Endocrinology of a Viviparous Amphibian

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The ability to give birth to live young occurs in all classes ofvertebrates except cyclostomes and birds. In a unique order of tropicalamphibians, the caecilian amphibians, the majority of species give birth tolive young but the physiological mechanisms which control this process areunknown. It is proposed that fetal caecilian gills function as endocrineorgans and produce hormones similar to those produced by mammalianplacentas. Such structures have not been described in non-mammals. Thegoal of this project is to determine whether fetal caecilian tissuesproduce steroid hormones. The methods to be used include identification ofsteroid metabolites produced by tissues in vitro and localization ofenzymes known to function in steroid synthesis. Maternal steroid hormonelevels will be determined.These studies will provide the first information on steroid endocrinologyand the control of live- bearing for this order of amphibians. They willthus contribute substantially to understanding of reproductive biology andconservation of these unique animals and also to hormonal control ofpregnancy in other vertebrates.