Comparative histological description of the intestine in platyfish (Xiphophorus maculatus) and swordtail fish (Xiphophorus helleri).

This study aimed to provide a comprehensive analysis of the histological structure of intestinal tissues of platyfish (Xiphophorus maculatus) and swordtail fish (Xiphophorus helleri). Specifically, the objectives were: (1) to compare the structural adaptations of their intestines related to their distinct feeding habits, diet, and digestive strategies; and (2) to explore their potential as animal models for intestinal disease research. Through detailed examination of tissue morphology, cell types, and structural features, this study found that both species lack a stomach, with the intestine directly connected to the esophagus. Additionally, this study proposes a new division of the intestine into anterior and posterior segments based on distinct histological characteristics. The anterior segment may be adapted for temporary food storage and digestion and was characterized by elongated epithelial cells and thin intestinal folds. In contrast, the posterior segment displayed shorter villi and higher concentrations of goblet cells. This study is the first to describe in detail the intestinal morphology of platyfish and swordtail fish. These findings contribute significantly to the understanding of the comparative anatomy and physiology of these fish species, highlighting their potential as valuable models for intestinal biology research.