Meeting Abstract

56.6  Saturday, Jan. 5  Deiodination and the control of metamorphosis in anuran amphibians INFANTE, C.R.; Museum of Comparative Zoology, Harvard University cinfante@oeb.harvard.edu

Metamorphosis in anuran amphibians (frogs) is a complex process characterized by the extensive remodeling of larval tissues via growth or resorption and the de novo formation of many adult structures. At the level of the organism, both the external environment and internal cues determine the onset and rate of metamorphosis. Within responding tissues, however, this process is completely controlled by thyroid hormone (TH). Therefore at the tissue level an opportunity exists for another layer of coordination and control, inserted between the circulating plasma levels of TH and its nuclear receptors. A specific group of enzymes, types 1, 2, and 3 (D1, D2, and D3) iodothyronine selenodeiodinases, play an integral role in this tissue level coordination of the metamorphic response by activating and deactivating the most active form of TH. To evaluate the role of the deiodinases in coordinating amphibian metamorphosis, I employ a comparative approach by examining the expression and activity of these enzymes during metamorphosis in ceratophryine frogs, a clade of arid-adapted anurans from the Chaco of South America. In addition to having very short larval periods, the three genera that comprise this group, Ceratophrys, Chacophrys, and Lepidobatrachus exhibit a diversity of larval feeding adaptations and larval jaw morphologies that is perhaps the most extreme among anurans. At metamorphosis, these morphologies undergo remodeling at different rates, and the differences in timing are reflected by differences in the activity of the deiodinases. I hope to show that the deiodinases play a pivotal role in coordinating anuran metamorphosis and species diversification, allowing divergent larval adaptations to be reintegrated into a relatively conserved adult form.