Biflagellate spermatozoon of the poison-dart frogs Epipedobates femoralis and Colostethus sp. (Anura, Dendrobatidae)

Abstract

This study describes the spermatozoa of the dendrobatids Epipedobates femoralis and Colostethus sp. using light and transmission electron microscopy. Both species possess a biflagellate spermatozoon, an unusual characteristic only previously reported in two anuran species belonging to the families Leptodactylidae and Racophoridae. The acrosomal complex of both species consists of a conical acrosomal vesicle and a subacrosomal cone, both of which cover the anterior portion of the nucleus, but to differing extents. In the midpiece, the centrioles are disposed parallel to each other and to the cell axis and give rise to two axonemes. Two paraxonemal rods were also seen entering the nuclear fossa. Both flagella are surrounded by a single mitochondrial collar. Each flagellum is formed by an axial fiber connected to the axoneme by an axial sheath; juxta-axonemal fibers are absent. Our data seem to support that Epipedobates femoralis should be placed in a separate clade possibly related to Colosthetus and that these two genera may not be monophyletic. © 2002 Wiley-Liss, Inc.