Life history and population dynamics of the Arctic sympagic amphipods Onisimus nanseni Sars and O. glacialis Sars (Gammaridea: Lysianassidae)

Origin and fate of ice fauna in the Fram Strait and Svalbard area

“…Apherusa glacialis and Onisimus glacialis, the smallest amphipod species (corresponding to maximum body lengths of approx. 14 mm for both species; Beuchel & Lønne 2002, Arndt & Beuchel 2005 were entirely absent from the pelagic trawls (Fig. 4).…”

“…For the other amphipod species, life spans range between 2 yr (A. glacialis; Beuchel & Lønne 2002) and 3 to 4 yr (O. nanseni and O. glacialis, respectively;Arndt & Beuchel 2005). As far as we know, all species feature a relatively high reproductive potential.…”

“…The relationship between Ls and total body length (Lt) is Ls = Lt/(19.49 + 1.62) for Apherusa glacialis and Gammarus wilkitzkii (Beuchel & Lønne 2002) and Ls = Lt/(19.52 -0.27) for both Onisimus species (Arndt & Beuchel 2005). The samples were stored frozen for later biomass determination.…”

“…It has been shown by Arndt & Lønne (2002) that origin and drift history of sea ice to a large extent determine species composition and degree of 'maturation' of the ice ecosystem. Colonization of new sea ice is time dependent and, considering the different life history traits of ice amphipods (Beuchel & Lønne 2002, Arndt & Beuchel 2005, the sympagic ecosystem needs time to become established, with 2 to 3 yr old ice still in the developing process (Arndt & Lønne 2002). Our analysis of population structure shows a more biased distribution towards smaller size classes for the dominating species Gammarus wilkitzkii (Fig.…”

Annual routines and life history of the amphipod Onisimus litoralis: seasonal growth, body composition and energy budget

“…It is however clear that there are annual routines that seem to follow the same patterns among Arctic amphipods. Most of the species studied lay eggs in autumn or early winter, to incubate them through the winter and release the hatched juveniles in spring or summer (Węs8awski & Legeż y?ska 2002, Arndt & Beuchel 2006, Nygård et al 2009). Annual routines in growth and development are observed in O. litoralis, with the main growth occurring in summer, and the ontogenic development taking place during summer and autumn leading up to reproduction in early winter.…”