ACTIN IN THE ACROSOME OF THE SPERMATOZOA OF THE CRAB, CANCER-PAGURUS L (DECAPODA, CRUSTACEA)

The cytoskeletal protein actin was identified in the mature spermatozo on of the European edible crab, Cancer pagurus Linnaeus, by indirect i mmunofluorescence with monoclonal and polyclonal anti-actin antibodies , fluorescent phalloidin, and DNAase I. The actin was localized in two distinct concentric rings within the acrosome vesicle of the spermato zoon and appeared to correlate with the internal zonation of the vesic le. Modifications of the fluorescent pattern for actin were observed i n sperm cells which were undergoing changes associated with the acroso me reaction. In these cases, fluorescent staining was observed in the nucleocytoplasm immediately subjacent to the perforatorial column and sometimes in the perforatorial column within the acrosome vesicle. Equ ally intense fluorescence was observed in an apical perforatorial proj ection. SDS-PAGE of C. pagurus sperm confirmed the presence of actin i n the cells. A single band of actin (approximately 43 kDa) comigrated with rabbit muscle actin when immunoblotted onto nitrocellulose with m ouse monoclonal anti-actin. The actin-associated cytoskeletal proteins cl-actinin, tropomyosin, and spectrin were also identified within the spermatozoon of C. pagurus using specific polyclonal antibodies, but their presence was not confirmed by SDS-PAGE and immunoblotting. (C) 1 994 Wiley-Liss, Inc.