Feeding in Arctic darkness: mid-winter diet of the pelagic amphipods Themisto abyssorum and T. libellula

The pelagic amphipods Themisto abyssorum and Themisto libellula represent important links between the herbivore zooplankton community and higher trophic levels of the Arctic marine food webs. Large double structured eyes of both of these hyperiid species are assumed to be used for visual prey detection. However, no information is available on the feeding strategies of these visually searching predators for the period of the polar night, a time of year with no or very low levels of daylight. Here, we report on the stomach and gut content of both Themisto species collected during a January expedition around Svalbard (78° to 81°N). Results indicate that T. abyssorum and T. libellula feed actively during the Arctic winter. The major food source of both amphipods consisted of calanoid copepods, most frequently Calanus finmarchicus.