ABOUT PHREATOICIDEAN ISOPODS IN AUSTRALIA

by Buz Wilson, Australian Museum

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Isopods of suborder Phreatoicidea are small elongate crustaceans ranging from a few millimetres up to several centimetres long. Their colour is typically brown or white, although some Victorian semiterrestrial species have colourful yellow patches on their heads. Phreatoicideans lack the carapace that is characteristic of many large fresh water Crustacea like yabbies, and their head is rounded with small or absent eyes, depending on the species. Phreatoicidean isopods have 7 pairs of similar legs, although the first one is often strong and claw-like. In life, the bodies of many species in Southeastern Australia are curled under at the end, with their spiny posteriors being used to push them along through the cryptic habitats that they favour. These isopods live in fresh water streams, burrowing in the soil in moist areas, in yabbie burrows, in ground waters, and in underground streams, with approximately a quarter of the species being entirely subterranean. Phreatoicideans belong the large order Isopoda, which has representatives in all environments from the deepest oceans (Isopoda Asellota) to the highest mountains in Australia (Mt. Kosciusko). The literature on the Phreatoicidea is limited to less than 100 publications, with the last major revision done in 1943-1944 by G.E. Nicholls. The first Australian phreatoicidean, Phreatoicus australis, was described by Charles Chilton in 1891 based on specimens collected near Mt. Kosciusko (this species was later placed in the genus Metaphreatoicus by Nicholls in 1944; pleotelson and uropods illustrated to the right). Phreatoicidea currently include 30 genera and 60 species, most of which occur in Australia and Tasmania. Pleotelson and Uropods of Metaphreatoicus australis
My research has shown that the phreatoicideans are an ancient offshoot from the phylogenetic line that gave rise to all other isopods. Their fossil record extends 325 million years into the Palaeozoic age of earth history. Their biogeography and fossil record indicates that phreatoicidean isopods have been living on and around the Australian continent before marsupial mammals even evolved, and yet they show surprisingly little morphological change compared to their fossil ancestors. Phreatoicideans are therefore "living fossils" in the truest sense of the phrase.

Hesslerella shermani Schram

Hesslerella shermani
(Image courtsey of Dr Frederick R. Schram,
Institute for Systematics and Population Biology, University of Amsterdam)

Species of the genus Crenoicus. This genus has 4 described species, although only 2 are from New South Wales (Wilson and Ho, 1996). Crenoicus is common in subalpine sphagnum moss mounds and swamps of relatively undisturbed habitats along the Great Dividing Range from the northern border of New South Wales to southern Victoria. The conservative morphology of these isopods has rendered identification of Crenoicus species difficult, and our efforts are aimed at providing means of placing specimens in a well defined species categories. Our work on the phreatoicidean isopods should improve our understanding of their diversity, morphology, and potential use as environmental indicators.
Other projects on phreatoicidean isopods are described on another page. See also new phreatoicidean genera.

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Selected Publications on Phreatoicidea (Isopoda) - See also Entire References

Banarescu, P. (1990). `Zoogeography of fresh waters', Volume 1. General distribution and dispersal of freshwater animals. (with 208 distribution maps) (Aula-Verlag: Wiesbaden, Germany.) [distribution of the entire group - but uses unpublished taxonomic names in some cases]

Brusca, R. C., and Wilson, G. D. F. (1991). A phylogenetic analysis of the Isopoda with some classificatory recommendations. Memoirs of the Queensland Museum 31, 143-204. [Phreatoicideans shown to be ancient offshoots from the Isopoda]

Chilton,C (1892): On a new and peculiar freshwater isopod from Mt. Kosciusko. Records of the Australian Museum 1, 149-171, pls. 23-26. [first description of a phreatoicidean from Australia]

Chilton, C. (1916). Some Amphipoda and Isopoda from Barrington Tops (4600 ft. alt.) N.S.W. Proceedings of the Royal Society of New South Wales 50, 82-98. [First description of Crenoicus]

Chilton, C. (1918). A fossil isopod belonging to the fresh-water genus Phreatoicus. Journal and Proceedings of the Royal Society of New South Wales 51, 365-388. [Jurassic fossils from Newtown, NSW; see Wilson & Edgecombe, 2003; below]

Nicholls, G. E. (1943). The Phreatoicoidea. Part I. The Amphisopidae. Papers and Proceedings of the Royal Society of Tasmania 1942, 1-145. [only major monograph on Phreatoicidea in two volumes. Many new genera and species named.]

Nicholls, G. E. (1944). The Phreatoicoidea. Part II. The Phreatoicoidae. Papers and Proceedings of the Royal Society of Tasmania 1943, 1-156. [only major monograph on Phreatoicidea in two volumes. Many new genera and species named.]

Ponder, W. (1986). Mound springs of the Great Artesian Basin. In `Limnology in Australia', pp. 403-420. (Eds P. De Deckker and W. D. Williams.) (CSIRO Australia Melbourne & Dr.W. Junk Publ.: Dordrecht.) [evidence of the necessity for permanent water for Phreatoicideans]

Williams, W. D. (1966). The phreatoicids. Australian Natural History March, 165-168. [popular article]

Williams, W. D. (1980). `Australian Freshwater Life - The Invertebrates of Australian Inland Waters', 2nd Edition. (The MacMillan Company of Australia Pty Ltd: Melbourne.) [general reference to the group]

Williams, W. D. (1981). The Crustacea of Australian inland waters. In `Ecological Biogeography of Australia', pp. 1101-1138. (Ed A. Keast.) In Series `Monographs on Biology', 41(2) . (W.Junk: The Hague/Boston.) [general reference to the group]

Wilson, G. D. F., and Ho, E. L. (1996). Crenoicus Nicholls, 1944 (Crustacea, Isopoda, Phreatoicidea): systematics and biology of a new species from New South Wales. Records of the Australian Museum 48(1):7-32. [Revision of the genus, first new species described in Australia for 52 years. ]

Wilson G. D. F., Fenwick G.D. (1999). Taxonomy and Ecology of Phreatoicus typicus Chilton, 1883 (Crustacea, Isopoda, Phreatoicidae). Journal of the Royal Society of New Zealand 29(1):41-64. [Type species of the Phreatoicidea redescribed with some ecological information]

Wilson G. D. F., Keable S.J. (1999). A new genus of phreatoicidean isopod (Crustacea) from the North Kimberley Region, Western Australia. Zoological Journal of the Linnean Society, London 126(1):51-79. [First new genus in the suborder since 1950. Cladogram based on new features. First use of a DELTA description. ] [Figure 1 here]

Wilson G. D. F., Johnson R. T. (1999). Ancient endemism among freshwater isopods (Crustacea, Phreatoicidea). In: "The Other 99%. The conservation and Biodiversity of Invertebrates," W.F. Ponder and D. Lunney, eds., pp. 264-268, Transactions of the Royal Zoological Society of New South Wales, Mossman.

Wilson G. D. F. , Keable S. J. (2001). Systematics of the Phreatoicidea. In: "Isopod Systematics and Evolution", R.C. Brusca & B. Kensley, eds., pp. 175-194. Special Publication of the Second Isopod Conference. Crustacean Issues 13. A.A.Balkema, Rotterdam.

Wilson G. D. F., Keable S. J. 2002. New genera of Phreatoicidea (Crustacea: Isopoda) from Western Australia.  Records of the Australian Museum 54: 41-70 (abstract; complete article)

Wilson G. D. F., Keable S. J. 2002. New Phreatoicidea (Crustacea: Isopoda) from Grampians National Park, with revisions of Synamphisopus and Phreatoicopsis.  Memoirs of Museum Victoria 59(2): 457-530 (abstract, complete article)

Poore G.C.B., Knott B., Lew Ton H.M., Wilson G.D.F. 2002. Suborder Phreatoicidea Stebbing, 1893. Pp. 62-80 in Poore, G.C.B. (ed.), “Crustacea: Malacostraca: Syncarida, Peracarida: Isopoda, Tanaidacea, Mictacea, Thermosbaenacea, Spelaeogriphacea”, Houston W.W.K., Beesley P.L. (series eds.), Zoological Catalogue of Australia. Vol. 19.2A. Melbourne: CSIRO Publishing, Australia, xii 434 pp

Wilson, G.D.F., Edgecombe G.D. 2003. The Triassic isopod Protamphisopus wianamattensis (Chilton) and comparison with extant taxa (Crustacea, Phreatoicidea)  Journal of Paleontology 77(3): 454-470. (abstract)


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