Wednesday, June 10, 2020
Why cavefish lose their eyes
A long-standing puzzle has been settled. How do cavefish lose their eyes? What's the exact mechanism?
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 cbsa gene is known to be responsible for a human disease called homocystinuria, which causes defective vision and can lead to hemorrhaging, stroke, heart attacks and premature death. Understanding how blind cavefish thrive with mutated cbsa may help researchers develop treatments for homocystinuria in the future.The question is important because it's the only commonly seen example of adaptation. We know that many species adapt minor details like coloration, and we know that viruses and bacteria are constantly stealing and trading DNA to adapt in all sorts of ways. But those adaptations are subtle or microscopic. Cavefish show a major change switched on by a situation. Many animals operate at night, or live underground, without losing their eyes. Only cavefish develop without eyes when they live in caves. Unsurprisingly the solution turns out to be epigenetic, a gene that acts like a neuron. Still, this wasn't known for sure until now. Another puzzle remains. How did the fish get into the caves? When I was young and immortal I did some spelunking. The cave we were exploring was in the Panhandle, dry territory with no real rivers, just transient creeks. At the base of the cave was a permanent pool of water with eyeless fish somehow thriving. Where did they come from? Do aquifers contain hidden 'pipes' where fish can migrate for long distances underground?
Labels: Grand Blueprint
¶ 6:46 AM
