''Achatinella'' is a

tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of colorful

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 ...

s in the

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

Achatinellidae Achatinellidae is a family of tropical air-breathing land snails, terrestrial pulmonate gastropod mollusks in the superfamily Pupilloidea. Taxonomy It was previously the only family in the superfamily Achatinelloidea (according to the taxonom ...

subfamily ''Achatinellinae''. Species are

arboreal Arboreal locomotion is the Animal locomotion, locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally, but others are exclusively arboreal. Th ...

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 ...

mollusk 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 e ...

s with some species called Oʻahu tree snails or kāhuli in the

Hawaiian language Hawaiian (', ) is a Polynesian language of the Austronesian language family that takes its name from Hawaii, the largest island in the tropical North Pacific archipelago where it developed. Hawaiian, along with English, is an official language o ...

. ''Achatinella'' species are all endemic to the island of

Oahu Oahu () (Hawaiian language, Hawaiian: ''Oʻahu'' ()), also known as "The Gathering place#Island of Oʻahu as The Gathering Place, Gathering Place", is the third-largest of the Hawaiian Islands. It is home to roughly one million people—over t ...

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...

, and all remaining

extant Extant is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Extant taxon, a taxon which is not extinct, ...

species are

endangered An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and inva ...

. They were once abundant and were mentioned extensively in Hawaiian folklore and songs, and their shells were used in lei and other ornaments. Many of the species are

sinistral Sinistral and dextral, in some scientific fields, are the two types of chirality ("handedness") or relative direction. The terms are derived from the Latin words for "left" (''sinister'') and "right" (''dexter''). Other disciplines use different ...

or left-handed

chirality Chirality is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is distinguishable from ...

in their

spiral In mathematics, a spiral is a curve which emanates from a point, moving farther away as it revolves around the point. Helices Two major definitions of "spiral" in the American Heritage Dictionary are:shell coiling, whereas most gastropod shells are

dextral Sinistral and dextral, in some scientific fields, are the two types of chirality ("handedness") or relative direction. The terms are derived from the Latin words for "left" (''sinister'') and "right" (''dexter''). Other disciplines use different ...

, with a right handed spiral.

Distribution

There were 41 species of ''Achatinella''

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

to the Hawaiian island of

Oʻahu Oahu () ( Hawaiian: ''Oʻahu'' ()), also known as "The Gathering Place", is the third-largest of the Hawaiian Islands. It is home to roughly one million people—over two-thirds of the population of the U.S. state of Hawaii. The island of O’ ...

, though only 13 species survive. Some species have less than 50 remaining individuals, and others have +300; many species fall in between.

Conservation status

All 13 species are listed under United States federal legislation as

. The

IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

lists a number of ''Achatinella'' species as

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually 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 ...

and the remainder as critically endangered. The main cause of decline has been attributed to over collection. In addition,

invasive species An invasive species otherwise known as an alien is an introduced organism that becomes overpopulated and harms its new environment. Although most introduced species are neutral or beneficial with respect to other species, invasive species ad ...

such as rats,

Jackson's chameleon Jackson's chameleon (''Trioceros jacksonii''), also known as Jackson's horned chameleon, three-horned chameleon or Kikuyu three-horned chameleon, is a species of chameleon (family Chamaeleonidae) native to East Africa, but also introduced to Haw ...

s, and the highly predatory snail ''

Euglandina rosea ''Euglandina rosea'', the rosy wolfsnail or 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.MolluscaBase eds. (2020). Moll ...

'' have been involved in the extinctions and declines of the native tree snails.

Shell description

''Achatinella'' species shells are diverse in patterns, colors, and shapes, but all average about in length. Most have smooth glossy, and oblong or ovate shells 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''. Subgenera 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 is the branch of the visual arts that operates in three dimensions. Sculpture is the three-dimensional art work which is physically presented in the dimensions of height, width and depth. It is one of the plastic arts. Durable sc ...

. 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 Lucius Junius Moderatus Columella (; Arabic: , 4 – ) was a prominent writer on agriculture in the Roman Empire. His ' in twelve volumes has been completely preserved and forms an important source on Roman agriculture, together with the wo ...

bears a strong callous fold. Type species of the genus ''Achatinella'' is ''

Achatinella apexfulva ''Achatinella apexfulva'' is a reportedly extinct species of colorful, tropical, arboreal pulmonate land snail in the family Achatinellidae, once present on Oahu, Hawaii. ''A. apexfulva'' is the type species of the genus ''Achatinella''. The spec ...

'' (Dixon). Subgenus '' Bulimella'' Pfeiffer, 1854: Shell shape is oblong-conic or ovate. The

spire A spire is a tall, slender, pointed structure on top of a roof of a building or tower, especially at the summit of church steeples. A spire may have a square, circular, or polygonal plan, with a roughly conical or pyramidal shape. Spires are ...

is obtuse, rounded or convexly-conic near the

apex The apex is the highest point of something. The word may also refer to: Arts and media Fictional entities * Apex (comics), a teenaged super villainess in the Marvel Universe * Ape-X, a super-intelligent ape in the Squadron Supreme universe *Apex, ...

. The outer lip is thickened by a strong callous rib within the

aperture In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane. An opt ...

(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).

Ecology

Habitat

These snails live in trees. Currently they are only found in mountainous dry to moist forests and shrublands above . Most individuals spend their entire life on just one tree.

Feeding

These tree snails are

nocturnal Nocturnality is an animal behavior characterized by being active during the night and sleeping during the day. The common adjective is "nocturnal", versus diurnal meaning the opposite. Nocturnal creatures generally have highly developed sens ...

, and feed by grazing

fungus A fungus ( : fungi or funguses) is any member of the 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, separately from th ...

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, ...

''. They also feed on

cornstarch Corn starch, maize starch, or cornflour (British English) is the starch derived from corn (maize) grain. The starch is obtained from the endosperm of the kernel. Corn starch is a common food ingredient, often used to thicken sauces or soups, ...

, which can be spread in

terraria ''Terraria'' is an action-adventure sandbox game developed by Re-Logic. The game was first released for Windows on May 16, 2011, and has since been ported to several other platforms. The game features exploration, crafting, building, painting, ...

with water and on cultures of

sooty mold Sooty mold (also spelled sooty mould) is a collective term for different Ascomycete fungi, which includes many genera, commonly ''Cladosporium'' and ''Alternaria''. It grows on plants and their fruit, but also environmental objects, like fences, ...

grown on laboratory

agar Agar ( or ), or agar-agar, is a jelly-like substance consisting of polysaccharides obtained from the cell walls of some species of red algae, primarily from ogonori (''Gracilaria'') and "tengusa" (''Gelidiaceae''). As found in nature, agar is ...

. In captivity,

cuttlebone Cuttlebone, also known as cuttlefish bone, is a hard, brittle internal structure (an internal shell) found in all members of the family Sepiidae, commonly known as cuttlefish, within the cephalopods. In other cephalopod families it is calle ...

is used as a source for

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...

Life cycle

Adult snails are

hermaphroditic In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many taxonomic groups of animals (mostly invertebrates) do not have separ ...

(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 Oʻahu tree snails are predation by the introduced

carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other sof ...

snail ''

'', predation by rats (''

Rattus exulans The Polynesian rat, Pacific rat or little rat (''Rattus exulans''), known to the Māori as ''kiore'', is the third most widespread species of rat in the world behind the brown rat and black rat. The Polynesian rat originated in Southeast Asia, a ...

'', ''

Rattus norvegicus ''Rattus'' is a genus of muroid rodents, all typically called rats. However, the term rat can also be applied to rodent species outside of this genus. Species and description The best-known ''Rattus'' species are the black rat (''R. rattus'') ...

'', ''

Rattus rattus The black rat (''Rattus rattus''), also known as the roof rat, ship rat, or house rat, is a common long-tailed rodent of the stereotypical rat genus ''Rattus'', in the subfamily Murinae. It likely originated in the Indian subcontinent, but is n ...

''), and loss of habitat due to the spread of non-native vegetation into higher elevation forests.

''Trioceros jacksonii'', that was introduced to Hawaii in early 1970s, is a serious threat to ''Achatinella'', because it directly preys on them and on other snails too.Holland B. S., Montgomery S. L. & Costello V. (2010). "A reptilian smoking gun: first record of invasive Jackson’s chameleon (''Chamaeleo jacksonii'') predation on native Hawaiian species". ''

Biodiversity and Conservation ''Biodiversity and Conservation'' is a peer-reviewed scientific journal covering all aspects of biological diversity, its conservation, and sustainable use. It was established in 1992 and is published by Springer Science+Business Media. Abstract ...

'' 19(5): 1437–1441. .Chiaverano L. M. & Holland B. S. (2014). "Impact of an invasive predatory lizard on the endangered Hawaiian tree snail ''Achatinella mustelina'': a threat assessment". ''

Endangered Species Research An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching and invas ...

'' 24: 115-123, . Other predators of ''Achatinella'' include the land

planarian A planarian is one of the many flatworms of the traditional class Turbellaria. It usually describes free-living flatworms of the order Tricladida (triclads), although this common name is also used for a wide number of free-living platyhelmint ...

Platydemus manokwari ''Platydemus manokwari'', also known as the New Guinea flatworm, is a species of large predatory land flatworm. Native to New Guinea, it has been accidentally introduced to the soil of many countries, including the United States. It was als ...

''. Predators of ''Achatinella'': File:Euglandina rosea.jpg, ''

'' File:Rattus rattus03.jpg,

Black rat The black rat (''Rattus rattus''), also known as the roof rat, ship rat, or house rat, is a common long-tailed rodent of the stereotypical rat genus ''Rattus'', in the subfamily Murinae. It likely originated in the Indian subcontinent, but is n ...

File:Starr 030526-0002 Hypochoeris radicata.jpg,

File:Platydemus manokwari.jpg, ''

Hawaiian folklore

According to

Ancient Hawaii Ancient Hawaii is the period of Hawaiian history preceding the unification in 1810 of the Kingdom of Hawaii by Kamehameha the Great. Traditionally, researchers estimated the first settlement of the Hawaiian islands as having occurred sporadicall ...

an folklore, the kāhuli are known as the ''pūpū kani oe'', which translates to "shell that sounds long" or the "singing shell". They are believed to be able vocalize and sing at night. Experts have attributed this association to the chirping of crickets at night when the snails are active. Native Hawaiians used the shells of the snails to create kahuli shell lei and their status as coveted souvenirs in the 19th-century may have contributed to the decline of the species. The summer palace of King

Kamehameha III Kamehameha III (born Kauikeaouli) (March 17, 1814 – December 15, 1854) was the third king of the Kingdom of Hawaii from 1825 to 1854. His full Hawaiian name is Keaweaweula Kīwalaō Kauikeaouli Kaleiopapa and then lengthened to Keaweaweula K� ...

was called

Kaniakapupu Kaniakapūpū ("the singing of the land shells"), known formerly as Luakaha ("place of relaxation"), is the ruins of the former summer palace of King Kamehameha III and Queen Kalama on the island of Oahu in Hawaii. Built in the 1840s, and si ...

("the singing of the land shells") because of the many snails which once inhabited the area during his lifetime.

Species

There are 41 species in the genus ''Achatinella'':

Subgenus ''Achatinella''

* †''

'' (Dixon, 1789) * '' Achatinella cestus'' Newcomb, 1853 * '' Achatinella concavospira'' Pfeiffer, 1859 * †''

Achatinella decora ''Achatinella decora'' is an extinct species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species was endemic to Oahu, Hawaii Hawaii ( ; haw, Hawaii or ) is a state in t ...

'' (Férussac, 1821) * ''

Achatinella leucorraphe ''Achatinella leucorraphe'' is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western U ...

'' (Gulick, 1873) * '' Achatinella lorata'' Férussac, 1824 * '' Achatinella mustelina'' Mighels, 1845 * '' Achatinella swiftii'' Newcomb, 1853 * '' Achatinella turgida'' Newcomb, 1853 * †''

Achatinella valida ''Achatinella valida'' is an extinct species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species was endemic to Oahu, Hawaii Hawaii ( ; haw, Hawaii or ) is a state in t ...

'' Pfeiffer, 1855 * '' Achatinella vittata'' Reeve, 1850

Subgenus ''Bulimella''

* †'' Achatinella abbreviata'' Reeve, 1850 * ''

Achatinella bulimoides ''Achatinella 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 The dextral or sinistral shell is ovate-oblong ...

'' Swainson, 1828 * '' Achatinella byronii'' (

Wood Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic materiala natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin th ...

, 1828) * ''

Achatinella decipiens ''Achatinella decipiens'' is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species is endemic to Hawaii. Cooke considered ''Achatinella decipiens'' to be a subspecies of '' A ...

'' Newcomb, 1854 * †'' Achatinella elegans'' Newcomb, 1853 * ''

Achatinella fuscobasis ''Achatinella 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 The sinistral shell is ovate, with slightly convex whorls ...

'' (E. A. Smith, 1873) * '' Achatinella lila'' Pilsbry, 1914 * '' Achatinella pulcherrima'' Swainson, 1828 * ''

Achatinella pupukanioe ''Achatinella pupukanioe'' is a species of land snail, a gastropod in the family Achatinellidae. It is endemic to Hawaii. Shell description The dextral shell is conic and solid. The shell has six whorls. The glossy color is a uniform white, or i ...

'' Pilsbry & Cooke, 1914 * '' Achatinella sowerbyana'' Pfeiffer, 1855 * '' Achatinella taeniolata'' Pfeiffer, 1846 * '' Achatinella viridans'' Mighels, 1845

Subgenus ''Achatinellastrum''

* ''

Achatinella bellula ''Achatinella 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 The United States of ...

'' E. A. Smith, 1873 * †''

Achatinella buddii ''Achatinella buddii'' is an extinct species of land snail, a gastropod in the family Achatinellidae. It was endemic to Oahu Oahu () ( Hawaiian: ''Oʻahu'' ()), also known as "The Gathering Place", is the third-largest of the Hawaiian Isl ...

'' Newcomb, 1853 * †'' Achatinella casta'' Newcomb, 1853 * †'' Achatinella caesia'' Gulick, 1858 * '' Achatinella curta'' Newcomb, 1853 * †'' Achatinella dimorpha'' Gulick, 1858 * '' Achatinella fulgens'' Newcomb, 1853 * †'' Achatinella juddii'' Baldwin, 1895 * †''

Achatinella juncea ''Achatinella juncea'' is an extinct species of air-breathing land snail, a terrestrial pulmonate gastropod mollusc in the family Achatinellidae. This species was endemic to Oahu, Hawaii Hawaii ( ; haw, Hawaii or ) is a state in ...

'' Gulick, 1856 * †''

Achatinella lehuiensis ''Achatinella lehuiensis'' is an extinct species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species was endemic to Oahu, Hawaii. Subspecies * ''Achatinella lehuiensis mienickei'' ...

'' E. A. Smith, 1873 * †''

Achatinella livida ''Achatinella livida'' is an extinct species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species was endemic to Oahu, Hawaii Hawaii ( ; haw, Hawaii or ) is a state in t ...

'' Swainson, 1828 * †''

Achatinella papyracea ''Achatinella papyracea'' is an extinct species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae. This species was endemic to Oahu, Hawaii Hawaii ( ; haw, Hawaii or ) is a state i ...

'' Gulick, 1856 * '' Achatinella phaeozona'' Gulick, 1856 * †''

Achatinella spaldingi ''Achatinella spaldingi'' is an extinct species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Achatinellidae, now extinct. This species was endemic to Oahu, Hawaii Hawaii ( ; haw, Hawaii or ) ...

'' Pilsbry & Cooke, 1914 * '' Achatinella stewartii'' (Green, 1827) * †''

Achatinella thaanumi ''Achatinella thaanumi'' is an extinct species of air-breathing land snail, a terrestrial pulmonate gastropod mollusc in the family Achatinellidae. This species was endemic to Oahu, Hawaii Hawaii ( ; haw, Hawaii or ) is a state i ...

'' Pilsbry & Cooke, 1914 * ''

Achatinella vulpina ''Achatinella vulpina'' is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusc in the family Achatinellidae. This species is endemic to Hawaii. Shell description The dextral or sinistral shell is ovate-conic, and c ...

'' (Férussac, 1824)

References

This article incorporates public domain text (a

public domain The public domain (PD) consists of all the creative work A creative work is a manifestation of creative effort including fine artwork (sculpture, paintings, drawing, sketching, performance art), dance, writing (literature), filmmaking, ...

work of the United States Government A work of the United States government, is defined by the United States copyright law, as "a work prepared by an officer or employee of the United States Government as part of that person's official duties." "A 'work of the United States Governmen ...

) from reference.

U.S. Fish and Wildlife Service The United States Fish and Wildlife Service (USFWS or FWS) is an agency within the United States Department of the Interior dedicated to the management of fish, wildlife, and natural habitats. The mission of the agency is "working with othe ...

. (1992) Endangered Species Recovery Plan for the O’ahu Tree Snails of the Genus ''Achatinella''. U.S. Fish and Wildlife Service, Portland, Oregon, 64 pp. + 64 pp. of appendices + 5 figures
PDF
Holland, B.S. & M.G. Hadfield. 2002. Islands within an island: phylogeography and conservation genetics of the endangered Hawaiian tree snail Achatinella mustelina. Molecular Ecology 11: 365-375.

External links

* *
Genus profile at U. S. Fish and Wildlife Service

{{Authority control . Gastropod genera Molluscs of Hawaii Endangered fauna of Hawaii Biota of Hawaii (island) Biota of Kauai Biota of Maui Biota of Oahu