''Glyptonotus antarcticus'' is a

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

marine

isopod Isopoda is an order of crustaceans that includes woodlice and their relatives. Isopods live in the sea, in fresh water, or on land. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, an ...

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

in the suborder

Valvifera The Valvifera are marine isopod crustaceans. Valviferans are distinguished, however, by the flat, valve-like uropods which hinge laterally and fold inward beneath the rear part of their bodies, covering the pleopods. Some species are omnivorou ...

. This relatively large isopod is found in the

Southern Ocean The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the World Ocean, generally taken to be south of 60° S latitude and encircling Antarctica. With a size of , it is regarded as the second-small ...

around Antarctica. It was first described by

James Eights James Eights (1798–1882) was an American physician, scientist, and artist. He was born in Albany, New York, the son of physician Jonathan Eights and Alida Wynkoop. James also became a physician and was appointed an examiner at a local engineering ...

in 1852 and the type locality is the

South Shetland Islands The South Shetland Islands are a group of Antarctic islands with a total area of . They lie about north of the Antarctic Peninsula, and between southwest of the nearest point of the South Orkney Islands. By the Antarctic Treaty of 195 ...

Description

''Glyptonotus antarcticus'' has a typical maximum length of , but may rarely reach up to . This is large for an isopod, most of which are between in length. It has two pairs of

compound eyes A compound eye is a visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidia, which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which distin ...

, a large pair on the dorsal surface and a smaller pair on the ventral surface. Glyptonotus antarticus has only five

ommatidia The compound eyes of arthropods like insects, crustaceans and millipedes are composed of units called ommatidia (singular: ommatidium). An ommatidium contains a cluster of photoreceptor cells surrounded by support cells and pigment cells. The ou ...

, which is unusual for

crustaceans Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

and

insects Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of j ...

. It is thought that the latter are useful when the animal is swimming, which it does in an upside-down position. With the exception of the eyes, certain mouthparts and feet, the whole surface of the animal has minute

cuticular A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...

outgrowths of feathery hairs and knobbly scales. It is thought that these may help to prevent attachment of

Foraminifera Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular Ectoplasm (cell biology), ectoplasm for catching food and ot ...

and marine

larval A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The l ...

organisms on the body surface.

Distribution and habitat

''Glyptonotus antarcticus'' is native to the Southern Ocean around Antarctica, where it occurs in large numbers. It lives on the seabed at depths ranging from the

intertidal zone The intertidal zone, also known as the foreshore, is the area above water level at low tide and underwater at high tide (in other words, the area within the tidal range). This area can include several types of habitats with various species o ...

down to more than .

Biology

''Glyptonotus antarcticus'' is a carnivore and

scavenger Scavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a herbivorous feeding b ...

and is often caught in baited traps on the seabed. It is an opportunistic

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

with a mixed diet which includes a high proportion of

echinoderm An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the sea ...

s, but it is also

cannibalistic Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species In biology, a species is the basic ...

. That the available food supply may be fairly constant is shown by the fact that it breeds at any time of year. Females can breed when at least long. The eggs and young are brooded for an extended period—more than 1½ year—in the female's marsupium where they are nourished by a maternal secretion. As typical of Antarctic isopods, there is no pelagic larval stage.

Research

Given its abundance and the fact that it is relatively easy to keep in aquaria, ''Glyptonotus antarcticus'' has become an important

model organism A model organism (often shortened to model) is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the model organism will provide insight into the workin ...

used as a research object in ecological, biochemical and physiological studies. A 2005 genetic study suggested that ''Glyptonotus antarcticus'' may in fact represent several distinct species.

References

{{Taxonbar, from=Q2239015 Valvifera Fauna of the Southern Ocean Crustaceans described in 1852