The ultrastructure of the spermatozoa of the lizard Micrablepharus maximiliani (Squamata, Gymnophthalmidae), with considerations on the use of sperm ultrastructure characters in phylogenetic reconstruction

We describe, for the first time, the ultrastructure of the spermatozoa of a member of the family Gymnophthalmidae. Mature spermatozoa of Micrablepharus maximiliani are characterized by: acrosome circular in transverse section, absence of perforatorial base plate, perforatorial tip pointed, absence of epinuclear lucent zone, midpiece short, mitochondria in transverse section forming a circlet interrupted by dense bodies, trapezoid mitochondria, dense bodies solid and arranged in regular rings and linear series, linear mitochondrial cristae, rounded nuclear shoulders, elongate nuclear shape, absence of endonuclear canal, fibers 3 and 8 enlarged, absence of multilaminar membranes, and fibrous sheath in midpiece. Phylogenetic analysis of the Squamata after the addition of the Gymnophthalmidae to the ultrastructure data set previously published by Jamieson, resulted in 8733 equally parsimonious trees that conflicted with phylogenetic hypotheses derived from morphological data sets. An analysis of tree-length distribution skewness, however, indicated that the ultrastructure data set contains significant phylogenetic information. We suggest that rates of evolution for spermatozoa ultrastructure characters might be higher than currently thought, resulting in incongruent tree topologies derived from distinct data sets. Finally, we suggest that because only optimal trees were selected, the heterogeneity between the data sets might be apparent and more analyses are necessary to evaluate the nature and degree of the heterogeneity between them.