Opsin Evolution in Stomatopod Crustaceans: Molecular Investigations of a Complex Visual System

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Evolution of sensory systems, and specifically the evolution of visual systems, is a research area of fundamental significance to ecologists, physiologists, neurobiologists, and evolutionary biologists. In particular, the evolution of visual pigments (the molecules that absorb light and in many ways determine primary features of visual sensitivity and color vision) has long served as a model system for understanding how genes and proteins evolve, how structural features of proteins affect function, and how sensory systems evolutionarily adjust to meet the functional requirements of different species. Research on stomatopod crustaceans, or mantis shrimps, has been central to this work. These marine animals have evolved a uniquely complex visual system, one that is unparalleled in the animal kingdom. They possess the most complicated systems of color vision of any animals, based on 16 or more different visual pigments (greater than the number known for any other animal group by a factor of more than two). These pigments are the light-capturing molecules in photoreceptor classes specialized to sense wavelengths of light from the deep ultraviolet to the far red. Stomatopods, therefore, have been favored subjects for studies of color vision, visual adaptation to habitat, color and polarizational signaling, and evolution of visual systems. Their visual pigments are often viewed as models of molecular machines for understanding protein design and function in all organisms.This project brings together a team of vision scientists, molecular biologists, and evolutionary biologists to investigate how mantis shrimp vision has evolved at the molecular level, to learn how their numerous classes of photoreceptors have become specialized over evolutionary time, and to discover how the evolutionary advances made by stomatopods actually operate to improve visual function. Because stomatopods have so many different types of visual pigments, all based on a single class of proteins called opsins, they provide a natural laboratory within which to study diversification of function and to learn how changes in these opsin proteins down to the level of specific amino acid substitutions foster the evolution of new visual pigments, produce new spectral classes, and tune the visual functions of different species to particular habitats. Using the opsins in retinas of selected species of mantis shrimps as a model system, the research of this project will characterize the genetic diversity within and among species and between habitats, identify the molecular mechanisms used to tune their visual pigments, and establish how the modern diversity evolved. The work will involve cutting-edge approaches, including genetic sequencing, cellular identification of gene expression, computational assessment of phylogenetic diversification, and molecular modeling. The results will serve as new and significant underpinnings for advances in understanding visual function and for inspiring advances in medical and technological aspects of vision science. The work will involve the training of post-doctoral fellows, graduate students and undergraduates as part of the project, and the PIs will give public lectures at schools and non-scientific professional meetings and plan to contribute to textbook development and museum exhibitions.