Urodele egg jelly and fertilization.

Fertilization of urodele amphibians is physiologically polyspermic. These amphibians lack sperm entry blocking mechanisms at the egg surface, such as a cortical reaction or a membrane depolarization. Although, egg jelly is necessary for sperm capacitation, a late block to sperm entry does occur about 30 min after fertilization at a precise interface between jelly layers. The jelly is secreted by oviductal cells. In order to investigate its role in fertilization, we studied some biochemical properties of the oviductal secretions of eight species. In double diffusion experiments on agarose plates, some components secreted by the anterior and the middle parts of the oviduct interacted together and formed precipitin lines. This reaction might be responsible for the formation of the dense zone that delimits the capsular chamber. A hemagglutinating activity was found in the anterior or in the posterior part of the oviduct depending on the species. A 18K or 26K lectin was purified respectively from the oviduct of Ambystoma mexicanum and Pleurodeles waltl. In both species, the site where the late block to sperm entry is operative was spatially related to the location of the lectin in the jelly. However, sperm in contact with the purified lectins did not undergo any visible morphological change.