Aldabra banded snail
Encyclopedia
The †Aldabra banded snail, scientific name Rhachistia aldabrae, was a species of land snail
, a pulmonate gastropod mollusc in the family Cerastidae
. It lived on one atoll in the Seychelles
Islands, Indian Ocean
, and was easily recognizable because of its purplish blue banded shell
. The species is thought to have died out because of climate change
.
The shell 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.
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 have been found at all since 1997. Researchers believe 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.
.
Land snail
A land snail is any of the many species of snail that live on land, as opposed to those that live in salt water and fresh water. Land snails are terrestrial gastropod mollusks that have shells, It is not always an easy matter to say which species are terrestrial, because some are more or less...
, a pulmonate gastropod mollusc in the family Cerastidae
Cerastidae
Cerastidae is a family of air-breathing land snails, terrestrial pulmonate gastropod mollusks.- Taxonomy :The Cerastidae family is classified within the informal group Orthurethra, itself belonging to the clade Stylommatophora within the clade Eupulmonata .The family Cerastidae has no...
. It lived on one atoll in the Seychelles
Seychelles
Seychelles , officially the Republic of Seychelles , is an island country spanning an archipelago of 115 islands in the Indian Ocean, some east of mainland Africa, northeast of the island of Madagascar....
Islands, Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
, and was easily recognizable because of its purplish blue banded shell
Gastropod shell
The gastropod shell is a shell which is part of the body of a gastropod or snail, one kind of mollusc. The gastropod shell is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage...
. The species is thought to have died out because of climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
.
Description
The shell of this snail was very unusual in its coloring: purple, indigo blue, and orange, and this made the snail very easy to recognize and identify. The Aldabra snail grazed on algae and thus was very low on the food chain.The shell 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
Whorl (mollusc)
A whorl is a single, complete 360° revolution or turn in the spiral growth of a mollusc shell. A spiral configuration of the shell is found in of numerous gastropods, but it is also found in shelled cephalopods including Nautilus, Spirula and the large extinct subclass of cephalopods known as the...
. The upper 3-4 whorls are blackish, the following are dim bluish.
Distribution
The Aldabra banded snail was endemic to AldabraAldabra
Aldabra, the world's second largest coral atoll, is in the Aldabra Group of islands in the Indian Ocean that form part of the Seychelles. Uninhabited and extremely isolated, Aldabra is virtually untouched by humans, has distinctive island fauna including the Aldabra Giant Tortoise, and is...
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 have been found at all since 1997. Researchers believe that this species became extinct during the late 1990s, after a series of unusually long, hot, and dry summers caused by climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
. These summers appear to have killed off a large number of the younger snails.
Cause of extinction
The habitat of this snail suffered a sudden decline in rainfall, which was essential to the survival of this species, and this dryness appears to have caused its extinctionExtinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
.
External links
- Photos of shells of this species (Note: there are spelling errors on the page.)