anemone Urticinopsis antarctica

Urticinopsis antarctica is found in Antarctica and the South Shetland Islands from 6 to 223+ meters depth [2,5,6].

U. antarctica is among the largest and most conspicuous benthic invertebrates in the Cape Armitage community between 15 and 33 meters depth and is found below 33 meters as well [1].



Urticinopsis antarctica has a cylindrical massive sandy-colored body column up to fifteen centimeters high and eleven centimeters in diameter [2].



The tentacles and oral disk of Urticinopsis antarctica are dirty white [2]. U. antarctica tentacles range in number from 120 (1.2 centimeter diameter anemone) to 600 - 800 (10 centimeter diameter anemone) [2,4]. Contracted tentacles are short and conical with slight longitudinal furrows and sometimes rounded on the end [2,4,6].



Urticinopsis antarctica feeds predominantly on seastars and sea urchins which are 77% of its diet [1].

U. antarctica may bend over to engulf a seastar (Perknaster fuscus antarcticus shown here).

The sea urchin Sterechinus neumayeri (as shown at left) is the most frequent prey of Urticinopsis antarctica at 65% of its diet [1]. S. neumayeri shields itself from the anemone's tentacled grasp with attached bits of shell, debris and algae; the shells and debris often have stinging hydroids on them (see the whitish polyps on top of the urchin at left). If the anemone touches the urchin's hydroids, it releases the urchin. If the urchin is aware of the anemone's tentacles, the urchin releases its protective camouflage and escapes. If this camouflage isn't present on the urchin, U. antarctica captures and eats the urchin [1].



The seastars Odontaster validus (shown being devoured at left) and Diplasterias brucei (see above) are significant prey items at 4% and 5% of the diet of Urticinopsis antarctica respectively [1]. Combined predation on the seastar Acodontaster conspicuus by U. antarctica and the seastar O. validus minimally killed 3.5% of the population of the seastar A. conspicuus in one year at Cape Armitage [3].



Urticinopsis antarctica also feeds on large medusae or jellyfish which get close enough to the bottom in shallow water to be captured by the anemone's tentacles; 21% of its diet are medusae [1].

Divers may occasionally see two anemones devouring the same medusa !



Here is a side-by-side comparision of Urticinopsis antarctica (on the right) and Isotealia antarctica (on the left).

1: Antarctic Ecology, Volume 1. MW Holdgate, ed. NY: Academic Press, 1970. pp. 244-258; 2: Soviet Journal of Marine Biology 1(5):307-315, 1975; 3: Ecological Monographs 44(1):105- 128, 1974; 4: Further Zoological Results of the Swedish Antarctic Expedition 1901-1903. Volume 2, Number 3. Actiniaria and Zoantharia. O Carlgren. Stockholm : PA Norstedt & Soner, 1927; 5: Polar Biology 20(4):229-247, 1998; 6: A Survey of the Ptychodactiaria, Corallimorpharia and Actiniaria. O. Carlgren. Stockholm : Almqvist & Wiksells Boktryckeri AB, 1949. Kungliga Svenska Vetenskaps-Akademiens Handlingar, 4th Series, Band 1, No. 1

Identification from photo only and not from collected specimen. Text ©Peter Brueggeman. Photographs ©Norbert Wu & M Dale Stokes. Photographs may not be used in any form without the express written permission of Norbert Wu & M Dale Stokes. Norbert Wu no longer grants permission for uncompensated use of his photos under any circumstances whatsoever; want more info?