Achatinella Dimorpha

''Achatinella'' is a tropical genus of colorful land snails in the monotypic Achatinellidae subfamily Achatinellinae.

Species are arboreal pulmonate gastropod mollusks with some species called Oʻahu tree snails or kāhuli in the Hawaiian language.

''Achatinella'' species are all endemic to the island of Oahu in Hawaii, and all remaining extant species are endangered. 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 or left-handed chirality in their spiral shell coiling, whereas most gastropod shells are dextral, with a right handed spiral.

Distribution

There were 41 species of ''Achatinella'' endemic to the Hawaiian island of Oʻahu, 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 endangered. The IUCN lists a number of ''Achatinella'' species as extinct and the remainder as critically endangered. The main cause of decline has been attributed to over collection. In addition, invasive species such as Norway rats, Jackson's chameleons, and the highly predatory snail ''Euglandina rosea'' 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 rainbow.

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. 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).

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, and feed by grazing fungus 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.

Life cycle

Adult snails are hermaphroditic (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 snail ''Euglandina rosea'', by rats (''Rattus exulans'', ''Rattus norvegicus'', ''Rattus rattus''), and loss of habitat due to the spread of non-native vegetation into higher elevation forests.

An additional threat is Jackson's chameleon (''Trioceros jacksonii)'' that were introduced to Hawaii in the early 1970s are a serious threat to ''Achatinella'', because the chameleons directly prey on them and other snails species.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'' 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'' 24: 115-123, . Other predators of ''Achatinella'' include the land planarian ''Platydemus manokwari''.
File:Euglandina rosea.jpg, ''Euglandina rosea''
File:Rattus rattus03.jpg, Black rat
File:Starr 030526-0002 Hypochoeris radicata.jpg, Jackson's chameleon
File:Platydemus manokwari.jpg, ''Platydemus manokwari''

Hawaiian folklore

According to Ancient Hawaiian 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 was called Kaniakapupu ("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'', of which 10 are currently known to be extant:

Subgenus ''Achatinella''

* †'' Achatinella apexfulva'' (Dixon, 1789)
* †'' Achatinella cestus'' Newcomb, 1853
* ''Achatinella concavospira'' Pfeiffer, 1859
* †'' Achatinella decora'' (Férussac, 1821)
* †'' Achatinella leucorraphe'' (Gulick, 1873)
* †'' Achatinella lorata'' Férussac, 1824
* ''Achatinella mustelina'' Mighels, 1845
* †'' Achatinella swiftii'' Newcomb, 1853
* †'' Achatinella turgida'' Newcomb, 1853
* †'' Achatinella valida'' Pfeiffer, 1855
* †'' Achatinella vittata'' Reeve, 1850

Subgenus ''Bulimella''

* †'' Achatinella abbreviata'' Reeve, 1850
* ''Achatinella bulimoides'' Swainson, 1828
* ''Achatinella byronii'' (Wood, 1828)
* ''Achatinella decipiens'' Newcomb, 1854
* †'' Achatinella elegans'' Newcomb, 1853
* ''Achatinella fuscobasis'' (E. A. Smith, 1873)
* ''Achatinella lila'' Pilsbry, 1914
* †'' Achatinella pulcherrima'' Swainson, 1828
* ''Achatinella pupukanioe'' Pilsbry & Cooke, 1914
* ''Achatinella sowerbyana'' Pfeiffer, 1855
* †'' Achatinella taeniolata'' Pfeiffer, 1846
* †'' Achatinella viridans'' Mighels, 1845

Subgenus ''Achatinellastrum''

* †'' Achatinella bellula'' E. A. Smith, 1873
* †'' Achatinella buddii'' 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'' Gulick, 1856
* †'' Achatinella lehuiensis'' E. A. Smith, 1873
* ''Achatinella livida'' Swainson, 1828
* †'' Achatinella papyracea'' Gulick, 1856
* †'' Achatinella phaeozona'' Gulick, 1856
* †'' Achatinella spaldingi'' Pilsbry & Cooke, 1914
* †'' Achatinella stewartii'' (Green, 1827)
* †'' Achatinella thaanumi'' Pilsbry & Cooke, 1914
* †'' Achatinella vulpina'' (Férussac, 1824)

Gallery

Extant species

File:Achatinella bulimoides.jpg, ''Achatinella bulimoides''
File:Naturalis Biodiversity Center - RMNH.MOL.239226 - Achatinella byronii (Wood, 1828) - Achatinellidae - Mollusc shell.jpeg, ''Achatinella byronii''
File:Achatinella concavospira, Palikea, Oahu, Hawaii. DR Sischo.jpg, ''Achatinella concavospira''
File:Naturalis Biodiversity Center - ZMA.MOLL.373485 - Achatinella decipiens Newcomb, 1854 - Achatinellidae - Mollusc shell.jpeg, ''Achatinella decipiens''
File:Naturalis Biodiversity Center - RMNH.MOL.239093 - Achatinella fulgens Newcomb, 1853 - Achatinellidae - Mollusc shell.jpeg, ''Achatinella fulgens''
File:Achatinella fuscobasis 63974826.jpg, ''Achatinella fuscobasis''
File:Achatinella lila 2.jpg, ''Achatinella lila''
File:Achatinella livida Oahu David R. Sischo.jpg, ''Achatinella livida''
File:Achatinella mustelina.jpg, ''Achatinella mustelina''
File:Naturalis Biodiversity Center - RMNH.MOL.239146 - Achatinella sowerbyana Pfeiffer, 1855 - Achatinellidae - Mollusc shell.jpeg, ''Achatinella sowerbyana''

References

This article incorporates public domain text (a public domain work of the United States Government) from reference. U.S. Fish and Wildlife Service. (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.

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''
10331
351.

External links

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Genus profile at U. S. Fish and Wildlife Service

{{Authority control

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Gastropod genera
Molluscs of Hawaii
Endangered fauna of Hawaii
Biota of Hawaii (island)
Biota of Kauai
Biota of Maui
Biota of Oahu
ESA endangered species