If funded, this project would result in the continuation of work towards understanding the reproductive and developmental biology of Eleutherodactylus frogs. Specifically, this would include work towards the objectives of defining the abilities of sympatric Eleutherodactylus species to hybridize using an in vitro fertilization assay, developing methods for sperm microinjection into unfertilized eggs, and development of methods to enucleate unfertilized eggs. This work will involve the development and use of techniques to manipulate both eggs and sperm from these frogs. The long-term goal is to use these methods to revive one or more extinct species of Eleutherodactylus frog using sperm from long-term frozen specimens. The intellectual merit of this project is that the genus Eleutherodactylus is the largest monophyletic genus of vertebrates and by understanding the reproductive and developmental biology of a few species in this genus, we gain insight into the biology of an incredibly large number of other species. In addition, the ability to revive an extinct species would be of considerable significance. The broader impact would include the first demonstration of the reversal of extinction. This would open the possibility of using these techniques for conservation, ecological remediation and the direct study of the causes of extinction.