What Fish Cannot Close Its Mouth?

The lamprey is a long, fishlike creature which resembles an eel. Lampreys differ from fish in that they have no limbs (fish have fins) and practically no scales. The lamprey secretes a slime, which makes it almost impossible to grasp.

The most outstanding feature of the lamprey, however, is its mouth. This animal has no jaws. Instead, its round sucker mouth is rimmed by cartilage, so the mouth always remains open. Inside this mouth is a set of small, strong teeth. Its tongue is also equipped with teeth.

To feed itself, the lamprey attaches itself to other fish, first by suction, then by its teeth. Next, its toothed tongue rips open its victim’s skin. As it holds on, the lamprey sucks out the blood and other vital juices of the unwilling host.

Most fish get oxygen by allowing water to flow into their mouths and over their gills. The lamprey’s gills are in pouches in its body so the animal doesn’t have to use its mouth to get oxygen. It never has to let go of its fish host.