Researchers notices tubelip wrasses, a type of coral reef fish, have slime on their “lips” to help them eat corals. These may not have been the fish Nick Cave referred to when hey sang the line “Well, you know those fish with the swollen lips that clean the ocean floor” in his dark ballad O’Malley’s Bar, but this news about the slime-covered lips of this reef fish brought it to our minds.
For anyone that’s been effected by a scrape on a stony coral knows, they tend to be sharp, venomous and coated with a protective mucus making them a tough meal for hungry fish. But the tubelip wrass (Labropsis australis), has developed an unusual strategy to get past the defenses and grab a bite — slime-covered kisses. The research team published their findings last month in Current Biology.
When looking at the differences between wrasses, the team noted those that don’t eat corals have thin lips and protruding teeth that resemble a beak. The difference for tubelip wrasses is they have elongated, fleshy lips that they use to suck up a reef’s protective mucous coating.
Some amazing pictures of scans taken with an electron microscope show the tubelip wrasse has plenty of little channels and divots of soft ribbing, akin to the bottom side of a mushroom. What makes these special? The grooves contain mucous glands that cover their lips in protective slime.
“We’ve never seen anything like this,” says David Bellwood, a marine biologist at James Cook University in Townsville, Australia, and a co-author of the paper. “Self-lubricating lips! Who would have predicted that?”
According to the news report, the mucus helps protect the lips from the corals’ stinging cells and in combination with the grooves, the mucus helps the tubelip wrasses to form a seal against jagged pieces of coral. “This enables them to suck up their meal of the coral’s mucus like someone drinking a milkshake through a straw. The seal is so strong that the kiss ends with an audible smacking sound.”