Zoological Studies

Spermatozoon Ultrastructure of Prisogaster niger (Wood, 1828) (Mollusca: Vetigastropoda): Supporting Affinities between the Prisogasterinae and Turbininae

Gonzalo A. Collado, Claudio L. Correa, Marco A. Méndez, and Donald I. Brown (2011) Recent phylogenetic analyses of Vetigastropoda using DNA sequences suggest that the subfamilies Prisogasterinae and Turbininae form a monophyletic group within the recently redefined family Turbinidae. To verify this systematic arrangement, we describe the spermatozoon ultrastructure of Prisogaster niger, a reproductive anatomical component that has been successfully used in phylogenetic investigations of vetigastropods, and compare the results with previously published information from other trochoidean taxa based on a phylogeny of the group. Prisogaster niger has a primitive spermatozoon, or aquaspermatozoon, typical of invertebrates with external fertilization. The sperm has a conical pointed acrosome which is > 50% of the head length, a barrel-shaped nucleus, a midpiece with 2 centrioles and 5 spherical mitochondria, and a simple flagellum with 9+2 axonemes. Compared to other trochoideans, the spermatozoon of P. niger is notably similar in structure to those of the Turbininae, with shared synapomorphies (e.g., an elongated conical pointed acrosome and a broad subacrosomal space) that suggest a close relationship between the Prisogasterinae and this subfamily, and that Prisogaster may have originated from an ancestral Turbininae.