Powelliphanta traversi
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Powelliphanta traversi ssp. traversi on Lake Papaitonga |
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| Powelliphanta traversi | ||||||||||||
| ( Powell , 1930) |
Powelliphanta traversi is the name of a predatory living snail from the family Rhytididae in the subordination of terrestrial snails (gastropod), which in New Zealand is widespread.
features
The surface of the bifurcated, moderately large snail shell of Powelliphanta traversi is dorsally sculpted with tiny wavy spiral strips that end abruptly at the periphery, while the ventral surface is smooth and shiny. The basic color of the house is light greenish-brown, darker on the first curbs and the base, dorsally with a few indistinct traces of spiral bands and ventrally dense with dark brown spiral bands, one or two of which are strong on the periphery and the others are of varying thickness and larger Dense at the navel where they form a dark area. The inside of the case mouth is bluish black. The parietal callus is smooth, dark purple-gray with irregular axial accretions. The surface of the case is yellowish brown, the pale yellowish, the inside of the case mouth dark gray. Dorsally the shell has pale spiral bands and darker brown lines; ventrally it is monochrome. The house of the adult snail has five whorls , of which the Protoconch is roughly striped one and a half whorls. The umbilicus is narrow, about one sixth the large diameter of the base. The case mouth is moon-shaped and oval. The interrupted, thin and downwardly slightly curved edge of the mouth protrudes upwards. The diameters of the house are 49.5 mm to 51.5 mm and 41.5 mm to 43 mm, the height around 28.5 mm to 32 mm. The tooth formula of the radula is 65 + 1 + 65. The teeth are similar to those of Powelliphanta hochstetteri , but the central tooth is significantly shorter than the neighboring lateral teeth. The pale olive brown eggs are 10 to 10.5 mm long and 8 mm wide.
Distribution and occurrence
Powelliphanta traversi is endemic to a small area of the Horowhenua Plains on the North Island of New Zealand around Levin and Shannon between Wellington and Lake Waikaremoana , where its range barely reached an area of 4,000 hectares even before the colonial era. Here there are deep wet soils, which are bounded to the west by sandy dunes , otherwise by swamps with Typha orientalis and Phormium tenax that are too wet for the snails, and to the east by the steep slopes of the Tararua Ranges . It occurs in swampy forests of the lowlands with Laurelia novae-zelandiae , Dacrycarpus dacrydioides and Syzygium maire , but also on somewhat drier soils under Beilschmiedia tawa , Dysoxylum spectabile , Corynocarpus laevigatus and Podocarpus totara . Due to the destruction of these forests, their area is now limited to around 40 hectares on the northeastern shore of Lake Papaitonga , Waiopehu Scenic Reserve and individual residual forests around Levin.
Life cycle
Like other species of the genus Powelliphanta , Powelliphanta traversi is long-lived and only lays a few eggs, which are about 10 mm by 8 mm in size , after the hermaphrodites have fertilized each other .
nutrition
The diet of Powelliphanta traversi consists, like other representatives of the genus Powelliphanta, predominantly of earthworms , which are grasped with the radula and crushed in the foregut with the radula teeth.
Predators and threats
Especially due to the drainage of the wetlands and their conversion into agricultural land by 1900, the stocks of Powelliphanta traversi have declined. Another threat is introduced predatory mammals and birds , especially rats , but also hedgehogs and song thrushes .
Subspecies
There are six subspecies of Powelliphanta traversi . All are classified as threatened by the New Zealand Department of Conservation:
- Powelliphanta traversi florida Powell, 1946 - Nationally Endangered
- Powelliphanta traversi latizona Powell, 1949 - Nationally Endangered
- Powelliphanta traversi koputaroa Powell, 1946 - Nationally Endangered
- Powelliphanta traversi otakia Powell, 1946 - Nationally Critical
- Powelliphanta traversi tararuaensis Powell, 1938 - Nationally Endangered
- Powelliphanta traversi traversi Powell, 1930 - Nationally Endangered
Web links
Individual evidence
- ^ Arthur William Baden Powell (1930): The Paryphantidae of New Zealand: their Hypothetical Ancestry, with descriptions of New Species and a New Genus. Records of the Auckland Institute and Museum 1 (1), pp. 17–56, here pp. 50f.
- ↑ a b c Kath Walker: Recovery plans for Powelliphanta land snails 2003-2013. Threatened Species Recovery Plan 49, 3. The recovery plans. Pp. 23-26.
- ^ AC 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 5 (1945-1946), pp. 54-57.
- ^ Arthur William Baden Powell : New Zealand Mollusca . William Collins Publishers Ltd., Auckland 1979. ISBN 0-00-216906-1
- ^ New Zealand Threat Classification System lists - 2002 - Terrestial (sic) invertebrate - part one. New Zealand Department of Conservation, 2002.