O'ahu tree snail
Encyclopedia
Oahu tree snails, genus
Achatinella, are a large genus of colorful, tropical, tree-living, air-breathing, land snail
s, arboreal pulmonate gastropod mollusks in the family Achatinellidae
.
This genus of tree snails live in Hawaii, and all are endangered species
. They were once abundant. They were mentioned in Hawaiian folklore and songs, and their shells were used in lei
and other ornaments.
Many of these arboreal snails are sinistral or left-handed in their spiral
shell coiling, whereas most gastropod shells are dextral. (See the section on chirality
in the article gastropod shell
.)
to Hawaiian island of O`ahu. About hundred of each specie is left.
federal legislation as endangered
. The IUCN lists a number of these species as extinct
and the remainder as critically endangered.
which show a variety of colors, including yellow, orange, red, brown, green, gray, black, and white.
There are three recognized subgenera within the genus Achatinella. Subnenera are distinguished according to shells characteristics only.
Genus Achatinella Swainson, 1828: The dextral or sinistral shell is imperforate or minutely perforate, oblong, ovate or globose-conic; smooth or
longitudinally corrugated, with only weak traces of spiral sculpture
. Shell color is in spiral bands or streaks in the direction of the growth lines. The lip is simple or thickened within and sometimes slightly expanding. The columella bears a strong callous fold. Type species of the genus Achatinella is Achatinella apexfulva
(Dixon).
Subgenus Bulimella Pfeiffer, 1854: Shell shape is oblong-conic or ovate. The spire
is obtuse, rounded or convexly-conic near the apex
. The outer lip is thickened by a strong callous rib within the aperture
(except in Achatinella abbreviata
and Achatinella lila
). Type species of the subgenus Bulimella is Achatinella byronii
Newcomb.
Subgenus Achatinellastrum Pfeiffer, 1854: The shell is imperforate, ovate-conic or oblong-conic and smooth. The embryonic whorls
are not flattened. The outer lip is thin or only slightly thickened within the apex but not expanded. These are the most generally distributed of
the Achatinella species and show a prolific area of intergrading color patterns. Type species of the subgenus Achatinellastrum is Achatinella stewartii
(Green, 1827).
to moist forests and shrublands above 1300 ft (396.2 m).
which grows on the surface of native plant leaves.
Although these tree snails are occasionally found on introduced plants, it is unknown whether or not the fungus which grows on these plants can provide long-term support for healthy breeding populations of these snails.
In captivity Achatinella feed on fungus growing on leaves of Metrosideros polymorpha
. They also feed on cornstarch
, which can be spread in terraria with water and on cultures of sooty mold
grown on laboratory agar
. In captivity, cuttlebone
is used as a source for calcium
.
(having both male and female reproductive organs) and can live for many years. These are live bearing snails (give birth to live snails instead of laying eggs).
The most serious threats to the survival of Oahu tree snails are predation by the introduced carnivorous
snail Euglandina rosea
, predation by rat
s, and loss of habitat due to the spread of non-native vegetation into higher elevation forests.
subgenus Achatinella
subgenus Bulimella
subgenus Achatinellastrum
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Achatinella, are a large genus of colorful, tropical, tree-living, air-breathing, land snail
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...
s, arboreal pulmonate gastropod mollusks in the family Achatinellidae
Achatinellidae
Achatinellidae is a family of tropical air-breathing land snails, terrestrial pulmonate gastropod mollusks in the superfamily Achatinelloidea.- Taxonomy :...
.
This genus of tree snails live in Hawaii, and all are endangered species
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
. They were once abundant. They were mentioned in Hawaiian folklore and songs, and their shells were used in lei
Lei (Hawaii)
Lei is a Hawaiian word for a garland or wreath. More loosely defined, a lei is any series of objects strung together with the intent to be worn. The most popular concept of a lei in Hawaiian culture is a wreath of flowers draped around the neck presented upon arriving or leaving as a symbol of...
and other ornaments.
Many of these arboreal snails are sinistral or left-handed in their spiral
Spiral
In mathematics, a spiral is a curve which emanates from a central point, getting progressively farther away as it revolves around the point.-Spiral or helix:...
shell coiling, whereas most gastropod shells are dextral. (See the section on chirality
Chirality
Chirality is a property of asymmetry important in several branches of science. It may refer to:* Chirality , a property of molecules having a non-superimposable mirror image...
in the article gastropod 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...
.)
Distribution
There are 40 species of Oahu tree snail endemicEndemic (ecology)
Endemism is the ecological state of being unique to a defined geographic location, such as an island, nation or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. For example, all species of lemur are endemic to the...
to Hawaiian island of O`ahu. About hundred of each specie is left.
Conservation status
All 40 species are listed under United StatesUnited States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
federal legislation as endangered
Endangered species
An endangered species is a population of organisms which is at risk of becoming extinct because it is either few in numbers, or threatened by changing environmental or predation parameters...
. The IUCN lists a number of these species as extinct
Extinction
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...
and the remainder as critically endangered.
Shell description
Oahu tree snails are diverse in patterns, colors, and shapes, but all average about 0.75 in (1.9 cm) in length. Most have smooth glossy, and oblong or ovate shellsGastropod 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...
which show a variety of colors, including yellow, orange, red, brown, green, gray, black, and white.
There are three recognized subgenera within the genus Achatinella. Subnenera are distinguished according to shells characteristics only.
Genus Achatinella Swainson, 1828: The dextral or sinistral shell is imperforate or minutely perforate, oblong, ovate or globose-conic; smooth or
longitudinally corrugated, with only weak traces of spiral sculpture
Sculpture (mollusc)
The sculpture of a mollusc shell is the three-dimensional ornamentation on the outer surface, as distinct from the basic shape of the shell itself or colouration. Sculpture may be concave as well as convex. Sometimes it has microscopic detail. Sculpture refers to the calcareous outer layer, not the...
. Shell color is in spiral bands or streaks in the direction of the growth lines. The lip is simple or thickened within and sometimes slightly expanding. The columella bears a strong callous fold. Type species of the genus Achatinella is Achatinella apexfulva
Achatinella apexfulva
Achatinella apexfulva is a species of colorful, tropical, tree-living, air-breathing, land snail, an arboreal pulmonate gastropod mollusk in the family Achatinellidae.Achatinella apexfulva is the type species of the genus Achatinella....
(Dixon).
Subgenus Bulimella Pfeiffer, 1854: Shell shape is oblong-conic or ovate. The spire
Spire (mollusc)
A spire is a descriptive term for part of the coiled shell of mollusks. The word is a convenient aid in describing shells, but it does not refer to a very precise part of shell anatomy: the spire consists of all of the whorls except for the body whorl...
is obtuse, rounded or convexly-conic near the apex
Apex (mollusc)
Apex is an anatomical term for the tip of the mollusc shell of a gastropod, scaphopod, or cephalopod mollusc.-Gastropods:The word "apex" is most often used to mean the tip of the spire of the shell of a gastropod...
. The outer lip is thickened by a strong callous rib within the aperture
Aperture (mollusc)
The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where part of the body of the animal emerges for locomotion, feeding, etc....
(except in Achatinella abbreviata
Achatinella abbreviata
† Achatinella abbreviata, an Oahu tree snail, was a species of colorful tropical tree-living air-breathing land snail, an arboreal pulmonate gastropod mollusk in the genus Achatinella.-Shell description :...
and Achatinella lila
Achatinella lila
Achatinella lila is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to the Hawaii, the United States.-Shell description :...
). Type species of the subgenus Bulimella is Achatinella byronii
Achatinella byronii
Achatinella byronii is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to the United States.Achatinella byronii is the type species of the subgenus Bulimella....
Newcomb.
Subgenus Achatinellastrum Pfeiffer, 1854: The shell is imperforate, ovate-conic or oblong-conic and smooth. The embryonic whorls
Protoconch
A protoconch is an embryonic or larval shell of some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod...
are not flattened. The outer lip is thin or only slightly thickened within the apex but not expanded. These are the most generally distributed of
the Achatinella species and show a prolific area of intergrading color patterns. Type species of the subgenus Achatinellastrum is Achatinella stewartii
Achatinella stewartii
Achatinella stewartii is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to Hawaii....
(Green, 1827).
Habitat
These snails live in trees. Currently they are only found in mountainous dryHawaiian tropical dry forests
The Hawaiian tropical dry forests are a tropical dry broadleaf forest ecoregion in the Hawaiian Islands. They cover an area of on the leeward side of the main islands and the summits of Niihau and Kahoolawe. These forests are either seasonal or sclerophyllous. Annual rainfall is less than and...
to moist forests and shrublands above 1300 ft (396.2 m).
Feeding
These tree snails are nocturnal, and feed by grazing fungusFungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
which grows on the surface of native plant leaves.
Although these tree snails are occasionally found on introduced plants, it is unknown whether or not the fungus which grows on these plants can provide long-term support for healthy breeding populations of these snails.
In captivity Achatinella feed on fungus growing on leaves of Metrosideros polymorpha
Metrosideros polymorpha
The ōhia lehua is a species of flowering evergreen tree in the myrtle family, Myrtaceae, that is endemic to the six largest islands of Hawaii. It is a highly variable tree, being tall in favorable situations, and much smaller when growing in boggy soils or on basalt...
. They also feed on cornstarch
Cornstarch
Corn starch, cornstarch, cornflour or maize starch is the starch of the corn grain obtained from the endosperm of the corn kernel.-History:...
, which can be spread in terraria with water and on cultures of sooty mold
Sooty mold
Sooty molds are Ascomycete fungi which grow on plant exudates and the sugary honeydew secreted by insects such as aphids, scales, the whitefly, and other insects which suck sap from their host plants. The name itself is descriptive, as sooty mold is a black, powdery coating adhering to the leaves...
grown on laboratory agar
Agar
Agar or agar-agar is a gelatinous substance derived from a polysaccharide that accumulates in the cell walls of agarophyte red algae. Throughout history into modern times, agar has been chiefly used as an ingredient in desserts throughout Asia and also as a solid substrate to contain culture medium...
. In captivity, cuttlebone
Cuttlebone
Cuttlebone, also known as cuttlefish bone, is a hard, brittle internal structure found in all members of the family Sepiidae, commonly known as cuttlefish....
is used as a source for calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
.
Life cycle
Adult snails are hermaphroditicHermaphrodite
In biology, a hermaphrodite is an organism that has reproductive organs normally associated with both male and female sexes.Many taxonomic groups of animals do not have separate sexes. In these groups, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which both...
(having both male and female reproductive organs) and can live for many years. These are live bearing snails (give birth to live snails instead of laying eggs).
Predation and other threats
Because growth rate and fertility are very low, these snails are especially vulnerable to loss of individuals through human collection, through predation, or because of other disturbances.The most serious threats to the survival of Oahu tree snails are predation by the introduced carnivorous
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
snail Euglandina rosea
Euglandina rosea
Euglandina rosea, common names the "rosy wolfsnail" or the "cannibal snail", is a species of medium-sized to large predatory air-breathing land snail, a carnivorous terrestrial pulmonate gastropod mollusk in the family Spiraxidae.-Distribution:...
, predation by rat
Rat
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...
s, and loss of habitat due to the spread of non-native vegetation into higher elevation forests.
Species
There are 40 species in the genus Achatinella:subgenus Achatinella
- Achatinella apexfulvaAchatinella apexfulvaAchatinella apexfulva is a species of colorful, tropical, tree-living, air-breathing, land snail, an arboreal pulmonate gastropod mollusk in the family Achatinellidae.Achatinella apexfulva is the type species of the genus Achatinella....
(Dixon, 1789) - Achatinella cestusAchatinella cestusAchatinella cestus is a species ofair-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to the United States....
Newcomb, 1853 - Achatinella concavospiraAchatinella concavospiraAchatinella concavospira is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to Hawaii....
Pfeiffer, 1859 - Achatinella decoraAchatinella decora† Achatinella decora was a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species was endemic to Hawaii....
(Férussac, 1821) - extinct - Achatinella leucorraphe (Gulick, 1873)
- Achatinella lorataAchatinella lorataAchatinella lorata is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to Hawaii....
Férussac, 1824 - Achatinella mustelinaAchatinella mustelinaAchatinella mustelina is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to the Waianae Range of the island of Oahu, Hawaii....
Mighels, 1845 - Achatinella swiftiiAchatinella swiftiiAchatinella swiftii is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to Hawaii....
Newcomb, 1853 - Achatinella turgidaAchatinella turgidaAchatinella turgida is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to Hawaii....
Newcomb, 1853 - Achatinella validaAchatinella valida† Achatinella valida was a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species was endemic to Hawaii....
Pfeiffer, 1855 - extinct - Achatinella vittata Reeve, 1850
subgenus Bulimella
- Achatinella abbreviataAchatinella abbreviata† Achatinella abbreviata, an Oahu tree snail, was a species of colorful tropical tree-living air-breathing land snail, an arboreal pulmonate gastropod mollusk in the genus Achatinella.-Shell description :...
Reeve, 1850 - extinct - Achatinella bulimoidesAchatinella bulimoidesAchatinella bulimoides is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to Hawaii.-Shell description :...
Swainson, 1828 - Achatinella byroniiAchatinella byroniiAchatinella byronii is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to the United States.Achatinella byronii is the type species of the subgenus Bulimella....
(Wood, 1828) - Achatinella decipiensAchatinella decipiensAchatinella decipiens is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to the Hawaii....
Newcomb, 1854 - Achatinella fuscobasisAchatinella fuscobasisAchatinella fuscobasis is a species of air-breathing land snail, a terrestrial pulmonate gastropod in the family Achatinellidae. This species is endemic to Hawaii.-Shell description :...
(E. A. Smith, 1873) - Achatinella lilaAchatinella lilaAchatinella lila is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to the Hawaii, the United States.-Shell description :...
Pilsbry, 1914 - Achatinella pulcherrimaAchatinella pulcherrimaAchatinella pulcherrima is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to the United States....
Swainson, 1828 - Achatinella pupukanioeAchatinella pupukanioeAchatinella pupukanioe is a species of land snail, a gastropod in the Achatinellidae family. It is endemic to Hawaii.-Shell description :...
Pilsbry & Cooke, 1914 - Achatinella sowerbyanaAchatinella sowerbyanaAchatinella sowerbyana is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to Hawaii.-Shell description :...
Pfeiffer, 1855 - Achatinella taeniolataAchatinella taeniolataAchatinella taeniolata, an O'ahu tree snail, is a species of colorful, tropical, tree-living, air-breathing land snail, an arboreal pulmonate gastropod mollusk in the family Achatinellidae....
Pfeiffer, 1846 - Achatinella viridansAchatinella viridansAchatinella viridans is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to the United States.-Shell description :...
Mighels, 1845 - Achatinella elegansAchatinella elegansAchatinella elegans was a species of a land snail, gastropod in the Achatinellidae family. It was endemic to Hawaii.-Shell description :...
Newcomb, 1853 - extinct
subgenus Achatinellastrum
- Achatinella bellulaAchatinella bellulaAchatinella bellula is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to the Hawaiian island of Oahu in the United States. No more than five specimens have been observed since 1979....
E. A. Smith, 1873 - Achatinella buddiiAchatinella buddiiAchatinella buddii was a species of land snail, a gastropod in the Achatinellidae family. It was endemic to Hawaii.-References:* Mollusc Specialist Group 1996. . Downloaded on 06 August 2007....
Newcomb, 1853 - extinct - Achatinella castaAchatinella casta†Achatinella casta was a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species was endemic to Hawaii.-References:* Mollusc Specialist Group 1996. . Downloaded on 6 August 2007....
Newcomb, 1853 - extinct - Achatinella caesiaAchatinella caesia†Achatinella caesia was a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species was endemic to the United States....
Gulick, 1858 - extinct - Achatinella curtaAchatinella curtaAchatinella curta is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to the United States....
Newcomb, 1853 - Achatinella dimorphaAchatinella dimorpha† Achatinella dimorpha was a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species was endemic to the United States....
Gulick, 1858 - extinct - Achatinella fulgensAchatinella fulgensAchatinella fulgens is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to the Hawaii....
Newcomb, 1853 - Achatinella juddiiAchatinella juddii† Achatinella juddii was a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species was endemic to Hawaii....
Baldwin, 1895 - extinct - Achatinella junceaAchatinella juncea† Achatinella juncea was a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species was endemic to Hawaii....
Gulick, 1856 - extinct - Achatinella lehuiensisAchatinella lehuiensis† Achatinella lehuiensis was a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species was endemic to Hawaii.- Subspecies :* Achatinella lehuiensis mienickei Pilsbry & Cooke, 1921...
E. A. Smith, 1873 - extinct - Achatinella lividaAchatinella livida† Achatinella livida was a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species was endemic to Hawaii....
Swainson, 1828 - extinct - Achatinella papyraceaAchatinella papyracea† Achatinella papyracea was a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species was endemic to Hawaii....
Gulick, 1856 - extinct - Achatinella phaeozonaAchatinella phaeozonaAchatinella phaeozona is a species of air-breathing tree snail, an arboreal pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to Hawaii....
Gulick, 1856 - Achatinella spaldingiAchatinella spaldingi† Achatinella spaldingi was a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae, now extinct. This species was endemic to Hawaii....
Pilsbry & Cooke, 1914 - extinct - Achatinella stewartiiAchatinella stewartiiAchatinella stewartii is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to Hawaii....
(Green, 1827) - Achatinella thaanumiAchatinella thaanumi† Achatinella thaanumi was a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species was endemic to Hawaii....
Pilsbry & Cooke, 1914 - extinct - Achatinella vulpinaAchatinella vulpinaAchatinella vulpina is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to Hawaii....
(Férussac, 1824)
Further reading
- Bland T. & Binney W. G. (1874) "On the lingual dentition and anatomy of Achatinella and other Pulmonata". Annals of the Lyceum of Natural History of New York. 10: 331-351.