THE MATERNAL POUCH AND DEVELOPMENT IN THE MARSUPIAL FROG GASTROTHECA RIOBAMBAE (FOWLER).

The pouch of Gastrotheca riobambae (Fowler) serves as the location for development of the embryo up to the swimming tadpole stage. The pouch lies under the dorsal integument of the female and, in nonpregnant females, is similar to the integument. Pregnancy is accompanied by increased vascularization of the pouch. Blood capillaries from the corium become closely associated with the epithelial lining of the pouch, and vascularized outgrowths of the pouch partially envelop the embryos. Embryonic development in the pouch is characterized by the presence of peculiar gills, the highly vascularized "bell gills," which expand and flatten against the inner surface of the jelly capsule, forming an individual sac about each embryo and thus establishing a close relationship between embryonic and maternal circulatory systems. After birth of the tadpoles, the gills are soon resorbed and there is regression of the vascularization of the pouch. Reorganization of the tissue and shedding of the lining epithelium restore the pouch to the condition found in the nonpregnant female.