Do Fish Have Tongues? Basihyal, Taste and the Tongue Louse

A steelhead with its mouth held wide open, showing the tongue on the floor of the mouth — Photo: U.S. Fish and Wildlife Service, Pacific Region (public domain)

Key takeaways

A fish tongue is the basihyal: a fold of bone on the floor of the mouth, with no muscles and few or no taste buds. It barely moves and probably began as a shield for an artery.
Fish taste with taste buds on the lips, the barbels and the skin. A channel catfish tastes with its whole body, which is why it finds cut bait in muddy water.
Some fish carry teeth on the tongue. Salmon and trout do; a goldfish has none, and chews in its throat instead.
An Atlantic salmon has a single small row of teeth on the vomer (the roof of the mouth), few or none at its front. A brown trout has a well-developed zig-zag row (Maine IFW).
In 1983 Brusca and Gilligan reported a louse in place of more than 90% of the tongue in two of 37 snapper: the first known case of a parasite replacing a host structure.

Fish have tongues, but a fish’s tongue is a fold of bone called the basihyal, with no muscles, few or no taste buds and almost no movement. It sits on the floor of the mouth and cannot lick or tell sweet from sour. Fish taste with their lips, their whiskers and, in catfish, their whole skin. That is how a catfish finds a chunk of cut bait in muddy water.

In a paper published in 1983, Brusca and Gilligan reported on 37 spotted rose snapper. Two had a female isopod sitting where more than 90% of the tongue had been. The authors called it the first known case of a parasite functionally replacing a host structure.

What is a fish tongue made of?

Your tongue is a bundle of muscle covered in taste buds. A fish’s tongue is a bone. The basihyal is the front end of the hyoid, the set of bones that works the floor of the mouth and the gill covers. It sits under the skin as a small, stiff pad with no muscle of its own, so it cannot move by itself. BBC Science Focus says it has no taste buds; a 2014 microscope study of five northern pike tongues found scattered ones on their surface. Either way, the tongue is not where a fish does its tasting.

So why have one at all? BBC Science Focus gives the best guess. Right beneath the floor of the mouth runs the ventral aorta, the vessel that carries blood from the heart to the gills. A fish swallows its prey alive and whole, and a struggling minnow or crayfish could tear that vessel. The bony basihyal probably began as a shield for the artery, not as a tool for eating.

Can fish taste?

Yes, very well. Fish simply keep their taste buds somewhere else: on the lips, inside the mouth, on the barbels (the whiskers of a catfish or a carp) and on the skin. Water carries flavor straight to them, so a fish can taste a bait before it opens its mouth.

Catfish are the champions. North Dakota Game and Fish calls the channel catfish a “swimming tongue”: its taste buds are densest near the mouth and on the barbels, and taste receptors cover its entire body. It swims through a cloud of scent the way you walk into a kitchen where dinner is cooking. A catfish tongue, the bone on the floor of its mouth, is the same plain basihyal as any other fish’s; the nickname comes from the skin. That is why it finds a chunk of cut shad in muddy water, and why what catfish eat is mostly a list of things that smell.

Do fish have teeth on their tongues?

Some do. In some bony fish, teeth on the tongue help hold prey, the Australian Museum notes. Salmon and trout are among them: their teeth line the jaws, the roof of the mouth and the tongue. A well-developed set on the basihyal bites against the teeth on the vomer above it, a “tongue-bite” that rainbow, brown and brook trout use to pin and shred prey after the catch (Sanford, SICB). A sea lamprey goes further. Its tongue sticks out and works as a rasp that files a hole in the side of another fish.

Do goldfish have tongues? A goldfish has the same bony floor of the mouth as every other bony fish, and no teeth on it, because it has no jaw teeth at all. It chews in its throat instead, where rows of pharyngeal teeth grind food against a horny chewing pad on the base of the skull, as in its relative the grass carp. Watch one take a flake: the throat works, the tongue does nothing.

Do sharks have tongues? Yes, and theirs is cartilage instead of bone: a small, thick slab on the floor of the mouth, also called the basihyal. The Florida Museum calls it useless in most sharks. The exception is the cookiecutter shark, which uses it to rip chunks of flesh out of its prey, leaving round holes in tuna, marlin, dolphins and whales. A shark does not taste with it either; its taste buds sit on small bumps lining the mouth and throat.

What is the tongue-eating louse?

The isopod Cymothoa exigua is a sea-going relative of the roly-poly in your yard. It settles in a fish’s mouth and clamps onto the tongue, which withers to a stump. The louse stays, gripping the stump, and the fish goes on eating with a parasite where its tongue used to be.

The numbers come from Brusca and Gilligan: one of them examined 37 spotted rose snapper caught near Guaymas, Mexico, in 1979, and the paper came out in 1983. Two carried a female isopod in place of more than 90% of the tongue. Brusca and Gilligan called the working-tongue idea a hypothesis: the parasitized fish showed no sign of eating or breathing worse. The Australian Museum records other tongue-biting isopods; this one was the first on record to take over the job of the part it destroyed.

Which fish has what tongue?

Fish	Tongue	Teeth on it	Tastes with
Atlantic salmon	Bony basihyal	Yes; above it the vomer carries a single small row, few or none at the front	Lips and the inside of the mouth
Brown trout	Bony basihyal	Yes; the vomer carries a well-developed zig-zag row	Lips and the inside of the mouth
Channel catfish	Bony basihyal	No	Barbels, lips and the whole skin
Goldfish and common carp	Bony basihyal	No; grinding teeth sit in the throat	Lips; a carp also with its barbels
Sharks	Small, thick slab of cartilage; useless in most sharks	No; the cookiecutter shark rips flesh with it	Taste buds lining the mouth and throat
Sea lamprey	Sticks out; a rasp	Yes, a rasping surface	Mouth, not the tongue
Spotted rose snapper with the louse	Gone; the isopod sits in its place	No	Lips and the inside of the mouth

Salmon or brown trout? Check the mouth

An Atlantic salmon and a brown trout look alike in the hand, and the rules for keeping them are rarely the same. Maine Inland Fisheries and Wildlife separates them by the mouth, with the tail as a second clue. The check takes ten seconds.

Keep the fish in the water or a wet net, and wet your hands. The fish should not pay for the check with its slime coat.
Open the mouth gently and look at the roof. Down the center runs a narrow bone, the vomer.
Count the teeth on the vomer. A single small row down the shaft and few or none at the front: Atlantic salmon. A well-developed row that zig-zags down the shaft, with teeth at the front too: brown trout.
Look at the tail. Slightly forked: salmon. Square and unforked: brown trout. If the two clues disagree, treat the fish as the one with the stricter rule.
Decide before the fish goes in the cooler. The two fish are often under different limits on the same water, so check the rules for each.

What does this mean for catfish bait?

A channel catfish does not need to see your bait. The taste buds on its flank pick up the scent trail, and the barbels find the bait in the dark. So the bait’s job is to leak flavor, and yours is to leave it there long enough. The best catfish baits do exactly that: cut shad, chicken liver, dip bait. A bait moved every two minutes never builds a trail.

Does scent on a soft plastic matter?

A bass has taste buds throughout the mouth, including the lips and the gills, says Dr. Keith Jones, the retired head of Berkley’s fish lab (In-Fisherman). So it tastes a worm the instant it closes on it. In a University of Florida lab study, largemouth bass inhaled food balls with or without a feeding stimulant equally often, but swallowed the flavored ones and promptly spat out the plain ones (Linser and colleagues, 1998). Salt, scent and flavor built into a soft plastic give the fish a reason to hold on a moment instead of spitting, and that moment is when the hook goes in. That study used food balls, not soft plastics, so treat the gain as a small edge, not a guarantee.

That tasting never switches off. A fish resting on the bottom at night still reads the water with its lips and skin, one reason a bait dropped on the nose of a quiet fish can work (do fish sleep?). More questions like this one, each with its number and its source: fish facts.

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