Fish Become Skilled Predators By Extending Their Jaws, Researchers Say

To grab a quick bite to eat, many fish extend their jaws to decrease the distance between them and their prey. After taking a closer look at the jaws of 60 living fish species, researchers now have a better understanding of how fish evolved with this nifty jaw protrusion trick.

"We take it for granted that all fishes can snap up elusive prey," David Bellwood, of James Cook University in Australia, said in a news release. "But it wasn't like that millions of years ago."

Researchers discovered that the ability of fish to extend their jaws in this manner is actually relatively new. In fact, it has only appeared within the last 100 million years of their 400-million-year history, the study revealed.

For their study, researchers developed a method in which they were able to predict a fish's jaw protrusion ability based on a simple anatomical measurement. Their measurements were derived from their analysis of living fishes' jaws. This allowed them to predict jaw protrusion in long-lost ancient fish.

"We knew that most [modern] fishes could protrude their jaws," Christopher Goatley, co-author of the study from James Cook University, said in the release. "The question was, when did this ability arise, and what anatomical features were required for protrusion?"

Fish were limited at first with how far they could extend their jaws to slurp up prey. But soon, jaw protrusion continued to increase for spiny-rayed fishes. Therefore this evolutionary development allowed the spiny-rayed fish to succeed and become dominate in modern oceans, the researchers noted.

Ultimately, the development of extendable jaws allowed fish to become enhanced predators and inevitably made prey more vulnerable to attack. This sheds light on why some modern crustaceans are so small.

"We think [that] over evolutionary time this drove prey to hide by becoming smaller, nocturnal, or hiding in holes," Bellwood explained in the release. "Today the average crustacean on a coral reef is less than a millimeter long. This may be a consequence of increasing predation pressure."

Their findings shed light on the predator-prey relationship among marine species. Their study was recently published in the Cell Press journal Current Biology.

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