Meeting Abstract

102.2  Saturday, Jan. 7  Evolution of albinism in a captive population of cavefish GROSS, Joshua B.*; WILKENS, Horst; University of Cincinnati, Cincinnati, Ohio, USA; Zoological Institute and Zoological Museum, University of Hamburg, Hamburg, Germany grossja@ucmail.uc.edu

One of the most common traits shared among cave-dwelling animals is the loss of pigmentation. This form of phenotypic regression evolves through diverse modes, including decreased numbers of pigment-producing cells (melanophones), decreased melanin content within melanophores, or the complete absence of melanin pigmentation (albinism). Collectively, populations of the blind Mexican cavefish demonstrate all three modes of pigmentation regression. Not all cave populations, however, harbor the same combination of defects. For instance, the Molino population demonstrates albinism, but not melanin reduction (the brown phenotype) while the Piedras population is brown, but not albino. Two critical genes, Mc1r and Oca2, have been identified as the causative regulators of the brown mutation and albinism, respectively. The order through which these changes evolve in nature remains unknown. Thus, it is unclear if the destructive phenotype (albinism) precedes mutations in other hypostatic genes, or alternatively if albinism evolves rapidly in populations demonstrating other reduced pigmentation phenotypes. This study investigates a population of lightly pigmented cavefish collected in the early 1970s. Remarkably, over the last several decades albinism has spontaneously arisen within this captive stock. We present results of a molecular analysis of the albino locus in which phenotype, coding sequence and expression levels are compared between the derived albino and “ancestral” pigmented individuals, along with representative individuals drawn from other surface and cave populations. In the context of cave-dwelling animals, which frequently experience population bottlenecks, this study provides direct evidence that cave-associated phenotypes can arise remarkably quickly in small populations.