The type of marine crustaceans whose characteristic features are the external gills. There are 86 species of these organisms inhabiting seas around the globe.
An adult krill is about 8-60 mm long and weighs only a few grams. Some species have the bioluminescence capacity, which means they have photophores that can emit light.
Krill live in large swarms at a depth even more than 2,000 meters. They lay there eggs in the pelagic zone, in open sea waters. The larva after hatching lifts towards the surface, undergoing several biological life cycles.
Krill are the basic element of the food chain — the feed for penguins, pinnipeds and whales. Krill are also commercially used by humans (mainly the most well-known species of this crustacean — Antarctic krill, Euphausia superba).
The name “krill” comes from the Norwegian language and means “small fry of fish”.