Hemicycla  (Hemicycla saulcyi)

Classified as Critically Endangered (CR) on the IUCN Red List (1).

Rediscovered as recently as 1992, some 150 years after it was first described (3), Hemicycla saulcyi is a medium-sized snail with a dark blue-grey body and a rather attractively marked shell, which is brown with long, irregular white lines that generally run at an angle to the axis of the shell. The shell is more or less spherical, although slightly conical, and the edge of the shell opening (peristome) extends into a well-developed lip (2) (3). Only one subspecies of this snail remains, Hemicycla saulcyi saulcyi; a second, Hemicycla saulcyi carta, is now extinct, and has only been found as fossils (2) (3) (4) (5). H. s. carta differed from H. s. saulcyi mainly in its more solid, wider shell, which had a thicker and wider lip (3).

Hemicycla saulcyi is endemic to Gran Canaria, in the Canary Islands (Spain) (1) (2) (6) (7). The remaining population occupies an area of less than four square kilometres, in La Isleta, just to the north of the capital, Las Palmas de Gran Canaria (2) (3) (4) (5). Fossils of H. s. carta have also been found in the north of the island, between Agaete and La Isleta (2) (3) (4).

This species inhabits a relatively arid area of sparse vegetation and lichen cover on stony-clay soil, at elevations between 120 and 238 metres, with most individuals having been found on north-facing slopes that receive moist sea air. Vegetation in the area includes the spurge Euphorbia aphylla, and shrubs such as Lycium intricatum and Suaeda vera (2) (3) (6).

There is no information currently available on the biology or life history of Hemicycla saulcyi, and only around thirty living specimens have been observed to date (2) (6).

The natural ecosystems of Gran Canaria are highly deteriorated, a situation which has had negative impacts on a variety of endemic species (4). Habitat loss has drastically reduced the range of Hemicycla saulcyi, and the species is now restricted to a small, isolated population occupying a total area of under four square kilometres (2) (4) (5) (6). Most of La Isleta is an old military base, which has so far prevented encroachment by the city of Las Palmas de Gran Canaria. However, this base is being closed, and the likely increase in building and development in the area could be disastrous for this species (2) (5) (7). A further potential threat may come from the spread of introduced snails, which are believed to compete with the endemic snail species, potentially displacing them from some areas (4). Predation by rats, mice and lizards may also be a problem (3).

No species of land snail in the Canary Islands currently receives direct legal protection, and therefore indirect protection through preservation of its habitat will be all the more vital to both Hemicycla saulcyi and other threatened endemic snails (2) (4) (7). It has been recommended that the north-western part of La Isleta be made a Special Nature Reserve, in order to prevent building and development in the area. A Recovery Plan has also been recommended to promote the restoration of the natural vegetation (2) (4). With only around thirty living specimens of Hemicycla saulcyi saulcyi observed to date, the total population may be tiny (2) (6), and, without adequate protection, the future for this highly endangered mollusc is uncertain.

View information on this species at the UNEP World Conservation Monitoring Centre.

To find out more about Hemicycla saulcyi and other threatened wildlife in the Canary Islands, see:

• Atlas of the Threatened Invertebrates of Spain (Atlas de los Invertebrados Amenazados de España - in Spanish):
  http://www.mma.es/portal/secciones/biodiversidad/inventarios/inb/atlas_inverte_amenazados/pdf/hemicycla_saulcyi.pdf
• Evaluation of the Threatened Species of the Canaries (Evaluación de Especies Amenazadas de Canarias - in Spanish):
  http://www.gobiernodecanarias.org/cmayot/medioambiente/medionatural/biodiversidad/especies/catalogodeespeciesamenazadas/index.html