Sensory adaptations in hydrothermal vent shrimps from the Mid-Atlantic Ridge

When discovered in 1985, Rimicaris exoculata Williams and Rona, 1986 and Chorocaris chacei (Williams and Rona, 1986) were assumed by most to be blind. Downwelling light at intensities useful for vision does not reach depths greater than 800-1300 m (rev. in Lakin et al., 1997), while the shrimps are found at depths of ~1700-3900 m. Nonetheless, R. exoculata possesses a dorsal organ with cellular, biochemical, and physiological characteristics of a retina that appears to be adapted to transduce the dim light emitted by the hydrothermal vents around which they feed (rev. in O'Neill et al., 1995). We have also examined the morphology of the eyes of R. aurantiaca Martin et al., 1997 (see Nuckley et al., 1996), C. chacei (see Lakin et al., 1997), Mirocaris fortunata (Martin and Christiansen, 1995), (see Kuenzler et al., 1997), and Alvinocaris markensis Williams, 1988 (see Wharton et al., 1997). Neurochemical analyses of the brain of R. exoculata are underway (Curra et al., 1996). Electrophysiological recordings of concentration-dependent sulphide sensitivity from the antennal nerves of Rimicaris (Renninger et al., 1995) have provided insight into the mechanisms whereby vent shrimps might locate active hydrothermal systems.