Suborder: GAMMARIDEA  Latreille, 1802
Infraorder: Gammarida  Latreille, 1802
Superfamily: Lysianassoidea  Dana, 1849
Genus: Onisimus Boeck, 1871  

Description:

Size: up to 25mm

Colour: whitish/yellowish/pinkish

Head deeper than long; lateral cephalic lobe narrow, subacute; eyes oval, bright red

Antenna1 short, peduncle article 1 short, not produced anterodistally, accessory flagellum 5-segmented; antenna 2 length 1.5 x antenna 1

Coxa 1 large, anterior margin concave, anteroventral corner produced; coxa 4 with weak posteroventral lobe; epimeral plate 3 with tiny tooth on posterodistal corner; first segment of urosome slightly depressed dorsally; urosomite 3 with small dorsal robust setae, proximal to telson

Gnathopod 1 subchelate, propodus subrectangular, length 1.6 x breadth, clearly longer than carpus; gnathopod 2 minutely subchelate with weakly developed palm; uropod 2 inner ramus strongly constricted; uropod 3 peduncle short, rami lanceolate, subequal in length

Habitat: soft sediments

Mobility: mobile

Feeding: opportunistic; herbivore, scavenger and predator

Distribution: circum-arctic and cold waters south to Hudson Bay, Saint Lawrence Estuary, Greenland, Iceland, Finmark in the Atlantic and to the Bering Sea in the Pacific, common in intertidal, shallow subtidal and sea ice, depth range 0-100m.

Distribution in Svalbard's fjords:

References:

Boudrias, MA., Carey, AG. Jr. 1988. Life history patterns of Pseudalibrotus litoralis (Crustacea: Amphipoda) on the inner continental shelf, SW Beaufort Sea . Mar Ecol Prog Ser 49 , pp. 249-257.

Bryazgin, V. 1997. Diversity, distribution and ecology of benthic amphipods (Amphipoda, Gammaridea) in the Barents Sea sublittoral. Pol. Polar Res. 18(2) , pp. 89-106.

Gurjanova, E. F. 1951. Bokoplavy morjej SSSR I sopredel'nykh vod (Amphipoda - Gammaridea). Akad. Nauk SSSR, Opredel. Faune SSSR 41 , pp. 184-186.

Holmquist, C. 1965. The amphipod genus Pseudalibrotus . Zeitschrift für Zoologische Systematik und Evolutionsforschung 3, pp. 19-46.

Legeżyńska , J. 2000. Distribution patterns and feeding strategies of lysianassoid amphipods in shallow waters of an Arctic fjord. Pol. Polar Res 22 (3-4), 173-186.

Legeżyńska , J., Węsławski, JM., Presler, P. 2000. Benthic scavengers collected by baited traps in the high Arctic . Polar Biology 23 , pp. 539-544.

Lowry, J. K., Stoddart, H. E. 1993. The Onisimus problem (Amphipoda, Lysianassoidea, Uristidae). Zoologica Scripta 22 (2) , pp. 167-181.

Nygard, H., Wallenschus, J., Camus, J., Varpe, O., Berge, J. 2010. Annual routines and life history of the amphipod Onisimus litoralis : seasonal growth, body composition and energy budget. Mar Ecol Prog Ser 417, pp. 115-126.

Sainte-Marie, B. 1984. Morphological adaptations for carrion feeding in four species of littoral and circalittoral lysianassid amphipods. Can J Zool 62(9) , pp. 1668-1674.

Sainte-Marie, B. 1986 . Feeding and swimming of lysianassid amphipods in a shallow cold-water bay. Mar Biol 91 , pp. 219-229.

Sainte-Marie, B., Percy, JA., Shea, JR. 1989. A comparison of meal size and feeding rate of the lysianassid amphipods Anonyx nugax , Onisimus (= Pseudalibrotus ) litoralis and Orchomenella pinguis . Mar Biol 102 , pp. 361-368.

Sainte-Marie, B., Lamarche, G., Gagnon, JM. 1990. Reproductive bionomics of some shallow-water lysianssoids in the Saint Lawrence Estuary, with a review on the fecundity of the Lysianassoidea (Crustacea: Amphipoda). Can J Zool 68, pp. 1639-1644.

Sars, G. O. 1890-1895. An account of the Crustacea of Norway with short descriptions and figures of all the species. vol. I: Amphipoda, Cammermeyers, pp. 102-104, pl. 35.

Shea, JR., Percy, JA. 1990. Salinity tolerance and osmoregulation of the arctic marine amphipods Onisimus litoralis (Kroyer) and Anonyx nugax (Phipps). Polar Biol 10, pp. 275-281.

Stephensen, K. 1923. Crustacea Malacostraca. V (Amphipoda I). Dan. Ingolf Exped. 3 (8) , pp. 56-58.

Stephensen, K. 1935. The Amphipoda of N. Norway and Spitsbergen with adjacent waters. Tromso Mus. Skr. 3(1) , pp. 45-46.

Stephensen, K. 1944. The zoology of East Greenland . Amphipoda. Medd. om Gronland. 121 (14) , p. 19-21.

Szaniawska, A., Wołowicz, M. 1986. Changes in the energy content of common species from Hornsund, Southwest Spitsbergen . Polar Res 4 , pp. 85-90.

Węsławski, J. M. 1990. Distribution and ecology of South Spitsbergen coastal marine Amphipoda (Crustacea). Pol. Arch. Hydrobiol. 37 (4) , pp. 503-519.

Węsławski, JM., Opaliński, K., Legeżyńska, J. 2000. Life cycle and production of Onisimus litoralis (Crustacea: Amphipoda): The key species In the Arctic soft sediment littoral. Pol. Arch. Hydrobiol 47 , pp. 585-596.

Węsławski, JM ., Legeżyńska , J. 2002. Life cycles of some Arctic amphipods, Pol. Polar Res. 23 (3-4), pp. 253-264.

http://www.arcodiv.org/seaice/amphipods/Onisimus_litoralis.html (04.07.2011, 12:37)