Newcomb's Snail

Erinna newcombi

Description

The Newcomb's snail has a smooth, black shell formed by a single, oval whorl, about 0.25 in (6 mm) long and 0.12 in (3 mm) wide. The other three Hawaiian species in the family Lymnaeidae have a more slender, tapering shape of their shell.

Behavior

The Newcomb's snail probably feeds on algae and vegetation growing on submerged rocks. Its eggs are attached to submerged rocks or plants. Its entire life cycle occurs in local freshwater.

Habitat

The Newcomb's snail inhabits tropical, freshwater, perennial, fast-flowing streams with overhanging rocks, springs, rock seeps, and waterfalls. It occurs in small feeder streams, seeps, and waterfalls, rather than in the more erosive, main channel of larger streams.

Distribution

The Newcomb's snail is an endemic (or locally evolved) species that only occurs on the island of Kauai.

Threats

The Newcomb's snail is limited to six stream systems, each of which supports a single population.Five of these populations were discovered before 1925. Of these, only two populations still exist, and only one (Kalalau) is relatively large (Waipahee is much smaller). Since 1990, surveys of more 46 potential habitats have located four additional populations, three of which are small (Hanalei, Makaleha, and Wailua) and one large (Lumahai; as many as about 75 snails/square foot (800 snails/ square meter). The total population of the Newcomb's snail has been estimated as 6,000 to 7,000 individuals, of which about 90% occur in the two large populations at Kalalau and Lumahai. A serious ongoing threat is predation by the introduced rosy glandina snail (Euglandina rosea ). It may also be threatened by other introduced invertebrate predators and parasites, by the non-native green sword-tail (a fish; Xyphophorus helleri ), and by two introduced frogs. Some of the known habitats of the Newcomb's snail are potentially threatened by water development and diversion projects. Because of the few populations of generally small size, the Newcomb's snail is also potentially threatened be events of severe weather, such as a hurricane or extended drought.

Conservation and Recovery

All six of the known populations of Newcomb's snail occur in streams in conservation areas managed by the State of Hawaii primarily for watershed protection, mostly to supply water for municipal, agricultural, and cultural use. However, the existing permitting process for water use lacks requirements for the protection of threatened aquatic species, although the state government is taking actions to change this circumstance. In addition, a task force advising the government has recommended that several streams be given "heritage" status, including some of the Kauai streams of Newcomb's snail. This would provide the designated streams with a higher level of protection. However, the recommendations have not yet been adopted by the government. Actions needed to conserve the Newcomb's snail include the strict protection of its known critical habitats, and research into its biology and the deleterious effects of introduced predators and parasites, and into the means of controlling those biological damages.

Contacts

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
(503) 231-6121
http://pacific.fws.gov/

U. S. Fish and Wildlife Service
Pacific Islands Ecoregion
300 Ala Moana Boulevard, Room 3-122
P. O. Box 50088
Honolulu, Hawaii 96850-5000
Telephone: (808) 541-3441
Fax: (808) 541-3470

Reference

U. S. Fish and Wildlife Service. 26 January 2000. "Endangered and Threatened Wildlife and Plants: Determination of Threatened Status for Newcomb's Snail From the Hawaiian Islands." Federal Register 65 (17): 4162-4169.