Photograph by Denham Parker
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This largespot pompano has had its tongue eaten, and replaced, by a female tongue-biter isopod.

Photograph by Denham Parker

Isopod Got Your Tongue? Naturally Tongueless Animals

Some animals are naturally tongueless, but certain unlucky fish lose their tongues to parasites.

Rarely do questions make us speechless.

“Is there any animal that naturally has no tongue?” Jeanette Thorpe asked Saturday’s Weird Animal Question of the Week via Facebook. (Check out Five of Nature’s Weirdest Tongues.)

There are, but this being Halloween, we’ll start with animals that have tongues…for dinner.

“If the host’s tongue is unoccupied…”

Isopods of the family Cymathoidae look like oversized fleas and inhabit shallow marine, brackish or fresh subtropical waters—and some of the fish that live there. These tiny invertebrates float along in the ocean mimicking prey items. When swallowed by a fish, the isopod first attaches itself to the fish’s gills. It then latches onto and eats the fish’s tongue—giving these isopods the nickname of “tongue biters”—and takes up residence as a replacement tongue for the fish.

That’s not the weirdest part of the story.

All tongue biters enter the fish’s gills as males, but that can change. “The majority of tongue-biting isopods are protandrous hermaphrodites,” says Denham Parker of Rhodes University in South Africa, via email. They start out as male but are able to transform into females.

“If the host’s tongue is unoccupied, the male isopod moves from the gills and attaches to the tongue,” Parker says. Once attached, it transforms into a female, which is much larger, and consumes and replaces the tongue, all of which probably happens simultaneously. It then waits for another male to occupy the fish’s gills.

They will stay there and breed, with the female releasing fertilized eggs into the water.

The fish survive the parasitism, but it may take a toll on them, Parker reported in 2013. He collected largespot pompano from a bay in South Africa and found that being parasitized with Cymothoa borbonica isopods affected the fish’s growth, probably because the tongue biters make eating and breathing more difficult. The fish, however, usually outlive the parasites.

Parker says there’s no evidence that eating an infected fish will cause any harm to humans.

Except for the nightmares.

View Images

This bat star and the purple sea urchins that surround it have no tongues.

Taste sensations

Other animals naturally have no tongues, such as sea stars, sea urchins and other echinoderms, as well as crustaceans, says Chris Mah via email. Mah is a marine invertebrate zoologist at the Smithsonian National Museum of Natural History and has discovered numerous species of sea stars.

Sea stars are omnivorous, Mah points out on his Echinoblog, and feed in different ways, including swallowing prey items whole or by pushing their stomach out through the mouth and using it to take in prey, no tongue required.

Insects, too, are tongueless, Philip Koehler, an entomologist at the University of Florida, writes via email. But they still manage to get along fine without one.

Butterflies and flies taste with their feet. And fruit flies have taste receptors all over their bodies, including on their wings and ovipositors, the opening through which they lay eggs.

“Cockroaches taste with the paraglossa, which is next to their mouth,” Koehler says. (Don’t think about a roach putting its whole face into your sugar.)

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This swallowtail butterfly has coiled its “tongue,” but it actually tastes with its feet.

Of tongues, real and fake

Sometimes what looks like a tongue isn’t one. Hawk moth “tongues,” for instance, are actually siphoning mouth parts that Koehler says are used to reach deep into flowers for nectar. These faux-tongues can reach up to 14 inches (36 centimeters) in length, twice as long as the moth’s body.

Some mollusks, such as snails and squids, have a tongue-like organ called a radula. The University of California Museum of Paleontology website describes this organ as a “ribbon of teeth” supported by a muscular structure. Though bivalves like clams and mussels are mollusks, they have lost this feature but don’t have tongues either, Jackie Cooper, senior aquarist at the National Aquarium in Baltimore, notes in an email.

Sometimes, though, there’s no substitute for the real thing.

“Alligator snapping turtles have the coolest tongue of all of the animals I have worked with,” Cooper says. They wiggle their bright red tongue to attract prey, she notes, “sometimes right into their mouth.” (Watch video of these amazing tongue traps.)

Hmmm…if only I could sit still and lure the ice cream to me.

Weird Animal Question of the Week answers your questions every Saturday. If you have a question about the weird and wild animal world, tweet me, leave me a note or photo in the comments below, or find me on Facebook.