Lord Howe Flax Snail
Encyclopedia
The Lord Howe Flax Snail or the Lord Howe placostylus, scientific name Placostylus bivaricosus, is a species
of large air-breathing land snail
, a terrestrial
pulmonate gastropod mollusc
in the family Placostylidae
, according to the taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)
.
This large snail is found only on Lord Howe Island
off the east coast of Australia. Its conservation status has declined from common to endangered since rats were accidentally introduced to this World Heritage island
in 1918.
is a group of large ground dwelling gastropods with a disjunct distribution in the South west Pacific from the Solomon Islands
, Fiji
, and New Caledonia
, to Lord Howe Island and the northern extremity of New Zealand
. The Lord Howe Flax Snail has a brown, pointed shell up to 7 cm long and 2 cm in diameter.
The Black Rat
is considered to be the major predator of this species and likely to be a significant threat to its survival. European Blackbirds and Song Thrush
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.
The Lord Howe Island Board, 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 How 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.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of large air-breathing land snail
Land snail
A land snail is any of the many species of snail that live on land, as opposed to those that live in salt water and fresh water. Land snails are terrestrial gastropod mollusks that have shells, It is not always an easy matter to say which species are terrestrial, because some are more or less...
, a terrestrial
Terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
pulmonate gastropod mollusc
Mollusca
The Mollusca , common name molluscs or mollusksSpelled mollusks in the USA, see reasons given in Rosenberg's ; for the spelling mollusc see the reasons given by , is a large phylum of invertebrate animals. There are around 85,000 recognized extant species of molluscs. Mollusca is the largest...
in the family Placostylidae
Placostylidae
Placostylidae is a family of land snails, gastropods in the superfamily Orthalicoidea.- Taxonomy :The Placostylidae family is classified within the informal group Sigmurethra, itself belonging to the clade Stylommatophora within the clade Eupulmonata .This family has no subfamilies Placostylidae is...
, according to the taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)
Taxonomy of the Gastropoda (Bouchet & Rocroi, 2005)
The taxonomy of the Gastropoda as it was revised by Philippe Bouchet and Jean-Pierre Rocroi is currently the most up-to-date overall system for classifying gastropod mollusks...
.
This large snail is found only on Lord Howe Island
Lord Howe Island
Lord Howe Island is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, directly east of mainland Port Macquarie, and about from Norfolk Island. The island is about 11 km long and between 2.8 km and 0.6 km wide with an area of...
off the east coast of Australia. Its conservation status has declined from common to endangered since rats were accidentally introduced to this World Heritage island
World Heritage Site
A UNESCO World Heritage Site is a place that is listed by the UNESCO as of special cultural or physical significance...
in 1918.
Subspecies
Subspecies of Placostylus bivaricosus include:- Placostylus bivaricosus bivaricosus (Gaskoin, 1855)
- Placostylus bivaricosus etheridgei (Hedley, 1891) - extinct
- Placostylus bivaricosus cuniculinsulae (Cox, 1872)
- Placostylus bivaricosus solidus (Brazier in Etheridge, 1889)
Description
The genus PlacostylusPlacostylus
Placostylus, or flax snails, are a genus of very large, air-breathing land snails, terrestrial pulmonate gastropod molluscs in the family Placostylidae.Placostylus is the type genus of the family Placostylidae....
is a group of large ground dwelling gastropods with a disjunct distribution in the South west Pacific from the Solomon Islands
Solomon Islands
Solomon Islands is a sovereign state in Oceania, east of Papua New Guinea, consisting of nearly one thousand islands. It covers a land mass of . The capital, Honiara, is located on the island of Guadalcanal...
, Fiji
Fiji
Fiji , officially the Republic of Fiji , is an island nation in Melanesia in the South Pacific Ocean about northeast of New Zealand's North Island...
, and New Caledonia
New Caledonia
New Caledonia is a special collectivity of France located in the southwest Pacific Ocean, east of Australia and about from Metropolitan France. The archipelago, part of the Melanesia subregion, includes the main island of Grande Terre, the Loyalty Islands, the Belep archipelago, the Isle of...
, to Lord Howe Island and the northern extremity of New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
. The Lord Howe Flax Snail has a brown, pointed shell up to 7 cm long and 2 cm in diameter.
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
Black Rat
The black rat is a common long-tailed rodent of the genus Rattus in the subfamily Murinae . The species originated in tropical Asia and spread through the Near East in Roman times before reaching Europe by the 1st century and spreading with Europeans across the world.-Taxonomy:The black rat was...
is considered to be the major predator of this species and likely to be a significant threat to its survival. European Blackbirds and Song Thrush
Song Thrush
The Song Thrush is a thrush that breeds across much of Eurasia. It is also known in English dialects as throstle or mavis. It has brown upperparts and black-spotted cream or buff underparts and has three recognised subspecies...
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, 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 How 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.