Definitions

gouland

Powelliphanta

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.

Distribution

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.

Habitat

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

Shell description

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.

Life habits

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.

Fossil record

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.

Human use

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

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 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.

Species and subspecies within the genus Powelliphanta

Undescribed species

Undescribed subspecies

References

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