Abstract: Objective To observe and analyze the structure and composition of intestinal mucosal barrier in zebrafish (Brachydanio rerio). Methods The morphology was observed by transmission electron microscopy, histochemistry and immunohistochemistry were undertaken on the organizational structure and cell composition of intestinal mucosal barrier in the zebrafish. Results The zebrafish intestinal absorptive cells had developed junctional complex, top-down followed by visible tight junctions, intermediate connections, and desmosomes. They form a closed mechanical barrier. The intestinal mucosa absorption cell distributed between rich goblet cells, especially in the largest number of the intestine. PAS reaction was significant positive. The goblet cells were the chemical major cells for the intestinal mucosa barrier, whose secretions in the intestinal cavity surface to form a layer of mucus layer. Their intestinal intraepithelial lymphocytes and mast cells were the intestinal mucosa of primary immune cells. The mucosal epithelium of endocrine cells in both open and closed, striated border developed in a linear (or membrane) in the intestinal epithelium lining the cavity surface. Conclusions The intestinal mucosa barrier system of zebrafish consisted of relative complete mechanical barrier, chemical barrier and immune barrier structure. So zebrafish could be used as animal models for the study of intestinal mucosal barrier.

Key words: Zebrafish, Intestine, Mucosal barrier, Structure