Thysanoessa raschii (Sars, 1864)
The most widespread Arctic krill
Size
- Eggs & nauplii 0.35-0.45 mm
- Adults 20-25 mm
Color & Characteristics
- Transparent, yellowish if rich in lipids, females might develop blue hue when spawning
- Eyes round, rostrum pointed, photophores red
- Anntennae lack lappet, carapace with 1 small denticle
- abdomen without keel-spines
Habitat
- Panarctic and subarctic in coastal waters (above 200m)
- Can be abundant in coastal embayments
- Most common in Arctic waters near Pacific or Atlantic inflows, uncommon in central basins
- Undergo diel vertical migrations, spending daytime near bottom, night-time in surface waters
Feeding
- Primarily herbivourous, may feed on detritous when food is scarse - known to feed directly on under-ice algae
- During open-water periods feed on phytoplankton when abundant (shifting to small zooplankton when phyoplankton less abundant)
- An important prey item for fish, birds, seals and whales
Life cycle
- Females lay several clutches of eggs during summer
- Females require repeated mating after each molt to form new egg clutches
- Life cycles is typcial: eggs, nauplius, metanauplius, followed by several stages of feeding calytopsis, and furcillia larvae
- Juveniles resemble adults, and molt regularly while growing to adulthood over the first year of life
- Life expectancy not known, likely 2-3 years
Page Authors: Alexei Pinchuk & Russ Hopcroft
Updated: Sept 5, 2010
