Iodine & tyroid hormone signaling in echinoid larvae

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Significant gaps exist in our knowledge on mechanisms underlying larval development and metamorphosis, in many marine invertebrate phyla. My long term objective is to gain insights into the signaling architecture underlying larval development and metamorphosis with specific emphasis on thyroid hormone (TH) signaling in echinoids (sea urchins and sand dollars). Although THs are generally viewed as classic vertebrate hormones, my preliminary data strongly suggests a function in echinoid larval life histories. Furthermore, while developmental signaling molecules are generally considered to be strictly endogenously produced, my research provides evidence that THs in the marine environment have both internal and external sources. In this program I will therefore evaluate the role of both, exogenous and endogenous sources of THs in the context of marine larval life histories and their evolution. My specific aims for this 5 year granting period are to: Aim 1: Confirm presence and precise identity of TH related compounds in echinoid larvae and phytoplankton. Aim 2: Identify putative TH signaling and synthesis genes in the sea urchin S. purpuratus. Aim 3: Compare mechanisms of TH synthesis in two congeneric sand dollar species. This research will produce novel data on TH signaling in echinoid larval development and metamorphosis. More generally, it will expand our understanding of hormonal signaling systems in invertebrate phyla and elucidate their role in life history evolution. Findings from this research program and specifically from the proposed project will elucidate 1) the extent of homoplasy (i.e. convergence, parallelism and reversal) in the mechanisms underlying the regulation of metamorphic life histories and 2) how these signaling systems may have been modified through evolution, leading to the extensive diversity of life history modes in these groups. In sum, by bridging the gap between classical larval life history and modern ontogenetic, cellular and genomic approaches, this program will exemplify the potential of multidisciplinary biological research to provide novel insights into animal development, evolution and ecology.