Achatinella apexfulva is an 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 specific name, apexfulva, meaning "yellow-tipped", refers to the yellow tip of the snail's shell. Inspired from the taxon, the species has been given common names such as yellow-tipped O'ahu tree snail or Hawaiian yellow-tipped tree snail. The last known member of the species, George, died in captivity in 2019.

Taxonomy The family Achatinellidae, to which Achatinella apexfulva belongs, represents a diverse adaptive radiation. All species of tree-snail in Hawaii are believed to have come from a single ancestral snail. How that ancestral snail made the trip across the ocean is unknown. A longstanding theory is that a bird carried a notably smaller ancestor across the ocean and dropped it on the islands, as bird mediated dispersal has been documented in other snail species. Alternative theories include that it floated across the ocean on a mat of debris, or that it island-hopped across the Pacific in a combination of the theories. Within the Achatinellidae, A. apexfulva belongs to the Oahu clade, which evolved on Oahu island and includes most other members of the genus Achatinella.

Subspecies

Achatinella apexfulva alba Sykes, 1900 Achatinella apexfulva albipraetexta Welch, 1942 Achatinella apexfulva albofasciata (E. A. Smith, 1873) Achatinella apexfulva aloha Pilsbry & C. M. Cooke, 1914 Achatinella apexfulva apexfulva (G. Dixon, 1789) Achatinella apexfulva apicata L. Pfeiffer, 1856 Achatinella apexfulva aureola Welch, 1942 Achatinella apexfulva bakeri Welch, 1942 Achatinella apexfulva bruneola Welch, 1942 Achatinella apexfulva brunosa Welch, 1942 Achatinella apexfulva buena Welch, 1942 Achatinella apexfulva cervixnivea Pilsbry & C. M. Cooke, 1914 Achatinella apexfulva cestus Newcomb, 1854 Achatinella apexfulva chromatacme Pilsbry & C. M. Cooke, 1914 Achatinella apexfulva cinerea Sykes, 1900 Achatinella apexfulva coniformis (Gulick, 1873) Achatinella apexfulva cookei D. D. Baldwin, 1895 Achatinella apexfulva duplocincta Pilsbry & C. M. Cooke, 1914 Achatinella apexfulva ewaensis Welch, 1942 Achatinella apexfulva flavida (Gulick, 1873) Achatinella apexfulva flavitincta Welch, 1942 Achatinella apexfulva forbesiana L. Pfeiffer, 1855 Achatinella apexfulva fumositincta Welch, 1942 Achatinella apexfulva fuscostriata Welch, 1942 Achatinella apexfulva glaucopicta Welch, 1942 Achatinella apexfulva globosa L. Pfeiffer, 1855 Achatinella apexfulva griseibasis Welch, 1942 Achatinella apexfulva gulickii (E. A. Smith, 1873) Achatinella apexfulva hanleyana L. Pfeiffer, 1856 Achatinella apexfulva ihiihiensis Welch, 1942 Achatinella apexfulva innotabilis (E. A. Smith, 1873) Achatinella apexfulva irwini Pilsbry & C. M. Cooke, 1914 Achatinella apexfulva kahukuensis Pilsbry & C. M. Cooke, 1914 Achatinella apexfulva kawaiiki Welch, 1942 Achatinella apexfulva laurani Welch, 1942 Achatinella apexfulva lemkei Welch, 1942 Achatinella apexfulva leucorraphe (Gulick, 1873) Achatinella apexfulva leucozona (Gulick, 1873) Achatinella apexfulva lilacea (Gulick, 1873) Achatinella apexfulva lineipicta Welch, 1942 Achatinella apexfulva meadowsi Welch, 1942 Achatinella apexfulva muricolor Welch, 1942 Achatinella apexfulva napus L. Pfeiffer, 1855 Achatinella apexfulva nigripicta Welch, 1942 Achatinella apexfulva oioensis Welch, 1942 Achatinella apexfulva oliveri Welch, 1942 Achatinella apexfulva ovum L. Pfeiffer, 1857 Achatinella apexfulva paalaensis Welch, 1942 Achatinella apexfulva parvicolor Welch, 1942 Achatinella apexfulva paumaluensis Welch, 1942 Achatinella apexfulva perplexa Pilsbry & C. M. Cooke, 1914 Achatinella apexfulva pilsbryi Welch, 1942 Achatinella apexfulva poamohoensis Welch, 1942 Achatinella apexfulva polymorpha (Gulick, 1873) Achatinella apexfulva punicea Welch, 1942 Achatinella apexfulva roseata Welch, 1942 Achatinella apexfulva roseipicta Welch, 1942 Achatinella apexfulva rubidilinea Welch, 1942 Achatinella apexfulva rubidipicta Welch, 1942 Achatinella apexfulva simulacrum Pilsbry & C. M. Cooke, 1914 Achatinella apexfulva simulans Reeve, 1850 Achatinella apexfulva simulator Pilsbry & C. M. Cooke, 1914 Achatinella apexfulva steeli Welch, 1942 Achatinella apexfulva suturafusca Welch, 1942 Achatinella apexfulva suturalba Welch, 1942 Achatinella apexfulva tuberans (Gulick, 1873) Achatinella apexfulva versicolor (Gulick, 1873) Achatinella apexfulva vespertina D. D. Baldwin, 1895 Achatinella apexfulva virgatifulva Welch, 1942 Achatinella apexfulva vittata Reeve, 1850 Achatinella apexfulva wahiawa Welch, 1942 Achatinella apexfulva waialaeensis Welch, 1942 Achatinella apexfulva wailelensis Welch, 1942 Achatinella apexfulva waimaluensis Welch, 1942

Description A. apexfulva was a small snail, with a shell measuring 19 mm in length and 12 mm in diameter.

The original description of subspecies A. apexfulva cestus, by Wesley Newcomb, provided: The shell is solid and ventricose, tapering to a sharp point at the summit. It may be either sinistral or dextral in its spiral and is composed of six rounded whorls. These whorls are corded along their upper edges, and the body whorl is notably tumid, forming the bulk of the structure.

The aperture is subovate in shape, leading to a short columella that features a strong, prominent tubercle. The outer lip is slightly expanded and thickened within.

The coloration of the shell is striking and complex. While the tip is a deep black, the second and third whorls are a clean white. The final three whorls exhibit a range of colors — white, yellowish, or black — often appearing in a mixed pattern. A white cincture traverses the sutures and cuts across the body whorl just below the center, sometimes accompanied by a broader band further down. The surface is occasionally shows bold blotches, black-and-white tessellations, or longitudinal undulating lines. The columella is a rich chestnut brown, a color mirrored on the lip, though the latter is frequently interrupted by splashes of white.

The original description of subspecies A. apexfulva cestus, by J. T. Gulick, provided: The shell is dextral and shaped into a short, ovate cone. It is marked by fine growth lines rather than spiral striations, giving the surface a distinct texture. The base color is a muted gray, adorned with irregularly interrupted streaks of deep ash-gray and a few indistinct, white spiral lines.The suture is framed by a broad, snowy-white margin. There are 6 1/2 whorls in total; while the apex is blackish, the first four whorls are white and relatively flat, while the remaining whorls are noticeably convex.The aperture is small and shaped somewhat like an ear, revealing a clean white interior. The peristome, or outer lip, is slightly dilated and thickened within. Finally, the columellar fold is large and tinted with a vibrant rose-pink.

Biology It was a hermaphrodite, having both male and female reproductive organs. They bore live young.

Ecology While A. apexfulva lived on the leaves of trees, it was not herbivorous. Its diet consisted of algae and mold that it ate off leaves. It lived in small packs. It consumed microscopic algae, fungi and detritis on leaf or bark surfaces. It was sedentary.

Distribution This species was endemic to forests of the island of Oahu in the Hawaiian archipelago, United States.

Conservation status

A. apexfulva is presumed extinct. It was listed as federally endangered since 1981. A major cause of its population decline in the wild was predation by the rosy wolfsnail. The rosy wolfsnail, a central-American native, was introduced to Hawaii in the 1950s to control agricultural pests. However, as a carnivore of other snails it does not discriminate in its choice of food and has been the cause of at least eight other snail extinctions in Hawaii.Kurt Auffenberg & Lionel A. Stange (November 2001). "Snail-eating snails of Florida, Gastropoda". University of Florida. EENY251. Retrieved 7 October 2012.

Other causes of the snail's decline included loss of habitat due to deforestation, introduction of rats, and the introduction of Jackson's chameleon. The problems that A. apexfulva faced are not unique: estimated extinction rates in the family Achatinellidae range between 75% and 90%. The International Union for Conservation of Nature's last study on A. apexfulva was conducted in 1996 and listed the species as critically endangered.

In 1997, in response to rapidly dwindling populations, all known remaining specimens of A. apexfulva were collected and bred in captivity. Most offspring died of unknown causes, but one successful offspring was born. This individual was named George, after Lonesome George, a Pinta Island tortoise from the Galapagos Islands who was also the last of his kind. By April 2011, George was the only remaining member of the species.Thom van Dooren (2013) "The last snail: conservation and extinction in Hawaiʻi" 28 February 2013. Retrieved 8 January, 2016. In January 2019, George died at age 14 leaving the species reportedly extinct.

Notes

External links

Picture of living Achatinella apexfulva

References

Cowie, R. H., Evenhuis, N. L. & Christensen, C. C. (1995). Catalog of the native land and freshwater molluscs of the Hawaiian Islands. vi + 248 pp. Leiden: Backhuys Publishers.