Paramoera walkeri explained

Paramoera walkeri is an amphipod of the genus Paramoera. It lives around Antarctica.

Description

Like all amphipods, P. walkeri are sexually dimorphic: the males may grow up to 21.7mm; females, 22.8mm. Newborns are approximately 2.5mm. Males mature after 14–15 months, at about 50% their final size.^[1] Juvenile P. walkeri are more sensitive to hydrocarbons, such as from oil spills, than older specimens.^[2]

Distribution

P. walkeri live in the benthic zone of the Southern Ocean, all around Antarctica, down to a depth of 310m (1,020feet). During the early winter, P. walkeri migrate upward to the ice, and many congregate around patches of algae,^[3] in such abundance that they nearly cover the underside of the sea ice sheets. They are also found in the sublittoral zone, and the bottom level of other shallow locations around the Antarctic coast.^[4]

Behavior

As omnivores, they eat phytoplankton, cryophilic flora, and Diphyllobothrium tapeworms, among other organisms, under the top level of ice. During the summer, their metabolism increases by 80% compared to winter levels.^[5] Predators include Trematomus borchgrevinki, T. newnesii, T. bernacchii, Notothenia corriiceps neglecta, and Adélie penguins.^[1]

During a female's second (occasionally third) winter, she releases pheromones, picked up by a male's antennae, signaling that readiness to mate.^[1] 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.^[6] When the sea water becomes diluted, the eggs may swell up, to keep the total salinity around the embryos constant. They develop for four-and-a-half months, then hatch in the marsupium. The brooding young remain there for up to a month.^{[6] [7] [8]}

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.^{[9] [10] [11]} It was named after Alfred O. Walker, a fellow of the Linnean Society.^[9]

Notes and References

1. Life Cycle and Growth of the Antarctic Gammarid Amphipod Paramoera walkeri (Stebbing, 1906). P. M.. Sagar. Zoology Department, University of Canterbury. Christchurch. Journal of the Royal Society of New Zealand. March 25, 1980. 259–270. Google Books.
2. The toxicity of physically and chemically dispersed fuels to Antarctic marine invertebrates. Frances Jane. Alexander. January 1, 2016. National Library of Australia.
3. Book: Biology of the Vestfold Hills, Antarctica: Proceedings of the symposium, Hobart, August 1984. December 6, 2012. Springer Science & Business Media. J.M.. Ferris. H.R.. Burton. G.W.. Johnstone. I.A.E. . Bayly. 9789400930896. Google Books. 147.
4. Book: Ecological Studies in the Antarctic Sea Ice Zone: Results of EASIZ Midterm Symposium. Google Books. 94. Wolf E.. Arntz. Andrew . Clarke. December 6, 2012. Springer Science & Business Media. 9783642594199.
5. Winter and summer metabolic rates of Arctic amphipods. Preliminary results. Marcin. Węsławski. Krzysztof W.. Opaliński. Polish Polar Studies. 24th Polar Symposium, Warsawa. 1997. 315. July 27, 2017.
6. Amphipods. Advances in Marine Biology. 51. September 26, 2006. Academic Press. 9780080464527. D.W.. Sims. Alan J.. Southward. 243, 259, 289. Google Books.
7. 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 — via Sea Life Base. Retrieved July 27, 2017.
8. 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. — via Sea Life Base. Retrieved July 27, 2017.
9. Book: Stebbing, Thomas Roscoe Rede. Amphipoda I. Gammaridea. 1906. Friedländer. Berlin. 21. 728. Internet Archive.
10. Paramoera walkeri (Stebbing, 1906). 237493. De Broyer, Claude. Lowry, Jim. 2010. July 27, 2017.
11. Mr. A. O. Walker on Amphipoda of the 'Southern Cross' Expedition: Genus Atylus, Leach, 1817. A. O.. Walker. 58. Zoological Journal of the Linnean Society. 29. Linnean Society of London. 1902. Internet Archive.