The mouth of the lamprey and the hagfish puts them high on the list of nature’s oddities. Instead of having jaws, the mouth is surrounded by a band of cartilage. The creatures are thus doomed to swim through life with their mouths always open.
However, the circular mouth is a very efficient sucker with which they can attach themselves to rocks and stones and even to other fish.
Most of the cyclostomes that live in fresh water do not eat at all during their adult stages and consequently are never taken on hooks. An occasional specimen is caught in a net or trap, much to the horror of fishermen, many of whom believe that the fish are venomous.
The creatures are not venomous, and since they do not have jaws it is improbable that they are capable of injuring human beings.
During the Middle Ages, lampreys were in demand as food, especially among the nobility, and it has been said that Henry the First of England died as a result of eating too many. Today, however, they are seldom eaten.