| Summary: | <p>Abstract</p> <p>Background</p> <p>Recent genome sequence analysis in the red flour beetle <it>Tribolium castaneum </it>indicated that this highly crepuscular animal encodes only two single opsin paralogs: a UV-opsin and a long wavelength (LW)-opsin; however, these animals do not encode a blue (B)-opsin as most other insects. Here, we studied the spatial regulation of the <it>Tribolium </it>single LW- and UV-opsin gene paralogs in comparison to that of the five opsin paralogs in the retina of <it>Drosophila melanogaster</it>.</p> <p>Results</p> <p><it>In situ </it>hybridization analysis reveals that the <it>Tribolium </it>retina, in contrast with other insect retinas, constitutes a homogenous field of ommatidia that have seven LW-opsin expressing photoreceptors and one UV-/LW-opsin co-expressing photoreceptor per eye unit. This pattern is consistent with the loss of photoreceptors sensitive to blue wavelengths. It also identifies <it>Tribolium </it>as the first example of a species in insects that co-expresses two different opsins across the entire retina in violation of the widely observed "one receptor rule" of sensory cells.</p> <p>Conclusion</p> <p>Broader studies of opsin evolution in darkling beetles and other coleopteran groups have the potential to pinpoint the permissive and adaptive forces that played a role in the evolution of vision in <it>Tribolium castaneum</it>.</p>
|
|---|