The Tubelip Wrasse Has Special Lips For Chowing Down On Coral

Of all the snacks in the sea, coral isn't the most tempting. After all, it's hard, it's sharp and it can seriously injure you. Despite all that, there's one kind of fish that makes a regular meal out of the stuff, and that has perplexed experts. According to a 2017 study, the tubelip wrasse's ability to nosh on coral is all in the lips.

This photo shows a tubelip wrasse feeding on coral.

Funny Name, Curious Fish

According to a study published in Current Biology, the fish don't eat the coral the way you might eat potato chips—it's more like you would eat a lollipop: They "kiss," or suck the soft flesh and mucus from the coral's skeleton, protecting themselves thanks to their self-lubricating lips.

Australian researchers discovered this using incredible microscopic images of the feeding fish, comparing them to other fish that don't feed on coral. "High-speed video images of feeding tubelip wrasses showed that they briefly place their lips in contact with the coral prior to delivering a powerful suck. Rather than grabbing onto coral, they appear to seal the mouth over a small area, presumably to increase suction-feeding efficiency," according to a press release.

In another press release, professor David Belwood of James Cook University in Australia said the tubelip wrasse's self-lubricating lips work kind of like a runny nose. "Their lips have a specialised feature that secretes mucus. This may help the wrasse to reduce damage from the sharp coral and from the stinging nematocysts." Those stinging nematocysts are how the coral itself dines on sea creatures swimming nearby.

Other sea experts are excited about the advance. "This paper significantly extends our knowledge of how fish eat coral—one of the rarest feeding habits found among reef fish," Peter Wainwright, a fish biologist at the University of California, Davis, told National Geographic. But because it's hard to test the findings, Wainwright told National Geographic the topic will remain a "wonderful mystery" for now.

This scanning electron microscope image shows a close-up of the mouth of a tubelip wrasse with self-lubricating lips. These lips enable the fish to 'kiss' mucus and flesh from the surface of corals.

A Rare Exception

While the tubelip wrasse has overcome the difficulties involved in eating coral, it's in the minority. Researchers report that less than 150 of the more than 6,000 neighboring sea creatures dare to dine on coral.

And that continued peace of mind for the dangerous invertebrates may be a good thing, considering coral reefs are in trouble. According to the National Oceanic and Atmospheric Administration (NOAA), "They are threatened by an increasing range of impacts including pollution, invasive species, diseases, bleaching, and global climate change."

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Written by Haley Otman June 28, 2017

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