Do Fish Have Tongues? The Bony Basihyal, How Fish Taste, and the Louse That Takes a Tongue's Place

Do fish have tongues? Yes, but not one like yours. On the floor of a fish’s mouth sits the basihyal: a fold of bone with no muscles, no taste buds and almost no movement. It cannot lick or tell sweet from sour. Fish taste with their lips, their whiskers and, in catfish, their whole skin. Below: what the tongue is for, which fish carry teeth on it, how a salmon and a brown trout differ inside the mouth, and the parasite that takes a tongue’s place.

In 1983, Brusca and Gilligan examined 37 spotted rose snapper. Two had a female isopod sitting where more than 90% of the tongue had been. It is the only known case of a parasite functionally replacing a host organ.

What a fish tongue is: the basihyal

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. It carries no taste buds, so it tastes nothing (Australian Museum).

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 (Australian Museum). Water carries flavor straight to them, so a fish can taste a bait before it opens its mouth.

Catfish are the champions. A channel catfish carries taste buds over its whole body, whiskers to tail. It swims through a cloud of scent the way you walk into a kitchen where dinner is cooking. That is why it finds a chunk of cut shad in muddy water at night, and why what catfish eat is mostly a list of things that smell.

Do fish have teeth on their tongues?

Some do. The Australian Museum lists fish that carry small teeth on the basihyal, pointing backward to hold prey while the fish swallows. Salmon and trout are among them: their teeth line the jaws, the roof of the mouth and the tongue. 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, where rows of pharyngeal teeth grind food against a bony plate (Burke Museum). Watch one take a flake: the throat works, the tongue does nothing.

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, who examined 37 spotted rose snapper in 1983. Two carried a female isopod in place of more than 90% of the tongue. Whether the fish uses the louse as a working tongue for life has not been shown, as the Ethogram’s review of the study points out. The Australian Museum records other tongue-biting isopods; this one is the only parasite known to take an organ’s place.

Fish, tongue, teeth and taste

The angler’s part: salmon or brown trout, by 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. The check takes ten seconds.

1. 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.
2. Open the mouth gently and look at the roof. Down the center runs a narrow bone, the vomer.
3. Count the teeth on the vomer. A single small row, a few teeth toward the front: Atlantic salmon. A well-developed row that zig-zags down the bone: brown trout.
4. Look at the tongue. Narrow and tapering: salmon. Broad and square at the end: brown trout.
5. Check that the two clues agree. If not, trust the vomer; the tongue shape is the confirmation.
6. 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.

Why catfish taste bait with their whole body

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.

Why scent and flavor on soft plastics matter

A bass has taste buds on its lips and inside its mouth, so it tastes a worm the instant it closes on it. 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. Nobody has measured how much longer a bass holds a scented worm, 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.