Achatinella

Oʻahu tree snails, genus Achatinella, form a large genus of colorful, tropical, tree-living, air-breathing, land snails, arboreal pulmonate gastropod mollusks in the family Achatinellidae. This genus of tree snails is endemic to Hawaii, and all 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 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.) There are 41 species of Oʻahu tree snail endemic to Hawaiian island of Oʻahu. All are endangered, there being only about hundred individuals of each species left. All 41 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. In many cases, the introduced and highly predatory snail Euglandina rosea has been involved in the extinctions and declines of the native tree snails. Oʻahu 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 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 orlongitudinally 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).