Principal Investigator • Tamara Frank, Ph.D. • frank@hboi.edu The Visual Ecology Department is conducting research on the visual ecology of deep-sea organisms. Field work is being carried out on ongoing NSF funded investigations of the effects of light on the daytime depth distribution and vertical migrations of oceanic organisms. In situ measurements of downwelling light are being made simultaneously with in situ quantifications of animal distribution patterns from the JOHNSON-SEA-LINK submersible. Results from these investigations are providing clues as to how light triggers vertical migrations. Vertical migrations are the most massive animal migrations on earth, and they occur every night as hundreds of thousands of organisms leave the deeper depths and migrate up into the food-rich surface waters to feed under cover of darkness. Many of the animals undertaking these migrations are the source of food for a large number of commercially important fish species, and are critical to their survival. These In situ investigations have determined that the daytime depth distributions of several species of crustaceans in Oceanographer Canyon are staggered with respect to daytime depth distributions, and photosensitivity determinations are being conducted (both behaviorally and electrophysiologically) to determine if deeper living species are restricted to deeper (and hence dimmer) depths due to an inherently greater sensitivity to light. This requires collection of animals with a midwater trawl net fitted with a closing cod-end, allowing for shipboard measurements of spectral and behavioral sensitivities of deep-sea organisms whose photoreceptors have not been irreparably damaged by exposure to surface light levels. Spectral sensitivities have also been determined in a variety of amphipods, sergestids, mysids, oplophorids, euphausiids, pasiphaeids, and penaeids. All of these crustaceans were found to have a single visual pigment peaking between 470 and 500 nm, with the exception of several species of oplophorids, which were found to have two visual pigments, including one that is sensitive to UV light. Studies of temporal resolution have determined that most deep-sea species have relatively low temporal resolution (12-24 Hz), as would be predicted for animals living in dim light environments. The surprising exception to this trend are bilobed euphausiids (daytime depth distribution = 400-600 m), who have extraordinarily high flicker fusion frequencies, ranging from 40-50 Hz. Listen to Dr. Frank's lecture at the 2001 Ocean Science Lecture Series (requires Flash 4). References relating to current work: Widder EA, Frank (2001) The Speed Of An Isolume: A Shrimp'S Eye View. Mar Biol 138: 669-677 Frank TM (2000) Temporal Resolution in Mesopelagic Crustaceans. Phil Trans Roy Soc B355: 1195 Ü 1198 Frank TM, Widder EA (1999) Comparative study of the spectral sensitivities of mesopelagic crustaceans. J Comp Physiol 185: 255-265 Frank TM (1999) Comparative study of temporal resolution in the visual systems of mesopelagic crustaceans. Biol Bull 136: 137-144 Lindsay SM, Frank TM, Kent J, Partridge JC, Latz MI (1999) Spectral sensitivity of vision and bioluminescence in the midwater shrimp Sergestes similis.. Biol Bull 197: 348 Ü 260 Frank TM, Widder EA (1997) The correlation of downwelling irradiance and staggered vertical migration patterns of zooplankton in Wilkinson Basin, Gulf of Maine. J Plank Res 19(12): 1975-1991 Frank TM, Widder EA (1996) UV light in the deep-sea: In situ measurements of downwelling irradiance in relation to the visual threshold sensitivity of UV-sensitive crustaceans. Mar Fresh Behav Physiol 27: 189-197 Cronin TW, Frank TM (1996). A short-wavelength photoreceptor class in a deep-sea shrimp. Proc Roy Soc Lond B 263: 861-865 Frank TM, Widder EA (1994) Comparative study of behavioral-sensitivity threshold to near-UV and blue-green light in deep-sea crustaceans. Marine Biology 121: 229-235 Frank TM, Widder EA (1994) Frank TM and EA Widder. (1994). Evidence for behavioral sensitivity to near-UV light in the deep-sea crustacean Systellaspis debilis. Mar Biol 118: 279-284