Spermiogenesis in the cattle egret (Bubulcus ibis). (February 2021)

• Record Type: Journal Article
• Authors: Roopnarine, Narindra H.; Gupta, Sunil K.; Plessis, Lizette du; Aire, Tom A.
• Is Part Of: Tissue & cell. Volume 68(2021)
• Publication Date: 2021-02
• Subjects: Cattle egret (Bubulcus ibis) -- Morphogenic variations -- Pelecaniformes -- Spermatid differentiation -- Ultrastructure -- Wild non-passerine; Cytology -- Periodicals; 571.5
• DOI: 10.1016/j.tice.2020.101457
• Languages: English
• ISSNs: 0040-8166

Abstract

Highlights: Variations in acrosomal and nuclear morphogenesis in a wild non-passerine bird, the Cattle egret. Spermiogenesis described in twelve (12) steps. The acrosome transforms from an oval to a smooth bullet-shape, with a bluntly rounded apex and a wider, flat, base. The acrosome neither overlaps nor indents the apex of the nucleus. Neither the circular manchette nor perforatorium (acrosomal rod) develops. Abstract: Avian species comprise more than half of all vertebrates yet there is a dearth of information regarding spermatid development in this class of animals. This report of spermiogenesis in the cattle egret, Bubulcus ibis, is the first in the order Pelecaniformes. Five sexually mature and reproductively active male cattle egrets were captured in the wild, humanely euthanized, the reproductive organs dissected out, and tissues from the testes routinely prepared for transmission electron microscopy. Twelve steps of spermatid development, using the step-wise system, were determined. Acrosomogenesis in the egret results in a relatively short, solid, bullet-shaped acrosome that ends bluntly anteriorly and flat posteriorly or basally. The nucleus displays remarkable morphological changes, with the anterior end of the mature spermatid becoming flat, lacking a rostrum and an endonuclear canal. A perforatorium does not develop. It is noteworthy that a longitudinal, but not a circular, manchette develops during spermiogenesis in this bird. The proximal centriole is attached to the nucleus, at the implantation fossa, by means of well-formed, electron dense struts of material. An amorphous fibrous sheath develops in the principal piece. The interesting development and peculiar features of the acrosome and nucleus, as well as the absence of the perforatorium and circular manchette in the spermatozoon of the cattle egret, may be of phylogenetic significance.