As with all creatures, fish require energy to move around and live. And since they are wading through water, which is denser than air, they would need to expend more energy which is why fish need good breathing strategies to conserve their energy. The coffinfish for example holds its breath by inflating itself and filling its gill with water.
“This is a unique behavior for water-breathing fishes,” says Stacy Farina, a biologist at Howard University in Washington, DC, and the author of a new report documenting the discovery. “It’s the only case we’ve ever seen.”
Farina and Nicholas Long, an undergraduate student at Dickinson College in Pennsylvania, discovered the distinctive adaptation while watching videos of several species of coffinfish captured by a US National Oceanic and Atmospheric Administration deep-sea submersible in the Gulf of Mexico and North Atlantic. They were surprised to see the fishes stop pumping their gills.
Based on their observations, they found that the coffinfish can hold its breath for four minutes at least. Though it's a pretty rare behavior for fish to stop breathing, the coffinfish can afford this energy conservation strategy because it doesn't require a lot of energy in the first place, living a low-key lifestyle on the seafloor.
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