Atlantic Molly Fish Types Have Different Predator Vulnerabilities

By on April 19, 2016
This hydrogen sulfide-rich spring in the Puyacatengo River in Mexico is one of many toxic environments where the Atlantic molly lives. (Credit: Kansas State University)

The Atlantic molly is an amazing fish and we have covered its abilities to survive before. But new research published in the journal Proceedings of the Royal Society B give new context to its durability.

The fish live in caves and springs throughout Mexico and thrive in water so toxic that most other forms of life would die within minutes of contacting it. The extremophile fish can even live in toxic water full of hydrogen sulfide from natural oil deposits and volcanic activity.

But there are two versions of this fish. One lives in the caves and another has adapted to living outside of them. The new research, led by Kansas State University, has uncovered a telling dynamic that is at play in ensuring that each molly fish can survive.

The K-State researcher, Michael Tobler, journeyed to the caves where the mollies live and observed the survival abilities of each type of molly when pursued by a predatory aquatic insect. What he found was that the cave mollies are more susceptible to being attacked in the light, a condition they are not accustomed to, while the surface mollies are more likely to be attacked in the dark.

The Atlantic molly is able to survive in toxic hydrogen sulfide water because of genetic mechanisms. (Credit: Kansas State University)

The Atlantic molly is able to survive in toxic hydrogen sulfide water because of genetic mechanisms. (Credit: Kansas State University)

To make those findings, Tobler used an interesting approach that relied on water bottles. As described in the journal article, he surveyed the Cueva del Azufre system in 2008. He would gather a few of each fish — surface molly or cave molly — and then put them in a bottle with openings to allow for the fish to take breaths at the surface while at the same time permitting a route for the predatory aquatic insect to attack.

After 24 hours, he would go back to the bottles, count the number of wounds on each fish and document any mortalities that took place. This cycle was completed 32 times. Tobler also conducted two other tests, wherein one he added the insect to a jar and didn’t add one to another.

The results of the effort help to show how the susceptibility to attacks from predators can help to shape genetic and phenotypic differentiation between different fish populations.

Top image: This hydrogen sulfide-rich spring in the Puyacatengo River in Mexico is one of many toxic environments where the Atlantic molly lives. (Credit: Kansas State University)

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