AMPHIBIAN CROSS-FERTILIZATION AND POLYSPERMY

A string of oocytes from Bufo arenarum (Ba) was inseminated with sperm atozoa from Ba, Leptodactylus chaquensis (Lch), or Bufo paracnemis (Bp ). Homologous insemination resulted in monospermic eggs and normal dev elopment, while in the case of heterologous fertilization both polyspe rmy and abnormal development were the rule. Oocytes from Ba inseminate d with homologous spermatozoa, when reinseminated 30 sec after the fir st insemination with heterologous spermatozoa, exhibit a high rate of polyspermy and abnormal development. A lower rate of abnormalities was observed when reinsemination was carried out 60 sec after the first i nsemination. Normal development and an absence of polyspermy were obse rved in the case of eggs reinseminated 300 sec after initial inseminat ion. This result indicated that the electrophysiological blockage of f ertilization either was not triggered or was ineffective. The establis hment of the permanent blockage of polyspermy, either by artificial ac tivation of oocytes or as a result of their incubation with the produc ts of the cortical granules, inhibited penetration of Ba eggs by heter ologous sperm. (C) 1994 Wiley-Liss, Inc.