Meeting Abstract

S8-1.5  Saturday, Jan. 5  Sperm Morphology and its Bearing on Decapod Phylogeny TUDGE, Chris; American University, Washington DC ctudge@american.edu

The use of spermatozoal characters in helping to elucidate animal phylogeny (spermiocladistics – Jamieson, 1991) has recently been successfully applied in the decapod crustaceans. Most of the decapod taxa investigated for sperm morphology are published in the last 17 years and cover 100% of the decapod infraorders, 50% of the families, 10% of the extant genera, but only 2% of the described, extant species. There is great diversity in sperm morphology within the Crustacea but overall the decapod spermatozoa are quite conservative in comparison. Still, it is difficult to describe a typical decapod sperm cell. Decapod sperm are unusual for several reasons: 1) they are aflagellate (lack a true 9 + 2 flagellum), although microtubular processes are often present; 2) there is no reliable record of motility of any individual sperm cells; 3) the acrosome vesicle is not Golgi-derived like all other described acrosomes of sperm in the animal kingdom, instead it is derived from endoplasmic reticulum vesicles; 4) the decapod sperm nuclear protein is unique with all other animal sperm nuclear proteins falling into four other categories; and 5) the sperm nucleus is composed of diffuse, filamentous, heterogeneous chromatin fibers rather than being uniformly dense. Spermatozoal characters are surveyed across the investigated decapod crustaceans highlighting those of phylogenetic utility such as acrosome vesicle presence, shape, dimensions and size, and internal complexity, nuclear morphology and shape, and microtubular arm presence, number, origin and composition. Examples of spermatozoal characters, or suites of characters, that define particular decapod taxa are also provided. Areas of future productive research in this field are identified.