Meeting Abstract

P3.186  Tuesday, Jan. 6  Intrageneric Sequence Diversity in Cichlid Opsin Arrays SMITH, A.R.*; CARLETON, K.L.; University of Maryland; University of Maryland adasmi@umd.edu

Peptide sequence diversity is not expected to be a source of significant variation in the visual arrays of Malawian cichlids due to the young age of the species flock. However, we know very little about the actual degree of opsin sequence diversity within the lake. Perhaps more importantly, we know even less about intrageneric polymorphisms. Amino acid changes in opsin structure can fine-tune visual spectral sensitivities, thereby contributing to divergence in visual arrays. In this study, we sequenced seven opsin genes in eight species from each of two divergent genera, Labidichromis and Metriaclima. The raw gene sequences were aligned to published reference sequences derived from Metriaclima zebra. The introns were excised and the genes were translated to their corresponding proteins. In addition, the amino acid sequence was threaded onto the bovine rhodopsin structure to determine the spatial relationships between polymorphic sites. Sequence divergence was found to be common, even within a genus. For example, the SWS1 and RH2Aβ in the genus Metriaclima had 14 and 17 polymorphic sites respectively. These numbers are on par with the number of sites that differ between M. zebra and the riverine tilapia O. niloticus. Several of the polymorphic sites are in close proximity to the retinal binding pocket, indicating that they may be functional variants with different spectral sensitivities. These data suggest two potential, but not mutually exclusive, possibilities: (i) balancing selection maintains polymorphisms in populations and (ii) ancient alleles have entered the lake repeatedly. Either scenario has profound implications for sensory evolution and sexual selection on visual signals.