A species
Antarctic krill
Euphausia superba
Finger-length shrimp-like animals that feed the great whales.
You and the antarctic krill last shared an ancestor about 580 million years ago (on 11 November, if life's history were one year).
Antarctic krill look like small shrimp, about as long as an adult little finger. Each one is mostly see-through with big black eyes and tiny red spots. They are not true shrimp. Like the insects shown beside them on the tree, they are arthropods. One krill weighs only about one or two grams. Together they may weigh about 300 million tonnes, roughly as much as all humans, among the greatest combined weight of any wild animal.
They live in the near-freezing ocean all around Antarctica. They gather in swarms so vast and dense they can be seen from space. Five pairs of tiny paddles under their bodies beat in rhythm to keep them swimming. A blue whale, the largest animal ever known, grows huge by filtering krill such as these, eating many tonnes in a day.
Hide by day, feed by night
Krill spend the day about 100 metres down to avoid predators, then rise toward the surface at night to feed on plankton.
Thousands of eggs
A female can lay about 6,000 to 10,000 eggs in one batch, sometimes several times in a summer. The eggs sink deep before hatching.
Shrink to survive
Without food, krill can live for about 200 days off their own body tissue, shrinking a little each time they moult.