Morphology and ultrastructure of the spermatozoa of Scaptotrigona xanthotricha moure (Hymenoptera, Apidae, Meliponini)

ABSTRACT

The spermatozoa of Scaptotrigona xanthotricha, a stingless bee under extinction in some Brazilian states, are described. Seminal vesicles of adult males were dissected and processed for light and transmission electron microscopy. The spermatozoa were long (about 90 µm) and slender. The head consisted of an acrosome formed by an acrosomal vesicle covering the perforatorium and the nucleus. The latter was homogeneous, compact and about 11 µm long. The flagellum consisted of an axoneme, with the typical 9+9+2 microtubule arrangement that began just below the nuclear base. The two mitochondrial derivatives were asymmetric in length and diameter, and had two accessory bodies. The nucleus was attached to the flagellum by a centriolar adjunct. These results indicate that the spermatozoa of S. xanthotricha are similar to those of other Meliponini but differ markedly from other insect groups. The ultrastructure of hymenopteran spermatozoa may be a useful character for phylogenetic studies.