Reef fish diversified quickly from biting their prey

Coral reefs are home to a spectacular variety of fish. A new study shows that much of this diversity is driven by a recent innovation among bony fish – feeding by biting prey from surfaces. 

Teleosts – a group of bony fish – did not feed, graze or nibble food off rocks and corals until after the dinosaur extinction at the end of the Cretaceous period, about 60 million years ago. 

Study lead author Katherine Corn is a graduate student in the UC Davis Department of Evolution and Ecology and Center for Population Biology.

“There may have been some biting done by teleosts before the end-Cretaceous, but our reconstructions suggest that it was very uncommon,” said Corn.

Modern reef fish feed in a variety of ways. Many suck floating food by rapidly expanding their heads, known as ‘suction feeding’. Suction feeding is thought to be ancestral in teleosts. A smaller number are “ram biters,” which catch food by swimming onto it with their mouths open. 

Many reef fish, including parrotfish, butterflyfish and triggerfish, bite their food off hard surfaces. This gives them access to prey such as snails and shellfish, algae and other animals and plants.

The research team classified 1,530 living species of reef fish by feeding method, then mapped them onto an evolutionary tree of the teleosts. They also studied the rate of body shape evolution in all of these fish. 

The experts found that at the end of the Cretaceous period, nearly all fish were suction feeders. Today, four in 10 reef species are “benthic biters” and are evolving in body shape at almost twice the rate of suction feeders.

What set off these changes? The end of the Cretaceous saw changes in coral reefs, with more complex and branching structures that made grazing more productive. This occurred at the same time teleosts evolved shorter jaws that were better for biting. 

“These two changes together really opened up biting as an effective mode for fishes,” explained Corn. Biting allowed reef fish to access diverse new prey, promoting the evolution of a wide variety of body shapes. This may explain the high rates of body shape evolution and diversity of biter species today.

The work was supported by the National Science Foundation. The research is published in the journal Proceedings of the National Academy of Sciences. 

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By Katherine Bucko, Earth.com Staff Writer