A kiss from a colourful reef fish called a tubelip wrasse is no one's idea of romance, being so full of slime and suction, but it is perfectly suited for eating a hazardous diet using one of the animal kingdom's most unique feeding strategies.
Scientists from Queensland's James Cook University on Monday described how the fish thrives in the Indian Ocean and central-western Pacific as one of the few creatures capable of dining on corals, one of the planet's most difficult menu items.
Corals are marine organisms boasting thin, mucus-covered flesh that contains venomous, stinging cells spread over a razor-sharp skeleton. Of the more than 6,000 fish species that live on reefs, only about 128 eat corals. Scientists knew that the yellow-and-purple tubelip wrasse was one of them, but how it did it was a mystery.
The researchers used a scanning electron microscope to determine the structure of its fleshy, pouty-looking lips and high-speed video to learn what it does while feeding.
"Kissing the mucus and flesh of corals with self-lubricating lips was not what we were expecting," marine biologist Victor Huertas said.
The thick lips of the fish, which reaches about 18 centimetres long, were found to be made of a tightly packed series of thin folds of tissue, like the underside of a mushroom top, covered in slime from mucus-secreting cells.
"To our knowledge, this type of lip has never been recorded before," marine biologist David Bellwood, also at James Cook University, said.
They discovered that the fish approaches the coral slowly and inspects its surface, protrudes its jaws, then produces powerful suction as its lips make contact with the coral for two-100ths of a second. In that scant time, it ingests the flesh and coral mucus off the coral skeleton.
"It looks exactly like a quick kiss with a distinctive 'tuk' sound," Huertas said, "often leaving a coral 'hickie,' which is actually a patch of flesh sucked off the skeleton."
The research was published in the journal Current Biology.
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