The Lord Howe flax snail or the Lord Howe placostylus,

scientific name In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''Placostylus bivaricosus'', is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of large air-breathing

land snail A land snail is any of the numerous species of snail that live on land, as opposed to the sea snails and freshwater snails. ''Land snail'' is the common name for terrestrial gastropod mollusks that have shells (those without shells are known as ...

, a

terrestrial Terrestrial refers to things related to land or the planet Earth. Terrestrial may also refer to: * Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on or near the ground, as opposed to ...

pulmonate Pulmonata or pulmonates, is an informal group (previously an order, and before that a subclass) of snails and slugs characterized by the ability to breathe air, by virtue of having a pallial lung instead of a gill, or gills. The group includ ...

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

in the family Bothriembryontidae. MolluscaBase eds. (2021). MolluscaBase. Placostylus bivaricosus (Gaskoin, 1855). Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=1149983 on 2022-01-22

Distribution

This large snail is found only on

Lord Howe Island Lord Howe Island (; formerly Lord Howe's Island) is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, part of the Australian state of New South Wales. It lies directly east of mainland P ...

off the east coast of Australia. Its conservation status has declined from common to

endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inva ...

since rats were accidentally introduced to this World Heritage island in 1918.

Subspecies

Subspecies of ''Placostylus bivaricosus'' include: * ''Placostylus bivaricosus bivaricosus'' (Gaskoin, 1855) Ponder W. F., Colgan D. J., Gleeson D. M. & Sherley G. H. (2003). "Relationships of ''Placostylus'' from Lord Howe Island: an investigation using the mitochondrial cytochrome c oxidase 1 gene". ''

Molluscan Research Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is est ...

'' 23(2): 159-178.
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* ''Placostylus bivaricosus etheridgei'' (Hedley, 1891) - extinct * ''Placostylus bivaricosus cuniculinsulae'' (Cox, 1872) * ''Placostylus bivaricosus solidus'' (Brazier in Etheridge, 1889)

Description

The genus ''

Placostylus ''Placostylus'', or flax snails, are a genus of very large, air-breathing land snails, terrestrial pulmonate gastropod molluscs in the family Bothriembryontidae.MolluscaBase eds. (2020). MolluscaBase. Placostylus H. Beck, 1837. Accessed thro ...

'' is a group of large ground dwelling gastropods with a disjunct distribution in the South west Pacific from the

Solomon Islands Solomon Islands is an island country consisting of six major islands and over 900 smaller islands in Oceania, to the east of Papua New Guinea and north-west of Vanuatu. It has a land area of , and a population of approx. 700,000. Its capita ...

Fiji Fiji ( , ,; fj, Viti, ; Fiji Hindi: फ़िजी, ''Fijī''), officially the Republic of Fiji, is an island country in Melanesia, part of Oceania in the South Pacific Ocean. It lies about north-northeast of New Zealand. Fiji consists ...

, and

New Caledonia ) , anthem = "" , image_map = New Caledonia on the globe (small islands magnified) (Polynesia centered).svg , map_alt = Location of New Caledonia , map_caption = Location of New Caledonia , mapsize = 290px , subdivision_type = Sovereign st ...

, to Lord Howe Island and the northern extremity of

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

. The Lord Howe flax snail has a brown, pointed shell up to 7 cm long and 2 cm in diameter.

Conservation

Species decline

Historical accounts and fossil evidence indicate that the Lord Howe Island flax snail was formerly widespread and abundant on the island. The decline was first noted in the 1940s and the species is now listed as critically endangered. The

black rat The black rat (''Rattus rattus''), also known as the roof rat, ship rat, or house rat, is a common long-tailed rodent of the stereotypical rat genus ''Rattus'', in the subfamily Murinae. It likely originated in the Indian subcontinent, but is n ...

is considered to be the major predator of this species and likely to be a significant threat to its survival.

European blackbird The common blackbird (''Turdus merula'') is a species of true thrush. It is also called the Eurasian blackbird (especially in North America, to distinguish it from the unrelated New World blackbirds), or simply the blackbird where this does not ...

s and

song thrush The song thrush (''Turdus philomelos'') is a Thrush (bird), thrush that breeds across the West Palearctic. It has brown upper-parts and black-spotted cream or buff underparts and has three recognised subspecies. Its distinctive Birdsong, song, ...

es (self-introduced around 1950) are also thought to be predators of the snail. Habitat clearing and modification and habitat disturbance, possibly herbicides and pesticides also add to the species decline.

Recovery

In 2001, a recovery plan was completed to protect and recover the Lord Howe Island flax snail in the wild. Actions include habitat and population surveys, community awareness raising and a captive-breeding program. The

Lord Howe Island Board The Lord Howe Island Board is a NSW Statutory Authority established under the ''Lord Howe Island Act, 1953'', to administer Lord Howe Island, an unincorporated island territory within the jurisdiction of the State of New South Wales, Australia, i ...

, responsible for implementation of the recovery plan, has since constructed a rodent and bird proof enclosure for the project and the first generation of captive bred Lord Howe Island land snails has hatched. Over a period of two years, schoolchildren will closely monitor the captive snail population and their eggs, and will then measure growth rates and survival rates of the juvenile snails. Rodent control or eradication on the island is crucial for the long-term survival of this snail in the wild.

References

External links

description in Latin languageThreatened Species Profile Lord Howe Island Land Snail (Australian Government, Department of Environment and Water Resources)

* ttps://web.archive.org/web/20060824150231/http://fnpw.org.au/enews3/lhiPhasmid.htm Rodent eradication on Lord Howe Island (Foundation for National Parks & Wildlife)
Gaskoin, J. S. (1855). Descriptions of two new species of land shells. Proceedings of the Zoological Society of London. 22: 152

Cox, J.C. (1872). Descriptions of new land-shells from Australia and the South-Sea islands. Poceedings of the Zoological Society of London. 1872: 18-23

Hedley, C. (1891). The land and freshwater shells of Lord Howe Island. Records of the Australian Museum. 1: 134-143

Brazier, J. (1889). Mollusca. In: Etheridge, R (ed.) The general zoology of Lord Howe Island; containing also an account of the collections made by the Australian Museum Collecting Party, Aug.–Sept., 1887, pp. 22-30. Memoirs of the Australian Museum. 2: 1-42.

Iredale, T. (1944). The land Mollusca of Lord Howe Island. The Australian Zoologist. 10(3): 299-334

Clench, W. J. (1941). The land Mollusca of the Solomon Islands (Succineidae, Bulimulidae and Partulidae). American Museum Novitates. 1129: 1-21
* Solem A. (1959). "Systematics of the land and fresh-water mollusca of the New Hebrides". ''

Fieldiana The Field Museum of Natural History (FMNH), also known as The Field Museum, is a natural history museum in Chicago, Illinois, and is one of the largest such museums in the world. The museum is popular for the size and quality of its educational ...

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{{Wikispecies-inline, Placostylus bivaricosus, ''Placostylus bivaricosus'' Gastropods of Lord Howe Island Placostylus Gastropods described in 1854