page_title: Southern Ocean
section_title: Arthropods
hierarchical_section_title: Southern Ocean / Biodiversity / Invertebrates / Arthropods
caption_attribution_description: English: Onykia ingens mature female (384 mm ML, 1875 g weight) from SW Chatham Rise (near New Zealand) at 44°21'S, 175°32'E (caught in bottom trawl at about 690 m depth)
context_page_description: The Southern Ocean, also known as the Antarctic Ocean or the Austral Ocean, comprises the southernmost waters of the World Ocean, generally taken to be south of 60° S latitude and encircling Antarctica. As such, it is regarded as the second-smallest of the five principal oceanic divisions: smaller than the Pacific, Atlantic, and Indian Oceans but larger than the Arctic Ocean. This oceanic zone is where cold, northward flowing waters from the Antarctic mix with warmer subantarctic waters.
  By way of his voyages in the 1770s, James Cook proved that waters encompassed the southern latitudes of the globe. Since then, geographers have disagreed on the Southern Ocean's northern boundary or even existence, considering the waters as various parts of the Pacific, Atlantic, and Indian Oceans, instead. However, according to Commodore John Leech of the International Hydrographic Organization, recent oceanographic research has discovered the importance of Southern Circulation, and the term Southern Ocean has been used to define the body of water which lies south of the northern limit of that circulation.
context_section_description: Five species of krill, small free-swimming crustaceans, have been found in the Southern Ocean. The Antarctic krill (Euphausia superba) is one of the most abundant animal species on earth, with a biomass of around 500 million tonnes. Each individual is 6 centimetres (2.4 in) long and weighs over 1 gram (0.035 oz).  The swarms that form can stretch for kilometres, with up to 30,000 individuals per 1 cubic metre (35 cu ft), turning the water red. Swarms usually remain in deep water during the day, ascending during the night to feed on plankton. Many larger animals depend on krill for their own survival. During the winter when food is scarce, adult Antarctic krill can revert to a smaller juvenile stage, using their own body as nutrition.
  Many benthic crustaceans have a non-seasonal breeding cycle, and some raise their young in a brood pouch. Glyptonotus antarcticus is an unusually large benthic isopod, reaching 20 centimetres (8 in) in length weighing 70 grams (2.47 oz). Amphipods are abundant in soft sediments, eating a range of items, from algae to other animals. The amphipods are highly diverse with more than 600 recognized species found south of the Antarctic Convergence and there are indications that many undescribed species remain. Among these are several "giants", such as the iconic epimeriids that are up to 8 cm (3.1 in) long.
  Slow moving sea spiders are common, sometimes growing as large as a human hand. They feed on the corals, sponges, and bryozoans that litter the seabed.
caption: A female warty squid (Moroteuthis ingens)
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