O'ahu tree snail

Oahu tree snails are a large group of colorful tropical tree-living air-breathing land snails, arboreal pulmonate gastropod mollusks in the genus Achatinella. They live in Hawaii, and they are all endangered.

Oahu tree snails 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.

Distribution

There are around 40 species of Oahu tree snail endemic to Hawaiian island of O`ahu.

Conservation status

All 40 species are listed under United States federal legislation as endangered. The IUCN lists a number of these species as extinct and the remainder as critically endangered.

Shell description

Oahu tree snails are diverse in patterns, colors, and shapes, but all average about 3/4 inch 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.

Habitat

These snails are found on trees. Currently they are only found in mountainous dry to wet forests and shrublands above 1,300 feet.

Life habits

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.

Reproduction

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 Oahu tree snails are predation by the introduced carnivorous snail (Euglandina rosea), predation by rats, and loss of habitat due to the spread of non-native vegetation into higher elevation forests.

Species

• Achatinella abbreviata
• Achatinella apexfulva
• Achatinella bellula
• Achatinella buddii
• Achatinella bulimoides
• Achatinella byronii
• Achatinella caesia
• Achatinella casta
• Achatinella clausinus
• Achatinella concavospira
• Achatinella curta
• Achatinella decipiens
• Achatinella decora
• Achatinella dimorpha
• Achatinella dolium
• Achatinella faba
• Achatinella fulgens
• Achatinella fuscobasis
• Achatinella juddii
• Achatinella juncea
• Achatinella lehuiensis
• Achatinella lila
• Achatinella livida
• Achatinella lorata
• Achatinella mustelina
• Achatinella papyracea
• Achatinella phaeozona
• Achatinella pulcherrima
• Achatinella pupukanioe
• Achatinella solitaria
• Achatinella sowerbyana
• Achatinella spaldingi
• Achatinella stewartii
• Achatinella taeniolata
• Achatinella thaanumi
• Achatinella turgida
• Achatinella valida
• Achatinella vestita
• Achatinella viridans
• Achatinella vulpina

References

• U.S. Fish and Wildlife Service