Stylodonta unidentata

Status_ne_offStatus_dd_offStatus_lc_offStatus_nt_offStatus_vu_onStatus_en_offStatus_cr_offStatus_ew_offStatus_ex_off

Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA MOLLUSCA GASTROPODA STYLOMMATOPHORA ACAVIDAE

Scientific Name: Stylodonta unidentata
Species Authority: (Holten, 1802)
Taxonomic Notes: Six subspecies of this snail are recongized:

Stylodonta unidentata unidentata (Holten, 1802)
Stylodonta unidentata sebertae Gerlach, 2003
Stylodonta unidentata pyramidata (Pfeiffer, 1841)
Stylodonta unidentata globata (Martens, 1869)
Stylodonta unidentata praslina Gerlach, 2003
Stylodonta unidentata parva Gerlach, 2003

Assessment Information [top]

Red List Category & Criteria: Vulnerable B2ab(iii) ver 3.1
Year Published: 2009
Date Assessed: 2006-01-11
Assessor(s): Gerlach, J.
Reviewer(s): Miller, R.M., Pollock, C.M. & Seddon, M.B.
Justification:
While populations of this species are stable, the species has a limited range (AOO = 87 km²; it is found in 8 locations) and there is ongoing deterioration in habitat quality throughout this range due to invasion by introduced plants, especially Cinnamomum verum.

Geographic Range [top]

Range Description:This snail species is endemic to the Seychelles. It is found on the islands of Mahé, Therèse, Conception, Silhouette, Praslin, Curieuse, La Digue and Felicite; it has become extinct on the island of St. Anne. Its total area of occupancy (AOO) is 87 km². Most of the populations on the different islands represent different subspecies; the distribution and the area of occupancy (AOO) of each is as follows:

S. u. unidentata: North Mahé, St. Anne (extinct), Therèse and Conception; AOO = 22 km²
S. u. sebertae: West Mahé; AOO = 11 km²
S. u. pyramidata: South Mahé; AOO = 22 km²
S. u. globata: Silhouette; AOO = 19 km²
S. u. praslina: Praslin and Curieuse; AOO = 8 km²
S. u. parva: La Digue; AOO = 5 km²
Countries:
Native:
Seychelles (Seychelles (main island group))
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population: The total population size of this species has been estimated to be 7.2 million individuals, though some subspecies are much more abundant than others. The numbers of individuals of each subspecies is estimated to be:

S. u.unidentata: 145,000
S. u. sebertae: 1,000
S. u. pyramidata: 15,000
S. u. globata: 7 million
S. u. praslina: 700
S. u. parva: 50,000

This snail's populations are considered to be stable.
Population Trend: Stable

Habitat and Ecology [top]

Habitat and Ecology: This snail is a terrestrial lowland forest species, found in leaf litter, and is one of the most important detritivores in the forest ecosystem. It does not lay eggs, but rather gives birth to live young.
Systems: Terrestrial

Threats [top]

Major Threat(s): It is threatened on Mahé and Praslin islands by habitat degradation caused by invasive exotic plants, especially Cinnamomum verum, and predation by the Common Tenrec (Tenrec ecaudatus), a small mammal that was introduced to the Seychelles. Small-scale farming and wood plantations have threatened this snail's habitat in the past.

Conservation Actions [top]

Conservation Actions: Some populations are protected in Morne Seychellois National Park (S. u. unidentata) and Praslin National Park (S. u. praslina). The other subspecies require the protection of Mt. Sebert on Mahé island (S. u. sebertae); the La Reserve/Brullee area on Mahé island (S. u. pyramidata); Silhouette island (S. u. globata); and the summit of La Digue (S. u. parva).

Bibliography [top]

Gerlach, J. 2003. New terrestrial Gastropoda (Mollusca) from Seychelles. Phelsuma 11: 39-51.

Gerlach, J., Matyot, P. and Samways, M.J. 2005. Developing strategies for invertebrate conservation, the case of the Seychelles islands. Phelsuma: 9-12.

IUCN. 2009. IUCN Red List of Threatened Species (ver. 2009.2). Available at: www.iucnredlist.org. (Accessed: 3 November 2009).


Citation: Gerlach, J. 2009. Stylodonta unidentata. In: The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 23 July 2014.
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