Evolution of Killifish Allows Adaptation to Polluted Waters of New Jersey

The Passaic River and Newark Bay in New Jersey are full of toxic pollutants, killing many fish and organisms in the area. However, one of the most diverse vertebrates, the Atlantic killifish, has managed to adapt to these conditions. Several independent populations of killifish have evolved different adaptations to the toxic environment. Biologist Diane Nacci with the Environmental Protection Agency (EPA) and other scientists compared 384 killifish genomes, finding that tolerance to this pollution is found on the aryl hydrocarbon receptor (AHR) signaling pathway for each of the populations, but that different nucleotide patterns were found in each one. An environment that would kill killifish without the mutation can house several different populations with slightly different mutations. Scientists believe that the ability for killifish to adapt quickly are due to very large populations, and therefore greater nucleotide diversity.

However, though some animal species have the capacity to adapt to large amounts of pollution and effects from climate change, that does not mean that all species are capable of that. It is likely that only a select few species will have the capacity to mutate or evolve resistance to human-induced effects such as pollution or accelerated climate change. On a different note, if the water is cleared up again, the killifish with the mutation for pollution resistance may not survive as well as killifish without the mutation, though by that point most if not all of the killifish without the pollution resistance in the area may have already gone extinct. It is very important to look at the grand scheme of things, and if people continue to contribute pollution and fossil fuels into the environment, species that are low in numbers are unlikely to develop a resistance and are likely to go extinct. Though this study gives clues into how natural selection operates under extreme conditions, people should not let the planet and its living creatures come to this point.

http://www.nytimes.com/2016/12/09/science/atlantic-killifish-evolution-pollution.html?rref=collection%2Fcolumn%2Ftrilobites

http://science.sciencemag.org/content/354/6317/1305.full

A Mutation in the Killifish Enables it to Survive in Harmful Conditions

The Atlantic killifish is native to the Atlantic coast of the United States. A large amount of killifish live in the Lower Passaic Superfund site. The State of New Jersey prohibits people to eat fish from this site because they are contaminated by toxic leftovers of DDT and Agent Orange. These chemicals are strong enough to wipe out the entire population in the area; however, plenty of killifish are still living and thriving in the area. This is because the fish are somehow tolerant to the toxins in the water. 

A new study discovered that in just a few decades, separate populations of killifish adapted a mutation to survive in abnormally extreme conditions. The scientists of the study looked at the genomes of 384 populations and found that, in all populations, "one particular genetic pathway was the source of the pollution tolerance." Typically, harmful chemicals set off changes in the fish, causing death in adults and problems in embryos. Tolerant fish are barely affected by the chemicals; they can survive in conditions that are thousands of times more polluted than what sensitive fish die in. In killifish, like in all animals, a big genome is used to their advantage. Genetic differences allow for the mutation to actually be advantageous. The fish that did not have the mutation died, and the fish that had the mutation lived and reproduced. Smaller populations that were less genetically diverse died off. 

The scientist from this study suggest that many other species can adapt to survive in extreme conditions caused by pollution and climate change. They add that while some species can adapt, many species can not. As people of the world, we must take it upon ourselves to stop pollution before it is too late. Humans are just another animal that inhabit the Earth. It is not our planet to destroy. Ignorance has got the world to close to a breaking point in global warming. We have not always known that our industries are polluting the world, but know we do. We can no longer just stand by and watch the world far apart. Clearly, no one is capable of saving the world alone. However, everyone can contribute simple things such as recycling, using less water, and conserving energy to put us on the step in the right direction.

Eastern Killifish Evolve to Handle More Pollution

Killifish of Eastern America have been found surviving pollution levels thousands of times over the typical tolerance levels, compared to a fee decades ago. Significant evolutionary changes have occurred in the killifish in only about half a century to allow them to tolerate such polluted conditions. The time frame of 50 years is impressive, since many people tend to think evolution takes millions of years. In fact this extremely rapid change is only possible when a species has immense diversity. Organisms that lack diversity can cope only with gradual, slow paced changes.
The increased trend in pollution, as well as the growing availability of genomic sequencing, there has been more ecological studies that employ these methods to find exact mutations leading to the successful mutations in question. This killifish exhibits alterations in the genome affect the AHR pathway which is related to the immune system and oestrogen signalling. Usually, this pathway is triggered by natural toxins, but the pollution can also trigger responses in young killifish leading to detrimental effects and death in young killifish. The mutation helps make this pathway more selective to avoid being active in young fish.

Links:

https://www.newscientist.com/article/2115635-fish-rapidly-adapt-to-pollution-thousands-of-times-lethal-levels/ 

http://science.sciencemag.org/content/354/6317/1305