Meeting Abstract
Variation in coloration within a species can result from selective pressures of the environment, genetic differences, or physiological constraints. The genetic basis for red carotenoid coloration in birds and turtles was recently identified as CYP2J19. This gene encodes a cytochrome p450 enzyme that catalyzes the bioconversion of dietary yellow carotenoids to red carotenoids. However, many other animal taxa display red coloration that arises from the bioconversion of yellow carotenoids to red, yet the genetic basis for this conversion remains unknown. Here, we investigated the molecular and genetic basis for population-specific levels of red coloration in the shrimp, Halocaridina rubra. H. rubra form discrete populations comprised of distinct genetic lineages that range from vibrant red to nearly translucent. We show that variation in red coloration among populations is due to differences in the accumulation of the red carotenoid, astaxanthin. Further, we show that astaxanthin accumulation is heritable and that environmental limitation of dietary carotenoids does not explain population-specific levels of coloration. Our phylogenetic analysis revealed that the transcriptomes of H. rubra, other crustaceans, and amphibians do not contain a paralog of CYP2J19. Instead, these taxa likely bioconvert carotenoids using a bifunctional hydroxylase like that found in yeast: a cytochrome p450 family 3A-like enzyme. This work is the first step in linking variation in the red phenotype of H. rubra to genotypic variation, providing the basis for future work including elucidating genes that function in the absorption, transport, degradation of dietary carotenoids.
