Cephalopods are renowned for changing the color and pattern of their skin for both camouflage and communication. Yet, we do not fully understand how cephalopods control the pigmented chromatophore organs in their skin and change their body pattern. Although these changes primarily rely on eyesight, we found that light causes chromatophores to expand in excised pieces of Octopus bimaculoides skin. We call this behavior light-activated chromatophore expansion (or LACE). To uncover how octopus skin senses light, we used antibodies against r-opsin phototransduction proteins to identify sensory neurons that express r-opsin in the skin. We hypothesized that octopus LACE relies on the same r-opsin phototransduction cascade found in octopus eyes. By creating an action spectrum for the latency to LACE, we found that LACE occurred most quickly in response to blue light. We fit our action spectrum data to a standard opsin curve template and estimated the λmax of LACE to be 480 nm. Consistent with our hypothesis, the maximum sensitivity of the light sensors underlying LACE closely matches the known spectral sensitivity of opsin from octopus eyes. LACE in isolated preparations suggests that octopus skin is intrinsically light sensitive and that this dispersed light sense might contribute to their unique and novel patterning abilities. Finally, our data suggest that a common molecular mechanism for light detection in eyes may have been co-opted for light sensing in octopus skin and then used for LACE.
The authors declare no competing or financial interests.
M.D.R. and T.H.O. designed the study and wrote the paper. M.D.R. performed the experiments, imaging and statistical analysis. T.H.O. created the R code for the Govardovskii opsin curve.
The confocal microscope was funded by a National Institutes of Health Shared Instrumentation grant [1 S10 OD010610-01A1] to Mary Raven at the NRI Microscopy Facility at UCSB. This project was funded by National Science Foundation grants to THO [IOS-1045257 and DEB-1146337]. Deposited in PMC for release after 12 months.
Supplementary material available online at http://jeb.biologists.org/lookup/suppl/doi:10.1242/jeb.110908/-/DC1
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