Powelliphanta

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Powelliphanta
Powelliphanta traversi on Lake Papaitonga

Powelliphanta traversi on Lake Papaitonga

Systematics
Superordinate : Heterobranchia
Order : Lung snails (pulmonata)
Subordination : Land snails (Stylommatophora)
Superfamily : Rhytidoidea
Family : Rhytididae
Genre : Powelliphanta
Scientific name
Powelliphanta
O'Connor , 1945

Powelliphanta is the name of a genus predatory mainly of earthworms living snails from the family Rhytididae in the subordination of terrestrial snails (gastropod), which in New Zealand are common. Many species are confined to small areas in humid forests and are endangered by introduced predatory mammal species. For a long time the species belonging to this group belonged to the genus Paryphanta .

features

The always bifurcated and depressed cases in the genus Powelliphanta are similar to those in the genus Paryphanta Albers, but the last contact is drawn in more towards the previous contact. The bowls at Powelliphanta also have a color pattern with concentric or radial bands, usually with alternating and contrasting colors. A noticeable feature - similar to Paryphanta - is the lack of lime in the shell compared to the periostracum made of conchin , which is why the houses quickly disintegrate when stored in a dry place. The eggs always have a cuticle and are therefore brownish yellow after laying.

Powelliphanta hochstetteri hochstetteri , Nelson-Marlborough Conservancy, 2011

The finely patterned shells of the various Powelliphanta species feature a range of shades ranging from brown or red to yellow or black. The largest species, Powelliphanta superba prouseorum, has a shell diameter of up to 9 cm and a body weight of up to 90 g.

Distribution and occurrence

The snail species of the genus Powelliphanta are endemic to New Zealand , with the range on the North Island from Waikaremoana Lake and Ruahine Range to the Kapiti Coast and on the South Island from Marlborough Sounds to Fiordland and Southland . The snails reach their greatest biodiversity in the mountains of northwest Nelson and northern Westland . Some species and subspecies have an extremely limited range, such as Powelliphanta gilliesi brunnea , which only occurs in a residual forest of around 1 hectare on the coast.

habitat

The snails live mainly in moist primeval forests. Some species and subspecies live in forests of the plains, including Powelliphanta traversi traversi that is classified at national level as threatened and where a 10-hectare nature reserve with forest of Dacrycarpus dacrydioides (Kahikatea) and marsh with Typha (raupo) at Levin was established . Other species live in forests in the highlands or above the tree line in grasslands ( tussock ). Several species only live in forests on limestone soils because they need calcium carbonate for their housings and eggshells. They gain this by eating various small animals, including snails, which have taken up the lime from the lime-rich environment, which is why the lime shells are also taken up by the predatory snail. The Powelliphanta snails need a moist environment, since they can not be sealed with a protective membrane of mucus in contrast to most other land snail its shell.

Life cycle

Powelliphanta snails can live to be 20 years old and reach sexual maturity at around 5 to 6 years. As hermaphrodites , like other lung snails, both sexual partners exchange their sperm when mating. A snail lays only 5 to 10 eggs each year, about 12 mm in size, with a thin pink-colored lime shell, similar to tiny bird eggs. In lowland species, the juvenile snails hatch 2 to 6 months after egg-laying, in highland species 12 to 14 months after egg-laying.

nutrition

The slugs of the genus Powelliphanta , as predatory slugs, feed mainly on earthworms and slugs , which they hold with the radula and pull into their mouths. They go hunting at night because they hide under leaf litter and wood during the day. The prey is crushed in the snail's mouth with the help of the radula teeth.

Predators and endangerment from humans

Shell remains of Powelliphanta traversi , eaten by Trichosurus vulpecula ( Fuchskusu )

The Wekaralle ( Gallirallus australis ) is considered the most important native predator of the Powelliphanta snails , but its importance for the mortality of the snails has taken a back seat . Introduced climbing sacs ( Trichosurus vulpecula ), pigs , hedgehogs and rats hunt the snails and have greatly reduced their populations in a short time. Land planarians also count among the enemies of snails .

Since a Powelliphanta snail only lays 5 to 10 eggs per year and the young animals only become sexually mature after about 5 years, these snail species are particularly sensitive to introduced snail-eaters. It is reported from the climbing bag Trichosurus vulpecula that an animal can eat up to 60 snails in one night.

In addition to predators, the destruction of the habitat through browsing and being represented by imported goats , deer and cattle is an important factor in the decline in snails.

The control or even the extermination of introduced predatory mammals is now considered necessary for the survival of the Powelliphanta species and this is what plans by the New Zealand Department of Conservation are aimed at. After the poison sodium fluoracetate (“1080”) was used against climbers by airplanes, the number of snails (undescribed species with auxiliary designation “ Powelliphanta Anatoki Range”) tripled in the investigated areas in the Kahurangi National Park , and there were numerous juvenile snails.

Between 1994 and 2010, a series of three Sodium Fluoroacetate aircraft missions over 3430 ha in the Ruahine Forest Park resulted in a significant increase in Powelliphanta marchanti .

The two subspecies Powelliphanta gilliesi brunnea and Powelliphanta traversi otakia are considered to be the most threatened. According to the Red List of IUCN is Powelliphanta marchantii "potentially at risk" ( near threatened ).

Since 1982 it has been banned in New Zealand to collect Powelliphanta snails or their shells. Collecting live snails for the shells is believed to be a possible reason that some species have become rarer. Some Powelliphanta species also require abandoned snail shells for consumption to meet their lime needs.

Systematics

The genus Powelliphanta was first described in 1945 by AC O'Connor as a subgenus of Paryphanta . With the naming, O'Connor honored the malacologist and expert for the family Rhytididae , Arthur William Baden Powell ", and with the second part of the name took into account the similarity to the genus Paryphanta .

Powelliphanta lignaria johnstoni , Mokihinui River
Powelliphanta marchanti
Powelliphanta annectens
Powelliphanta hochstetteri hochstetteri

1977 FM raised Climo Powelliphanta to a genus and left only two species in the genus Paryphanta . There are at least 21 species and 51 subspecies in the genus.

The species in the genus Powelliphanta include:

In addition, there are a number of undescribed species.

literature

Web links

Commons : Powelliphanta  - collection of images, videos and audio files

Individual evidence

  1. ^ A b c A. C. O'Connor (1945): Notes on the Eggs of New Zealand Paryphantidae, With Description of a New Subgenus. Transactions of the Royal Society of New Zealand 75 (1945-1946), 54 -57.
  2. ^ Warren Judd (July – September 1990): Slow, slimy and surprising! New Zealand Geographic No. 7, pp. 84-110.
  3. ↑ a b c New Zealand Land Snails. RD&I Wellington, Department of Conservation, Wellington 2006.
  4. ^ Arthur William Baden Powell : New Zealand Mollusca . William Collins Publishers Ltd, Auckland 1979. ISBN 0-00-216906-1
  5. ↑ a b c d e Gerard Hutching: The Natural World of New Zealand. Reader's Digest, Auckland 1998. p. 315. ISBN 0-86449-261-8
  6. ↑ Paddy Ryan: Snails and slugs - Flax snails, giant snails and veined slugs. Te Ara - the Encyclopedia of New Zealand, July 13, 2012.
  7. ^ A b Geoff Collett: It's so hard being a snail. Nelson Mail, September 19, 2009.
  8. ↑ Hedgehogs pose prickly problem for native fauna. Landcare Research media release, September 17, 2003.
  9. ↑ a b Kath Walker: Recovery plans for Powelliphanta land snails 2003-2013. Threatened Species Recovery Plan 49, 3. The recovery plans.
  10. ↑ Rod Morris: New Zealand Invertebrates - Giant flatworm ('Australopacifica' sp.) 'Digesting' a Denniston giant land snail (Powelliphanta patrickensis) which it has captured at night.
  11. ↑ Giant snails the winners. New Zealand Department of Conservation / Te Papa Atawhai, October 26, 2010.
  12. ↑ FM Climo (1977): A new higher level classification of the New Zealand Rhytididae (Mollusca: Pulmonata). Journal of the Royal Society of New Zealand 7 (1), pp. 59-65. doi 10.1080 / 03036758.1977.10419336
  13. ^ Powelliphanta snail. New Zealand Department of Conservation / Te Papa Atawhai.