Powelliphanta augusta
| Powelliphanta augusta | ||||||||||||
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Powelliphanta augusta |
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| Scientific name | ||||||||||||
| Powelliphanta augusta | ||||||||||||
| Walker , Trewick & Barker , 2008 |
Powelliphanta augusta is the name of a predatory living snail from the family Rhytididae in the subordination of terrestrial snails (gastropod), which in a small area on the former to 2007 by Stockton Mine for coal mining abgebaggerten Mount Augustus on the western slope of the Stockton Plateau near the west coast was common in the north of the South Island of New Zealand . Today there is an offspring project and attempts to release them into the wild in other places.
features
The flattened, round snail shell of Powelliphanta augusta is small with a maximum diameter of 44 mm compared to other species of the genus. It has a raised rounded thread and, without the thread, has an almost rectangular side profile. In adult animals it appears like a corkscrew with a pronounced departure of the body around the horizontal plane. The house of the adult snail, including the protoconch , has about four to five rapidly increasing, slightly inflated, blunt-shouldered coils with a handle. The end seam is indented and has a keeled ridge above the seam around the body. The rather broad, but flat navel only reveals the previous handling and reaches about a fifth of the large case diameter. The thin shell has only a slight layer of lime, but a strong, flexible periostracum . From the protoconch to the periphery, the surface has microscopically narrow spiral lines that make the shell appear dorsally matt. The ventral surface is smooth and shiny. The case mouth is elongated oval with a thin smooth edge. The parietal callus is smooth and pale grayish white. The base color of the shell is old gold with narrow reddish brown spiral lines that are always present on the entire surface, indistinct and sparse below the periphery, but more distinct on the dorsal surface. The spiral lines are superimposed by broad, irregular, mahogany-red axial stripes, which are occasionally so extended over the periphery that they appear like a diffuse whitewash over the entire surface. The axial stripes are more dominant below the periphery and appear alternately as brown and old gold shades. The color of the snail shells varies considerably. North of the northern summit of the Augustus massif, the houses are smaller and darker with a tendency to black, maroon and old gold axial bands, while to the southwest they are larger and lighter in color. The snails on the summit of Mount Augustus have only sparse mars-brown axial bands, narrow reddish brown spiral lines and occasionally a small circular yellow zone around the navel without spiral lines.
The foot of the snail is flesh-colored to light gray with dark slate-gray tints that form a wide-meshed net pattern. The coat is usually pale and the mucus is clear, but both are sometimes a deep dark blue color in young animals. The short, wide tail end of the active snail protrudes only a little from under the shell.
Distribution and occurrence
Powelliphanta augusta was endemic to a small area around the summit of Mount Augustus on the western slope of the Stockton Plateau near the west coast in the north of New Zealand's South Island . Most recently, the snail was found mainly on the northern summit of the Augustus massif at heights of 940 to 980 meters above sea level, but also in places on the ridge and on the slopes to the northwest and southeast. The 1011 m high main peak of Mount Augustus was demolished in 2004 before the snail research. In 2006 and 2007, the last part of Mount Augustus with the summit was dredged by Stockton Mine for coal mining , so that the natural habitat of the snail has been lost.
Powelliphanta augusta lived mainly on moist soils above the gravelly, quartz-rich sandstone of the Augustus massif under dense knee-high vegetation, which ensured a very moist microclimate and, thanks to its productivity, sufficient leaf litter . The snail only lived on the highest peaks, which have now disappeared, at low temperatures with fog and frequent rain at the tree line and above in the litter layer of all possible types of vegetation in a mosaic-like distribution pattern. She seemed complex areas with many plant species from subalpine forest with niedrigwüchsiger Nothofagus solandri , halocarpus biformis , umbellata Metrosideros , longifolium Dracophyllum and Olearia colensoi and shrub land with Leptospermum scoparium , Olearia colensoi Chionochloa flavescens Chionochloa rubra Phormium cookianum Astelia fragrans Dracophyllum uniflorum Pseudopanax linear and Gahnia procera and between shrubland and rush grassland ( tussock ) with Juncus spp., Chionochloa juncea, Celmisia dubia and Leptospermum scoparium . The sandstone was acidic with a pH of 4.3, but less acidic than further north outside the range of the snail with a pH of 4.1.
Life cycle
Powelliphanta augusta , like other lung snails, is a hermaphrodite , in which both partners fertilize each other during mating and then lay eggs. Individuals kept alone, however, were also able to lay eggs, either through sperm stored in the receptaculum seminis or self-fertilization , whereby the fertility of these eggs has not been investigated. In captivity, after mating, the snails lay an average of 2 to 3 eggs with a hard lime shell in the New Zealand spring, usually at the end of September or October, but sometimes as early as August or in the summer months up to March. After mating in captivity, in an experiment from five eggs laid at the end of October and beginning of December, the juvenile snails only hatched in December of the following year or even in the following January, when after 12 to 15 months of development (compared with 2 to 6 months in lowland species of the genus Powelliphanta ). Forty eggs measured outdoors were an average of 8 mm (7 mm to 8.6 mm) long and 6.8 mm (5.5 mm to 7.5 mm) wide. The snail becomes sexually mature with a shell diameter of about 36 mm, but loses fertility with increasing age (i.e. also increasing shell diameter, over 40 mm).
The snails have growth rates of 2.6 mm per year on the shell and reach sexual maturity at the age of 8.
nutrition
Native earthworms have been observed as the natural food of Powelliphanta augusta without the species being determined. In captivity, the animals were fed European earthworms such as Lumbricus rubellus , Aporrectodea caliginosa and Eisenia andrei .
Predators
The predators of Powelliphanta augusta on the Augustus massif were the indigenous Wekaralle ( Gallirallus australis ) as well as imported climbing sacs ( Trichosurus vulpecula ), rats ( Rattus rattus ) and song thrushes ( Turdus philomelos clarkei ).
Discovery, first description, destruction and offspring
The Powelliphanta snails on Mount Augustus were discovered in 1996 by members of the Botanical Society of Nelson , but initially assigned to Powelliphanta patrickensis , which was previously known in the region . A new investigation in 2003 indicated a species of its own, but the New Zealand Department of Conservation (DOC ) only became aware of this in 2004, which initially assumed that the total population of the species would be less than 1000 snails.
The Stockton Plateau with the former Mount Augustus is the property of the state-owned coal -Konzerns Solid Energy New Zealand Ltd. When the snail species was discovered, large parts of the Augustus massif and thus the assumed original distribution area had already been eroded. Since 2004 the plans of the group had been to dredge the remaining area of Mount Augustus for hard coal extraction. Environmentalists formed the Save Happy Valley Coalition and ran a campaign to try to stop these plans. At the same time, the biologists Kath J. Walker, Steven A. Trewick and Gary M. Barker used the time to examine the snails on the then remaining mountain ridge and to publish an initial description of the species Powelliphanta augusta in 2008. In May 2005 Solid Energy applied to the New Zealand nature conservation authority DOC for permission to transfer Powelliphanta snails from the proposed mining area and, regardless of the outcome of the application, prepared the mining work. The nature conservation association Royal Forest and Bird Protection Society of New Zealand ( Forest and Bird for short ) took legal action against it and was able to obtain a court decision from the High Court in December 2005 that the nature conservation minister and the energy minister both a snail transfer and the transport of heavy machinery for would first have to agree to mining in the area. Such permission was granted in April 2006 but what of Forest and Bird , Save Happy Valley Coalition and the Green Party of New Zealand ( Green Party of Aotearoa New Zealand ) was sentenced. Forest and Bird in particular questioned the chances of success of a relocation campaign with reintroduction in another habitat. The nature conservation authority DOC maintained a special breeding center in Hokitika about 200 km south of Mount Augustus, to which more than 6000 snails and 1000 eggs from Mount Augustus were brought between July 2006 and June 2007. However, a small residual population remained on the slopes of the eroded Mount Augustus below the mining zone.
In early December 2006, twenty snails were moved from the original to a nearby location outside the mine. In mid-December 2006 one of these snails found an empty shell. In April 2010, according to the Department of Conservation, there were 1,552 snails in their cooling units in Hokitika.
In August 2010, Rod Morris, who had visited the resettlement sites northwest of the destroyed Mount Augustus, reported in the conservation magazine Forest and Bird on the situation of Powelliphanta Augusta . The soil and vegetation had also been transferred. The larger trees were now dead, and neophytes such as gorse ( Ulex ) and rushes ( Juncus ) had invaded. The once complex mosaic of dense, low subalpine shrubs and deep undisturbed leaf litter no longer existed in his opinion. 1,600 snails had been brought here from the refrigeration units of the nature conservation authority in Hokitika and a further 2,300 snails to two other locations near Mount Rochfort . 50 snails were provided with transponders at each of the three locations . After 18 months, 30% of these snails, which had otherwise lived for many years, were dead. According to Landcare Research , these snail populations have no chance of survival at such a mortality rate. Investigations at the release sites indicated after 5 years, however, that the survival rates were consistently over 80% and that there were stable populations that were growing in places. According to Mark Patrick Hamilton, a reliable assessment of the success of the reintroductions can only be made after decades.
While a total of around 4,000 snails were released into the wild, around 810 snails of around 1,600 Powelliphanta augusta individuals kept in the facility in Hokitika died in one of the three refrigeration units, which rose from the intended 10 ° C to 0 , due to a technical failure in November 2011 ° C and in which only a single animal survived. In its magazine of the same name, the nature conservation organization Forest and Bird spoke of a tragedy that could have been avoided. After this disaster, the keeping of snails was changed from individual keeping to groups of up to 6 snails in order to promote pairings and offspring. In 2012, a total of 1200 juvenile snails hatched in the facility in Hokitika, so that in June 2013 the snail population there was again around 2000 snails with a survival rate of around 90%. Young snails are fed four small European earthworms per month and adult snails six adult European earthworms as food. In total, around 11,600 earthworms per month have to die for snail food in the facility for Powelliphanta augusta .
literature
- Kath J. Walker, Steven A. Trewick, Gary M. Barker (2008): Powelliphanta augusta, a new species of land snail, with a description of its former habitat, Stockton coal plateau, New Zealand. Journal of the Royal Society of New Zealand 38 (3), pp. 163-186.
Web links
Individual evidence
- ^ A b Mark Patrick Hamilton: Monitoring Powelliphanta land snails: an assessment of the current technique and the development of a new mark-recapture technique. Master of Science thesis, Victoria University of Wellington, 2015. pp. Iv, 117, 121.
- ↑ a b c Thomas Edward Allan: Husbandry of the Carnivorous Land Snail, Powelliphanta augusta (Gastropoda: Pulmonata: Rhytdidae). Master of Science thesis, Victoria University of Wellington, 2010. pp. 1f.
- ^ High risk land snail translocation. TerraNature Inc, April 12, 2006.
- ↑ Permits approved to move Mt Augustus snails. NZ Government press release, April 12, 2006.
- ↑ Carter signs off on species extinction. Save Happy Valley Coalition, April 12, 2006.
- ^ Snails sold out by State to Solid Energy. ( Memento of the original from June 30, 2006 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. Green Party of Aotearoa New Zealand, April 12, 2006.
- ↑ Kim Fulton: Buller snails going strong. NZPA, The New Zealand Herald, October 3, 2013.
- ↑ One of 20 relocated snails found eaten. Stuff.co.nz, Fairfax Media NZ Ltd, December 19, 2006.
- ↑ At least one rare snail eat at mine. NZPA, The New Zealand Herald, December 18, 2006.
- ↑ Kiran Chug: Dam solution cold comfort for endangered snails. The Dominion Post, Fairfax Media NZ Ltd, April 10, 2010.
- ↑ Rod Morris: An unfortunate experiment. Forest and Bird 337, pp. 14-18. The Royal Forest and Bird Protection Society, August 2010.
- ↑ Kathy Marks: Breeders shellshocked as snail trail goes cold. The Independent, November 11, 2011.
- ↑ Snail fridge deaths an avoidable tragedy. Forest and Bird, Jan. November 2011. "Nature conservation organization Forest & Bird is devastated that 800 native giant land snails from the West Coast have died in a Department of Conservation fridge."
- ↑ DOC Accidentally Kills 800 Rare Powelliphantia Snails. Stuff, November 10, 2011.
- ↑ Deidre Mussen: Rescue a triumph for conservation. Stuff.co.nz, Fairfax Media NZ Ltd, June 22, 2013.
