Ultrastructural Organization of Epididymis in the Cattle Egret (Bubulcus ibis) During Breeding Season.

This study presents an ultrastructural analysis of the epididymal epithelium in the cattle egret (Bubulcus ibis), aimed at elucidating its cellular diversity and regional specialization. Using transmission electron microscopy, we examined the proximal and caudal regions of the epididymis to identify and compare constituent cell types based on established morphological criteria. Principal cells were distinguished by large euchromatic nuclei and abundant rough endoplasmic reticulum, narrow cells by elongated nuclei and slender cytoplasmic profiles, and clear cells by pale cytoplasm with endocytic vesicles. Myeloid cells exhibited irregular nuclear morphology and cytoplasmic vacuolation, with two morphologically distinct populations observed. The distribution of these cell types across proximal and distal regions underscores the compartmentalization necessary for sperm maturation, storage and protection. Specialized organelles, including large mitochondria, secretory granules and rough endoplasmic reticulum, highlight the metabolic and secretory demands placed on the epithelium. Observations of apoptotic bodies, immune cell heterogeneity and clearance mechanisms suggest ongoing cellular turnover and possible immune involvement. However, given the descriptive nature of this study and the absence of complementary molecular or immunohistochemical data, interpretations regarding immune surveillance must remain tentative. Collectively, these findings provide the first detailed ultrastructural description of the cattle egret epididymis, contributing to a broader understanding of avian reproductive physiology and comparative anatomy. Future studies integrating advanced imaging, immunohistochemistry and molecular profiling will be essential to validate the hypothesized roles of these cell populations and to clarify their contributions to male fertility and reproductive health.