Duck lips or fish lips are a constant fixture on millennials obsessed with selfies. However, for a tropical fish, these protruding lips are essential to its survival.
A new study found that the tubelip wrasse — scientifically known as the Labropsis australis — depends on its slimy lips to feed on sharp stinging coral.
Though corals look pretty and fragile from outside, they are one of the toughest and most challenging organisms to consume courtesy their thin, mucus-covered skin which is protected by stinging venomous cells and are distributed over the razor-sharp skeleton.
As the coral are not fit as food for the over 6,000 fish species that dwell on the reef, only 128 of them live on coral. During the study of these fish, researchers discovered how the tubelip wrasse fish feed on coral.
Tubelip Wrasse Fish Specialized Lips Helps In Eating Coral
The study’s first author Víctor Huertas and his colleague David Bellwood identified that the problem of feeding arose when the tubelip wrasse’s lips came in contact with the corals’ stinging skin. The researchers wanted to gain in-depth knowledge on exactly how the tubelip wrasses overcame this difficulty.
To make this assessment, Bellwood and Huertas used an electron scanning microscope to observe the slimy lips and mouth of the tubelip wrasse fish species and compared them with a non-coral eating wrasse species in detail.
During the study the researchers observed that both the coral-feeding and non-coral feeding wrasse fish species sported similar jaw and teeth bones, but their lip structure and composition was vastly different.
The scientists observed that the coral feeding tubelip wrasse fish had thin membranes arranged from the center of its slimy lips in an outward direction, whereas the other species of wrasse fish had smooth narrow lips, which were devoid of membranes.
Once the researchers discovered the membranes in the lips, they delved deeper into the internal structure of the lips. To do so, the researches took cross-sections of tubelip wrasse fish’s lips and discovered that they were packed with mucus-secreting cells.
“The lips are like the gills of a mushroom but covered in slime. It is like having a running nose but having running lips instead,” Bellwood explained.
Both Huertas and Bellwood also analyzed the high-speed video images of tubelip wrasses eating coral. It was during this examination that the researchers found that the tubelip wrasse fish “kisses,” or more accurately sucks on the corals powerfully along with an audible “tuk” sound. Thus, instead of grabbing the coral, the fish creates a seal over a small area of the corals to suction-off the flesh and mucus.
Tubelip Wrasse Fish Slimy Lips: How Do They Help?
The latest discovery reveals that the tubelip wrasse fish mainly survives by feeding on coral mucus. Bellwood states that now the researchers will know that lips can also be used as an important feeding tool in fish.
The researchers feel that the mucus-laden slimy lips of the tubelip wrasse fish may act like a protective coating between the fish’s lips and the coral’s venomous stinging skin cells, apart from helping it create suction.
The study’s findings were published in the journal Current Biology on Monday, June 5.