Powelliphanta: Difference between revisions

Powelliphanta
The shell of a species of Powelliphanta land snail.
Conservation status
Endangered
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
Subclass:	Orthogastropoda
Superorder:	Heterobranchia
Order:	Pulmonata
Suborder:	Eupulmonata
Family:	Rhytididae
Genus:	Powelliphanta O’Connor, 1945
Species
See text.

Powelliphanta, common name amber snails, is a genus of large, carnivorous land snails, terrestrial pulmonate gastropod molluscs. As a group their survival status is endangered.

There are 21 species and 51 subspecies within the genus. 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 large snails are endemic to New Zealand, in small areas of the North and South Islands, with the greatest diversity of species in the mountains of northwest Nelson in the South Island.

These snails live mostly in tiny pockets of moist native bush.

These gastropods are large, 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. These snails need moist surroundings, otherwise the outer layer (periostracum) dries, shrinks and cracks. This happens often in museum shells of this genus which are stored dry; when they dry too much, the shell shatters explosively into fairly small pieces.

Species in the genus Powelliphanta are carnivorous and eat mostly earthworms or slugs. They are nocturnal. They need moist surroundings and thus they live buried under leaf mould and logs.

They can live for 20 years or more and are slow to mature, reaching sexual maturity around 5 years of age. 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 in New Zealand, they have evolved a unique set of characteristics. They are a clear demonstration of New Zealand’s unique biodiversity.

An unspecified species of Powelliphanta recently appeared on a New Zealand 40-cent postage stamp.

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 vulpecula, and rats. Many recovery plans are being launched by the New Zealand Department of Conservation. The subspecies Powelliphanta gilliesi brunnea and Powelliphanta traversi otakia are the most threatened.

• Department of Conservation information.
• K. Walker (2003). "Recovery plans for Powelliphanta land snails 2003–2013 (Threatened Species Recovery Plan 49)" (PDF). Department of Conservation, Wellington, New Zealand. Retrieved 2007-09-05.