Meeting Abstract
26.4 Monday, Jan. 4 Spectral sensitivity of the concave mirror eyes of scallops: The influence of habitat and longitudinal chromatic aberration SPEISER, D.I.*; LOEW, E.R.; JOHNSEN, S.; Duke University; Cornell University; Duke University dis4@duke.edu
Scallops have unique eyes that use a concave spherical mirror to form images by reflection. Scallop eyes also contain a lens and two retinas, one proximal and one distal. Molecular evidence suggests that each retina expresses a different visual pigment, but it is not known if these pigments differ in their spectral sensitivity. We used microspectrophotometry (MSP) to measure the absorption spectra of photoreceptors from both of the retinas of the shallow-dwelling bay scallop Argopecten irradians and the deeper-dwelling sea scallop Placopecten magellenicus. Photoreceptors from the P. magellenicus proximal retina had an average wavelength of maximum light absorption (λmax) of 488 ± 1 nm (mean ± SE; N = 20), while photoreceptors from the distal retina had a λmax of 513 ± 3 nm (N = 26). In comparison, the proximal and distal photoreceptors of A. irradians had a λmax of 506 ± 1 nm (N = 21) and 535 ± 3 nm (N = 14), respectively. Inter-specific variation in spectral sensitivity suggests that environment may influence the evolution of scallop visual pigments. The shorter wavelength visual pigments in P. magellenicus are consistent with the bluer water where this scallop lives, while the longer wavelength pigments of A. irradians match the greener water of this species’ habitat. Intra-specific differences in spectral sensitivity may be influenced by longitudinal chromatic aberration (LCA), a problem commonly produced by biological lenses and one which animals have solved in a variety of ways. In the scallop eye, it appears that longer and shorter wavelengths fall, respectively, on the distal and proximal retinas, a pattern consistent with the spectral sensitivities of the two retinas and one which may serve to minimize the effects of LCA in the scallop eye.
