Fine structure of the neck of epididymal spermatozoa of Schreiber’s long-fingered bat (Chiroptera: Mammalia)

The structure of the spermatozoon of the long-fingered bat (Miniopterus schreibersii) was studied using transmission electron microscopy. The neck is characterized by two asymmetrically arranged features that allow the orientation of sections in different planes and therefore aid the interpretation of the structure. There are six segmented columns, two major and four minor, in the anterior 79% of the neck, and it is only posterior to this that the major columns split. One major column is associated with doublets 9,1, and 2, and the other major column, with doublets 5 and 6. The proximal centriole is surrounded by the capitulum and segmented columns, and the distal centriole persists and is apparent in both longitudinal and transverse sections. The central pair of microtubules pass through the distal centriole and terminate at the proximal centriole. A line drawn through the two central microtubules divides the head into left and right halves. Development of the neck begins during early spermiogenesis at which time the two centrioles are associated with the production of the capitulum, segmented columns, and axoneme complex.