Meeting Abstract

P3.25  Tuesday, Jan. 6  Can you smell that? Using genomics to demystify Daphnia‘s (Crustacea) chemical senses PENALVA-ARANA, D. Carolina*; ROBERTSON, Hugh; LYNCH, Michael; Indiana University, Bloomington; University of Illinois, Urbana-Champaign; Indiana University, Bloomington dcpenalv@indiana.edu

For years the debate of if, how and which chemical signals can be detected by Daphnia has plagued freshwater biologists. Daphnia pulex, a sentinel and keystone species of freshwater systems, thought to be the sister group to the terrestrial insects, is the first aquatic invertebrate to have its genome sequenced. Using representative Grs and Ors from all available insects as queries, we present the chemoreceptor superfamily of D. pulex, finding six distinct gustatory-like receptors (Grs) clusters, for a total of 58 genes. These 58 Grs form a major species-specific cluster of 49 genes, a smaller cluster of 5 genes, as well as a highly divergent singleton (Gr58). The final three genes, Grs55-57, share distinctive amino acid motifs and cluster with the sugar receptors of insects, and may illuminate the origin of this distinctive subfamily and the potential for Daphnia to detect sugars. This chemoreceptor gene repertoire presumably mediates the many taste and smell functions of this crustacean. Consistent with the prediction of Robertson et al. (2003), we find no evidence of Olfactory receptors (Ors), in particular, no homolog of the otherwise highly conserved DmOr83b protein, which has orthologs in all available insect genomes, was found. While it is always possible that this entire Or gene lineage was lost at some point in the history of Daphnia pulex, we think it more likely that the insect Or lineage is indeed a relatively recently expanded lineage concomitant with the evolution of terrestriality in insects or their hexapod ancestors. We present ESTs and tiling array support for the predicted gene models, and expression data comparing expression between the sexes.