Meeting Abstract
P1.125 Wednesday, Jan. 4 Uncovering the molecular basis of dispersed photoreception in the cephalopod, Octopus bimaculoides RAMIREZ, M. Desmond*; OAKLEY, Todd H.; Univ. of California, Santa Barbara; Univ. of California, Santa Barbara ramirez@lifesci.ucsb.edu
Where do the molecular components of complex traits come from? Do they arise de novo, or are they co-opted from existing systems? Photoreception is excellent for exploring these questions, as we understand both the molecular basis and evolutionary histories of animal phototransduction cascade genes. Cephalopod molluscs possess three distinct photoreception systems; most have camera-type eyes, light-sensitive brain regions, and likely some dispersed photoreception (Mathger et al., 2010, reviewed in Ramirez et al., 2011). The cuttlefish Sepia officinalis expresses r-opsin in the skin (Mathger et al. 2010). We have identified five r-opsin phototransduction genes expressed in the skin of the octopus, Octopus bimaculoides, including r-opsin and G-protein α-q. Although these data are limited, they suggest a common origin of dispersed phototransduction genes for these two cephalopod groups. The sequences of dispersed r-opsins in both S. officinalis and O. bimaculoides are highly similar to the sequences of eye r-opsins, and the same cascades may mediate both photoreception systems. However, this may not be the case at broader taxonomic scales; dispersed photoreception responses in the gastropod snail Lymnea stagnalis are abolished by a pharmacological agent that affects cyclic nucleotide gated (CNG) ion channels (Pankey et al., 2010). CNG is typically associated with the c-opsin pathway, rather than the r-opsin cascade we have identified in octopus skin. Thus, dispersed photoreception may have evolved multiple times within different molluscan lineages. Overall these results suggest that dispersed photoreception genes may have been co-opted from existing systems in cephalopods, but that this is likely not true of all dispersed photoreception systems in molluscs.
