Meeting Abstract

P2.51  Monday, Jan. 5  Eye development in a sexually dimorphic species of ostracod (Crustacea) RIVERA, Ajna; OAKLEY, Todd*; University of California, Santa Barbara; University of California, Santa Barbara ajna@berkeley.edu

One of the standout questions in evolutionary biology is the novelty question: How do new features evolve? In a broad sense, this question explores how similar genomes can make different phenotypes. One way to look at this is to examine sexually dimorphic species, where nearly identical genetic backgrounds can make radically different organs. To this end, we are studying the philomedid ostracods (Crustacea). The Philomedidae nearly all have at least a simple median eye but also exhibit a wide array of lateral eye sizes. These range from completely absent in Igene, to huge compound eyes in Euphilomedes carcharodonta. We present a phylogeny showing that loss of eyes occured several times and gain of eyes is also likely. On top of this is a pattern of extreme sexual dimorphism which has also likely to have been lost and gained several times. In dimorphic species, females have rudimentary eyes while males have compound eyes with up to 33 large ommatidia. We examine the development of 3 philomedine species native to California E. morini, E. carcharodonta, and E. longiseta. In these species, male eyes appear to arise via a tissue furcation event male eye tissue splits or doubles to form a stagnant rudimetary field homologous to the female eye and a fast growing ommatidial field. This suggests that novel features can be gained by tissue duplication events. In this scenario, the duplicated tissue can now follow a new evolutionary trajectory, analogous to the gene duplication and neofunctionalization model of gene evolution. To examine the potential trajectory of a duplicated tissue, we compare gene expression between male and female E.morini during eye development.