- by Wynn K. Meyer, Sidi Zhang, Sachiko Hayakawa, Hiroo Imai and Molly Przeworski
“How many distinct molecular paths lead to the same phenotype? One approach to this question has been to examine the genetic basis of convergent traits, which likely evolved repeatedly under a shared selective pressure. We investigated the convergent phenotype of blue iris pigmentation, which has arisen independently in four primate lineages: humans, blue‐eyed black lemurs, Japanese macaques, and spider monkeys. Characterizing the phenotype across these species, we found that the variation within the blue‐eyed subsets of each species occupies strongly overlapping regions of CIE L*a*b* color space. Yet whereas Japanese macaques and humans display continuous variation, the phenotypes of blue‐eyed black lemurs and their sister species (whose irises are brown) occupy more clustered subspaces. Variation in an enhancer of OCA2 is primarily responsible for the phenotypic difference between humans with blue and brown irises. In the orthologous region, we found no variant that distinguishes the two lemur species or associates with quantitative phenotypic variation in Japanese macaques. Given the high similarity between the blue iris phenotypes in these species and that in humans, this finding implies that evolution has used different molecular paths to reach the same end” (read more/not open access).
(Source: American Journal of Physical Anthropology, in press 2013; top image: Kyoto University, Section of Ecology and Conservation )
Before and after surgery to repair traumatic mydriasis.
Before and after surgery to repair a traumatic iridodialysis; a localized separation or tearing away of the iris from its attachment to the ciliary body.
Scarred anterior capsular tear (identified by arrow) and hydrated traumatic cataract.