Meeting Abstract
Visual physiologies are diverse, and an organism’s ability to perceive a visual signal depends on its sensory capabilities; as a result, visual biases in receivers influence phenotypic evolution in senders. Cleaner shrimp exhibit strikingly colorful phenotypes, often with fine patterns, which might function as signals during intraspecific interactions, such as mating and agonistic encounters. However, the extent to which pressure from conspecific viewers has influenced phenotype evolution in cleaner shrimp is unknown, as their visual capabilities are unstudied. We examined the visual systems of three cleaner shrimp species that differ in size, color, and geographic range (Lysmata amboinensis, Ancylomenes pedersoni, and Urocaridella antonbruunii). In each, we quantified spectral sensitivity and temporal resolution via electroretinography (ERG), and spatial resolution using an optomotor assay. Although many coastal decapod crustaceans are dichromatic, our study species were all monochromatic with peak spectral sensitivity near 510nm. Temporal resolution was 34-39Hz (dark adapted) and 39-48Hz (light adapted); these values are lower than predicted, given that cleaner shrimp live in high light environments. Spatial resolution was between 8.2° and 11.4°, low compared to similarly-sized insect compound eyes. Our ERG and optomotor results together suggest that cleaner shrimp cannot perceive the many colors, or resolve the intricate patterns, that comprise their own phenotypes, and thus that conspecific viewers have not played a primary role in the evolution of their appearance. Cleaner shrimp engage in mutualistic cleaning interactions with reef fish, many of which possess tri- and tetra-chromatic color vision and high spatial acuity, so shrimp phenotypes may have evolved to attract client fish.
