''Paramoera walkeri'' is an

amphipod Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far descr ...

of the genus '' Paramoera''. It lives around Antarctica.

Description

Like all amphipods, ''P. walkeri'' are sexually dimorphic: the males may grow up to ; females, . Newborns are approximately . Males mature after 14–15 months, at about 50% their final size. Juvenile ''P. walkeri'' are more sensitive to hydrocarbons, such as from oil spills, than older specimens.

Distribution

''P. walkeri'' live in the

benthic zone 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 " ...

of the Southern Ocean, all around Antarctica, down to a depth of . During the early winter, ''P. walkeri'' migrate upward to the ice, and many congregate around patches of

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

, in such abundance that they nearly cover the underside of the sea ice sheets. They are also found in the

sublittoral zone The neritic zone (or sublittoral zone) is the relatively shallow part of the ocean above the drop-off of the continental shelf, approximately in depth. From the point of view of marine biology it forms a relatively stable and well-illuminated ...

, and the bottom level of other shallow locations around the Antarctic coast.

Behavior

omnivore An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nutr ...

s, they eat

phytoplankton Phytoplankton () are the autotrophic (self-feeding) components of the plankton community and a key part of ocean and freshwater ecosystems. The name comes from the Greek words (), meaning 'plant', and (), meaning 'wanderer' or 'drifter'. Ph ...

cryophilic Psychrophiles or cryophiles (adj. ''psychrophilic'' or ''cryophilic'') are extremophilic organisms that are capable of growth and reproduction in low temperatures, ranging from to . They have an optimal growth temperature at . They are found in ...

flora, and ''

Diphyllobothrium ''Diphyllobothrium'' is a genus of tapeworms which can cause diphyllobothriasis in humans through consumption of raw or undercooked fish. The principal species causing diphyllobothriasis is ''D. latum'', known as the broad or fish tapeworm, or b ...

'' tapeworms, among other organisms, under the top level of ice. During the summer, their metabolism increases by 80% compared to winter levels. Predators include '' Trematomus borchgrevinki'', '' T. newnesii'', '' T. bernacchii'', '' Notothenia corriiceps neglecta'', and

Adélie penguin The Adélie penguin (''Pygoscelis adeliae'') is a species of penguin common along the entire coast of the Antarctic continent, which is the only place where it is found. It is the most widespread penguin species, and, along with the emperor p ...

s. During a female's second (occasionally third) winter, she releases pheromones, picked up by a male's

antenna Antenna ( antennas or antennae) may refer to: Science and engineering * Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves * Antennae Galaxies, the name of two collid ...

e, signaling that readiness to mate. The male then clings on to the female until she molts. The male releases its sperm into the female's marsupium, and the female releases up to 200 eggs. When the sea water becomes diluted, the eggs may swell up, to keep the total salinity around the

embryo An embryo is an initial stage of development of a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male spe ...

s constant. They develop for four-and-a-half months, then hatch in the marsupium. The brooding young remain there for up to a month.De Broyer, C., J.K. Lowry, K. Jazdzewski and H. Robert 2007 Catalogue of the Gammaridean and Corophiidean Amphipoda (Crustacea) of the Southern Ocean, with distribution and ecological data. In C. De Broyer (ed.), Census of Antarctic Marine Life: Synopsis of the Amphipoda of the Southern Ocean. Vol. I. Bulletin de l'Institut royal des Sciences naturelles de Belgique van het koninklijk Belgisch Instituut voor Natuurwetenschappen. Biologie 77(suppl.1):1–325 — vi
Sea Life Base
Retrieved July 27, 2017.Ruppert, E.E., R.S. Fox and R.D. Barnes 2004 Invertebrate Zoology. A functional evolutionary approach. 7th Ed. Brooks/Cole, Thomson Learning learning, Inc. 990 p. — vi

Retrieved July 27, 2017.

Taxonomic history

This species was discovered by Thomas Roscoe Rede Stebbing in 1878, named ''Atylus antarcticus'' in 1903, and described as ''Atylus walkeri'' in 1906. It was named after Alfred O. Walker, a fellow of the Linnean Society.

References

{{Taxonbar, from=Q14019598 Amphipoda Fauna of the Southern Ocean Crustaceans described in 1906 Taxa named by Thomas Roscoe Rede Stebbing