Unique Genetic Process Discovered in Extremophile Fish


A biologist from the Washington State University has discovered the genetic mechanism that enables fish to survive in acidic or toxic environments. This finding represents a breakthrough in extremophile research, explains Joanna Kelley, a genome scientist at the University’s School of Biological Sciences.

ZME Science reports that the “very extreme” Atlantic Molly, found in Southern Mexico are the only fish on earth than can exist in hydrogen sulfide water. In their own environment, they live in tropical freshwater and volcanically influenced springs containing hydrogen sulfide acid.

“In the fresh water system, there are 30-plus species of fish,” said Joanna Kelley in the Washington State University press release. “In the sulfidic springs, there’s the molly . . . Ordinary fish, when you put them in that water, are belly up in about a minute.”

Along with her peers from Kansas State University, Stanford University and Universidad Juarez Autonoma de Tabasco in Mexico, Kelley conducted a natural experiment to measure the three sets of genes of the Atlantic Molly against freshwater fish. They were surprised to discover that the fish did not have a filtering system, as expected. Instead, the molly was able to “turn on” genes in order to detoxify their bodies of hydrogen sulfide. Approximately 170 of the fish’s 35,000 genes were enhanced during this process.

“It’s not that they are necessarily turning on some other unrelated genes,” explains Kelley. “It’s really that the genes that have been previously implicated in hydrogen sulfide detoxification are turned on or turned up.” The findings have been published in the journal Molecular Biology and Evolution, according to

Kelley comments that extreme environments such as the molly’s are important places to examine evolutionary processes. The scientists hope that this discovery will help to answer questions about extremophiles and address challenges in evolutionary research. For example, the findings could lead to developments in ageing research, evolutionary ecology and even further understanding of human tolerance to hydrogen sulfide.

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