nephtheid soft coral Gersemia antarctica

Gersemia antarctica is found in McMurdo Sound, South Georgia Island, South Sandwich Islands, and Bouvet Island from 12 to 3,144 meters depth [3,6,7,8,11]. Gersemia spp. have been reported from the eastern Weddell Sea, Bransfield Strait off the Antarctic Peninsula, and the South Shetland Islands [13].

In McMurdo Sound, G. antarctica is found possibly on White Island and on the coastline from Granite Harbor down to Cape Chocolate at depths from 18 to 250 meters, and has been found at the south end of Cape Evans from 12 to 18 meters depth [3,7,11].

In Explorer's Cove at New Harbor, G. antarctica is found in soft sediment communities where it is anchored to scallop shells, small rocks, or clay substrate [3]. At Explorer's Cove, G. antarctica averages 0.04 colonies per square meter and is found there between 18 and 33 meters depth, with most colonies found from 27 to 33 meters depth [3].

G. antarctica colonies can inflate to over two meters in height [1].

G. antarctica colonies have been observed surviving for at least 4.5 years [4].



In addition to an upright feeding posture, Gersemia antarctica can bend its entire colony down so that the polyps reach the bottom to feed there [1].

The food that G. antarctica seeks on the bottom includes benthic diatoms, foraminiferans, and particulate organic matter [1].

This grazing behavior has likely evolved to supplement plankton capture from the water and is useful in Antarctica where plankton in the water column is seasonal [1].



A Gersemia antarctica colony can move like an inch worm, to reach undisturbed sediments for grazing [1].

G. antarctica colonies have been observed moving over fourteen meters in one year's time [1].

When a G. antarctica colony encounters sediment previously grazed by G. antarctica, it contracts from it [1].

Here are sea spiders Achelia sp. clinging to Gersemia antarctica. Adult Achelia sea spiders are small, spending their lives clinging to the substrate on which they feed [12]. The protonymphon stage of Achelia may be passed in the tissues of the organism on which juveniles and adults feed [12].

The sea spider Thavmastopycnon sp. is a predator of G. antarctica [3].

G. antarctica produces chemicals that it releases into the water surrounding itself to deter predators and bacterial growth [2].


Rob Robbins shot this video capture image of Gersemia antarctica at the south end of Cape Evans at 12 to 18 meters depth; this is the first recorded location for G. antarctica on Ross Island [3,6,7,8,11].


Found here at 24 meters depth, Gersemia antarctica hangs down from the wall at the south end of Cape Evans [14].

Taxonomic Note: First described by Kukenthal as Eunephthya antarctica in 1906 and discussed in 1914 by Gravier in comparision with another species of Eunephthya [6,10]. In 1961, Utinomi revised the family Nephtheidae for the genera Gersemia, Duva, Drifa, and Pseudodrifa and renamed Eunephthya antarctica to ?Drifa antarctica and also synonymized Paraspongodes antarctica under ?Drifa antarctica [5]. Recent non-taxonomic work referred to this soft coral as Gersemia antarctica; those authors verified the ID as Gersemia antarctica with Frederick M Bayer of the Dept of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution [7,1,2,3,4]. The Smithsonian's US National Museum Polar Invertebrate Catalog refers to Gersemia antarctica [8]. In 1981, Bayer published a key to Octocorallia genera which sorted out Gersemia and Drifa so it is assumed his later identification of the organism as Gersemia antarctica is based on that published key [9]. A reassignment of Eunephthya antarctica or ?Drifa antarctica to the genus Gersemia appears to be unpublished as of 17 September 1999.

1: Marine Ecology Progress Series 149(1- 3):299-304, 1997; 2: Marine Ecology Progress Series 161:133-144, 1997; 3: Marine Biology 122(3):461-470, 1995; 4: Antarctic Communities: Species, Structure, and Survival. B Battaglia, J Valencia, and DWH Walton, eds. Cambridge: Cambridge University Press, 1997. pp.309-315; 5: Publications of the Seto Marine Biological Laboratory 9(1):229-246, 1961. Contributions from the Seto Marine Biological Laboratory, Number 366; 6: Alcyonacea. W Kukenthal. Wissenschaftliche Ergebnisse der Deutschen Tiefsee-Expedition auf dem Dampfer "Valdivia" 1898-1899. Volume 13, Part 1. Jena: G Fischer, 1906; 7: Marc Slattery, personal communication, 1999; 8: US National Museum Polar Invertebrate Catalog at http://www.nmnh.si.edu/iz/usap/usapdb.html; 9: Proceedings of the Biological Society of Washington 94(3):902-947, 1981; 10: Alcyonaires. C Gravier. Deuxieme Expedition Antarctique Francaise (1908-1910). Sciences Naturelles: Documents Scientifiques. Extrait. Paris: Masson, 1914; 11: Rob Robbins, personal communication (south end of Cape Evans at 12-18 meters), 1999; 12: Fauna of the Ross Sea, Part 7. Pycnogonida, 1. Colossendeidae, Pycnogonidae, Endeidae, Ammotheidae. WG Fry & JW Hedgpeth. New Zealand Department of Scientific and Industrial Research Bulletin 198. New Zealand Oceanographic Insitute Memoir 49. 1969; 13: Berichte zur Polar- und Meeresforschung 402:76-81, 2001; 14: Luke Hunt, personal communication (south end of Cape Evans at 24 meters/80 feet), 2003

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