%0 Journal Article
%T The chemoreceptor genes of the waterflea Daphnia pulex: many Grs but no Ors
%A D Carolina Pe£żalva-Arana
%A Michael Lynch
%A Hugh M Robertson
%J BMC Evolutionary Biology
%D 2009
%I BioMed Central
%R 10.1186/1471-2148-9-79
%X We describe 58 Grs (gustatory receptors), belonging to the insect chemoreceptor superfamily, which were identified bioinformatically in the draft genome of the crustacean waterflea Daphnia pulex. No genes encoding proteins similar to the insect odorant receptors (Ors) were identified. These 58 Grs form 3 distinctive subfamilies of 37, 12, and 5 genes, as well as a highly divergent singleton (Gr58). In addition, Grs55¨C57 share distinctive amino acid motifs and cluster with the sugar receptors of insects, and may illuminate the origin of this distinctive subfamily. ESTs, tiling array, and PCR amplification results support 34 predicted gene models, and preliminary expression data comparing the sexes indicates potential female-biased expression for some genes.This repertoire of 58 chemoreceptors presumably mediates the many chemoperception abilities of waterfleas. While it is always possible that the 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 gene lineage concomitant with the evolution of terrestriality in the insects or their hexapod ancestors.The ability of Daphnia to detect chemical cues released by prey or predator have been glimpsed through studies on feeding behavior and predator avoidance [1,2]. Daphnids reject food particles, adjust feeding currents according to food availability, quality and surrounding chemical cues, and appear to swim and remain in areas where food is abundant [3-6]. However, their presence in food abundant areas can be altered by the presence of predators, and their vertical distribution is often associated with the presence or absence of predators [6,7].Kairomones from predators, fish or invertebrate, affect Daphnia's swimming patterns, dial vertical migration, and even affect morphology [2,8-11]. Species of Daphnia can develop neck teeth, thicker carapaces, and/or long head spines to reduce their vulnerability to
%U http://www.biomedcentral.com/1471-2148/9/79