Actin and major sperm protein in spermatozoa of a nematode, Graphidium strigosum (Strongylida : Trichostrongylidae)

In most amoeboid cells, the main protein involved in motility is actin. Nem atode sperm are an exception, and their amoeboid motility is based on major sperm protein (MSP). We have studied the localization of actin and MSP in spermatids and spermatozoa of Graphidium strigosum (Dujardin, 1845), a spec ies which has elongate male germ cells in which organelles are easily ident ified. Electrophoreses of G. strigosum sperm proteins indicate that the mai n protein band, about 15 kDa in molecular weight, is specifically recognize d by an anti-MSP polyclonal antibody developed against MSP of Caenorhabditi s elegans (Burke and Ward 1983). Actin is present in small quantities. Immu nocytochemical observations reveal that actin and MSP have an identical loc alization in precise areas of the male germ cells. Spermatids are labelled as dots around a central unlabelled zone, and spermatozoa are labelled only at the level of the anterior cap. Observations in G. strigosum are similar to that previously obtained in Heligmosomoides polygyrus (Mansir and Justi ne 1996). Go-localization of actin and MSP in the anterior cap of the sperm atozoon, the region associated with pseudopod production, does not demonstr ate directly that actin is involved in amoeboid movements, but shows that t he role of actin in the cytoskeleton of nematode sperm should be re-investi gated.