Meeting Abstract
111.5 Sunday, Jan. 6 Color vision in coral larvae? Insights into settlement behavior and possible function of fluorescent proteins STRADER, ME*; MATZ, MV; University of Texas at Austin strader@utexas.edu
Corals express multiple GFP-like fluorescent proteins (FPs) that result in an array of phenotypes within and between species. The suggested functions of fluorescent proteins range from visual communication with fish to innate immunity, but thus far the support for any of these hypotheses has been scarce. In Acropora millepora larvae, red fluorescent protein (RFP) is expressed in epidermal cells located on the aboral pole, which is the region with which the larva probes the substrate prior to settlement metamorphosis. We hypothesize that RFP serves a sensory function involved in this behavior. We set up an experiment to see if light field modifications would affect the process of larval settlement and also whether this response would correlate with the fluorescent phenotype of the larva. We monitored settlement of individual larvae of two species, A. millepora and Diploria strigosa, under light of different color equalized for total photon flux (intensity) over 3 days. A. millepora exhibits red/green fluorescent polymorphism between full sibs, while D. strigosa expresses only green. In A. millepora, green light strongly enhanced settlement while red light reduced settlement, compared to the settlement rate in the dark. The larvae that settled in the dark were almost exclusively red-fluorescent. In D. strigosa, both green and red light strongly reduced settlement compared to the blue light and darkness. The correlations between fluorescence of the larvae and settlement rate, as well as specific response to green light in A.millepora both agree with our hypothesis of the sensory function of the RFP. It is reasonable to expect that coral larvae would need to avoid light of longer wavelengths since in situ its abundance would indicate direct downwelling light and therefore exposed nature of the location.
