Mexican cavefish spend their entire lives in the dark. With no need for vision, many of them lost functional eyes. In more than 30 varieties of Mexican cavefish, the eyes stop developing as embryos grow into larvae. Although they are still the same species as a sighted, surface-dwelling fish (Astyanax mexicanus), the cave-dwelling varieties carry genetic mutations that scientists have yet to fully unravel.
In a new study led by University of Maryland researchers, scientists have discovered that a mutation to the gene cystathionine beta-synthase “a” (cbsa) prevents blood flow to cavefish eyes during a critical phase of development. The lack of blood leads to withered, underdeveloped eyes covered by skin and connective tissue in all blind varieties of Mexican cavefish. The study was published in the journal Nature Communications on June 2, 2020.