Morphological changes in the efferent ducts during the main phases of the reproductive cycle of birds.

Abstract

The changes that take place in the efferent ducts during the major phases of the reproductive cycle of birds were studied morphologically using standard histological, morphometric, and ultrastructural methods in prepuberal, sexually mature and sexually active, and sexually mature but sexually inactive domestic fowl (Gallus domesticus), drake (Anas platyrhynchos), and guinea fowl (Numida meleagris). Profound structural and dimensional changes occurred in both segments (proximal and distal) of the efferent ducts and, in particular, in the nonciliated (Type I) cell of the proximal duct of sexually mature but inactive birds. The subapical tubulovacuolar system was markedly atrophic in nonciliated (Types I and II) cells and the numerous round dense globules of Type I cells that normally occurred in sexually active birds were replaced by fewer and more pleomorphic bodies containing lipofuscin granules in sexually resting birds. Lipid droplets, few and extremely large in inactive drakes but numerous and smaller in size in guinea fowls and domestic fowls, occurred in the Type I cell at both infra- and supranuclear levels of resting but not in prepuberal or sexually active birds. Ciliated cells in both segments of the ducts exhibited fewer and less profound phase-dependent changes ultrastructurally. Generally, the Type I cells of the proximal efferent duct appeared to be more sensitive to androgen deprivation than the Type II cell of the distal efferent duct or ciliated cells in both ducts. These morphologically phase-dependent features of the efferent ducts of birds may be used, together with or independent of testicular changes, in the determination of the status of the testis and epididymis of a male bird with regard to the reproductive cycle, especially in seasonally breeding species.