ONLY ONE IN SEVEN SURVIVE

So it can suck blood for as long as possible, the lamprey uses one of the most cunning methods in the entire animal kingdom: it injects an anticoagulant mucus into its prey. This prevents any blood clots, which could lead to the premature death of the fish, from forming.

The longer the host lives, the more time the lamprey has to sap the juiciest-looking blood vessels. Provided that the wounds are not infected, some particularly robust fish can survive the attack.

In general, though, as few as one in seven fish live to fight another day. Every day millions of them, sucked entirely dry of their blood, sink to the bottom of the world’s lakes and seas having fallen victim to this ancient predator.

The lamprey is one of the last survivors of the Cambrian period, making the blood-sucking hunter one of the last living fossils. But why has it been so much more successful than other species?

The answer lies in its adaptability: it can survive in cold as well as temperate zones. And it doesn’t matter to the lamprey whether it lives in freshwater or saltwater – because, after all, it’s not a fish. It forms its own class of vertebrates, with a skeleton made of cartilage – beyond the evolutionary lines of fish, reptiles, amphibians and mammals.

What is the secret to its success? The lamprey family underwent two gene duplications during its development. Faced with meteorite impacts, climate disasters or lack of oxygen, the extra gene meant the lamprey could become more flexible. It could react to changes in the environment more quickly than any other animal – something that’s enabled it, quite literally, to suck legions of animal species dry.