Structural and ultrastructural studies of male reproductive tract and spermatozoa in Xylocopa frontalis (Hymenoptera, Apidae)

Abstract

AbstractFiorillo, B. S., Zama, U., Lino‐Neto, J. and Báo, S. N. 2010. Structural and ultrastructural studies of male reproductive tract and spermatozoa in Xylocopa frontalis (Hymenoptera, Apidae). —Acta Zoologica (Stockholm) 91: 176–183.In Xylocopa frontalis the reproductive tract is composed of testes, deferent ducts, seminal vesicles, accessory glands and an ejaculatory duct. Each testis comprises four testicular tubules in which multiple cysts are present containing approximately 64 spermatozoa per cyst. The seminal vesicle consists of an epithelium, a thick basement lamina and a muscular external sheet. In the luminal region some vesicles can be observed; however, the epithelial cells of the seminal vesicle do not display morphological features associated with secretory functions. The spermatozoa, measuring approximately 260 µm long, are similar to the hymenopteran pattern. The head region consists of an acrosome with an inner perforatorium that penetrates an asymmetrical nuclear tip. The nucleus is linear, electron‐dense and its posterior tip projects into the beginning of the axoneme. The centriolar adjunct is asymmetric with many electron‐lucent lacunae interspersed throughout. The axoneme has the 9 + 9 + 2 pattern of microtubules and in the posterior region the central microtubules finish first, followed by the doublets and finally the accessory microtubules. The mitochondrial derivatives are asymmetric in both length and diameter with paracrystalline material present only in the larger one. These features may be useful characters for taxonomy and phylogenetic studies.