Meeting Abstract
25.10 Monday, Jan. 5 The optics and evolution of scallop eyes SPEISER, D.I.*; JOHNSEN, S.; Duke Univ.; Duke Univ. dis4@duke.edu
Scallops can possess upwards of one hundred eyes along their valve margins. These eyes contain two distinct retinas and form images by the reflection of light off a concave spherical mirror. It is thought that focused light falls on only one of the two retinas and that the scallop lens corrects for spherical aberration caused by the mirror. Here, we report the results of a comparative study of scallop eye morphology conducted using confocal microscopy and optical modeling software. Via antibody stains for tropomyosin we have identified muscle fibers surrounding the scallop eye. The presence of these fibers suggests that the scallop eye may be a dynamic structure that can alternately focus light on either retina through small changes in its shape controlled by muscular contraction and relaxation. Contrary to expectation, we also found that some scallop species, such as Argopecten irradians and Chlamys hastata, have a lens with a spherical front curvature that does little to correct for spherical aberration. However, we found that other species, such as Amusium balloti and Placopecten magellenicus, have a lens with a hyperbolic front curvature that does help correct for spherical aberration and nearly doubles the spatial resolution potentially provided by the eye. Studying scallop eyes in a phylogenetic context reveals that these corrective lenses may have evolved at least twice in Pectinoidea, in the subfamilies Pectininae and Palliolinae, and that their appearances may coincide with the evolution of improved swimming ability within these clades. A positive correlation between scallop swimming ability and visual acuity is further supported by evidence that swimming scallops have eyes with smaller inter-receptor angles than those of non-swimmers, with values ranging from 1, for the eyes of the highly mobile Amusium balloti, to 4, for those of the sessile Spondylus americanus.
