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Krill are small, shrimp-like ocean crustaceans. These pink, translucent animals congregate in large, dense masses called "swarms" or "clouds," that turn areas of the ocean's surface pink. Krill are very important in the food web since many animals eat them.


 


Krill have a hard exoskeleton, many legs (used for swimming and gathering food), and a segmented body. Females produce almost 1,000 eggs each summer; the eggs are laid at the surface, but fall to great depths. The hatchlings swim back to the surface to feed. Like all crustaceans, krill molt their exoskeleton as they grow.


Species: There are about 85 species of krill, ranging in size from less than 0.5 inch (1 cm) up to 5.5 inches (14 cm) long. The dominant krill in the southern polar oceans is the Antarctic krill, which is up to 2.3 inches (6 cm) long and weighs about 0.035 ounces (1 g). Antarctic krill have a life span of about 5 to 10 years. Antarctic Krill is considered to be a keystone species, an organism upon which very many Antarctic predators depend.

Krill eat phytoplankton, single-celled plants that float in the seas near the surface. Krill spend their days in the dark depths of the ocean (about 320 feet = 100 m deep), safe from their major predators (like whales and sea birds). They swim to the surface each night to eat, but can fast for up to 200 days, shrinking in size during that time.

 

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 Kingdom: Animalia

 Phylum: Arthropoda

 Subphylum: Crustacea

 Class: Malacostraca

 Superorder: Eucarida

 Order: Euphausiacea