Multiple genetic mechanisms contribute to visual sensitivity variation in the Labridae

<p>Coral reefs are one of the most spectrally diverse environments, both in terms of habitat and animal color. Species identity, sex, and camouflage are drivers of the phenotypic diversity seen in coral reef fishes, but how the phenotypic diversity is reflected in the genotype remains to be answered. The labrids are a large, polyphyletic family of coral reef fishes that display a diverse range of colors, including developmental color morphs and extensive behavioral ecologies. Here, we assess the opsin sequence and expression diversity among labrids from the Great Barrier Reef, Australia. We found that labrids express a diverse palette of visual opsins, with gene duplications in both <em>RH2</em> and <em>LWS</em> genes. The majority of opsins expressed were within the mid-to-long wavelength sensitive classes (<em>RH2</em> and <em>LWS</em>). Three of the labrid species expressed <em>SWS1</em> (ultra-violet sensitive) opsins with the majority expressing the violet-sensitive <em>SWS2B</em> gene and none expressing <em>SWS2A</em>. We used knowledge about spectral tuning sites to calculate approximate spectral sensitivities (λ_max) for individual species’ visual pigments, which corresponded well with previously published λ_max values for closely related species (SWS1: 356–370 nm; SWS2B: 421–451 nm; RH2B: 452–492 nm; RH2A: 516–528 nm; LWS1: 554–555 nm; LWS2: 561–562 nm). In contrast to the phenotypic diversity displayed via color patterns and feeding ecology, there was little amino acid diversity within the known opsin sequence tuning sites. However, gene duplications and differential expression provide alternative mechanisms for tuning visual pigments, resulting in variable visual sensitivities among labrid species.</p>