Mystery solved: This is how some fish managed to survive toxic pollution levels

Scientists decode how some fish survived even in toxic environment!

Scientists know that the Atlantics killifish can survive in very harsh environment and has the ability to tolerate large fluctuations in temperature, salinity and oxygen levels. However, what amazed researchers, was the ability of the fish to rapidly adapt to toxic pollution found in estuaries in the US.

After observing them closely, researchers found that the Atlantic killifish has a very high level of DNA diversity which enables them to survive in toxic environment and makes them nearly 8,000 times more resistant to highly toxic industrial pollutants.

For the study, a team of researchers from the University of Birmingham in the UK, observed and compared genomes of four non-tolerant populations of killifish with four wild populations of pollution tolerant killifish.

After analysing the collected data, study authors found aryl hydrocarbon receptor (AHR) pathway enabled them to survive in toxic environment and it is a key target of natural selection. AHR signalling pathway led to the desensitisation of toxicity among tolerant populations.

Apparently, desensitisation of the AHR pathway would have brought some potentially negative effects, however, they were ameliorated through compensatory adaptations in terms of cell cycle regulation and immune system function. Killifish living in polluted estuaries have relatively different and complex genome when compared to other populations of killifish living in freshwater or in laboratory.

“This report highlights the complexity of the processes involved in the adaptation of wild fish to lethal levels of environmental pollution,” Professor Colbourne said. “It also demonstrates how the DNA of populations that differ in their susceptibility to pollutants can reveal ‘signatures’ of the adverse effects of chemicals in the environment.”

He further explained that killifish has relatively high level of DNA diversity among different populations and they have evolved very well to adapt different environments even if they are toxic enough to kill other species. Unfortunately, this unique ability is not present in most of the species present on earth because they can’t evolve so rapidly due to lack of high levels of genetic variation.

The study appeared in the journal Science.

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