sea spider Ammothea clausi

Ammothea clausi is found in Antarctica and the Antarctic Peninsula, Peter I Island, South Shetland Islands, South Orkney Islands, South Sandwich Islands, and South Georgia Island at depths from 3 to 860 meters [1,2,7]. A. clausi is small for its genus with a leg span of five centimeters for males and nine centimeters for large females and a trunk up to six millimeters long [1].

Ammothea clausi has two morphs which are almost separated geographically:

• Magellanic: erect abdomen, longer ocular tubercle;
• Victoria Land: almost horizontal abdomen, ocular tubercle about half as tall as Magellanic [1].

A. clausi appears similar in appearance to A. minor, but the proboscis on A. minor is longer and wider, and A. clausi has a pencil-like abdomen [4].


Here is Ammothea clausi.

Ammothea species are found predominantly in Antarctic and subantarctic regions (19 of 31 known species); seven other species are known from the southern hemisphere and only five from the northern hemisphere [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 [6].



Ammothea clausi appears to be climbing over or mating with another of the same species; without seeing them move, it is difficult to tell in a photo what they are doing when entwined [4].

Here's a closer look at these two entwined Ammothea clausi, so that you can see if they are being naughty or nice. The male finds a female with eggs, climbs under or over, and extrudes sperm from each of his leg vents (under one of the short joints near the trunk) as she extrudes eggs from similar vents in the same place [5]. In some sea spider genera, the eggs are relatively large and the female pops out only 4-5; in other genera, the eggs are not as wide as the smallest leg segment and the female puts out sometimes more than 100 eggs [5]. Sometimes males collect balls of eggs (they supply the binding cement) from 5-7 different females and walk with them carried under their body [5].

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: 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; 2: US National Museum Polar Invertebrate Catalog at http://www.nmnh.si.edu/iz/usap/usapdb.html; 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: C Allan Child, personal communication, 2002; 5: C Allan Child, personal communication, 2000; 6: Polar Biology 24:941-945, 2001; 7: Antarctic Science 13(2):144-149, 2001

Text ©Peter Brueggeman. Identification provided by C Allan Child. Photographs ©M Dale Stokes & Norbert Wu. Photographs may not be used in any form without the express written permission of M Dale Stokes & Norbert Wu. Norbert Wu no longer grants permission for uncompensated use of his photos under any circumstances whatsoever; want more info?