Meeting Abstract

50.7  Monday, Jan. 5 11:30  Three visible light sensitive opsins are specific to Limulus median ocelli and are co-expressed BATTELLE, B-A*; KEMPLER, K.E.; SARAF, S.R.; MARTEN, C; DUGGER, D.R.; SPEISER, D.I.; OAKLEY, T.H.; Whitney Lab., University of Florida; Whitney Lab., University of Florida; Whitney Lab., University of Florida; Whitney Lab., University of Floirda; Dept. Ophthalmology, University of Florida; Univ. of South Carolina; Univ. of California, Santa Barbara battelle@whitney.ufl.edu

The eyes of the American horseshoe crab Limulus polyphemus, a chelicerate arthropod, are major preparations for studies of vision. Limulus has three different types of eyes: lateral compound eyes, median ocelli and larval eyes. Much is known about the structure and function of Limulus photoreceptors. Recent work has focused on identifying the opsins they express. Previous studies showed that three visible light sensitive opsins, LpOps1, 2 and 5, are co-expressed in the retinular cells of the compound eye and giant photoreceptors of larval eyes and that LpUVOps1 and LpOps5 are co-expressed in small photoreceptors of larval eyes. The median ocelli or median eyes (ME) were known to be sensitive to both UV and visible light, and LpUVOps1 is expressed in a population of ME photoreceptors. However the visible light sensitive opsins expressed in ME photoreceptors were not identified. LpOps1, 2 and 5 are not detected in the rhabdoms of ME photoreceptors. Here we report that three previously unidentified visible light sensitive opsins, LpOps6, 7, and 8, are co-expressed in a population of ME photoreceptors that are different from those expressing LpUVOps1. We also show that these opsins are not expressed in the compound or larval eyes so they are unique to the ME. Differential expression of visible light sensitive opsins in compound eyes and ocelli has also been described in insects and crustaceans. Our results now show this is a feature common to all three major arthropod groups. Our results also show that in Limulus, all visible light sensitive photoreceptors express more than one opsin.