Euphausiidae

Euphausiidae is a family of small, shrimp-like crustaceans belonging to the order Euphausiacea. Commonly known as krill, these marine animals are found in all of the world's oceans, from polar waters to tropical seas. They are characterized by their bioluminescent organs, called photophores, which they use for communication, camouflage, and attracting prey. Krill are typically small, ranging from 1 to 6 centimeters in length, and have a translucent body. They possess five pairs of swimming legs and five pairs of feathery appendages called pleopods, used for locomotion and filter-feeding.

The diet of krill consists primarily of phytoplankton, microscopic algae that form the base of the marine food web. They filter these tiny organisms from the water using their specialized mouthparts. Krill are an essential part of the oceanic ecosystem, serving as a crucial food source for a wide variety of larger marine animals, including whales, seals, penguins, fish, and seabirds. Their abundance and biomass make them a pivotal link in transferring energy from primary producers to higher trophic levels.

Krill exhibit a range of behaviors, including schooling, vertical migration, and aggregation. They often form dense swarms, which can be visible from space. Their vertical migration, moving from deeper waters to the surface at night to feed and returning to the depths during the day to avoid predators, is a significant phenomenon in oceanography. Reproduction in krill involves external fertilization, with females releasing eggs into the water column. The larval stages develop through several molts before reaching maturity. Due to their ecological importance and potential as a food source for humans, krill populations are subject to scientific monitoring and management.