Visual pigment diversity and function in larval stomatopods and other malacostracan pancrustaceans

Abstract

Stomatopods have among the most complex eyes of any pancrustacean, with up to 33 opsin proteins, the basis of visual pigments, found in a single retina. While the adult visual system has been the subject of many studies, visual capabilities of stomatopod larvae are comparatively less well understood. Learning how larval stomatopods perceive the world can help us further understand the signals that drive their behavior. Adult stomatopods generally live in shallow waters containing a wide range of wavelengths in the visible spectrum, while larvae are pelagic and live in environments dominated by blue and green light. Previous work has thus suggested that larval stomatopod visual systems contain a single photoreceptor type and correspondingly a single visual pigment that absorbs maximally in the blue/green portion of the spectrum. However, more recent studies have found anatomical and physiological complexity in larval stomatopod eyes which exceeded expectations. In this dissertation I have further investigated the visual ecology of larval stomatopods, focusing on the thus far uncharacterized visual pigments which form the basis of light perception. I first looked at the extent of larval diversity at one of my study locations, to understand how larval versus adult stomatopod sampling efficiency differ and affect estimates of species richness. I then investigated the expression of opsin proteins in different developmental stages of stomatopods, testing the hypothesis that larval stomatopods have only one unique visual pigment. The unexpected expression of multiple ultraviolet sensitive opsins in all stomatopod developmental stages prompted a detailed study of these proteins and the molecular mechanisms that affect their specific ultraviolet absorbance in malacostracans. Finally, I investigated the significance of ultraviolet light perception in larval stomatopods by quantifying the effect of different light spectra on behavior period and opsin expression. Taken together this work offers evidence that larval stomatopod visual systems are surprisingly complex at the molecular level and gives insight into the ecology of these early life stages.