Meeting Abstract

17-2   10:45 - 10:30  A deep-sea game of hide and glow: Light organ function and diversification in sergestid shrimps Bracken-Grissom, HD*; Golightly, C; Schweikert, L; DeLeo, DM; Florida International University ; Florida International University ; University of North Carolina-Wilmington; Haverford College, Smithsonian Institution heather.bracken@gmail.com http://brackengrissomlab.com

Deep-sea shrimp belonging to the family Sergestidae provide a unique system for studying the evolution of bioluminescence. Most species within the family have one of three distinct forms of photophores including lensed photophores, unlensed photophores or internal organs of Pesta, while other species lack light organs completely. In this group, photophores are known to function in counterillumination, in which they can alter light emission to match downwelling sunlight and camouflage themselves from predators below. Over the past few years, our research group has used integrative methods to study the diversification of photophores and their role in counterillumination and congeneric recognition. Phylogenetic investigations suggest light organ type may be correlated with species’ depth distributions. Non-lensed photophores evolved once across the family but were lost in the deepest living genus. Lensed photophores also evolved once within benthopelagic genera, suggesting a potential link between the evolution of lenses and the seafloor. The internal organs of Pesta represent the ancestral state for the family and can be found in species with the shallowest depth profiles. Photophore diversity extends beyond light organ type, as each species displays unique light organ patterns. We investigated if species-specific arrangements play a role in conspecific recognition, as darkness and low biomass make it challenging for animals to identify one another in the deep sea. By combining morphology and visual modeling we found sergestids to be capable of detecting bioluminescence over ecologically relevant distances, however they cannot resolve organ pattern. More recent studies suggest light organs play a role in eye size evolution, with larger eyes being found in shrimp with lensed and unlensed photophores. These results suggest a potential role in bioluminescent signaling and an expanded role beyond counterillumination.