnivorous hemiraphid native to Southeast Asia, the structure of its digestive information is not known. Here is the first report on basic histology of digestive system of D. pusilla, as a representative from Family Hemiramphidae. All specimens (n=20) were collected in October 2016 from Pranburi River estuary, Thailand. The digestive system of D. pusilla was divided into digestive tract and accessory organs (liver and pancreas). The mouth part of this fish was sub-terminal. It had elongated oral cavity. Epithelial mucosa of the oral cavity was covered with stratified epithelium with mucous secreting cells. The epithelial pharynx was similar to that of oral cavity with infiltration of prominent pharynge-al teeth. Although this hemiramphid fish had no stomach, the long intestine was divided into anterior and posterior intestines. All intestinal regions were lined with simple columnar epithelium and goblet cells; however, the goblet cell abundance in the posterior intestine was greater than in the anterior intestine. Several polyhedral hepatocytes of liver tissue appeared to be distinctive sinusoid, 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 carnivorous nature of this fish.