Introduction
In a groundbreaking discovery, marine biologists from the University of California, Davis, have revealed that some reef fish possess a rare ability among vertebrates—the ability to move their jaws from side to side. This lateral jaw movement allows fish to efficiently graze algae and other food sources from hard reef surfaces, helping them thrive in competitive coral reef ecosystems.
Published in the Proceedings of the National Academy of Sciences (PNAS, 2025), this research sheds new light on the functional evolution of fish feeding mechanisms.
Why Lateral Jaw Movement in Fish Matters
Humans and other mammals routinely move their jaws sideways while chewing, but among the over 30,000 species of fish, this motion is nearly unheard of. According to senior author Professor Peter Wainwright of UC Davis, this rare capability carries important ecological and evolutionary implications.
“Among vertebrates, lateral jaw motion is extremely unusual,” said Wainwright. “Its presence in reef fish provides a major feeding advantage in algae-rich environments.”
High-Speed Video Reveals the Secret in Action
Lead researcher Dr. Michalis Mihalitsis captured the lateral jaw movements using high-speed cameras while studying the Zanclus cornutus, commonly known as the Moorish Idol. This striking reef fish, known for its elongated snout, was seen manipulating both its upper and lower jaws side-to-side—allowing it to dislodge food from crevices and reef cracks.
The researchers also examined surgeonfish (Acanthurus chirurgus), a dominant group of herbivores on coral reefs. These fish showed similar sideways jaw movements, which help them bite and tear algae more efficiently from rock surfaces.
“They take a mouthful of algae and rotate their jaws to shear it off the reef,” Wainwright explained.
CT Scans Confirm Anatomical Adaptations
To verify the observations, researchers conducted CT scans and detailed dissections of the Moorish Idol and surgeonfish. The scans confirmed the structural adaptations that allow for lateral jaw rotation—a trait not visible to the naked eye due to its speed and subtlety.
“For the Moorish Idol, this jaw flexibility appears to help them access food in tight reef spaces,” said Mihalitsis. “In surgeonfish, it likely enhances feeding efficiency on open surfaces.”
Implications for Coral Reef Ecology and Fish Evolution
These discoveries offer deeper insight into how herbivorous reef fish have adapted their feeding mechanics over millions of years. Reef ecosystems are highly competitive, and efficient algae grazing is crucial for survival.
Understanding these jaw mechanisms may help marine scientists better predict how reef fish populations adapt to changing habitats and food sources—especially as coral reefs face increasing threats from climate change and pollution.
Looking Ahead: Exploring More Benthic Feeders
The research team plans to investigate additional reef fish species with similar benthic feeding strategies to see whether lateral jaw movement is more widespread than previously believed.
About the Study and Authors
The study, titled “Lateral jaw motion in fish expands the functional repertoire of vertebrates and underpins the success of a dominant herbivore lineage”, was published in PNAS in 2025.
Lead Author: Dr. Michalis Mihalitsis (now Assistant Professor, University of Guam)
Senior Author: Prof. Peter Wainwright, UC Davis
Co-authors: Denise Yamhure-Ramirez, Maelan Beil, Nathan Cole, Nicole Shum, Bryson Zheng (UC Davis); HoWan Chan (Rice University); Isabella Paglione, Hallee Petri, and Dylan Wainwright (Purdue University)
Reference:
Michalis Mihalitsis et al., Proceedings of the National Academy of Sciences (2025). DOI: 10.1073/pnas.2418982122