Gastrocopta chichijimana   (Pilsbry)


 
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Chichijima Whorl Snail
(Gastrocopta chichijimana)

 
syn. -

 
distribution:

Japan: Chichijima / Ogasawara Islands

 
local name: -

 
size: 0,24 cm (shell heigth)

extinction date: (?)

 
The reasons for the extinction of the Chichijima Whorl Snail and many other native snail species of the island of Chichijima, are quite easy to find.

At about the middle of the 19th century Japanese settlers begun to cultivate the Ogasawara Islands, which were at that time only sparsely populated, mostly by whalers. During that period, large areas of native vegetation were destroyed and many animal and plant species, both domestic and wild ones, were imported. Later, in the beginning of the 20th century, when the islands where something like Japans biggest agricultural region, Giant East African Snails (Achatina fulica (Bowdich)) were introduced as a food resource.

These snails soon were established and - as in all other places, where they have been introduced, became a pest for agriculture. To stop the uncontrolled spreading of the Giant East African Snails, Rosy Wolf Snails (Euglandina rosea (Férussac)) were introduced to the Ogasawara Islands (to Chichijima in the year 1965), a snail species that has adapted to stalk and kill other snail species.

The worst snail killer, the Snail-eating Land Planarian (Platydemus monokwari (De Beauchamp)), however, was introduced to Chichijima in the 1990s. This creature indeed preys on the Giant East African Snails, on young as well as on adult ones, and it even preys on the Rosy Wolf Snails too. But unfortunately the planarian doesn't make a difference between introduced, invasive species and such that are native or endemic and rare.

This - the destruction of large parts of the native vegetation plus the persecution by introduced predators - are the reasons for the loss of about 70 % of the native or endemic snail species on the island of Chichijima.

 
left:

Chichijima Whorl Snail (Gastrocopta chichijimana)


Depiction from: 'G. W. Tryon; H. A. Pilsbry: Manual of Conchology. Second series: Pulmonata, Vol. 24, 1918-1920'

http://www.biodiversitylibrary.org

 
References:

- Takashi Ohbayashi; Isamu Okochi; Hiroki Sato; Tsuyoshi Ono: Food habit of Platydemus manokwari De Beauchamp, 1962 (Tricladida: Terricola: Rhynchodemidae), known as a predatory flatworm of land snails in the Ogasawara (Bonin) Islands, Japan. Entomology and Zoology 40: 609-614. 2005
- Takashi Ohbayashi, Isamu Okochi, Hiroki Sato; Tsuyoshi Ono; Satoshi Chiba: Rapid decline of endemic snails in the Ogasawara Islands, Western Pacific Ocean. Restoring the Oceanic Island Ecosystem, Part 2: 27-33. 2010