The ultrastructure of the spermatozoa of Epipedobates flavopictus (Amphibia, Anura, Dendrobatidae), with comments on its evolutionary significance

Abstract

We describe, for the first time, the spermatozoon ultrastructure of a dendrobatid frog, Epipedobates flavopictus. Mature spermatozoa of E. flavopictus are filiform, with a moderately curved head and a proportionally short tail. The acrosomal vesicle is a conical structure that covers the nucleus for a considerable distance. A homogeneous subacrosomal cone lies between the acrosome vesicle and the nucleus. The nucleus contains a nuclear space at its anterior end, and electron-lucent spaces and inclusions. No perforatorium is present. In the midpiece, the proximal centriole is housed inside a deep nuclear fossa. Mitochondria are scattered around the posterior end of the nucleus and inside the undulating membrane in the anterior portion of the tail. In transverse section the tail is formed by an U-shaped axial fiber connected to the axoneme through an axial sheath, which supports the undulating membrane. The juxta-axonemal fiber is absent. The spermatozoon of E. flavopictus has several characteristics not observed before in any anurans, such as a curved axial fiber, absence of a juxta-axonemal fiber, and presence of mitochondria in the typical undulating membrane. Our results endorse the view that, in anurans, the conical perforatorium and subacrosomal cone are homologous and that Dendrobatidae should be grouped within Bufonoidea rather than Ranoidea.

A novel mechanism of sperm motility in a viscous environment: Corkscrew‐shaped spermatozoa cruise by spinning

“…In the case of amphibians, frogs that fertilize in fresh water, such as Rana, tend to have simple sperm morphology [Poirier and Spink, 1971]. In contrast, urodeles [Picheral, 1979] and frogs with internal or terrestrial fertilization [Garda et al, 2002] tend to have more complicated sperm morphology.…”

Chromosome analysis of five Brazilian species of poison frogs (Anura: Dendrobatidae)

“…Studies on morphology, behaviour, sperm ultrastructure, cytogenetics and molecular analyses have been used to study dendrobatids in an attempt to elucidate their intra-family and inter-family relationships (Toft 1995;Zimmermann and Zimmermann 1988;Aguiar et al 2002Aguiar et al , 2003Aguiar et al , 2004aGarda et al 2002;Veiga-Menoncello et al 2003a,b, 2006a,b, 2007.…”

An ultrastructural comparative study of the sperm of Hyla pseudopseudis, Scinax rostratus, and S. squalirostris (Amphibia: Anura: Hylidae)

“…Several detailed studies on many taxa, including fishes (Jamieson 1991;Tanaka et al 1995), amphibians Lee and Jamieson 1993;Meyer et al 1997;Garda et al 2002), reptiles (Jamieson 1995;Teixeira et al 1999), annelids (Rouse and Jamieson 1987), and mollusks (Buckland-Nicks 1995), revealed that sperm ultrastructure provides an alternative source of useful characters for systematic purposes. According to Teixeira et al (1999), sperm ultrastructural characters contain significant phylogenetic information that can be profitably used in phylogenetic analyses for reptiles.…”