S6-1.4 Jan. 5 Urbilaterian Reproduction: the evolution of metazoan germ cell specification mechanisms EXTAVOUR, Cassandra G M; University of Cambridge email@example.com
A key focus of evolutionary developmental biology in recent years has been to elucidate the evolution of developmental mechanisms as a means to reconstructing hypothetical last common ancestors of various sister clades. Promiment among such reconstructions have been proposals as to the mythical "Urbilaterian", defined as the last common ancestor of the extant Biltaeria. Drawings of this animal now exist in many textbooks, including detailed information on the genetics and morphological processes that it used to construct its gut, heart, eyes, appendages, segments, and body region identities. Perhaps surprisingly, however, no explanations have been offered as to how this animal might have achieved the successful reproduction that must have been necessary for it to give rise to the lineages ancestral to today's diverse clades. I will examine the comparative data available to date on the specification of reproductive systems during development, with special emphasis on the cells containing the genetic hereditary material, the germ cells, and suggest a gonad structure and reproductive strategy for "Urbilateria".