A team of researchers reveal novel feeding adaptations surgeonfish use to remove algae from coral reefs

Globally, coral reefs are under siege by multiple stressors, one of which is herbaceous algae. An overabundance of algae on reefs can lead to regime shifts of reefs from being coral-dominated to algal-dominated. 

University of Guam Marine Lab Assistant Professor Michalis Mihalitsis, and a group of scientists from California and Australian have been investigating the mechanisms of how algae-loving fish remove algae from reef substrates. Their study — published in the Proceedings of the Royal Society B (Biological Sciences)— focused on 15 species of surgeonfish (Acanthuridae), which are one of the most dominant herbivores removing algae from reefs. Their results provide crucial insights into the biology of the species.

“Specifically, we aimed to understand how different species use different parts of their bodies, such as teeth, jaws, and fins, to detach algae, as well as how frequently they use these motions during feeding,” said Michalis Mihalitsis, an assistant professor of vertebrate morphology at the UOG Marine Lab and first author on the study.

Using high-speed videography in aquaria, Mihalitsis and his team filmed at 1,000 frames per second to capture how individuals feeding on tufts of filamentous algae moved different body parts during a bite that lasted only a few milliseconds.

Surgeonfish species utilize three main bite types to feed on algae. Each technique requires a different set of adaptations, such as the evolution of different teeth and jaw structures.

The study showed that surgeonfish use various combinations of feeding movements and that each species uses a particular pattern more often — the pattern matching one of the three types of bites. By extracting teeth from these species for examination, the researchers were able to reconstruct the evolutionary history of bite mode across surgeonfish.

“Our results may help in the understanding of why some species of surgeonfish exhibit a preference for certain types of algae while ignoring others, or why some species feed in areas that others don’t. This may provide deeper clues as to how reefs are changing and what drivers (such as herbivory) are contributing to various reef processes,” Mihalitsis said.

Future studies will look at the impact and dynamics of these different feeding types in the wild, which may reveal differences in surgeonfish diets and the places they feed on the reef.