Meeting Abstract
Scallops, molluscs within the Family Pectinidae, are a group of swimming bivalves with dozens of surprisingly complex eyes. Their eyes include a cornea, lens, mirror, and two layered retinas: a proximal and a distal retina. The proximal retina is positioned well behind the focal point of the eye, receiving images that are significantly less focused than the images the distal retina registers (since the distal retina does lie at the focal point of the eye). Although the anatomy of scallops has been studied since the late 19th century, no one knows to this date why the eyes of scallops have two retinas. An astonishing difference between the two retinas is that the distal retina contains ciliary photoreceptors while the proximal retina consists of rhabdomeric photoreceptors. The proximal retina may therefore be sensitive to the polarization of light. Regretfully, not enough histological work has been done to ascertain if scallop rhabdoms have or do not have the ordered morphology required for spatial polarization vision. The possibility of polarization sensitivity in scallops is well worth the additional effort of a closer look because linear polarization is common underwater and could prove useful for scallop navigation and/or threat detection. I will therefore investigate the scallops’ polarization vision by testing their response to a stimulus which contains only polarization contrast (i.e. an object that is identical to its background in spectrum and intensity but is different in the degree and/or angle of the linear polarization of the light).
