Meeting Abstract
The nudibranch mollusk, Hermissenda opalescens, has been shown in previous experiments to have extraocular photoreceptors because of the presence of light-sensitive neurons located in the pedal ganglia. Berghia stephanieae is another nudibranch that is a promising organism for future studies of circadian rhythms and extraocular photoreception. The goals of this study were to: 1) identify the rhabodmeric opsin (r-opsin) sequence for Hermissenda and 2) to determine whether r-opsin is located in dermal and/or neural tissue in both Hermissenda and Berghia. Using bioinformatics, the Hermissenda r-opsin sequence was identified and alignment with orthologues in other species indicated that it contains the highly-conserved lysine residue involved in photopigment binding. This r-opsin sequence was used to develop complementary RNA probes for fluorescent in situ hybridization in Hermissenda. We also used a commercially available antibody raised again r-opsin in octopus, for immunohistochemistry in both nudibranchs. Regardless of the histological technique, r-opsin was localized in all of the integumentary structures investigated in both species, including the cerata, dorsal skin, oral tentacles, and the rhinophores. This dermal r-opsin localization was diffuse, as would be expected of extraocular photoreceptors. R-opsin was not present in the brain of either species. This evidence suggests that r-opsin may be used for dermal extraocular photoreception in both Hermissenda and Berghia.
