CONICET | Buscador de Institutos y Recursos Humanos

he sperm cell ultrastructure provides important insights into fertilization3 mechanism and phylogenetic relationships. However, it has rarely been included in4 phylogenetic analysis of anurans. This work aims to characterize the ultrastructure of5 the mature spermatozoa in the genus Leptodactylus, to relate the observed variations6 with the different reproductive strategies and define characters to optimize in a previously published cladogram of this genus. We studied 24 species distributed into8 four groups: L. fuscus, L. latrans, L. melanonotus and L. pentadactylus where9 morphological characters were coded and optimized using the parsimony method. The10 analyzed spermatozoa have three conspicuous regions: head, middle zone and tail.11 Regarding the head, a short and thin acrosomal vesicle is observed in species of the12 groups L. fuscus and L. pentadactylus, but it is long and thick in most of the studied13 species of the groups L. latrans and L. melanonotus. Furthermore, nuclear lacunae are14 observed in most species. In relation to the middle zone, an organelle-free cytoplasmic15 region was observed in species of the groups L. fuscus, L. latrans and L. melanonotus,16 but it was absent in species of the L. pentadactylus group. Most of the studied species17 showed a mitochondrial collar and cytoplasmic canal. Finally, in the tail all of the species18 have an axoneme, an undulating membrane, and an axial fiber, but only some have a19 juxtaxonemal fiber. Results show the thick acrosomal vesicle as a synapomorphy of the20 clade L. latrans + L. melanonotus. The presence of nuclear lacunae and the absence of21 a sub-acrosomal cone optimizes as a putative synapomorphy of Leptodactylidae. In22 conclusion, we observed a relationship between reproductive strategies and23 spermatozoa morphology, which also supports the phylogenetic relationships in this24 genus.