Cyclic variation of the oviduct structure of Boulengerula taitana, an oviparous species of Gymnophiona: morphological changes, proliferation and apoptosis

Abstract Functioning of the amphibian oviduct is the subject of many studies, but detailed understanding of caecilian reproduction exists for very few species. In this study, a description is made of morphological changes of the oviduct of the caecilian Boulengerula taitana throughout the year, using conventional histology and immunohistochemistry. The reproductive cycle of this little-known species, originating from the Taita Hills in southeast Kenya, is annual. During the reproductive period (November–February), both lamina propria and the epithelium of the oviduct exhibit a maximum degree of development. The epithelial mucosa is more secretory and the cilia cells are abundant. Histological analysis shows the distribution of the different type of cells according to a specific pattern in the pars recta, pars convoluta and pars utera. Evaluation of proliferative (Ki-67 positive cells) and apoptotic cells (TUNEL and Apostain assays) into the different tissues brings out cyclic modifications of the lamina propria and epithelial cells throughout a seasonal cycle. The results demonstrate that the balance between cell proliferation and apoptosis reflects the functionality of the oviduct during the sexual cycle.