MORPHOLOGICAL AND KINETIC CHANGES OF CARP (CYPRINUS-CARPIO) SPERMATOZOA AFTER INITIATION OF MOTILITY IN DISTILLED WATER

Studies on the flagellar movement of carp spermatozoa induced by dilut ion in distilled water allowed us to describe a sequence of early, rap id morphological and kinetic changes which begin at the very tip of th e flagellum. They cause the progressive folding of the axoneme which e nds stuck to the head within 90-120 seconds after the initiation of mo tility. However, the axonemal machinery remains functional as the fold ing can be reversed after transfer back into a high osmolality medium and partially folded flagella were able to propagate efficient waves a long the non-folded proximal portion of the axoneme. The data also rev ealed that the membrane area of the terminal piece exhibits strong sen sitivity to hypotonicity. These results suggest that in the normal fre shwater medium, the brief swimming period allowing fertilization of oo cytes is limited by the osmotic stress induced coiling of the carp spe rm tail and not by ATP stores. (C) 1996 Wiley-Liss, Inc.