Euphausia lucens

Euphausia lucens is a species of krill endemic to the temperate waters of the Southern Hemisphere.

Euphausia lucens
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Malacostraca
Order:	Euphausiacea
Family:	Euphausiidae
Genus:	Euphausia
Species:	E. lucens
Binomial name
Euphausia lucens Hansen, 1905
Synonyms[1]
Euphausia uncinata Colosi, 1917

Distribution and habitat

Euphausia lucens is an epipelagic species restricted to the Southern Hemisphere, where it has a circumpolar distribution including parts of the Atlantic, Indian and Pacific Oceans.^[2][3] It is most common in the temperate waters between 41°S and 45°S, avoiding the cooler waters of the Southern Ocean, but may be found as far north as 37°S and as far south as 52°S.^[2][3] It prefers water temperatures between 5–18 °C (41–64 °F) and typically occurs in waters no shallower than 100 m (330 ft) deep; it is generally not encountered closer to the coast.^[2][4]

In the eastern South Pacific, Euphausia lucens occupies the area directly north of the range of Euphausia vallentini.^[3]

Description

Adult Euphausia lucens measure 10–18 mm (0.39–0.71 in) long.^[5] The eyes are large and spherical and the rostrum is noticeably short. There is a small tooth on the lower edge of the carapace, but the abdomen lacks any spines. Adults may closely resemble Euphausia vallentini.^[3]

Ecology

Euphausia lucens is a diurnal vertical migrator, with adults and juveniles spending the day at depths of up to 300 m (980 ft) and moving towards the surface at night,^[5][6][7] though it has also been observed swarming at the surface during the day at some locations.^[4] It is an opportunistic omnivore, known to feed on diatoms, dinoflagellates, tintinnids, fish larvae, copepods, and other zooplankton and phytoplankton.^[7][6][8][9] It aggregates in swarms and is a food source for baleen whales, seabirds, and several commercially valuable fish species including Engraulis capensis, Merluccius capensis, Merluccius paradoxus, Sardinops sagax, and Thyrsites atun.^[5][9][10]

Euphausia lucens is a continuous spawner, with spawning most intense from late winter to early spring.^[11] Mature females are capable of releasing a batch of eggs approximately every other day and may be reproductively active for up to eight to ten months per year.^[11][12] Eggs and nauplii remain near the surface and do not migrate vertically throughout the water column, with older larva in the calyptopis and furcilia stages engaging in some vertical migration while largely remaining in the upper layers of the water column. Post-larval juveniles and adults are capable of migrating from the bottom layers of the water column to the surface,^[13] with individuals reaching sexual maturity at around six months of age.^[11]