Powelliphanta
Encyclopedia
Powelliphanta, common name
amber snails, is a genus of large, carnivorous land snail
s, terrestrial
pulmonate gastropod molluscs. As a group their survival status is endangered.
, and derived from the genus's similarity to Paryphanta
.
Powelliphanta was originally described by A. C. O'Connor in 1945 as a subgenus of Paryphanta.
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.
to New Zealand, in small areas of the North
and South Island
s, with the greatest diversity of species in the mountains of northwest Nelson
in the South Island.
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 chitin
ous 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.
They can live for 20 years or more and are slow to mature, reaching sexual maturity around 5 years of age. They are hermaphrodite
s, having both male and female characteristics. They lay 5 to 10 large eggs a year.
Powelliphanta uses a rudimentary radula to devour its prey. The radula is like a belt of teeth, which scrapes chunks of flesh into the oesophagus. Far from being ingested whole, its prey are subjected to prolonged radulation.
. Through their isolation in New Zealand, they have evolved a unique set of characteristics.
.
s, Trichosurus vulpecula, and rat
s. Possums have been shown to eat up to 60 snails in one night. Controlling predatory mammals is now critical to the survival of Powelliphanta, and many recovery plans are being undertaken by the Department of Conservation
. After aerial 1080 operations, Powelliphanta "Anatoki Range" numbers increased threefold at sites in Kahurangi National Park
, with large numbers of juveniles present. Pre 1080, there were 54 snails found on 500sq grid. One year after the 1080 drop, 147 snails were found on the same plot. Between 1994 and 2010, a series of three aerial 1080 operations over 3430ha of the Ruahine Forest Park
has resulted in significant increases in Powelliphanta marchanti
.
The subspecies Powelliphanta gilliesi brunnea and Powelliphanta traversi otakia are the most threatened.
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
amber snails, is a genus of large, carnivorous land snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
s, 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 molluscs. As a group their survival status is endangered.
Taxonomy
The generic name was given in honour of New Zealand's malacologist Arthur William Baden PowellArthur William Baden Powell
Dr Arthur William Baden Powell CBE was a New Zealand malacologist, naturalist and palaeontologist, a major influence in the study and classification of New Zealand molluscs through much of the twentieth century. He was known to his friends and family by his third name, "Baden".Powell was born at...
, and derived from the genus's similarity to Paryphanta
Paryphanta
Paryphanta, common name kauri snails, is a genus of large predatory land snails, terrestrial pulmonate gastropod mollusks in the family Rhytididae.-Species:Species within the genus Paryphanta include:* Paryphanta busbyi...
.
Powelliphanta was originally described by A. C. O'Connor in 1945 as a subgenus of Paryphanta.
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
Ring species
In biology, a ring species is a connected series of neighboring populations, each of which can interbreed with closely sited related populations, but for which there exist at least two "end" populations in the series, which are too distantly related to interbreed, though there is a potential gene...
.
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 endemicEndemic (ecology)
Endemism is the ecological state of being unique to a defined geographic location, such as an island, nation or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. For example, all species of lemur are endemic to the...
to New Zealand, in small areas of the North
North Island
The North Island is one of the two main islands of New Zealand, separated from the much less populous South Island by Cook Strait. The island is in area, making it the world's 14th-largest island...
and South Island
South Island
The South Island is the larger of the two major islands of New Zealand, the other being the more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman Sea, to the south and east by the Pacific Ocean...
s, with the greatest diversity of species in the mountains of northwest Nelson
Nelson, New Zealand
Nelson is a city on the eastern shores of Tasman Bay, and is the economic and cultural centre of the Nelson-Tasman region. Established in 1841, it is the second oldest settled city in New Zealand and the oldest in the South Island....
in the South Island.
Shell description
These gastropods are large, with shells up to 9 cm across (Powelliphanta superbaPowelliphanta superba
Powelliphanta superba is a species of large, carnivorous land snail in the family Rhytididae, which is endemic to the South Island of New Zealand...
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
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...
, covered by a thicker chitin
Chitin
Chitin n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world...
ous outer layer. These snails need moist surroundings, otherwise the outer layer (periostracum
Periostracum
The periostracum is a thin organic coating or "skin" which is the outermost layer of the shell of many shelled animals, including mollusks and brachiopods. Among mollusks it is primarily seen in snails and clams, i.e. in bivalves and gastropods, but it is also found in cephalopods such as the...
) 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 hermaphrodite
Hermaphrodite
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...
s, having both male and female characteristics. They lay 5 to 10 large eggs a year.
Powelliphanta uses a rudimentary radula to devour its prey. The radula is like a belt of teeth, which scrapes chunks of flesh into the oesophagus. Far from being ingested whole, its prey are subjected to prolonged radulation.
Fossil record
Their origin goes back 200 million years to the continent GondwanaGondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
. Through their isolation in New Zealand, they have evolved a unique set of characteristics.
Human use
An unspecified species of Powelliphanta recently appeared on a New Zealand 40-cent postage stampPostage stamps and postal history of New Zealand
Postage stamps have been issued in New Zealand since around the 18th to 20th of July 1855 with the "Chalon head" stamps figuring Queen Victoria. The design was based on a full face portrait of the Queen in her state robes at the time of her coronation in 1837, by Alfred Edward Chalon...
.
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 defence against introduced predators, such as common brushtail possumCommon Brushtail Possum
The Common Brushtail Possum is a nocturnal, semi-arboreal marsupial of the family Phalangeridae, it is native to Australia, and the largest of the possums.Like most possums, the Common Brushtail is nocturnal...
s, Trichosurus vulpecula, and rat
Rat
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...
s. Possums have been shown to eat up to 60 snails in one night. Controlling predatory mammals is now critical to the survival of Powelliphanta, and many recovery plans are being undertaken by the Department of Conservation
New Zealand Department of Conservation
The Department of Conservation , commonly known by its acronym, "DOC", is the state sector organisation which deals with the conservation of New Zealand’s natural and historic heritage...
. After aerial 1080 operations, Powelliphanta "Anatoki Range" numbers increased threefold at sites in Kahurangi National Park
Kahurangi National Park
Kahurangi National Park is a national park in the northwest of the South Island of New Zealand. It was gazetted in 1996 and covers 4,520 km². It is the second largest of New Zealand's fourteen national parks...
, with large numbers of juveniles present. Pre 1080, there were 54 snails found on 500sq grid. One year after the 1080 drop, 147 snails were found on the same plot. Between 1994 and 2010, a series of three aerial 1080 operations over 3430ha of the Ruahine Forest Park
Ruahine Range
The Ruahine Range is one of several mountain ranges in the North Island of New Zealand which form a ridge running parallel with the east coast of the island between East Cape and Wellington....
has resulted in significant increases in Powelliphanta marchanti
Powelliphanta marchanti
Powelliphanta marchanti, known as one of the amber snails, is a species of large, carnivorous land snail, a terrestrial pulmonate gastropod mollusc in the family Rhytididae.-Conservation status:...
.
The subspecies Powelliphanta gilliesi brunnea and Powelliphanta traversi otakia are the most threatened.
Species
Species within the genus Powelliphanta include:
|
Undescribed species:
|
Further reading
- Department of Conservation. (2000) "Recovery plans for Powelliphanta land snails 2002–2012". Department of Conservation, Wellington, New Zealand.
- Walker K. J. (2003) "Recovery plans for Powelliphanta land snails 2003–2013". Threatened Species Recovery Plan 49. Wellington, New Zealand Department of Conservation. x +208 p. + 64 pl. pages 1-12, 13-140, 141-196, 197-208.
- Meads M. J., Walker K. J. & Elliot G. P. (1984) "Status, conservation, and management of the land snails of the genus Powelliphanta (Mollusca: Pulmonata)". New Zealand Journal of Zoology 11: 277–306.