Meeting Abstract
106.6 Sunday, Jan. 6 Dispersed sensory neurons express opsin in the skin of Octopus bimaculoides RAMIREZ, D*; OAKLEY, TH; Univ. of California, Santa Barbara ramirez@lifesci.ucsb.edu
Although we have known for some time that animals can detect light with dispersed, dermal photoreceptor cells and can guide behavior, in most cases we do not know which molecules or dispersed cells actually confer this light sense. This holds true for molluscs, which have well documented photo-behaviors likely mediated by dispersed cells, but very limited data about the cells or molecules involved. In cephalopod molluscs, behavioral evidence of dispersed photoreception is scarce, but there are two brief reports of a direct chromatophore response to light in Octopus spp. As for molecular data, r-opsin is expressed in the skin of the cuttlefish Sepia officinalis. We have also found five major phototransduction components expressed in the skin of Octopus bimaculoides, including r-opsin and G-protein &alpha-q. Further, we found primary sensory neurons (PSNs) expressing opsin in octopus skin using antibodies raised against octopus eye opsin and mouse tubulin. These cells consist of small ciliary bundles emerging from the skin surface connected to cell bodies within the epidermis. They are relatively evenly spaced across the entire surface of the animal, except for a subset of these PSNs. These form lines on the siphon and dorsal head and mantle, and have previously described as mechanoreceptors based on both morphology and electrophysiology. We propose that these opsin-expressing PSNs are octopus dispersed photoreceptor cells and may contribute to a dermal light sense in both octopus and other coleoid cephalopods. Further, ultrastructure studies have identified this same cell type in several other classes of molluscs, including bivalves and gastropods. They may underlie the known dispersed photoreception behaviors in these other taxa, although it remains to be seen whether these other putative molluscan dispersed cells also use opsin-based phototransduction pathway genes.
