Antarctic krill

Antarctic krill are tiny crustaceans that swarm in the icy Southern Ocean. These shrimp-like animals form massive groups so dense they can number tens of thousands per cubic meter. They're a vital food source for whales and penguins, and their total weight adds up to about 500 million tons.

• Grows up to 6 cm long—about the length of a paperclip.
• Lives for six years, much longer than most small ocean creatures.
• Eats microscopic algae, turning sunlight energy into food for bigger animals.