The Cytoskeletal Proteins Actin and Tubulin in the Spermatozoa of Four Decapod Crabs (Crustacea, Decapoda)

The mature spermatozoa of four species of European decapod crabs (Clibanarius erythropus, Maja squinado, Cancer pagurus and Potamon fluviatile) have been investigated using indirect immuno‐fluorescence techniques for the presence of the cytoskeletal proteins actin and tubulin. Indirect immunofluorescence labelling with monoclonal anti‐actin antibody and three different monoclonal anti‐tubulin antibodies indicate that actin is present in the spermatozoa of all four species, but tubulins are restricted to the two species with microtubular arms, Clibanarius and Maja. The pattern of actin fluorescence varies between the spermatozoa of the four species, with Maja and Cancer showing intense fluorescence in the acrosome vesicle and in elements of the sperm cell involved in the acrosome reaction. The spermatozoon of each species is described ultrastructurally using transmission electron microscopy and correlations made between observed patterns of fluorescence and the cellular components described. No obvious filamentous actin (F‐actin) is visible in the electron micrographs of the spermatozoa of any of the species. In most cases the fluorescence is sufficiently specific to indicate in which region of the mature sperm cell the actin and tubulin occurs. Actin is acrosomal in Maja, Cancer and Potamon but appears to be cytoplasmic in Clibanarius , while the tubulins appear only to be present in the cytoplasm of Clibanarius, Maja and Cancer.