37.2 Saturday, Jan. 5 Jurassic marine photonics: Squid dynamic iridescence and predation by large extinct marine reptiles SWEENEY, A.M.*; JOHNSEN, S; GAGNON, Y; MORSE, D.E.; STRAMSKI, D.; University of Pennsylvania; Duke University; Duke University; Scripps Institute of Oceanography; UCSB email@example.com
Dynamic iridescence in Loliginid squids has been fascinating and well-studied from an ultrastructural and biochemical point of view. However, its function has remained mysterious, especially the fact that the predominant color of the dynamic iridescence has a peak in the far-red, at 670 nm, which is counter-intuitive for a marine organism. Here we demonstrate that the dynamic red reflectance of the Loligo dorsal surface is likely an adaptation for camouflage against upwelling long wavelength Raman-scattered ocean light, and that this camouflage likely originated at the time of the Jurassic origin of this group in response to predation by large marine reptiles. At the time of origin of the Loliginidae, several major groups of apex marine predators such as Ichthyosaurs, Metriorhynchids, Mosasaurs and Teleosaurs included squids as major portions of their diets. An evolutionary analysis demonstrates that all these groups were likely to have a tetrachromatic visual system with oil droplet filters to increase wavelength specificity of the four cone types. Visual system modeling of an extant squid-eating member of this lineage, the Shearwater Puffinus pacificus, demonstrates that Raman-scattered light is easily visible to these animals, and that prey without an ability to camouflage against this phenomenon will be more visible to these birds. Our findings are an intriguing insight into the visual world of large Jurassic reptiles and suggest other possibilities for reconstructing the visual ecology of these extinct animals.