Class POLYPLACOPHORA
Chitons
Compiler and date details
31 December 1999 - K. Gowlett-Holmes, CSIRO Marine Research, Hobart, Tasmania, Australia
Introduction
The Polyplacophora is an ancient class of exclusively marine molluscs, commonly known as chitons or coat-of-mail shells. Polyplacophorans are bilaterally symmetrical, dorso-ventrally flattened, dorsally with eight articulating shell plates bearing sensory aesthetes, ventrally with a large foot and simple head lacking eyes and tentacles. They occur from the littoral to abyssal depths, and the majority of species live attached to solid substrates, usually rock. Chitons are dioecious, but lack any form of sexual dimorphism.
Most chitons are grazers, feeding by scraping matter from the substrate using a complex radula with some teeth with cutting edges reinforced with magnetite. In Australian waters, most species consume varying amounts of encrusting marine invertebrates, particularly sponges and bryozoans, as well as plant material. Some species have become specialist carnivorous grazers, feeding selectively and sometimes exclusively on particular encrusting animals. A few species have become active carnivores, trapping free-living invertebrates, particularly small crustaceans, with the enlarged and flexible anterior end of the girdle.
The global chiton fauna numbers about 800 species. The Australian fauna is extremely rich and diverse, with 171 species currently recognised (including Lord Howe Island, Norfolk Island, Cocos (Keeling) Islands, Christmas Island, Macquarie Island, Heard and McDonald Islands, and the Australian Antarctic Territory waters). Of these species, 136 are endemic to Australian waters, mainly to southern areas. The chiton fauna of southern Australia is the most diverse and species-rich of any region in the world. Of the 35 non-endemic species, 25 are found elsewhere in the tropical Indo-Pacific region, including three deep sea species, another three also occur in New Zealand (including one species that was accidentally introduced from New Zealand to south-eastern Tasmania prior to 1900), and the remaining seven species are widespread in sub-Antarctic and Antarctic waters. There are five endemic genera, among which are a group of highly specialised sand dwellers, and a group adapted to live on seagrass. The chiton fauna of tropical Australia is generally far more poorly known than that of southern Australia, and it is highly likely that when the tropical regions are studied in more detail, a number of additions to the fauna (and possibly new species) will be discovered. The distribution of species in Tasmanian waters was updated to concur with Grove et al. (2006).
Acknowledgements
The author thanks the following for assistance with this work: for supplying information on the collections in their care, Ms Kathie Way and Miss Amelia Campbell (BMNH); Mr Ian Loch (AM); Mr Bruce Marshall (NMNZ); Mr Wolfgang Zeidler (SAMA); Mr Darryl Potter and Mr John Stanisic (QM); Ms Sue Boyd (NMV); Ms Elizabeth Turner (TMH); and Dr Fred Wells (WAM); for assistance and critical advice on the MS, Dr Richard Willan (Northern Territory Museums and Art Galleries); and for editorial assistance, Drs Alice Wells and Keith Houston (Australian Biological Resources Study (ABRS)). Mr Peter Middlefart (AM), and the staff of the libraries of the Australian National Botanic Gardens, Canberra, and the SAMA are thanked for assistance with difficult reference material. The project was funded by ABRS.
Database Notes
The information on the Australian Faunal Directory site for the Polyplacophora is derived from the Zoological Catalogue of Australia database compiled on the Platypus software program. It incorporates a few minor changes made to the work published on 2 July 2001 as .
All illustrations used in the published work are taken from Kaas et al. (1998). The names from Carpenter's unpublished manuscript have been used by several authors, including Pilsbry (1892–1894) who prefaced his 'Monograph of the Polyplacophora' as follows: '[t]he new species described herein which are credited to Carpenter rest upon his types when the descriptions are quoted from his manuscript …' [his italics]. Thus, most of the Carpenter names are cited here as 'Carpenter in Pilsbry'. Other Carpenter names published by Dall, E.A. Smith and other authors are treated similarly.
The distribution of species in Tasmanian waters was updated, January 2007, to concur with Grove et al. (2006).
Limital Area
Distribution data in the Directory is by political and geographic region descriptors and serves as a guide to the distribution of a taxon. For details of a taxon's distribution, the reader should consult the cited references (if any) at genus and species levels.
Australia is defined as including Lord Howe Is., Norfolk Is., Cocos (Keeling) Ils, Christmas Is., Ashmore and Cartier Ils, Macquarie Is., Australian Antarctic Territory, Heard and McDonald Ils, and the waters associated with these land areas of Australian political responsibility. Political areas include the adjacent waters.
Terrestrial geographical terms are based on the drainage systems of continental Australia, while marine terms are self explanatory except as follows: the boundary between the coastal and oceanic zones is the 200 m contour; the Arafura Sea extends from Cape York to 124 DEG E; and the boundary between the Tasman and Coral Seas is considered to be the latitude of Fraser Island, also regarded as the southern terminus of the Great Barrier Reef.
Distribution records, if any, outside of these areas are listed as extralimital. The distribution descriptors for each species are collated to genus level. Users are advised that extralimital distribution for some taxa may not be complete.
General References
Cotton, B.C. 1964. South Australian Mollusca. Chitons. Adelaide : S.A. Govt. Printer 150 pp.
Gowlett-Holmes, K.L. 2001. Polyplacophora. pp. 19-84 in Wells, A. & Houston, W.W.K. (eds). Zoological Catalogue of Australia. Vol. 17.2 Mollusca: Aplacophora, Polyplacophora, Scaphopoda, Cephalopoda. Melbourne : CSIRO Publishing, Australia xii 353 pp. [Date published 3 July 2001]
Kaas, P., Jones, A.M. & Gowlett-Holmes, K.L. 1998. Class Polyplacophora. pp. 161-194 in Beesley, P.L., Ross, G.J.B. & Wells, A. (eds). Mollusca: The Southern Synthesis. Fauna of Australia. Melbourne : CSIRO Publishing Vol. 5(Part A) pp. xvi, 1-563.
Sigwart, J.D., Stoeger, I., Knebelsberger, T. & Schwabe, E. 2013. Chiton phylogeny (Mollusca: Polyplacophora) and the placement of the enigmatic species Choriplax grayi (H. Adams & Angas). Invertebrate Systematics 27: 603-621
History of changes
| Published | As part of group | Action Date | Action Type | Compiler(s) |
|---|---|---|---|---|
| 09-Apr-2014 | MODIFIED |