A species
Sea lamprey
Petromyzon marinus
A jawless cousin with a toothy suction-cup mouth.
You and the sea lamprey last shared an ancestor about 520 million years ago (on 16 November, if life's history were one year).
Meet a jawless cousin with a suction-cup mouth full of teeth. The sea lamprey sits just outside the great group of jawed vertebrates that includes you. It comes from a jawless family line going back about 350 million years, well before the dinosaurs. It has no jaws, and its skeleton is made of cartilage rather than bone.
Its round mouth works like a suction cup and is ringed with more than 100 small, sharp, hooked teeth. It presses onto another fish and uses a file-like tongue to feed on blood and body fluids. Its long, smooth body looks like an eel, but it is not an eel: it has no scales and no side fins.
After feeding in the sea or a lake, it stops feeding and swims up a river in spring and early summer to breed. Adults from the sea are commonly about 60 to 80 centimetres long, about as long as an adult's arm. Adults in the Great Lakes are smaller, about 30 to 50 centimetres long. Adults are blotchy brown, sometimes with a greenish tint, with a pale belly and a row of seven small gill holes behind each eye. Its native home is on both sides of the North Atlantic.
Blind babies in the mud
The babies have no eyes and stay buried in soft sand or mud. They sieve tiny food from the water for about 3 to 10 years, sometimes longer, before growing eyes and leaving the mud.
Stone-carrying parents
Adults build a nest in gravel, carrying stones with the mouth. The female lays about 100,000 eggs in the stones, sometimes more, then both parents die.
Canal trip to the upper lakes
They spread past Niagara Falls through a human-made shipping canal to reach Lake Erie by 1921 and the other Great Lakes later. There, where they were introduced, each lamprey can kill up to about 18 kilograms of fish such as trout and salmon while feeding.