Themisto (crustacean)
Themisto is a genus of marine amphipods in the family Hyperiidae. Their distribution is cosmopolitan. Ecological role. "Themisto" are obligate carnivores. "Themisto gaudichaudii" has been found to feed opportunistically on copepods and chaetognaths, as juveniles also on diatoms. "Themisto" are important prey in many food webs. For example, "Themisto gaudichaudii" reaches high densities (up to 61 individuals/m) in Kerguelen waters and is a major food item for blue petrels, thin-billed prions, Antarctic prions, common diving petrels, and southern rockhopper penguins. In the Barents Sea, "Themisto libellula" is very abundant in the Arctic waters and important food  item for cod, polar cod, and marine mammals near the ice edge, whereas "Themisto abyssorum" is important in Atlantic/boreal waters. Life history. "Themisto gaudichaudii" matures at lengths between or more. Reproduction can be nearly continuous but becomes more seasonal at higher latitudes. The offspring emerging from the marsupium are in length. "Themisto abyssorum" has a life span of 1–2 years and reaches a maximum length of . "Themisto libellula" lives 2–3 years and grows to a maximum length of . Species. There are seven recognized species: