|Scientific Name:||Erinna newcombi|
|Species Authority:||Adams, 1855|
|Taxonomic Notes:||Considered under the genus Lymnaea by Hubendick (1952), but most other researchers support placement under Erinna.|
|Red List Category & Criteria:||Vulnerable B1ab(iii,v) ver 3.1|
|Assessor(s):||Smith, R. (data provider) & Seddon, M.B. (Mollusc Specialist Group)|
|Reviewer(s):||Cowie, R., Miller, S., Seddon, M.B. & Smith, R. (Mollusc Red List Authority)|
Erinna newcombi meets Vulnerable B1ab(iii). The species is found only in remote waterfalls, seeps and springs of six stream systems on the Hawaiian island of Kauai. Extent of occurrence estimated to be less than 20,000 km² (VU B1). It is known to exist at fewer than 10 locations (VU B1a), with a predicted continuing decline in habitat quality as a result of invasive alien species (VU B1b(iii)).
|Range Description:||E. newcombi is found only in remote waterfalls, seeps, and springs of six stream systems on the Hawaiian island of Kauai. Each stream supports a single subpopulation of Newcomb's snail (USFWS listing). These subpopulations are located in the Hanalei River, Kalalau Stream, the Lumahai River, the North Fork of the Wailua River, Makaleha Stream and Waipahee Stream. Makaleha and Waipahee Streams both flow into Kapaa Stream.|
Native:United States (Hawaiian Is.)
|Range Map:||Click here to open the map viewer and explore range.|
The population falls into two groups: subpopulations first observed prior to 1925 and subpopulations observed since 1993. Five subpopulations were identified prior to 1925. Three of these (Wainiha, Hanakapiai, and Hanakoa) no longer exist. Of the two remaining pre-1925 subpopulations, one (Waipahee) is small and the other (Kalalau) is relatively large (see below). These data indicate that the number of Newcomb's snail subpopulations has been greatly reduced since 1925, perhaps by as much as 60 percent.
Since 1990, surveys of at least 46 streams, tributaries and springs on Kauai have located four previously unknown subpopulations of Newcomb's snail. Three of these are small (see below), and the fourth subpopulation has been described as large.
USFWS cite information estimating that the six known subpopulations of Newcomb’s snail include a total of approximately 6,000 to 7,000 individuals. Most of these, perhaps more than 90 percent, occur in two of the subpopulations, making the species vulnerable to random events such as hurricanes that could destroy entire subpopulations of the snail. The small sizes of four of the six subpopulations and limited distribution make them vulnerable to extinction from reduced reproductive vigour or from random environmental events.
|Habitat and Ecology:||
The species occurs in fast flowing perennial streams with stable overhanging rocks, springs, rock seeps, and waterfalls (Michael Kido, University of Hawaii, in litt. 1994; Stephen Miller, U.S. Fish and Wildlife Service, pers. obs. 1994).
This small snail spends its entire life cycle in the same stream system, as do other Hawaiian lymnaeids but unlike other freshwater Hawaiian snails in the family Neritidae, which have marine larvae that colonize streams following a period of oceanic dispersal (Kinzie 1990). Historic dispersal probably relied on long-term erosion events that captured adjacent stream systems. Newcomb’s snails generally feed on algae and vegetation growing on submerged rocks.
The direct impact of a variety of intentional and accidental introductions of non-native fish, snails, flies, and frogs threaten the survival of Newcomb’s snail. The most serious threat is predation from Euglandina rosea (the rosy wolf snail), introduced to Hawaii in 1955. This species can apparently fully submerge itself underwater to eat aquatic snails such as the Newcomb’s snail and has had a serious impact on native snail species on many islands throughout the Pacific.
Two species of marsh flies prey upon eggs and adults of Hawaiian freshwater snails. The marsh flies were introduced in 1958 and 1966 as biological control agents for a non-native snail that is an intermediate host of the cattle liver fluke. Other introduced predators include the green swordtail, a fish introduced to Hawaii in 1922 to control mosquitoes; the American bullfrog (first recorded in 1867); and the wrinkled frog (first seen in 1896). The two frog species were accidental introductions.
Other threats include potential water development projects that could affect the fresh water springs providing the species’ habitat.
|Conservation Actions:||On January 26, 2000, the U.S. Fish and Wildlife Service (USFWS) designated Newcomb's snail as Threatened in the Entire Range. USFWS, under the Endangered Species Act, will bring together a team of biologists to develop a recovery plan that will identify steps to be taken to recover the species, including habitat restoration and control of alien species.|
|Citation:||Smith, R. (data provider) & Seddon, M.B. (Mollusc Specialist Group) 2003. Erinna newcombi. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 06 July 2015.|