Mexican Religious Rite Has Created Super Poison-Tolerant Cave Fish Discover by Eliza Strickland September 15th, 2010
Any culture’s religious ceremonies can seem strange to outsiders: For example, take the indigenous Zoque people of southern Mexico. To ask their gods for bountiful rains during the growing season they head to a sulfur cave where molly fish swim in the subterranean lake. They then toss in leaf bundles that contain a paste made from the mashed-up root of the Barbasco plant, which has a powerful anesthetic effect.
In lab experiments they compared molly fish from the ritual cave to others from an area upstream that had never swam in poisoned water, and found that the cave fish had a much higher tolerance for the Barbasco toxin.
Study coauthor Mark Tobler of Texas A&M University told New Scientist the results show that within the ritual cave, evolution has selected for fish that can survive the poison.