Meeting Abstract
Recent advances in genomics have led to the discovery of diverse arrays of opsins in a myriad of tissues, which, together with behavioral and histological approaches, has greatly advanced the field of extraocular photoreception. It now appears that extraocular photoreception, particular in marine phyla such as the Mollucsa, is the rule rather than the exception. However, many questions remain unanswered. First, we still do not understand the function of extraocular photoreception in most species. Suggested functions include entrainment of circadian rhythms, mediation of camouflage and bioluminescent responses, and shadow detection and crude image formation in eyeless animals. However, these hypotheses primarily remain speculative. Second, it is unknown why animals that have evolved eyes often retain extraocular light sensing. Is this form of photoreception better suited than eyes for certain tasks, or are we merely looking at a historical remnant? For that matter, in most cases we do not know whether extraocular photoreception preceded or followed vision. The fact that the classes and spectral sensitivities of the photoreceptors involved in the two senses generally differ makes this an especially intriguing set of questions. Finally how is the information gathered by extraocular photoreceptors encoded by the nervous system and interpreted by the brain? These concluding remarks address these unsolved issues and suggest methods by which we might further our understanding of this poorly known sense.
