Meeting Abstract

45.1  Monday, Jan. 5  Visual spectral sensitivity underlying orientation and rhythmic behaviors in the talitrid amphipod Talorchestia longicornis COHEN, Jonathan/H*; FORWARD, JR., Richard/B; CRONIN, Thomas/W; Eckerd College; Duke University Marine Laboratory; University of Maryland, Baltimore County cohenjh@eckerd.edu

Talorchestia longicornis is a supratidal talitrid amphipod inhabiting coastal and estuarine sandy beaches along the Atlantic coast of the US. It is nocturnal, spending days in shallow nonpermanent burrows in damp sand, emerging at night to forage along the beach. An endogenous rhythm entrained by light:dark, tidal, and/or temperature cycles controls its diel activity pattern. Visually-mediated behaviors including y-axis orientation using sun- and moon-compasses have been found in the European species Talitrus saltator, yet little is know about the visual physiology of the talitrid eye that underlies these behaviors. The present study examined the visual physiology of the Talorchestia longicornis eye, and the functional role of its visual pigments in the behavior of this amphipod. Visual spectral sensitivity was determined using behavioral, electrophysiological, and microspectrophotometric methods. All three approaches suggest dual visual pigments in T. longicornis, with sensitivity maxima near 420 and 520 nm. The distal and proximal regions of the retina have short and long-wavelength sensitivity, respectively. Behavioral studies using broadband-filtered light sources targeting each visual pigment individually suggest T. longicornis, in addition to its routine visual functions, specifically uses the short wavelength visual pigment for y-axis orientation, while the long wavelength visual pigment functions for entrainment of the endogenous activity rhythm.