Meeting Abstract

S5-2.1  Friday, Jan. 4  Maternally-derived steroids in amphibian eggs WIDDER, P.D.*; BELDEN, L.K.; Virginia Tech

Most amphibian eggs differ from bird and reptile eggs by being smaller in size and larger in number. While they share these traits with fish, the cleavage of a newly fertilized amphibian egg is holoblastic, with the yolk completely incorporated in the developing embryo, whereas in fish it is meroblastic, with the yolk separate from the embryo. Also in amphibian eggs, maternal provisioning is in the form of yolk platelets that are generally deposited over the course of several weeks to months, although the timing of vitellogenic egg development varies among species. These differences among amphibian species are likely driven by differences in life history traits (such as the timing of breeding), as well as differences in reproductive physiology. While the presence of maternally-derived steroids has been documented in all other vertebrate classes, only recently have we confirmed that androgens and corticosterone are present in amphibian eggs, and that these hormones vary by female and among species. The consequences of maternally-derived yolk hormones in amphibians currently remain largely unexplored; however, we have also found that, in at least one species, the level of testosterone circulating in the actively spawning female correlates with the testosterone measured in her eggs. Given the influence that yolk hormones have in other vertebrate taxa, it seems likely that they could play an important role in amphibian development as well.