Fertilization and aqueous development of the puerto rican terrestrial-breeding frog, Eleutherodactylus coqui

The Puerto Rican tree frog, Eleutherodactylus coqui, has internal fertilization and direct development on land. In light of these reproductive adaptations, the events of fertilization and early development were studied. Cytological examination of just-fertilized eggs showed that sperm entry is restricted to about 10% of the surface of these large, yolky eggs, and all nuclear events of the first cell cycle occur near the animal pole. Although the oocytes have cortical granules, a number of polyspermic fertilizations were found. One clutch consisted of eggs with a high frequency of polyspermy and of normal development. This raises the possibility that normal development can occur despite multiple sperm entry, a situation not found in other anuran amphibians. With respect to saline requirements, the sperm and the embryo are similar to those in amphibians with external fertilization and aqueous development. Sperm motility was high in low-tonicity conditions, and the normally terrestrial embryo could develop completely from a fertilized egg to a froglet in a low-tonicity aqueous solution.