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10 amazing things about Antarctic krill

Posted by Willie Mackenzie - 19th March 2018


With beautiful black eyes, and otherworldly translucent pink bodies, Antarctic krill are alien-looking animals. And they’re a lot more than just whale food. To get to know them a bit better, we’ve pulled together a list of some of the best bits about these tiny shrimp-like ocean critters. Antarctic krill are massively important for the Antarctic Ocean, but they also happen to be fascinating animals in their own right.

  1. There are about 85 species of krill around the world, but by far the biggest and arguably most important on the planet is the Antarctic krill: they can grow to a gargantuan 5 or 6cm long, and live to be maybe 5 years old.
  2. They are ‘arthropods’, which means they have jointed bodies and lots of pairs of legs. The legs at the back end of the body are adapted for swimming, whilst those at the front are ideal for catching food.

  3. They are able to generate their own light – a fancy ability known as bioluminescence. That basically means krill swarms are one big pulsating crustacean disco party.

  4. They are the basis for the entire Antarctic food web, where they are eaten directly by penguins, seabirds, seals, fish, and whales. Anything in the Antarctic that doesn’t eat krill, probably eats something else that does. Blue and humpback whales migrate to the Antarctic from warmer waters every year just to feast on krill.
    Humpback whales feeding for krill in the Antarctic © Christian Åslund / Greenpeace
  5. It’s easy to tell when penguins have been eating krill, because it turns their poo pink!
  6. Krill migrate up and down every day, between the safety of the depths during the day to the food-filled surface waters at night.
  7. They have sex near the seafloor. Foreplay for krill involves diving down several hundred metres first.
  8. Though tiny by human standards, krill swarm together in massive numbers, with as many as 30,000 animals in a cubic metre of a krill swarm.

    Macro detail of krill in the sea at night.
  9. In a neat trick to avoid predators, it’s thought that krill have the ability to spontaneously moult their shell and make a quick getaway. When times are tough they can also shrink in size, conserving energy by staying smaller when they moult shells rather than growing ever bigger. Because of this, you can’t tell how old a krill is just by size.
  10. Antarctic krill are climate heroes! Scientists have recently discovered that krill play a vital role in capturing carbon and depositing it on the sea floor – thereby locking it up and keeping it out of the atmosphere.

Krill are awesome. They are also essential for all other life in the Antarctic Ocean, and much further afield too. But they are at risk from industrial fishing – being scooped up in their thousands to be made into Omega 3 pills and fish meal. This year, we have the chance to put a massive part of the Antarctic off limits as a protected ocean sanctuary.

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