Newcomb's snail
Newcomb's snail | |
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Drawing of Erinna newcombi. | |
Scientific classification | |
Kingdom: | Animalia |
Phylum: | |
Class: | |
(unranked): | clade
Hygrophila |
Superfamily: | |
Family: | |
Genus: | |
Species: | E. newcombi
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Binomial name | |
Erinna newcombi |
Newcomb's snail (Erinna newcombi) is a species of air-breathing
Erinna newcombi is the type species of the genus Erinna.[2]
Taxonomy
The scientific collection efforts of the United States Exploring Expedition of 1838 to 1842 obtained the first known specimens of Newcomb's snails. Historical documents indicate that the specimens were collected sometime between 25 October and 6 November 1840, at "Hanapēpē Falls," presumably what is now called
As
A Japanese lymnaeid exhibits a very similar reduced shell shape, but a study of chromosome numbers suggests that Newcomb's snail's evolutionary ties lie with the rest of the Hawaiian lymnaeids, all of which are derived from North American ancestors. Therefore, it appears that parallel evolution of similar shell morphology occurred between these two distinct lineages of lymnaeid snails.[3]
At the present time, no completely accepted nomenclature exists for the genera of Hawaiian lymnaeids, although each of these snail species, including Newcomb's snail, is recognized as a valid species. Bengt Hubendick (1952) did not believe the distinctive shell form (described below) and reduced structures of the nervous system of Newcomb's snail warranted a genus (second species of the genus Erinna is considered extinct). In fact, Hubendick included all Hawaiian lymnaeids in the genus Lymnaea. Joseph Paul Eldred Morrison (1968) contradicted Hubendick and argued the distinctive shell characters of Newcomb's snail supported the generic name Erinna. John B. Burch (1968), Charlotte M. Patterson and Burch (1978), Dwight Willard Taylor (1988), and Robert H. Cowie et al. (1995) all followed Morrison and referred to Newcomb's snail as Erinna newcombi, which is the currently accepted scientific name.[3]
Description
Newcomb's snail is unique among the Hawaiian
The shell is semi-globose, thin, horny, olivaceous, longitudinally finely striated. The spire is very short, obtuse. The apex is rather eroded. The last whorl is ventricose. The aperture is large and semi-ovate. The inner-lip is posteriorly ascending on the body whorl. The columella is straight, excavated, and with a curved, elevated, external ridge continued in front into the outer lip which is simple and acute.[4]
The jaw is low, wide, slightly arcuate, ends pointed; a decided median projection to the cutting edge. The anterior surface of the jaw is smooth.[5]
The radula is as usual in the Helicidae. The central tooth is long and narrow, small in proportion to the laterals, the reflected portion has one long median cusp, the side cusps being subobsolete. The lateral teeth are wide, broad as long, the reflected portion almost as large as the whole base of attachment, and tricuspid, the inner cusp very small, the median cusp large and bluntly truncated, the outer cusp smaller than the median and bluntly pointed. The marginal teeth are subquadrate, wider than high, the apex reflected, obliquely produced and bearing five or more blunt, short denticles, of which the inner two are the largest.[5]
Distribution
Newcomb's snail is
Until about 1925, snails were collected from small sites located in
Recent survey work conducted from 1994 to 2003, limits the known range of Newcomb's snail to small sites located in a total of six watersheds in north- and east-facing drainages on Kauaʻi. They are: Kalalau Stream, Lumaha`i River, Hanalei River (four subpopulations), Keālia Stream, Makaleha Stream (two subpopulations), and the North Fork Wailua River. The term "
Ecology
Newcomb's snail is an obligate freshwater species. The details of its ecology, such as life span, reproductive cycle, and number of eggs/young, are unknown.[3]
Newcomb's snail is active during the day.[6]
Newcomb's snail probably shares life history similarities with other members of its family. Lymnaeid snails generally feed on
Habitat
On the basis of past and recent field observations, the specific habitat requirements of Newcomb's snail include fast-flowing perennial streams and associated springs, seeps, and vertical or overhanging waterfalls. Surveys of main stream channels of many of the perennial streams of Kaua`i indicate Newcomb's snail is only found in areas protected from high scouring flows within main stream channels. The limited occurrence of this snail in main stream channels is likely due to periodic channel scouring by sediment, rocks, and boulders that are moved downstream during high flow runoff events. Consequently, suitable habitat is generally restricted to protected, small, spring-fed tributaries, or to stream segments with overhanging waterfalls that have perennial flows supported by stable groundwater input. The common element among sites harboring snail populations is that the water source appears to be consistent and permanent, even during severe drought.[3]
Limited to a relatively narrow zone of mid-elevation sites, populations of Newcomb's snail are found at an average elevation of 306 meters (1,005 feet), and range between 196 and 396 meters (643 feet to 1,299 feet).[3]
It is suspected that the four species of introduced caddisflies
Predators
Predation by the non-native rosy glandina snail
Predation on the eggs and adults of native Hawaiian lymnaeid snails by two non-native species of
Several introduced, predatory aquatic species, including the green swordtail fish
Population size
On the basis of these data from the 6 existing populations of Newcomb's snails can be estimated a total population of approximately 6,000 to 7,000 individuals. The great majority of these snails, perhaps over 90%, were located in the two populations at Kalalau and Lumaha`i. Terrain occupied by Newcomb's snail populations is remote and extremely rugged. Three of the six populations can only be visited using helicopter transport, although the Kalalau Stream population potentially could be accessed in summer months with boat support and strenuous hiking. Because of the difficulty in accessing the sites, no comprehensive Newcomb's snail population census has been undertaken since 1995, and changes to the population since that time remain undocumented.[3]
The total area inhabited by Newcomb's snails at any one location is remarkably small, from just 2 square meters (22 square feet; Makaleha waterfall, Hanalei subpopulations) to a maximum of 30 square meters (323 square feet; Makaleha Springs subpopulation). Microhabitat characteristics limiting suitable habitat remain unknown. Because known populations are confined to such small areas, they are highly vulnerable to eradication by unpredictable catastrophic events.
Conservation
Newcomb's snails face a continued threat from human-caused changes to the hydrologic landscape of Kauaʻi, that causes severe degradation of natural aquatic environments. Such changes include large irrigation, extensive plantation style agriculture diverting water out of both surface waterbodies and groundwater sources.[3]
In 1995, prior to Newcomb's snail being listed as threatened, the County of Kaua`i planned a major water diversion project to capture flow from Makaleha Springs for domestic use. The project construction and operation was expected to eliminate the entire subpopulation of Newcomb's snail at Makaleha Springs. The application process was continued by the
Erinna newcombi is listed as vulnerable species in 2006 IUCN Red List[1] and also in 2009 IUCN Red List.[1]
This species is listed as threatened on the
Critical habitat (specific geographic area essential for the conservation) for the Newcomb's snail was designated 20 August 2002. The designation includes eight stream segments and associated tributaries, springs, seeps, and adjacent riparian areas totaling 1,812 hectares (4,479 acres), and including 19.76 kilometers (12.28 mi) of stream channel. Critical habitat for the Newcomb's snail includes the six stream locations known to be occupied and two sites where snails were observed historically but are now thought to be extirpated (Hanakoa Stream and Hanakāpī`ai Stream).[3]
Newcomb's snail is the first and only freshwater organism found in Hawai`i listed under Federal and State law as threatened. The Hawaii Department of Land and Natural Resources, Division of Aquatic Resources is building its capacity to undertake research and implement management directed towards conservation of rare and vulnerable aquatic species such as the Newcomb's snail. Interaction between the State Division of Aquatic Resources management and staff and our endangered species biologists will assist development of an institutional framework to accomplish effective conservation for the Newcomb's snail. To date, no conservation measures have been implemented.[3]
References
This article incorporates public domain text from references
- ^ . Retrieved 16 November 2021.
- ^ Proceedings of the Zoological Society of London. Part XXIII. 119-124.
- ^ U.S. Fish and Wildlife Service (18 September 2006). "Recovery plan for the Newcomb's snail (Erinna newcombi)". U.S. Fish and Wildlife Service, Portland, Oregon. 52 pp.
- ^ a b Adams H. & Adams A. (1858). The genera of recent Mollusca: arranged according to their organization. Volume 2. John Van Voorst, London. p. 644
- ^ .
- ^ (2009). Erinna newcombi – Adams and Adams, 1855. NatureServe Explorer. Data last updated 17 July 2009. Retrieved 3 November 2009.
- ^ (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.
Further reading
- Burch J. B. (1968). "Erinna newcombi of Hawai`i and Limnea onychia of Japan". Malacological Review 1: 15–30.
- Cowie R. H., Evenhuis N. L. & Christensen C. C. (1995). Catalog of the native land and freshwater molluscs of the Hawaiian islands. Backhuys Publishers, Leiden. vi + 248 pp.
- Hubendick B. (1952). "Hawaiian Lymnaeidae". Bishop Museum Occasional Papers 20: 307–328.
- Morrison J. P. E. (1968). "Notes on Hawaiian Lymnaeidae". Malacological Review 1: 31–33.
- Patterson C. M & Burch J. B. (1978). Chapter 4. Chromosomes of pulmonate molluscs. pp. 172–217. In: Fetter V. & Peake J. (eds.) Pulmonates. Vol. 2A. Systematics, Evolution and Ecology. Academic Press, San Francisco.
- Taylor D. W. (1988). "Aspects of freshwater mollusc ecological biogeography". Palaeogeography, Palaeoclimatology, and Palaeoecology 62: 511–576.
- Sharp, David, 1840–1922; Royal Society (Great Britain); British Association for the Advancement of Science; Bernice Pauahi Bishop Museum; p. 393