sea spider Achelia sp.

Here are Achelia sp. clinging to the nephtheid soft coral Gersemia antarctica.

Adult Achelia pycnogonids are small, spending their lives clinging to the substrate on which they feed [1]. The protonymphon stage of Achelia may be passed in the tissues of the organism on which juveniles and adults feed [1].

Achelia species are tangled and would be a good subject for molecular biology study to determine speciation [2]. Achelia species are found worldwide with almost half found around the perimeter of the Pacific Ocean [3].

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 [4].

Sea spiders are also called pycnogonids. Sea spiders are exclusively marine and mostly bottom dwelling (benthic) [3]. 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 [3]. 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 [3].

1: 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; 2: Antarctic and Subantarctic Pycnogonida : Ammotheidae and Austrodecidae. CA Child. Antarctic Research Series Volume 63, Biology of the Antarctic Seas 23. Washington DC : American Geophysical Union, 1994; 3: Marine Fauna of New Zealand: Pycnogonida (Sea Spiders). CA Child.. Wellington : National Institute of Water and Atmospheric Research, 1998. NIWA Biodiversity Memoir 109; 4: Polar Biology 24:941-945, 2001

Achelia sp. identification by Roger Bamber, British Museum of Natural History. Text ©Peter Brueggeman. Photograph ©Canadian Museum of Nature (Kathleen Conlan). Photograph may not be used in any form without the express written permission of Canadian Museum of Nature (Kathleen Conlan).