Powelliphanta snail
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| Powelliphanta snail Conservation status: Endangered | ||||||||||||||||||
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Powelliphanta gilliesi |
Powelliphanta_shell.jpg
Image:Powelliphanta shell.jpg
The shell of a species of land snail.
Powelliphanta is a genus of giant, carnivorous land snails from New Zealand. They live mostly in tiny pockets of moist native bush in small areas of the North and South Islands, with the greatest diversity of species in the mountains of North West Nelson. They are sometimes known as amber snails.
There are 21 species and 51 subspecies. The relationship between the species is complex, and it has been suggested that the group Powelliphanta gilliesi-traversi-hochstetteri-rossiana-lignaria-superba forms a ring species. .In November 2003 a subspecies, thought to be extinct, was rediscovered alive on the West Coast; it had last been documented on the basis of shell fragments in 1934.
These snails are real giants, with shells up to 9 cm across (Powelliphanta superba prouseorum) !
Their striking delicately-patterned shells come in an array of shades, from brown or red to yellow or black. The structure of these shells is very delicate, with a very thin layer of calcium carbonate, covered by a thicker chitinous outer layer. That is why these snails need moist surroundings. Otherwise the outer layer (periostracum) dries up, shrinks and cracks.
They are carnivorous and eat mostly earthworms or slugs. They are nocturnal. They need moist surroundings and live buried under leaf mold and logs. They can live up to 20 years (or even more !) and are slow to mature, having to be around 5 years old before they even begin to breed. They are hermaphrodites, having both male and female characteristics. They lay 5 to 10 large eggs a year.
Their origin goes back 200 million years to the continent Gondwana. Through their isolation on New Zealand, they have evolved into a unique set of characteristics. They are a testimony for New Zealand’s unique biodiversity.
Conservation status
The IUCN Red List states for Powelliphanta marchantii a lower risk, near threatened. But most of these snails are under serious threat or even in danger of extinction. They have no defense against introduced predators, such as Common Brushtail Possums (Trichosurus velpecula) and rats. Many recovery plans are being launched by the Department of Conservation of New Zealand..The subspecies Powelliphanta gilliesi brunnea and Powelliphanta traversi atakia are the most threatened.
An unspecified species of Powelliphanta recently appeared on a New Zealand 40-cent postage stamp.
External link
- Department of Conservation information. (http://www.doc.govt.nz/Conservation/001~Plants-and-Animals/001~Native-Animals/Powelliphanta-Land-Snail.asp)