Newcomb's snail
Encyclopedia
Newcomb's snail, scientific name Erinna newcombi, is a species of air-breathing freshwater snail
, a gastropod mollusk in the family Lymnaeidae
. This species is endemic to Hawaii, in the United States
. Its natural habitat
is river
s. It is threatened by habitat loss.
Erinna newcombi is the type species
of the genus Erinna
.
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 Historical documents indicate that the specimens were collected sometime between 25 October and 6 November 1840, at "Hanapēpē Falls," presumably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 Manuwaiopuna Falls, or possibly one of several other waterfalls located in the middle Hanapēpē watershed of southeast Kauaʻi. Individuals from this early collection made their way to the British Museum of Natural History and were used as the type specimens from which the species was later described in 1855.
As type locality is referred: "Heneta River, Kami, Sandwich Islands", which means Hanalei River
, Kauai, Hawaii. English common name
and also specific name is in honor of Dr. Wesley Newcomb
, that collected them in Hawaii.
Erinna newcombi is one of four species of Lymnaeidae snails are native to Hawaii. Three of these species inhabit two or more of the eight main islands. The fourth species, Newcomb's snail, is restricted to the island of Kauaʻi.
A Japanese lymnaeid exhibits a very similar reduced shell shape, but a study of chromosome
numbers suggests that Newcomb's snail's evolution
ary 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.
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 bellow) 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.
spire
typically associated with lymnaeids is substantially reduced. The result is a nearly smooth, brown to black shell formed by a single, oval whorl
, 6 mm (0.25 inch) long and 3 mm (0.12 inch) wide.
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.
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.
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.
Newcomb's snail is endemic and restricted to the island of Kauaʻi. A number of very large watersheds traverse the southeast quadrant of the Kauaʻi island, including Olokele Stream, Hanapēpē Stream and Waimea River, all of which have numerous tributaries. No recent surveys for Newcomb's snails have been undertaken in the Hanapēpē watershed, or in any of the large neighboring stream systems, because they are located on privately owned lands
and are difficult to reach because of the rough terrain. It is possible that Newcomb's snail populations remain in that region of Kauaʻi.
Until about 1925, snails were collected from small sites located in Kalalau Stream, Hanakoa Stream, Hanakāpī`ai Stream, Wainiha River, and Keālia Stream. Three of these populations (Hanakoa Stream, Hanakāpī`ai Stream, Wainiha River) are now thought to be extirpated. Since about 1993, Federal and State agencies, academic researchers, and other interested parties have conducted opportunistic surveys at approximately 50 sites along numerous streams and their associated tributaries and springs on Kaua'i, and have located four previously unknown populations of Newcomb's snail. These recently discovered populations are located in Lumaha`i River, the Hanalei River
, Makaleha Stream (a tributary to Kapa`a Stream), and the North Fork Wailua River
. With the exception of the snails at Makaleha Springs, most of these populations have only been observed once or twice. Recently, two individual snails were reported from a single site in Limahuli Stream in the Hanalei District of Kauaʻi's north shore. However, if a viable population of Newcomb's snail exists in the Limahuli watershed, its location remains unknown, therefore Limahuli Stream is not considered to have a "population
" of Newcomb's snails.
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 "subpopulation" refers to a discreet group of individuals, separated from other discrete groups within a single watershed
. Because of low mobility
, no interaction between subpopulations exists. No historical information is available on the population size
s of Newcomb's snail. However, anecdotal reports indicate the Kalalau Stream and Lumaha`i River populations of Newcomb's snails are larger in comparison to the other four.
unknown.
Newcomb's snail is active during the day.
Newcomb's snail probably shares life history similarities with other members of its family. Lymnaeid snails generally feed on algae
and vegetation growing on submerged rocks. Snails attach eggs to submerged rocks or vegetation and larval stages do not disperse widely; the entire life cycle is tied to the stream system in which the adults live. Little is known about the biological or environmental factors affecting Newcomb's snail population size, however, important factors may include: annual, multi-year, or decadal changes in stream flows; severe weather, high flow, or channel-scouring events; and periods of prolonged drought. Snail dispersal
both upstream and downstream within a stream system probably plays an important function in colonizing or recolonizing suitable habitat, particularly microhabitat protected from channel scour. Dispersal of Newcomb's snail between stream systems is likely infrequent because of their obligate freshwater habitat requirements; historic dispersal probably relied on long-term erosional events that captured adjacent stream systems. This life history differs greatly from the freshwater Hawaiian neritid snails (Neritina granosa
, Neritina vespertina) that have marine larvae that migrate into and up streams following a period of oceanic dispersal. Most likely, the planktonic larvae of the neritid snails disperse across the oceanic expanses that separate the main Hawaiian Islands and can colonize streams on any or all of these islands. Newcomb's snail lacks this dispersal capacity.
s 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.
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).
It is suspected that the four species of introduced caddisflies Trichoptera
are adversely impacting native aquatic invertebrate populations either through competition
for space and resources, or because of its large body size and sheer abundance in Hawaiian streams. For example a single caddisfly species accounted for 57% of all biota collected in the upper elevation Kauaʻi streams.
Predation by the non-native rosy glandina snail Euglandina rosea
remains a serious threat to the survival of Newcomb's snail. This predatory snail, introduced into Hawai`i in 1955, has established populations throughout the main islands. The rosy glandina feeds on snails and slugs, and field studies document that it readily feeds on native snails found in Hawai`i. Furthermore the rosy glandina snail exhibits remarkable hunting behaviors leading to capture and predation of submerged prey. Although terrestrial, the rosy glandina will fully immerse itself in water to locate and feed on aquatic molluscs such as Newcomb's snail. The rosy glandina has been observed on the wet, algae-covered rocks of the Makaleha Stream in close proximity to individual Newcomb's snails, and is believed to prey on them. The rosy glandina snail is responsible for the extirpation
of many populations and even the extinction of numerous species of native snails throughout the Pacific Islands
, and represents a significant threat to the survival of Newcomb's snail.
Predation on the eggs and adults of native Hawaiian lymnaeid snails by two non-native species of sciomyzid flies marsh fly Sepedomerus macropus and Sepedon aenescens represents a significant threat to the survival of Newcomb's snail. They feed on lymnaeid snails and were introduced into Hawaii in 1958 and 1966, respectively. These predatory flies were intended to act as biological control agents for the non-native lymnaeid snail Fossaria viridis and for another non-native lymnaeid snail Galba viridis (an intermediate host of the cattle liver fluke Fasciola gigantica
). These biological control species may represent a significant threat to Newcomb's snail and other native lymnaeid snails.
Several introduced, predatory aquatic species, including the green swordtail fish Xyphophorus helleri, the American bullfrog Rana catesbiana, the wrinkled frog Rana rugosa, and the cane toad Bufo marinus potentially threaten populations of Newcomb's snail. All potentially prey on the Newcomb's snail.
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.
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. Flooding due to hurricanes and tropical storms, catastrophic landslide
s, drought, infestation by introduced invasive species
, and other localized phenomena that occur unpredictably could eradicate Newcomb's snail habitat across significant portions of the island. Recent examples of such recurring natural events include Hurricane Iniki
(a Category IV hurricane that devastated
Kaua`i on 11 September 1992), Hurricane Iwa
(23 November 1982), and the large upper Olokele Valley landslide of 31 October 1981. Each of these events greatly impacted and may have eliminated large areas of unsurveyed potential Newcomb's snail habitat. Any recovery planning effort must take the island-wide distribution of Newcomb's snails into account to ensure maintenance of separate populations in watersheds geographically distributed throughout the island.
natural aquatic environments. Such changes include large irrigation, extensive plantation style agriculture diverting water out of both surface waterbodies and groundwater sources.
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 Kaua`i Board of Water Supply and cleared a number of State and local regulatory reviews. Ultimately, the State Commission on Water Resource Management denied the applicable permits on the basis of numerous unresolved environmental issues, including impacts to aquatic life.
Erinna newcombi is listed as vulnerable species
in 2006 IUCN Red List
and also in 2009 IUCN Red List.
This species is listed as threatened on the United States Fish and Wildlife Service list of endangered species
under the authority of the Endangered Species Act
of 1973, since 26 January 2000. Such Hawaiian species are automatically added to the State of Hawaii's list of protected species.
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 kilometres (12.3 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).
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.
Freshwater snail
A freshwater snail is one kind of freshwater mollusc, the other kind being freshwater clams and mussels, i.e. freshwater bivalves. Specifically a freshwater snail is a gastropod that lives in a watery non-marine habitat. The majority of freshwater gastropods have a shell, with very few exceptions....
, a gastropod mollusk in the family Lymnaeidae
Lymnaeidae
Lymnaeidae is a taxonomic family of small to large air-breathing freshwater snails, aquatic pulmonate gastropod mollusks, that belong to the clade Hygrophila....
. This species is endemic to Hawaii, in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
. Its natural habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
is river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
s. It is threatened by habitat loss.
Erinna newcombi is the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
of the genus Erinna
Erinna (gastropod)
Erinna is a genus of air-breathing, freshwater snails, aquatic pulmonate gastropod mollusks in the family Lymnaeidae, the pond snails. This genus is endemic to the Hawaiian Islands, United States.- Species :Species within the genus Erinna include:...
.
Taxonomy
The scientific collection efforts of the United States Exploring ExpeditionUnited States Exploring Expedition
The United States Exploring Expedition was an exploring and surveying expedition of the Pacific Ocean and surrounding lands conducted by the United States from 1838 to 1842. The original appointed commanding officer was Commodore Thomas ap Catesby Jones. The voyage was authorized by Congress in...
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 Manuwaiopuna Falls, or possibly one of several other waterfalls located in the middle Hanapēpē watershed of southeast Kauaʻi. Individuals from this early collection made their way to the British Museum of Natural History and were used as the type specimens from which the species was later described in 1855.
As type locality is referred: "Heneta River, Kami, Sandwich Islands", which means Hanalei River
Hanalei River
The Hanalei River on the island of Kauai in Hawaii flows north from the eastern slopes Mount Waialeale for until entering the Pacific Ocean at Hanalei Bay as an estuary...
, Kauai, Hawaii. English common name
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
and also specific name is in honor of Dr. Wesley Newcomb
Wesley Newcomb
Wesley Newcomb was an American Physician and malacologist specializing in land snails.-Life:Wesley Newcomb was born in New York 20 October 1808. His father was physician Simon Newcomb...
, that collected them in Hawaii.
Erinna newcombi is one of four species of Lymnaeidae snails are native to Hawaii. Three of these species inhabit two or more of the eight main islands. The fourth species, Newcomb's snail, is restricted to the island of Kauaʻi.
A Japanese lymnaeid exhibits a very similar reduced shell shape, but a study of chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
numbers suggests that Newcomb's snail's evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
ary 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.
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 bellow) and reduced structures of the nervous system
Nervous system of gastropods
The nervous system of gastropods consists of a series of paired ganglia connected by major nerve cords, and a number of smaller branching peripheral nerves.The brain of a gastropod consists of three pairs of ganglia, all located close to the oesophagus...
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
Lymnaea
Lymnaea is a genus of small to large-sized air-breathing freshwater snails, aquatic pulmonate gastropod mollusks in the family Lymnaeidae, the pond snails.Lymnaea is the type genus of the family Lymnaeidae.-Species:...
. 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
John B. Burch
John Bayard Burch is an American zoologist, a biology professor at the University of Michigan, and is the Curator of Mollusks at the University of Michigan Museum of Zoology. His research interests are broad, and have encompassed not only the anatomy, systematics, and genetics of mollusks, but...
(1968), Charlotte M. Patterson and Burch (1978), Dwight Willard Taylor
Dwight Willard Taylor
Dwight Willard Taylor was an American malacologist and paleontologist, a researcher on mollusks. His undergraduate work was at the University of California, Berkeley and his PhD was from Harvard University....
(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.
Description
Newcomb's snail is unique among the Hawaiian lymnaeids in that the shellGastropod shell
The gastropod shell is a shell which is part of the body of a gastropod or snail, one kind of mollusc. The gastropod shell is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage...
spire
Spire (mollusc)
A spire is a descriptive term for part of the coiled shell of mollusks. The word is a convenient aid in describing shells, but it does not refer to a very precise part of shell anatomy: the spire consists of all of the whorls except for the body whorl...
typically associated with lymnaeids is substantially reduced. The result is a nearly smooth, brown to black shell formed by a single, oval whorl
Whorl (mollusc)
A whorl is a single, complete 360° revolution or turn in the spiral growth of a mollusc shell. A spiral configuration of the shell is found in of numerous gastropods, but it is also found in shelled cephalopods including Nautilus, Spirula and the large extinct subclass of cephalopods known as the...
, 6 mm (0.25 inch) long and 3 mm (0.12 inch) wide.
The shell is semi-globose, thin, horny, olivaceous, longitudinally finely striated. The spire is very short, obtuse. The apex
Apex (mollusc)
Apex is an anatomical term for the tip of the mollusc shell of a gastropod, scaphopod, or cephalopod mollusc.-Gastropods:The word "apex" is most often used to mean the tip of the spire of the shell of a gastropod...
is rather eroded. The last whorl
Body whorl
Body whorl is part of the morphology of a coiled gastropod mollusk.- In gastropods :In gastropods, the body whorl, or last whorl, is the most recently-formed and largest whorl of a spiral or helical shell, terminating in the aperture...
is ventricose. The aperture
Aperture (mollusc)
The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where part of the body of the animal emerges for locomotion, feeding, etc....
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.
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.
The radula
Radula
The radula is an anatomical structure that is used by molluscs for feeding, sometimes compared rather inaccurately to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus...
is as usual in the Helicidae
Helicidae
The Helicidae, sometimes known as the typical snails, are a taxonomic family of small to large, air-breathing, land snails. In other words, they are terrestrial pulmonate gastropod mollusks....
. 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.
Distribution
Property
Property is any physical or intangible entity that is owned by a person or jointly by a group of people or a legal entity like a corporation...
and are difficult to reach because of the rough terrain. It is possible that Newcomb's snail populations remain in that region of Kauaʻi.
Until about 1925, snails were collected from small sites located in Kalalau Stream, Hanakoa Stream, Hanakāpī`ai Stream, Wainiha River, and Keālia Stream. Three of these populations (Hanakoa Stream, Hanakāpī`ai Stream, Wainiha River) are now thought to be extirpated. Since about 1993, Federal and State agencies, academic researchers, and other interested parties have conducted opportunistic surveys at approximately 50 sites along numerous streams and their associated tributaries and springs on Kaua'i, and have located four previously unknown populations of Newcomb's snail. These recently discovered populations are located in Lumaha`i River, the Hanalei River
Hanalei River
The Hanalei River on the island of Kauai in Hawaii flows north from the eastern slopes Mount Waialeale for until entering the Pacific Ocean at Hanalei Bay as an estuary...
, Makaleha Stream (a tributary to Kapa`a Stream), and the North Fork Wailua River
Wailua River
The Wailuā River is a river on the island of Kauai in the U.S. state of Hawaii. It is formed by the confluence of its North and South forks just west of Wailua and enters the Pacific Ocean at . It is the only navigable river in the Hawaiian Islands...
. With the exception of the snails at Makaleha Springs, most of these populations have only been observed once or twice. Recently, two individual snails were reported from a single site in Limahuli Stream in the Hanalei District of Kauaʻi's north shore. However, if a viable population of Newcomb's snail exists in the Limahuli watershed, its location remains unknown, therefore Limahuli Stream is not considered to have a "population
Population
A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...
" of Newcomb's snails.
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 "subpopulation" refers to a discreet group of individuals, separated from other discrete groups within a single watershed
Drainage basin
A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...
. Because of low mobility
Population mobility
Population mobility, geographic mobility or more simply mobility is a statistic that measures migration within a population. It is most commonly used in demography and human geography, it may also be used to describe the movement of animals between populations.Mobility estimates in the Current...
, no interaction between subpopulations exists. No historical information is available on the population size
Population size
In population genetics and population ecology, population size is the number of individual organisms in a population.The effective population size is defined as "the number of breeding individuals in an idealized population that would show the same amount of dispersion of allele frequencies under...
s of Newcomb's snail. However, anecdotal reports indicate the Kalalau Stream and Lumaha`i River populations of Newcomb's snails are larger in comparison to the other four.
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, areunknown.
Newcomb's snail is active during the day.
Newcomb's snail probably shares life history similarities with other members of its family. Lymnaeid snails generally feed on algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
and vegetation growing on submerged rocks. Snails attach eggs to submerged rocks or vegetation and larval stages do not disperse widely; the entire life cycle is tied to the stream system in which the adults live. Little is known about the biological or environmental factors affecting Newcomb's snail population size, however, important factors may include: annual, multi-year, or decadal changes in stream flows; severe weather, high flow, or channel-scouring events; and periods of prolonged drought. Snail dispersal
Biological dispersal
Biological dispersal refers to species movement away from an existing population or away from the parent organism. Through simply moving from one habitat patch to another, the dispersal of an individual has consequences not only for individual fitness, but also for population dynamics, population...
both upstream and downstream within a stream system probably plays an important function in colonizing or recolonizing suitable habitat, particularly microhabitat protected from channel scour. Dispersal of Newcomb's snail between stream systems is likely infrequent because of their obligate freshwater habitat requirements; historic dispersal probably relied on long-term erosional events that captured adjacent stream systems. This life history differs greatly from the freshwater Hawaiian neritid snails (Neritina granosa
Neritina granosa
Neritina granosa is a species of freshwater snail with an operculum, an aquatic gastropod mollusk in the family Neritidae, the nerites.-Distribution:This species of nerite is endemic in Hawaii: Maui.- Ecology :...
, Neritina vespertina) that have marine larvae that migrate into and up streams following a period of oceanic dispersal. Most likely, the planktonic larvae of the neritid snails disperse across the oceanic expanses that separate the main Hawaiian Islands and can colonize streams on any or all of these islands. Newcomb's snail lacks this dispersal capacity.
Habitat
On the basis of past and recent field observations, the specific habitat requirements of Newcomb's snail include fast-flowing perennial streamPerennial stream
A perennial stream or perennial river is a stream or river that has continuous flow in parts of its bed all year round during years of normal rainfall. "Perennial" streams are contrasted with "intermittent" streams which normally cease flowing for weeks or months each year, and with "ephemeral"...
s 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
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
input. The common element among sites harboring snail populations is that the water source appears to be consistent and permanent, even during severe drought.
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).
It is suspected that the four species of introduced caddisflies Trichoptera
Trichoptera
The caddisflies are an order, Trichoptera, of insects with approximately 12,000 described species. Also called sedge-flies or rail-flies, they are small moth-like insects having two pairs of hairy membranous wings...
are adversely impacting native aquatic invertebrate populations either through competition
Competition
Competition is a contest between individuals, groups, animals, etc. for territory, a niche, or a location of resources. It arises whenever two and only two strive for a goal which cannot be shared. Competition occurs naturally between living organisms which co-exist in the same environment. For...
for space and resources, or because of its large body size and sheer abundance in Hawaiian streams. For example a single caddisfly species accounted for 57% of all biota collected in the upper elevation Kauaʻi streams.
Predators
Euglandina rosea
Euglandina rosea, common names the "rosy wolfsnail" or the "cannibal snail", is a species of medium-sized to large predatory air-breathing land snail, a carnivorous terrestrial pulmonate gastropod mollusk in the family Spiraxidae.-Distribution:...
remains a serious threat to the survival of Newcomb's snail. This predatory snail, introduced into Hawai`i in 1955, has established populations throughout the main islands. The rosy glandina feeds on snails and slugs, and field studies document that it readily feeds on native snails found in Hawai`i. Furthermore the rosy glandina snail exhibits remarkable hunting behaviors leading to capture and predation of submerged prey. Although terrestrial, the rosy glandina will fully immerse itself in water to locate and feed on aquatic molluscs such as Newcomb's snail. The rosy glandina has been observed on the wet, algae-covered rocks of the Makaleha Stream in close proximity to individual Newcomb's snails, and is believed to prey on them. The rosy glandina snail is responsible for the extirpation
Local extinction
Local extinction, also known as extirpation, is the condition of a species which ceases to exist in the chosen geographic area of study, though it still exists elsewhere...
of many populations and even the extinction of numerous species of native snails throughout the Pacific Islands
Pacific Islands
The Pacific Islands comprise 20,000 to 30,000 islands in the Pacific Ocean. The islands are also sometimes collectively called Oceania, although Oceania is sometimes defined as also including Australasia and the Malay Archipelago....
, and represents a significant threat to the survival of Newcomb's snail.
Predation on the eggs and adults of native Hawaiian lymnaeid snails by two non-native species of sciomyzid flies marsh fly Sepedomerus macropus and Sepedon aenescens represents a significant threat to the survival of Newcomb's snail. They feed on lymnaeid snails and were introduced into Hawaii in 1958 and 1966, respectively. These predatory flies were intended to act as biological control agents for the non-native lymnaeid snail Fossaria viridis and for another non-native lymnaeid snail Galba viridis (an intermediate host of the cattle liver fluke Fasciola gigantica
Fasciola gigantica
Fasciola gigantica is a parasitic flatworm of the class Trematoda, which causes tropical fascioliasis. It is regarded as one of the most important single platyhelminth infections of ruminants in Asia and Africa...
). These biological control species may represent a significant threat to Newcomb's snail and other native lymnaeid snails.
Several introduced, predatory aquatic species, including the green swordtail fish Xyphophorus helleri, the American bullfrog Rana catesbiana, the wrinkled frog Rana rugosa, and the cane toad Bufo marinus potentially threaten populations of Newcomb's snail. All potentially prey on the Newcomb's snail.
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 helicopterHelicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by one or more engine-driven rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally...
transport, although the Kalalau Stream population potentially could be accessed in summer months with boat support and strenuous hiking
Hiking
Hiking is an outdoor activity which consists of walking in natural environments, often in mountainous or other scenic terrain. People often hike on hiking trails. It is such a popular activity that there are numerous hiking organizations worldwide. The health benefits of different types of 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.
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. Flooding due to hurricanes and tropical storms, catastrophic landslide
Landslide
A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...
s, drought, infestation by introduced invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....
, and other localized phenomena that occur unpredictably could eradicate Newcomb's snail habitat across significant portions of the island. Recent examples of such recurring natural events include Hurricane Iniki
Hurricane Iniki
Hurricane Iniki was the most powerful hurricane to strike the U.S. state of Hawaii in recorded history. Forming on September 5 during the strong El Niño of 1991–1994, Iniki was one of eleven Central Pacific tropical cyclones during the 1992 season. It attained tropical storm status on...
(a Category IV hurricane that devastated
Kaua`i on 11 September 1992), Hurricane Iwa
Hurricane Iwa
Hurricane Iwa, taken from the Hawaiian language name for the frigatebird , was at the time the costliest hurricane to affect the state of Hawaii. Iwa was the twenty-third tropical storm and the twelfth and final hurricane of the 1982 Pacific hurricane season. It developed from an active trough of...
(23 November 1982), and the large upper Olokele Valley landslide of 31 October 1981. Each of these events greatly impacted and may have eliminated large areas of unsurveyed potential Newcomb's snail habitat. Any recovery planning effort must take the island-wide distribution of Newcomb's snails into account to ensure maintenance of separate populations in watersheds geographically distributed throughout the island.
Conservation
Newcomb's snails face a continued threat from human-caused changes to the hydrologic landscape of Kauaʻi, that causes severe degradation ofnatural aquatic environments. Such changes include large irrigation, extensive plantation style agriculture diverting water out of both surface waterbodies and groundwater sources.
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 Kaua`i Board of Water Supply and cleared a number of State and local regulatory reviews. Ultimately, the State Commission on Water Resource Management denied the applicable permits on the basis of numerous unresolved environmental issues, including impacts to aquatic life.
Erinna newcombi is listed as vulnerable species
Vulnerable species
On 30 January 2010, the IUCN Red List of Threatened Species identified 9694 Vulnerable species, subspecies and varieties, stocks and sub-populations.-References:...
in 2006 IUCN Red List
IUCN Red List
The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...
and also in 2009 IUCN Red List.
This species is listed as threatened on the United States Fish and Wildlife Service list of endangered species
United States Fish and Wildlife Service list of endangered species
This list contains only the bird and mammal species described as endangered by the United States Fish and Wildlife Service. It contains species not only in the U.S. and its territories, but also species only found abroad. It does not contain fish, amphibians, reptiles, plants, or invertebrates,...
under the authority of the Endangered Species Act
Endangered Species Act
The Endangered Species Act of 1973 is one of the dozens of United States environmental laws passed in the 1970s. Signed into law by President Richard Nixon on December 28, 1973, it was designed to protect critically imperiled species from extinction as a "consequence of economic growth and...
of 1973, since 26 January 2000. Such Hawaiian species are automatically added to the State of Hawaii's list of protected species.
Critical habitat
Critical habitat
Critical habitat is a habitat area essential to the conservation of a listed species, though the area need not actually be occupied by the species at the time it is designated. This is a specific term and designation within the U.S...
(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 kilometres (12.3 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).
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.
Further reading
- Burch J. B.John B. BurchJohn Bayard Burch is an American zoologist, a biology professor at the University of Michigan, and is the Curator of Mollusks at the University of Michigan Museum of Zoology. His research interests are broad, and have encompassed not only the anatomy, systematics, and genetics of mollusks, but...
(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.