sea spider Colossendeis megalonyx sensu lato

Colossendeis megalonyx is found throughout Antarctica and the South Shetland Islands, South Georgia Island, Antipodes Islands off New Zealand, Peter I Island, Marion and Prince Edward Islands, South Africa, southern Madagascar, South America, New Zealand, and the South Atlantic from depths of 3 to 4,900 meters [1,5,6,7,9]. C. megalonyx is the most common of its genus in Antarctic waters [1]. C. megalonyx has a long proboscis, short eighth palp segment in relation to the two longer distal segments, and long slender legs bearing a tarsus longer than the propodus and a long slender claw [1]. Legs vary in length; the femur can be the longest segment or the first tibia can be longest [1]. C. megalonyx is shown here walking over an anchor ice formation with possibly some food in its mouth. C. megalonyx eats the soft corals Alcyonium antarcticum and Clavularia frankliniana, and has been observed eating small hydroids on sponges [2,3,4].

Two Colossendeis megalonyx crossing paths.

C. megalonyx subspecies are insufficiently defined and would be a good subject for molecular biology study to determine speciation [1].

Sea spiders are also called pycnogonids and sometimes whip scorpions. Sea spiders are exclusively marine and mostly bottom dwelling (benthic) [7]. Adult sea spiders either suck the juices from soft-bodied invertebrates or browse on hydroids and bryozoans. Male sea spiders carry cemented egg clutches gathered from females until hatching and often after hatching in the larval stages [7]. Since sea spider larvae are not planktonic, sea spider dispersal is slow and intermittent leading to the development of many endemic species among shallow-water sea spiders [7].

Colossendeis megalonyx orcadense or C. australis with stalked lepadiform barnacles attached .

The Colossendeis sea spiders are mostly giant deep-sea species though some Antarctic species live in shallow depths [1,7]. The Colossendeis sea spiders are the largest sea spiders with some having leg spans as wide as fifty centimeters and trunks of five centimeters or more [1,7]. Antarctic and subantarctic sea spiders comprise 251 species, representing 21.5% of worldwide species, with 101 species endemic to Antarctica and 60 endemic to subantarctic areas [8].

1: Antarctic and Subantarctic Pycnogonida : Nymphonidae, Colossendeidae, Rhynchothoraxidae, Pycnogonidae, Endeididae, and Callipallenidae. CA Child Antarctic Research Series Volume 69, Biology of the Antarctic Seas 24. Washington DC : American Geophysical Union, 1995; 2: Antarctic Ecology, Volume 1. MW Holdgate, ed. NY: Academic Press, 1970. pp.244-258; 3: Marine Biology 122(3):461-470, 1995; 4: Ecological Monographs 44(1):105-128, 1974; 5: South African Journal of Antarctic Research 21(1):65-71, 1991; 6: US National Museum Polar Invertebrate Catalog at www.nmnh.si.edu/iz/usap/usapdb.html; 7: Marine Fauna of New Zealand: Pycnogonida (Sea Spiders). CA Child.. Wellington : National Institute of Water and Atmospheric Research, 1998. NIWA Biodiversity Memoir 109; 8: Polar Biology 24:941-945, 2001; 9: Antarctic Science 13(2):144-149, 2001

Text ©Peter Brueggeman. Identification of Norbert Wu photos provided by C Allan Child. Barnacled C. australis or C. megalonyx orcadense identification by Roger Bamber, British Museum of Natural History. Photographs © Norbert Wu & Canadian Museum of Nature (Kathleen Conlan). Photographs may not be used in any form without the express written permission of Norbert Wu & Canadian Museum of Nature (Kathleen Conlan). Norbert Wu no longer grants permission for uncompensated use of his photos under any circumstances whatsoever; want more info?