Chuck Bednar for redOrbit.com – @BednarChuck
As its ecosystem transformed from a relatively cool lake region to a desert with just a handful of hot springs and temperatures of up to 95 degrees Fahrenheit, one critically-endangered species of fish responded in extreme ways, according to a new University of Nevada, Las Vegas study.
In response to those changing conditions, the desert pupfish developed the ability to go without oxygen for up to five hours at a time, UNLV life sciences professor Frank van Breukelen and his colleague Stanley Hillyard discovered. Their research, due out later this year, was discussed last week at the American Physiological Society’s Experimental Biology Meeting.
Replacing oxygen with ethanol for respiration
The pupfish, which lives in pools of water near California’ Death Valley, is living, breathing (or not, in this case) proof that species can adapt and endure despite relatively rapid changes to their environment, according to National Geographic. As their home grew increasingly hotter, the fish responded by spending less time in the shallower, warmer shelf where they breed.
That’s not exactly good news for the species, the website said, especially when combined with habitat loss and increased competition with non-native species. So how have the fish been able to survive? By adapting and randomly alternating between aerobic (or oxygen-based) and anaerobic (or oxygen-free) respiration, which allows it to go several hours without breathing.
Breaking down inhaled oxygen is a great way to generate energy, but this process can be harmful for the pupfish at high temperatures because it produces chemically-reactive molecules known as free radicals that can damage proteins, cell membranes and DNA, the website said. So at times, it generates ethanol, which is then broken down for energy without the need for oxygen.
Choosing “the lesser of two evils” in order to survive
This isn’t as easy as it sounds, van Breukelen explained. During periods of anaerobic respiration, the pupfish’s metabolism works roughly 15 times harder to produce energy than when it is using oxygen to produce energy. The process can be taxing on the creature, but changing conditions pretty much left them with no alternative – it’s “the lesser of two evils,” he told Nat Geo.
Interestingly enough, van Breukelen told redOrbit via email that he and Hillyard had “stumbled into the work by accident. The fish were available and we thought we’d quickly measure oxygen consumption to estimate their energetic needs. We knew that their native environment is severely energy limited and we really wanted to know how many fish could be supported.”
“We were not expecting what we found,” the professor added. “Much of physiology is based on the idea that animals need to use energy as efficiently as possible. Our results emphasize an idea that other ‘costs’ may actually require animals to use less efficient processes. If these fish can do it, what else can do it? Many researchers equate oxygen consumption with metabolic rate and that may not be a great assumption.”
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