Limacina helicina
Encyclopedia
Limacina helicina is a species
of small swimming predatory sea snail
in the family Limacinidae
, which belong to the group commonly known as sea butterflies
(Thecosomata).
Limacina helicina is a keystone species
of mesozooplankton in Arctic
pelagic ecosystems.
The first written record of this species was by Friderich Martens
from Spitsbergen
in 1675. Limacina helicina was also observed during an 1773 expedition to the Arctic
led by Constantine John Phipps on the ships HMS Racehorse and on HMS Carcass
and the species was described
one year later, in 1774.
Limacina helicina is the type species
of the genus Limacina.
In contrast to the traditional view, it was shown in 2010 that the distribution of this species is not bipolar; Arctic and Antarctic individuals belong to two genetically distinct species: Limacina helicina in the Arctic, and Limacina antarctica
in the Antarctic.
Limacina helicina has been recognised as a species complex comprising two sub-species and at least five forms. In addition, the taxonomic category “forma” has been applied to designate at least three morphotypes of Limacina helicina helicina (acuta, helicina and pacifica) and two morphotypes of Limacina helicina antarctica (antarctica and rangi). It is also known as Limacina helicina rangii (d'Orbigny, 1835). These forms typically have different geographical ranges, but it remains unclear as to whether forms represent morphological responses to different environmental conditions or are indeed taxonomically distinct, and if the latter, their level of taxonomic separation.
However, at the species level the geographical distribution is considered to be bipolar, as it occurs in both the Arctic and Antarctic
oceans. Remigio and Hebert (2003) provided initial evidence for the genetic separation of Limacina helicina helicina and Limacina helicina antarctica. Hunt et al. (2010) have quantified genetic distance
within these taxa. Hunt 2010 found a 33.56% difference in cytochrome c oxidase subunit I (COI) gene sequences between the "Limacina helicina" which were collected from the Arctic and the Antarctic oceans. This degree of separation is sufficient for ordinal level taxonomic separation in other organisms, and provides strong evidence for the Arctic and Antarctic populations of Limacina helicina differing at least at the species
level. Subspecies Limacina helicina antarctica Woodward, 1854 can be considered as a separate species Limacina antarctica
Woodward, 1854. A conservative divergence time estimate
of 31 Ma (95% HPD interval 12–53 Ma) for Arctic and Antarctic taxa, indicates that they have undergone rapid independent evolution
since the establishment of cold water provinces in the early Oligocene. Also there is different structure of the shell between Limacina helicina and Limacina antarctica.
The distribution of Limacina helicina is arctic
and subarctic
(subpolar
–polar
) especially in the Arctic Ocean
and countries include:
In this species, the color of the soft parts is dark purple
or violet
, with paler pellucid (translucent) parapodia.
The shell
is sinistral, subglobose, subdiscoidal, hyaline
and very thin. The spire
is depressed but it can be considered rather high in comparison of other Limacina species. The shell has 5-6 transversally striated whorls
. The suture is distinct. The last whorl is large and with very obscure keel next to its umbilicus. The shell has a wide umbilicus. The aperture is higher than it is wide.
The width of the shell is 5-10 mm or up to 13 mm. The height of the shell is up to 6 mm (when maximum width was 8 mm).
Adult specimens in the genus Limacina have usually lost the operculum
.
The radula
consist of 10 rows. Each row consist of one central tooth and two lateral teeth. The Digestive system
also includes an esophagus, gizzard sac and gut.
ic species. Habitat of Limacina helicina is upper epipelagic and glacial. It lives in temperatures from -0.4 °C to +4.0 °C or rarely up to 7 °C.
Vertical distribution is affected by the size and also by other factors. Limacina helicina of the size from 0.2 to 0.4 mm lives mainly in depths from 0 m to 50 m. Larger pteropods lives from 0 m to 150 m. For example Gilmer & Harbison (1991) have found larger specimen of Limacina helicina to occur mainly in depths 5-25 m with abundance up to 2.5 adults in m3. They do not occur much in upper 4 m probably because of turbulence.
Already Constantine John Phipps mentioned its "innumerable quantities" in arctic seas in 1774. Limacina helicina is a major component of the polar zooplankton
. It can comprise >50% of total zooplankton abundance (number of individuals per unit volume).
Species of the clade Thecosomata produce a fragile external calcium carbonate
shell, which could serve as a ballast
enabling large vertical migrations and as a protection against predators. The aragonitic composition of the shell makes it very sensitive to dissolution. Aragonite
is a metastable form of calcium carbonate and it is more soluble in seawater than calcite
. Because of its highly soluble aragonite shell and polar distribution, Limacina helicina may be one of the first organisms affected by ocean acidification
, and it is therefore a key indicator species
of this process. As a key indicator of the acidification process, and a major component of polar ecosystems, Limacina helicina has become a focus for acidification research. Based on labolatory experiments, they are able to precipitate calcium carbonate at low aragonite saturation state. Limacina helicina seems to be relatively more resilient to elevated concentration of carbon dioxide
(CO2) than other aragonitic organisms such as coral
s. Labolatory experiments results support the current concern for the future of Arctic pteropods, as the production of their shell appears to be very sensitive to decreased pH
. A decline of pteropod populations would likely cause dramatic changes to various pelagic ecosystems. Shelled pteropods also play a geochemical role in carbon cycle
in the oceans, as they contribute to the export of calcium carbonate
and can represent a major component of the carbon transport to the deep ocean.
. Webs are easier to see at night. Limacina helicina is easily disturbed (like all other Thecosomata); when disturbed, it retracts into its shell and destroys its web. Gilmer & Harbison (1991) have assumed, that Limacina helicina feeds while motionless (without actively swimming). Its web enables them neutral buoyancy
or allow them slow sinking only.
Limacina helicina it plays a significant ecological role as a phytoplankton
grazer. Limacina helicina is obligate ciliary feeder. Gilmer & Harbison (1991) hypothetized, that Limacina helicina are "web trappers", who are also chemically attracting its motile prey.
Major parts of the food of Limacina helicina include tintinnid
(Tintinnida), small crustaceans - copepod
s (Copepoda) and juvenile specimen of its own species (cannibalism
). Danish zoologist Johan Erik Vesti Boas
reported diatom
s (Bacillariophyceae), dinoflagellate
s (Dinoflagellata) and tintinnids in the digestive system
of Limacina helicina in 1888 already. Diatoms and dinoflagellates appear to pass the digestive system of adults largely intact. Fecal pellets of Limacina helicina contains small cells, dinoflagellates and diatoms as main largely intact food items and also few small fragments of tintinnids, Limacina and copepods. All experiments performed on Limacina helicina in the laboratory were done on starved specimens, because they do not feed in unnatural conditions.
Gilmer & Harbison (1991) also suggested that smaller specimens may be herbivore
s feeding preferentially on phytoplankton
and protozoans and that larger specimens became omnivores.
s during copulation. They lay eggs in ribbon-like clusters mainly in summer, but also a little in winter.
The size of the veliger
larvae is about 0.15 mm. When animals reached 0.7 mm in size, gonad
s have been detected in them. Fully mature individuals are 0.8 mm in size.
The life cycle of Limacina helicina lasts about 1 year or 1.5-2 years.
as a major dietary component for predators such as large zooplankton
, herring
Clupea sp., chum salmon
Oncorhynchus keta, pink salmon
Oncorhynchus gorbuscha, rorqual
whale
s, Phoca hispida and other seals
and birds.
The pteropod Clione limacina
feeds only on the genus Limacina: on Limacina helicina and on Limacina retroversa
. Also the pteropod Paedoclione doliiformis feeds on those two species only, but solely on juveniles with shells smaller than 1 mm.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of small swimming predatory sea snail
Sea snail
Sea snail is a common name for those snails that normally live in saltwater, marine gastropod molluscs....
in the family Limacinidae
Limacinidae
Limacinidae is a family of small sea snails, pteropods, pelagic marine gastropod mollusks in the clade Thecosomata .-Genera:Genera within the family Limacinidae include:...
, which belong to the group commonly known as sea butterflies
Sea butterfly
Sea butterflies, also known as Thecosomata or flapping snails, are a taxonomic suborder of small pelagic swimming sea snails. These are holoplanktonic opisthobranch gastropod mollusks in the informal group Opisthobranchia. They include some of the world's most abundant gastropod species.This group...
(Thecosomata).
Limacina helicina is a keystone species
Keystone species
A keystone species is a species that has a disproportionately large effect on its environment relative to its abundance. Such species play a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and...
of mesozooplankton in Arctic
Arctic
The Arctic is a region located at the northern-most part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Greenland, the United States, Norway, Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost...
pelagic ecosystems.
The first written record of this species was by Friderich Martens
Friderich Martens
Friderich Martens, was a German physician and naturalist who conducted the first scientific observations of the nature, animal life and climate of Svalbard...
from Spitsbergen
Spitsbergen
Spitsbergen is the largest and only permanently populated island of the Svalbard archipelago in Norway. Constituting the western-most bulk of the archipelago, it borders the Arctic Ocean, the Norwegian Sea and the Greenland Sea...
in 1675. Limacina helicina was also observed during an 1773 expedition to the Arctic
Arctic
The Arctic is a region located at the northern-most part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Greenland, the United States, Norway, Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost...
led by Constantine John Phipps on the ships HMS Racehorse and on HMS Carcass
HMS Carcass (1759)
HMS Carcass was an of the Royal Navy, later refitted as a survey vessel. A young Horatio Nelson served aboard her as a midshipman on an expedition to the Arctic.-Design and construction:The Infernal class were designed by Thomas Slade...
and the species was described
Species description
A species description or type description is a formal description of a newly discovered species, usually in the form of a scientific paper. Its purpose is to give a clear description of a new species of organism and explain how it differs from species which have been described previously, or are...
one year later, in 1774.
Limacina helicina 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 Limacina.
In contrast to the traditional view, it was shown in 2010 that the distribution of this species is not bipolar; Arctic and Antarctic individuals belong to two genetically distinct species: Limacina helicina in the Arctic, and Limacina antarctica
Limacina antarctica
Limacina antarctica is a species of swimming sea snail in the family Limacinidae, which belong to the group commonly known as sea butterflies ....
in the Antarctic.
Subspecies
- Limacina helicina helicina (Phipps, 1774)
- Limacina helicina acuta Van Der Spoel, 1967
- Limacina helicina ochotensis Shkoldina, 1999
- Limacina helicina pacifica DallW. H. DallWilliam Healey Dall was an American naturalist, a prominent malacologist, and one of the earliest scientific explorers of interior Alaska...
, 1871
Limacina helicina has been recognised as a species complex comprising two sub-species and at least five forms. In addition, the taxonomic category “forma” has been applied to designate at least three morphotypes of Limacina helicina helicina (acuta, helicina and pacifica) and two morphotypes of Limacina helicina antarctica (antarctica and rangi). It is also known as Limacina helicina rangii (d'Orbigny, 1835). These forms typically have different geographical ranges, but it remains unclear as to whether forms represent morphological responses to different environmental conditions or are indeed taxonomically distinct, and if the latter, their level of taxonomic separation.
However, at the species level the geographical distribution is considered to be bipolar, as it occurs in both the Arctic and Antarctic
Antarctic
The Antarctic is the region around the Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica and the ice shelves, waters and island territories in the Southern Ocean situated south of the Antarctic Convergence...
oceans. Remigio and Hebert (2003) provided initial evidence for the genetic separation of Limacina helicina helicina and Limacina helicina antarctica. Hunt et al. (2010) have quantified genetic distance
Genetic distance
Genetic distance refers to the genetic divergence between species or between populations within a species. It is measured by a variety of parameters. Smaller genetic distances indicate a close genetic relationship whereas large genetic distances indicate a more distant genetic relationship...
within these taxa. Hunt 2010 found a 33.56% difference in cytochrome c oxidase subunit I (COI) gene sequences between the "Limacina helicina" which were collected from the Arctic and the Antarctic oceans. This degree of separation is sufficient for ordinal level taxonomic separation in other organisms, and provides strong evidence for the Arctic and Antarctic populations of Limacina helicina differing at least at the species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
level. Subspecies Limacina helicina antarctica Woodward, 1854 can be considered as a separate species Limacina antarctica
Limacina antarctica
Limacina antarctica is a species of swimming sea snail in the family Limacinidae, which belong to the group commonly known as sea butterflies ....
Woodward, 1854. A conservative divergence time estimate
Bayesian inference in phylogeny
Bayesian inference in phylogeny generates a posterior distribution for a parameter, composed of a phylogenetic tree and a model of evolution, based on the prior for that parameter and the likelihood of the data, generated by a multiple alignment. The Bayesian approach has become more popular due...
of 31 Ma (95% HPD interval 12–53 Ma) for Arctic and Antarctic taxa, indicates that they have undergone rapid independent 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...
since the establishment of cold water provinces in the early Oligocene. Also there is different structure of the shell between Limacina helicina and Limacina antarctica.
Distribution
The type locality of Limacina helicina is "Arctic seas". Limacina helicina is the only thecosome pteropod in Arctic waters.The distribution of Limacina helicina is arctic
Arctic
The Arctic is a region located at the northern-most part of the Earth. The Arctic consists of the Arctic Ocean and parts of Canada, Russia, Greenland, the United States, Norway, Sweden, Finland, and Iceland. The Arctic region consists of a vast, ice-covered ocean, surrounded by treeless permafrost...
and subarctic
Subarctic
The Subarctic is a region in the Northern Hemisphere immediately south of the true Arctic and covering much of Alaska, Canada, the north of Scandinavia, Siberia, and northern Mongolia...
(subpolar
Subarctic climate
The subarctic climate is a climate characterized by long, usually very cold winters, and short, cool to mild summers. It is found on large landmasses, away from the moderating effects of an ocean, generally at latitudes from 50° to 70°N poleward of the humid continental climates...
–polar
Polar region
Earth's polar regions are the areas of the globe surrounding the poles also known as frigid zones. The North Pole and South Pole being the centers, these regions are dominated by the polar ice caps, resting respectively on the Arctic Ocean and the continent of Antarctica...
) especially in the Arctic Ocean
Arctic Ocean
The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region, is the smallest and shallowest of the world's five major oceanic divisions...
and countries include:
- Northern Atlantic Ocean between 50–60 °N, Norwegian SeaNorwegian SeaThe Norwegian Sea is a marginal sea in the North Atlantic Ocean, northwest of Norway. It is located between the North Sea and the Greenland Sea and adjoins the North Atlantic Ocean to the west and the Barents Sea to the northeast. In the southwest, it is separated from the Atlantic Ocean by a...
, Faroe IslandsFaroe IslandsThe Faroe Islands are an island group situated between the Norwegian Sea and the North Atlantic Ocean, approximately halfway between Scotland and Iceland. The Faroe Islands are a self-governing territory within the Kingdom of Denmark, along with Denmark proper and Greenland...
, SpitsbergenSpitsbergenSpitsbergen is the largest and only permanently populated island of the Svalbard archipelago in Norway. Constituting the western-most bulk of the archipelago, it borders the Arctic Ocean, the Norwegian Sea and the Greenland Sea...
, North of IcelandIcelandIceland , described as the Republic of Iceland, is a Nordic and European island country in the North Atlantic Ocean, on the Mid-Atlantic Ridge. Iceland also refers to the main island of the country, which contains almost all the population and almost all the land area. The country has a population... - Greenland: Denmark StraitDenmark StraitThe Denmark Strait or Greenland Strait |Sound]]) is an oceanic strait between Greenland and Iceland...
and Davis StraitDavis StraitDavis Strait is a northern arm of the Labrador Sea. It lies between mid-western Greenland and Nunavut, Canada's Baffin Island. The strait was named for the English explorer John Davis , who explored the area while seeking a Northwest Passage.... - Canada: Anticosti IslandAnticosti IslandAnticosti Island is an island at the outlet of the Saint Lawrence River into the Gulf of Saint Lawrence, in Quebec, Canada, between 49° and 50° N., and between 61° 40' and 64° 30' W. At in size, it is the 90th largest island in the world and 20th largest island in Canada...
, Laurentian ChannelLaurentian ChannelThe Laurentian Channel is a submarine valley in eastern Canada.The channel is of glacial origin and is the submerged valley of the historic St. Lawrence River, running 1400 km from a sharp escarpment downstream from the confluence of the St. Lawrence with the Saguenay River, past Anticosti Island...
, Magdalen IslandsMagdalen IslandsThe Magdalen Islands form a small archipelago in the Gulf of Saint Lawrence with a land area of . Though closer to Prince Edward Island and Nova Scotia, the islands form part of the Canadian province of Quebec....
, Prince Edward IslandPrince Edward IslandPrince Edward Island is a Canadian province consisting of an island of the same name, as well as other islands. The maritime province is the smallest in the nation in both land area and population...
, Newfoundland, Strait of Belle Isle. - area between Cape HatterasCape HatterasCape Hatteras is a cape on the coast of North Carolina. It is the point that protrudes the farthest to the southeast along the northeast-to-southwest line of the Atlantic coast of North America...
(North CarolinaNorth CarolinaNorth Carolina is a state located in the southeastern United States. The state borders South Carolina and Georgia to the south, Tennessee to the west and Virginia to the north. North Carolina contains 100 counties. Its capital is Raleigh, and its largest city is Charlotte...
, USA) and Newfoundland island - Pacific Ocean: from the Gulf of AlaskaGulf of AlaskaThe Gulf of Alaska is an arm of the Pacific Ocean defined by the curve of the southern coast of Alaska, stretching from the Alaska Peninsula and Kodiak Island in the west to the Alexander Archipelago in the east, where Glacier Bay and the Inside Passage are found.The entire shoreline of the Gulf is...
to Friday Harbor, Washington state, USA - Russia: White SeaWhite SeaThe White Sea is a southern inlet of the Barents Sea located on the northwest coast of Russia. It is surrounded by Karelia to the west, the Kola Peninsula to the north, and the Kanin Peninsula to the northeast. The whole of the White Sea is under Russian sovereignty and considered to be part of...
and Novaya ZemlyaNovaya ZemlyaNovaya Zemlya , also known in Dutch as Nova Zembla and in Norwegian as , is an archipelago in the Arctic Ocean in the north of Russia and the extreme northeast of Europe, the easternmost point of Europe lying at Cape Flissingsky on the northern island...
Description
Limacina helicina has wing-like parapodia which evolved from the original gastropod foot (as is the case in all other pteropods).In this species, the color of the soft parts is dark purple
Purple
Purple is a range of hues of color occurring between red and blue, and is classified as a secondary color as the colors are required to create the shade....
or violet
Violet (color)
As the name of a color, violet is synonymous with a bluish purple, when the word "purple" is used in the common English language sense of any color between blue and red, not including either blue or red...
, with paler pellucid (translucent) parapodia.
The shell
Gastropod 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...
is sinistral, subglobose, subdiscoidal, hyaline
Hyaline
The term hyaline denotes a substance with a glass-like appearance.-Histopathology:In histopathological medical usage, a hyaline substance appears glassy and pink after being stained with haematoxylin and eosin — usually it is an acellular, proteinaceous material...
and very thin. The 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...
is depressed but it can be considered rather high in comparison of other Limacina species. The shell has 5-6 transversally striated whorls
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...
. The suture is distinct. The last whorl is large and with very obscure keel next to its umbilicus. The shell has a wide umbilicus. The aperture is higher than it is wide.
The width of the shell is 5-10 mm or up to 13 mm. The height of the shell is up to 6 mm (when maximum width was 8 mm).
Adult specimens in the genus Limacina have usually lost the operculum
Operculum (gastropod)
The operculum, meaning little lid, is a corneous or calcareous anatomical structure which exists in many groups of sea snails and freshwater snails, and also in a few groups of land snails...
.
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...
consist of 10 rows. Each row consist of one central tooth and two lateral teeth. The Digestive system
Digestive system of gastropods
The digestive system of gastropods has evolved to suit almost every kind of diet and feeding behavior. Gastropods as the largest taxonomic class of the mollusca are very diverse indeed: the group includes carnivores, herbivores, scavengers, filter feeders, and even parasites.In particular, the...
also includes an esophagus, gizzard sac and gut.
Habitat
Pteropods are strict pelagic mollusks that are highly adapted to life in the open ocean. They are actively swimming in the water. Limacina helicina is a holoplanktonHoloplankton
Holoplankton are organisms that are planktonic for their entire life cycle. Examples of holoplankton include some diatoms, radiolarians, some dinoflagellates, foraminifera, amphipods, krill, copepods, and salps.-Sources:Asexual Holoplankton:...
ic species. Habitat of Limacina helicina is upper epipelagic and glacial. It lives in temperatures from -0.4 °C to +4.0 °C or rarely up to 7 °C.
Vertical distribution is affected by the size and also by other factors. Limacina helicina of the size from 0.2 to 0.4 mm lives mainly in depths from 0 m to 50 m. Larger pteropods lives from 0 m to 150 m. For example Gilmer & Harbison (1991) have found larger specimen of Limacina helicina to occur mainly in depths 5-25 m with abundance up to 2.5 adults in m3. They do not occur much in upper 4 m probably because of turbulence.
Already Constantine John Phipps mentioned its "innumerable quantities" in arctic seas in 1774. Limacina helicina is a major component of the polar zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
. It can comprise >50% of total zooplankton abundance (number of individuals per unit volume).
Species of the clade Thecosomata produce a fragile external calcium carbonate
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...
shell, which could serve as a ballast
Sailing ballast
Ballast is used in sailboats to provide moment to resist the lateral forces on the sail. Insufficiently ballasted boats will tend to tip, or heel, excessively in high winds. Too much heel may result in the boat capsizing. If a sailing vessel should need to voyage without cargo then ballast of...
enabling large vertical migrations and as a protection against predators. The aragonitic composition of the shell makes it very sensitive to dissolution. Aragonite
Aragonite
Aragonite is a carbonate mineral, one of the two common, naturally occurring, crystal forms of calcium carbonate, CaCO3...
is a metastable form of calcium carbonate and it is more soluble in seawater than calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
. Because of its highly soluble aragonite shell and polar distribution, Limacina helicina may be one of the first organisms affected by ocean acidification
Ocean acidification
Ocean acidification is the name given to the ongoing decrease in the pH and increase in acidity of the Earth's oceans, caused by the uptake of anthropogenic carbon dioxide from the atmosphere....
, and it is therefore a key indicator species
Indicator species
An indicator species is any biological species that defines a trait or characteristic of the environment. For example, a species may delineate an ecoregion or indicate an environmental condition such as a disease outbreak, pollution, species competition or climate change...
of this process. As a key indicator of the acidification process, and a major component of polar ecosystems, Limacina helicina has become a focus for acidification research. Based on labolatory experiments, they are able to precipitate calcium carbonate at low aragonite saturation state. Limacina helicina seems to be relatively more resilient to elevated concentration of carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
(CO2) than other aragonitic organisms such as coral
Coral
Corals are marine animals in class Anthozoa of phylum Cnidaria typically living in compact colonies of many identical individual "polyps". The group includes the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.A coral "head" is a colony of...
s. Labolatory experiments results support the current concern for the future of Arctic pteropods, as the production of their shell appears to be very sensitive to decreased pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
. A decline of pteropod populations would likely cause dramatic changes to various pelagic ecosystems. Shelled pteropods also play a geochemical role in carbon cycle
Carbon cycle
The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth...
in the oceans, as they contribute to the export of calcium carbonate
Calcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...
and can represent a major component of the carbon transport to the deep ocean.
Feeding habits
They produce large mucus webs to filter-feed on phytoplankton but also small zooplankton. They eat the web with the captured prey and then re-reproduce a web net. The web is large and spherical and it is difficult to see during the day because of diffuse reflectionDiffuse reflection
Diffuse reflection is the reflection of light from a surface such that an incident ray is reflected at many angles rather than at just one angle as in the case of specular reflection...
. Webs are easier to see at night. Limacina helicina is easily disturbed (like all other Thecosomata); when disturbed, it retracts into its shell and destroys its web. Gilmer & Harbison (1991) have assumed, that Limacina helicina feeds while motionless (without actively swimming). Its web enables them neutral buoyancy
Neutral buoyancy
Neutral buoyancy is a condition in which a physical body's mass equals the mass it displaces in a surrounding medium. This offsets the force of gravity that would otherwise cause the object to sink...
or allow them slow sinking only.
Limacina helicina it plays a significant ecological role as a phytoplankton
Phytoplankton
Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye...
grazer. Limacina helicina is obligate ciliary feeder. Gilmer & Harbison (1991) hypothetized, that Limacina helicina are "web trappers", who are also chemically attracting its motile prey.
Major parts of the food of Limacina helicina include tintinnid
Tintinnid
Tintinnids are ciliates of the choreotrich taxon Tintinnida, distinguished by vase-shaped shells called loricae, which are mostly protein but may incorporate minute pieces of minerals. Although appearing as early as the Ordovician period, tintinnids became abundant in the fossil record during the...
(Tintinnida), small crustaceans - copepod
Copepod
Copepods are a group of small crustaceans found in the sea and nearly every freshwater habitat. Some species are planktonic , some are benthic , and some continental species may live in limno-terrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests,...
s (Copepoda) and juvenile specimen of its own species (cannibalism
Cannibalism (zoology)
In zoology, cannibalism is the act of one individual of a species consuming all or part of another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded for more than 1500 species...
). Danish zoologist Johan Erik Vesti Boas
Johan Erik Vesti Boas
Johan Erik Vesti Boas , also J.E.V. Boas, was a Danish zoologist and a disciple of Carl Gegenbaur and Steenstrup. During the beginning and end of his career, Johan Erik Vesti Boas worked at the Zoological Museum of Copenhagen...
reported diatom
Diatom
Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...
s (Bacillariophyceae), dinoflagellate
Dinoflagellate
The dinoflagellates are a large group of flagellate protists. Most are marine plankton, but they are common in fresh water habitats as well. Their populations are distributed depending on temperature, salinity, or depth...
s (Dinoflagellata) and tintinnids in the digestive system
Digestive system of gastropods
The digestive system of gastropods has evolved to suit almost every kind of diet and feeding behavior. Gastropods as the largest taxonomic class of the mollusca are very diverse indeed: the group includes carnivores, herbivores, scavengers, filter feeders, and even parasites.In particular, the...
of Limacina helicina in 1888 already. Diatoms and dinoflagellates appear to pass the digestive system of adults largely intact. Fecal pellets of Limacina helicina contains small cells, dinoflagellates and diatoms as main largely intact food items and also few small fragments of tintinnids, Limacina and copepods. All experiments performed on Limacina helicina in the laboratory were done on starved specimens, because they do not feed in unnatural conditions.
Gilmer & Harbison (1991) also suggested that smaller specimens may be herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
s feeding preferentially on phytoplankton
Phytoplankton
Phytoplankton are the autotrophic component of the plankton community. The name comes from the Greek words φυτόν , meaning "plant", and πλαγκτός , meaning "wanderer" or "drifter". Most phytoplankton are too small to be individually seen with the unaided eye...
and protozoans and that larger specimens became omnivores.
Life cycle
Limacina helicina is a protandric hermaphrodite. Males are smaller, at sizes of 4-5 mm and then they change to females, which are larger than 5 mm. Sperm is transferred by spermatophoreSpermatophore
A spermatophore or sperm ampulla is a capsule or mass created by males of various animal species, containing spermatozoa and transferred in entirety to the female's ovipore during copulation...
s during copulation. They lay eggs in ribbon-like clusters mainly in summer, but also a little in winter.
The size of the veliger
Veliger
A veliger is the planktonic larva of many kinds of marine and freshwater gastropod molluscs, as well as most bivalve mollusks.- Description :...
larvae is about 0.15 mm. When animals reached 0.7 mm in size, gonad
Gonad
The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells. For example, spermatozoon and egg cells are gametes...
s have been detected in them. Fully mature individuals are 0.8 mm in size.
The life cycle of Limacina helicina lasts about 1 year or 1.5-2 years.
Predators
Limacina helicina plays an important role in the marine food webFood web
A food web depicts feeding connections in an ecological community. Ecologists can broadly lump all life forms into one of two categories called trophic levels: 1) the autotrophs, and 2) the heterotrophs...
as a major dietary component for predators such as large zooplankton
Zooplankton
Zooplankton are heterotrophic plankton. Plankton are organisms drifting in oceans, seas, and bodies of fresh water. The word "zooplankton" is derived from the Greek zoon , meaning "animal", and , meaning "wanderer" or "drifter"...
, herring
Herring
Herring is an oily fish of the genus Clupea, found in the shallow, temperate waters of the North Pacific and the North Atlantic oceans, including the Baltic Sea. Three species of Clupea are recognized. The main taxa, the Atlantic herring and the Pacific herring may each be divided into subspecies...
Clupea sp., chum salmon
Chum salmon
The chum salmon, Oncorhynchus keta, is a species of anadromous fish in the salmon family. It is a Pacific salmon, and may also be known as dog salmon or Keta salmon, and is often marketed under the name Silverbrite salmon...
Oncorhynchus keta, pink salmon
Pink salmon
Pink salmon or humpback salmon, Oncorhynchus gorbuscha, is a species of anadromous fish in the salmon family. It is the smallest and most abundant of the Pacific salmon.- Appearance :...
Oncorhynchus gorbuscha, rorqual
Rorqual
Rorquals are the largest group of baleen whales, with nine species in two genera. They include the largest animal that has ever lived, the Blue Whale, which can reach , and another that easily reaches ; even the smallest of the group, the Northern Minke Whale, reaches .-Characteristics:Rorquals...
whale
Whale
Whale is the common name for various marine mammals of the order Cetacea. The term whale sometimes refers to all cetaceans, but more often it excludes dolphins and porpoises, which belong to suborder Odontoceti . This suborder also includes the sperm whale, killer whale, pilot whale, and beluga...
s, Phoca hispida and other seals
Pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...
and birds.
The pteropod Clione limacina
Clione limacina
Clione limacina, common name Naked Sea Butterfly or Common Clione, is a sea angel found from the surface to 350 m in depth. Lives in both Arctic and Antarctic Oceans....
feeds only on the genus Limacina: on Limacina helicina and on Limacina retroversa
Limacina retroversa
Limacina retroversa is a species of swimming predatory sea snail in the family Limacinidae, that belong to the group commonly known as sea butterflies .- Ecology :...
. Also the pteropod Paedoclione doliiformis feeds on those two species only, but solely on juveniles with shells smaller than 1 mm.
See also
- What appears to be "Limacina helicina" occurring in Antarctica is in fact a separate species, Limacina antarcticaLimacina antarcticaLimacina antarctica is a species of swimming sea snail in the family Limacinidae, which belong to the group commonly known as sea butterflies ....
. All pre-2010 works refer to this Antarctic taxon as Limacina helicina.
Further reading
Arshavskiĭ Iu. I., Orlovskiĭ G. N. & Panchin Iu V. (1985). "[Generation of locomotor rhythms in Limacina helicina]". Neirofiziologiia 17(3): 397-400.- Falk-Petersen S., Sargent J. R., Kwasniewski S., Gulliksen B. & Millar R.-M. (2001). "Lipids and fatty acids in Clione limacina and Limacina helicina in Svalbard waters and the Arctic Ocean: trophic implications". Polar Biology 24(3): 163-170. doi:10.1007/s003000000190.
- Lalli C. M. & Wells F. E. (1978). "Reproduction in the genus Limacina (Opisthobranchia, Thecosomata)". Journal of ZoologyJournal of ZoologyThe Journal of Zoology is a scientific journal concerning zoology, the study of animals. It was founded in 1830 by the Zoological Society of London and is published by Wiley-Blackwell. It carries original research papers, which are targeted towards general readers...
186(1): 95-108. doi:10.1111/j.1469-7998.1978.tb03359.x.
External links
- distribution map at Marine Species Identification Portal