eusirid amphipod Paramoera walkeri

Paramoera walkeri is found throughout Antarctica and the Antarctic Peninsula, South Shetland Islands, and South Georgia Island from intertidal to 310 meters depth [1]. P. walkeri is usually found in shallow water and, at some locations, can be the most abundant benthic animal from 0 to 15 meters depth [2,3].

Here Paramoera walkeri is swarming on an anchor ice formation. Though living in close association with ice, P. walkeri doesn't freeze because its haemolymph ("blood") is hyperosmotic compared to seawater; seawater freezes at -1.86°C whereas P. walkeri haemolymph freezes at -2.06°C [3]. P. walkeri is a major benthic species during summer and dominates the sub-fast ice community during winter [2]. P. walkeri moves off the bottom during late autumn and is found clinging to the underside of young fast ice soon after diatoms begin populating that ice; P. walkeri returns to the gravel bottom after the breakout of the fast ice [3]. P. walkeri is a detritivore-omnivore and feeds near the bottom or under fast ice upon the fungi, bacteria, and algae associated with ice [2]. Predators of P. walkeri include the fish Trematomus bernacchii, Trematomus borchgrevinki, Trematomus newnesii, and Notothenia corriiceps neglecta and the Adelie penguin [3,4].

Here is a closer view of Paramoera walkeri on anchor ice. P. walkeri grows rapidly during summer phytoplankton blooms, doesn't grow during winter, and breeds seasonally after its first or second year [2]. P. walkeri lays its large yolky eggs into a brood pouch in June [3]. The young hatch after 4.5 months and then remain in the pouch for another month while they do not grow or feed [3]. Newly-released young P. walkeri migrate offshore populating the fast ice and then return to shallow water starting in December [3]. P. walkeri has been collected at lengths up to 2.28 centimeters and lives up to four summers [3].

1: Catalogue of the Marine Gammaridean Amphipoda of the Southern Ocean. JK Lowry, S Bullock. Wellington : Royal Society of New Zealand, 1976. Royal Society of New Zealand Bulletin 16; 2: Hydrobiologia 337(1-3):107-112, 1996; 3: Journal of the Royal Society of New Zealand 10(3):259-270, 1980; 4: Polar Biology 13:291-296, 1993

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