Meeting Abstract

32.5  Jan. 5  Are there physiological differences between the photoreceptors of juvenile and adult ontogenetic migrators? FRANK, T.M.; Harbor Branch Oceanographic Institution, Ft. Pierce, FL frank@hboi.edu

For all visually competent organisms, the driving force behind the adaptation of photoreceptors involves obtaining the best balance of resolution to sensitivity in the prevailing light regime, as in increase in sensitivity often results in a decrease in resolution. In the aquatic environment, obtaining this balance may be quite difficult for species that under ontogenetic migrations, as they live at shallower depths with relatively bright light as juveniles, and migrate to deeper darker waters as adults. Metamorphosis from the larval stage to the post-larvae (juvenile) is clearly the opportune time for the photoreceptor to undergo dramatic changes in both structure and visual pigment complement to adapt to different light environments. However, a number of crustaceans have juvenile stages that are found up to 500 meters shallower than the deep living adults, and very little is known about how these two life history stages deal with these substantially different light environments. Data will be presented on two life history stages of the ontogenetically migrating lophogastrid Gnathophausia ingens. Live, visually competent juveniles (175-250 m) and deep-living adult stages (650-750 m) were collected with an opening/closing Tucker Trawl fitted with a closing cod-end. Recordings of the electroretinogram (ERG) were utilized to determine the spectral sensitivity of the juveniles, as well as the temporal dynamics of the photoreceptors in both life history stages. Results indicate that juveniles have slightly greater short wavelength sensitivity than adults, but the only differences in temporal dynamics appear to be related to the warmer temperatures occupied by the shallower living juveniles. Supported by NSF Grant #IBN-0343871.