Meeting Abstract

P1.2  Friday, Jan. 4  Mechanisms, ultrastructure and behavioral function of flashing in Ctenoides ales: “electric scallops” DOUGHERTY, L/F*; CALDWELL, R/L; University of California, Berkeley; University of California, Berkeley

At 20m, the ocean is an environment in which light is variable as long wavelengths are absorbed rapidly with depth, yet many organisms use visual displays that require ambient light for reflection. The mechanisms that produce and perceive light underwater are remarkable examples of biological engineering and unique sensory systems specialized for dynamic habitats. Ctenoides ales are bivalves that live at depths up to 20m inside small crevices. Despite their light-limited habitat, they evolved an iridescent mantle edge that flashes bright blue light, leading to their common name “electric scallops”. They are the only species of bivalve known to have a light display. The flashing was investigated using electron microscopy, spectrometry, molecular phylogenetics and high speed video. Spectrometry indicated the light is within the blue range of 445-483nm with a peak reflection of 22.8%. High-speed video revealed that the mantle edge furls and then unfurls the reflective tissue to produce the flashing. Transmission electron microscopy (TEM) indicated the presence of electron-dense reflective vesicles roughly 0.2µm in diameter on the ventral half of the mantle tip, while TEM of the related C. scaber, which does not produce a light display, lacked any similar cells. There are no published sequences for C. ales, so molecular phylogenetics were done for comparative studies. These placed C. ales nearest two Acesta species, one Lima species and C. annulata using a 16S primer. Additional sequencing is being done using 28S and CO1 primers. The behavioral purpose of the light display remains unknown. We are testing the hypotheses that the light display acts in phototaxic prey luring or as a deimatic anti-predation display.