thecate hydroid Ophiodes arboreus

Ophiodes arboreus is found throughout Antarctica and Bouvet Island, Kerguelen Island, Marion and Prince Edward Islands, and Patagonia at depths from 18 to 558 meters [3,4,5,9,10,13]. Ophiodes arboreus is found in shrubby colonies with thick fascicled stems and irregular branching in different planes, reaching up to 35 centimeters high [3,4,7,10,13]. Color is typically light greenish-brown but may be darker [7]. The center of the colony may have a mass of sex cells with developing larvae, clustered on a specialized branch, that are 15-25 millimeters in diameter [6,10]. O. arboreus is a conspicuous organism in Cape Armitage's third benthic faunal zone below 33 meters depth and is also found scattered around in the second benthic faunal zone between 15 and 33 meters depth [8].

Several Doto antarctica nudibranchs are shown here on Ophiodes arboreus.

O. arboreus is preyed upon by the seastar Odontaster validus, the nudibranch Doto antarctica, and two unidentified aeolid nudibranchs (possibly Eubranchus sp. and Coryphella sp.) [1].

Hydroids feed on plankton suspended in the water. During the Antarctic winter, it is dark for four months and plankton is greatly reduced though still present during that period; Antarctic suspension feeders may continue to feed at a low level or suspend their feeding activity for a few months centered on July [2].

Taxonomic Note: Genus was Halecium arboreum in 1966 [3], then changed to Hydrodendron arborea in 1977 [4], followed by a change to Ophiodes arboreus in 1979 [5]. Several subsequent authors have used the Hydrodendron genus and Hydrodendron arboreum [6,10,11,12,13]

1: Ecological Monographs 44(1):105-128, 1974; 2: Polar Biology 15(5):335-340, 1995; 3: Hydroidea (Thecaphora) Collected by the Soviet Antarctic Expedition on the M/V "Ob", in Antarctic and Subantarctic Waters. DV Naumov and SD Stepaniants. IN: Biological reports of the Soviet Antarctic Expedition, 1955-1958 (Rezultaty biologicheskikh issledovanii Sovetskoi antarkticheskoi ekspeditsii, 1955-1958). Volume 1. EP Pavlovskii, ed. Jerusalem: Israel Program for Scientific Translations. 1966. pp.68-106; 4: Annals of the South African Museum 73(1):1-47, 1977; 5: Hydroids of the Antarctic and Subantarctic Waters. SD Stepanjants. Biological Results of the Soviet Antarctic Expeditions Volume 6. Explorations of the Fauna of the Seas 20(30). Academy of Sciences of the USSR, Zoological Institute. 1979; 6: Fauna der Antarktis. J Sieg & JW Wagele, eds. Berlin : P. Parey, 1990; 7: Hydroida. EA Briggs. Australasian Antarctic Expedition 1911-1914, Scientific Reports. Series C, Zoology and Botany. Volume 9, Part 4. Sydney : David Harold Paisley, Government Printer, 1938; 8: Antarctic Ecology, Volume 1. MW Holdgate, ed. NY: Academic Press, 1970. pp244-258; 9: Proceedings of the Royal Society of Edinburgh 33(part 1 number 2):9-34, 1913; 10: South African Journal of Antarctic Research 23(1-2):3-24, 1993; 11: Scientia Marina 63(Supplement 1):209-218, 1999; 12: Polar Biology 27(12):767-774, 2004; 13: Polar Biology 29(9):764-771, 2006

Text ©Peter Brueggeman. Photographs ©Canadian Museum of Nature (Kathleen Conlan), Rob Robbins, & Norbert Wu. Photographs may not be used in any form without the express written permission of Canadian Museum of Nature (Kathleen Conlan), Rob Robbins, & Norbert Wu. Norbert Wu no longer grants permission for uncompensated use of his photos under any circumstances whatsoever; want more info?