Ultrastructural features of the excurrent ducts of the testis of a wild bird, the cattle egret (Bubulcus ibis)

Abstract

The structure and functions of components of the excurrent ducts of the testis of birds are still poorly understood. Most of the few reports on these ducts are on domesticated avian species. This report on the cattle egret is one of the very few studies on wild birds. Tissues from the ducts of five sexually mature and active male birds were routinely prepared and stained for light and transmission electron microscopy. The epididymis and ductus deferens of the cattle egret are generally similar structurally to those reported for domestic birds, with a number of cellular differences. The epithelium of certain segments of the egret’s rete testis displayed numerous, large intercellular spaces, not usually observed in most domestic avian species. As in the domestic species of birds, the proximal efferent ducts in the cattle egret displayed a robust endocytic apparatus as well as abundant lysosomes, but there were very few heterolysosomes and telolysosomes, which were common in domestic species. The border between the proximal and distal efferent ducts also demonstrated active spermiophagy. In addition to evidence of moderate secretary activities, the presence of extremely large heterolysosomes and telolysosomes also demonstrated the endocytic and digestive ability of cells lining the ductus deferens.

HIGHLIGHTS • Dilated intercellular spaces in the rete epithelium. • Considerable spermiophagy at the junction between the proximal and distal efferent ducts • Numerous coupling organelles involved in the desmosome-mitochondria complexes (DMC) as well as in the (endoplasmic reticulum (ER)–mitochondria encounter structure (ERMES) in the epididymis and ductus deferens. • Dense bodies (lysosomes), heterolysosomes as well as telolysosomes abound in the proximal efferent duct, indicating considerable endocytic and phagocytic activities of luminal materials.