''Rhachistia aldabrae'', the Aldabra banded snail, is a
species of air-breathing
land snail
A land snail is any of the numerous species of snail that live on land, as opposed to the sea snails and freshwater snails. ''Land snail'' is the common name for terrestrial gastropod mollusks that have shells (those without shells are known as ...
, a
pulmonate
Pulmonata or pulmonates, is an informal group (previously an order, and before that a subclass) of snails and slugs characterized by the ability to breathe air, by virtue of having a pallial lung instead of a gill, or gills. The group includ ...
gastropod
The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda ().
This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...
mollusc
Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...
in the family
Cerastidae. The species lives on one atoll in the
Seychelles Islands,
Indian Ocean, and is easily recognizable for its purplish-blue banded
shell. The species was thought to have died out because of
climate change,
but was rediscovered in 2014.
Description
The shell of this snail is very unusual in its coloring: purple, indigo blue, and orange, and this makes the snail very easy to recognize and identify. The Aldabra snail grazes on algae, and thus it is very low on the food chain.
The shell of this species is oblong, ovate-conical, rather thick, slightly striated, glossy, in the upper part is pale, in the lower part it is black brown.
The shell has seven slightly curved and regularly increasing
whorls.
The upper 3-4 whorls are blackish, the following are dim bluish.
Distribution
The Aldabra banded snail is
endemic to
Aldabra
Aldabra is the world's second-largest coral atoll, lying south-east of the continent of Africa. It is part of the Aldabra Group of islands in the Indian Ocean that are part of the Outer Islands of the Seychelles, with a distance of 1,120 k ...
Atoll in the Indian Ocean. In 1906 it was the most common snail species on the atoll.
After 1976 however, only adult snails were found on Aldabra, and no live individuals had been found at all between 1997 and August 2014.
Researchers had believed that this species became extinct during the late 1990s, after a series of unusually long, hot, and dry summers caused by
climate change. These summers appear to have killed off a large number of the younger snails.
Cause of apparent extinction
The habitat of this snail suffered a sudden decline in rainfall in the 1990s, which was essential to the survival of this species, and this dryness appeared to have caused its
extinction. Living snails were discovered on 23 August 2014.
Rediscovery
A number of specimens of the snail were discovered on August 23, 2014. A team of Seychelles Islands Foundation (SIF) staff were exploring infrequently visited parts of
Malabar Island, the second largest island of Aldabra, when the snails were found. Dr Frauke Fleischer-Dogley, CEO of the CIF, commented:
References
This article incorporates public domain text from the reference.
External links
Photos of shells of this species(Note: there are spelling errors on the page.)
{{Taxonbar, from=Q4713410
Cerastidae