When scientists X-rayed the head of a banded wrasse, they discovered a parasitic crustacean that had eaten away and replaced the host’s tongue.
Our planet is home to many terrifying parasites, but few creatures can match the horror brought by the tongue-eating louse, also known as Cymothoa exigua.
This organism enters fish through their gills, attaching itself until it matures. At this point, it undergoes a sex change from male to female.
Once this process is complete, the parasite begins its journey to the fish’s mouth. Here, it firmly attaches to the fish’s tongue using sharp claws on its legs and starts to “feed wildly” on its blood.
After some time, the blood vessels in the fish’s tongue can no longer meet the demands of the parasite. Eventually, the fish’s tongue becomes anemic, leading to necrosis and eventually falling off.
At this moment, a horrifying process occurs as the tongue-eating louse becomes a “replacement” for the fish’s tongue, acting like a prosthetic. Notably, Cymothoa exigua is the only organism on Earth that can completely replace a host’s organ without causing the host’s death during this process.
The tongue-eating louse (green) in the mouth of a banded wrasse. (Photo: Live Science).
There are approximately 380 species of tongue-eating lice, primarily targeting specific types of fish, according to the Two Oceans Aquarium in Cape Town, South Africa. They enter the fish’s body through its gills, attach to the tongue, and secrete anticoagulants to ensure a continuous blood flow. They firmly latch onto the base of the tongue using seven pairs of legs, reducing the blood supply, which ultimately leads to the organ’s atrophy and loss, according to the Australian Museum.
Afterward, the body of the tongue-eating louse functions as a normal tongue while continuing to siphon mucus from the fish. The symbiotic relationship between the fish and the louse can last for many years. In many cases, the fish even outlives the parasite, according to Stefanie Kaiser, a postdoctoral researcher at the National Institute of Water and Atmospheric Research in Wellington, New Zealand.
Biologist Kory Evans, an associate professor at Rice University in Houston, Texas, encountered the fish and its living tongue during a project aimed at creating a 3D X-ray database of the skeletal structures of this fish family living on coral reefs. The goal of the project is to provide resources for researchers worldwide.
“That morning, I was comparing the skull shapes of different fish and had to place digital markers on various body parts. When examining the fish scientifically named Odax cyanomelas in New Zealand, I noticed something strange in its mouth. It looked like some kind of insect. Then I thought about how this fish eats algae. So, I reviewed the images and discovered the tongue-eating louse,” Evans recounted.
