Thysanoessa inermis Kroyer, 1846
A common krill of the subarctic Atlantic and Pacific, and adjacent Arctic seas
Size
- Eggs & nauplii 0.35-0.45 mm (0.65 mm with capsule)
- Adults 25-32 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 without denticle
- well-developed spine on 6th abdominal segment
Habitat
- Subarctic in deeper coastal waters and shelf breaks
- Common in Arctic waters near Pacific or Atlantic inflows, uncommon in central basins
- Undergo diel vertical migrations, spending daytime near bottom or to maxiamum of ~500 m, night-time in surface waters
Feeding
- Primarily herbivourous, may feed on detritous when food scarse
- 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 (140 per brood on average) during spring
- 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 1-2 years
Page Authors: Alexei Pinchuk & Russ Hopcroft
Created: Sept 3, 2010
