Overview

Comprehensive Description

The shelled pteropod mollusk Limacina helicina is a key organism in polar pelagic ecosystems, where it can can account for 50% of total zooplankton abundance (number of individuals per unit volume). Pteropods are strictly pelagic mollusks that are highly adapted to life in the open ocean. They are commonly referred to as ‘‘sea butterflies’’ due to their wing-like parapodia, which are evolutionary modifications of the gastropod foot. Pteropods produce large mucus webs to filter-feed on phytoplankton as well as small zooplankton (including their own juveniles). Species of the Order Thecosomata, including L. helicina (the only thecosome pteropod in Arctic waters), produce a fragile external calcium carbonate (aragonite) shell. Shelled pteropods play a significant geochemical role 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. The likely effects of ocean acidification (resulting from the absorption of increasing quantities of CO2 from the atmosphere) have been studied in a variety of shell-building marine organisms, including L. helicina, which may be especially vulnerable as a result of its aragonite shell and its distribution in polar oceans, which acidify especially quickly due to their particular chemical and physical characteristics. (Comeau et al. 2010 and references therein; Hunt et al. 2010)

Although L. helicina was formerly believed to have a bipolar distribution, further investigation has shown that the Arctic and Antarctic forms are genetically distinct species. Traditionally, northern and southern hemisphere forms were recognized as subspecies and referred to as L. h. helicina and L. h. antarctica, respectively. Three morphotypes, or "forma", of the subspecies L. h. helicina have often been recognized (acuta, helicina, and pacifica) along with two morphotypes of L. h. antarctica (antarctica and rangi). However, genetic studies have revealed that L. h. helicina and L. h. antarctica differ by around 34% in mitochondrial COI sequence, far more divergence than would be seen intraspecifically. Sequence data are not yet available to help clarify the taxonomic status of the various morphotypes, which may or may not actually be genetically distinct. (Hunt et al. 2010)

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Biology

The most common shelled pteropod of arctic waters
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Foot modified into a pair of large pad-shapped lobes; Body often darkly pigmented; Left coiled shell with depressed spire; 5 to 6 transparent, striated shell whorls; Several subspecies and forms recognized, with differing shell shape and differeing polar/subpolar distribution
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Distribution

Greenland, South and North slope of Anticosti Island, Laurentian Channel (bathyal zone)(=Honguedo Strait), northern Gaspe waters, Magdalen Islands (from Eastern Bradelle valley to the west, as far as Cape North, including the Cape Breton Channel), Prince Edward Island (from the northern tip of Miscou Island, N.B. to Cape Breton Island south of Cheticamp, including the Northumberland Strait and Georges Bay to the Canso Strait causeway), middle North Shore (from Sept- Iles to Cape Whittle including the Mingan Islands), southern Gaspe waters (Baie des Chaleurs, Gaspe Bay to American, Orphan and Bradelle banks; eastern boundary: eastern Bradelle Valley), lower north Shore, Laurentian Channel (bathyal zone) to the northeast of Anticosti Island (=Jacques Cartier Strait), Laurentian Channel (bathyal zone)(=Esquiman Channel), lower Laurentian Channel (bathyal zone as far as Cabot Strait: Cape North, N.S., St. Paul Island to Cape Ray, NL.); western slope of Newfoundland, including the southern part of the Strait of Belle Isle but excluding the upper 50m in the area southwest of Newfoundland
  • North-West Atlantic Ocean species (NWARMS)
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Ecology

Habitat

upper epipelagic and glacial
  • North-West Atlantic Ocean species (NWARMS)
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Depth range based on 2045 specimens in 2 taxa.
Water temperature and chemistry ranges based on 1521 samples.

Environmental ranges
  Depth range (m): 0 - 1800
  Temperature range (°C): -1.883 - 10.476
  Nitrate (umol/L): 0.007 - 43.962
  Salinity (PPS): 22.208 - 35.068
  Oxygen (ml/l): 0.499 - 9.319
  Phosphate (umol/l): 0.055 - 3.251
  Silicate (umol/l): 1.537 - 145.708

Graphical representation

Depth range (m): 0 - 1800

Temperature range (°C): -1.883 - 10.476

Nitrate (umol/L): 0.007 - 43.962

Salinity (PPS): 22.208 - 35.068

Oxygen (ml/l): 0.499 - 9.319

Phosphate (umol/l): 0.055 - 3.251

Silicate (umol/l): 1.537 - 145.708
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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Panarctic, bipolar and subpolar; Epipelagic (shallow dwelling); Often found in swarms
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Trophic Strategy

Mucus nets are produced on foot-wings to trap phytoplankton and small particles; Net is periodically eaten to acquire the food stuck to it; Animals must regularly swim upward to offset their sinking
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Life History and Behavior

Life Cycle

protandrous hermaphrodite (males first, then females later); Spermatophores used for sperm transfer; Eggs are released in ribbons early spring and hatch into ciliated veligers; Generation times thought to be 1 year in the arctic and perhaps 2 per year in the subarctic
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Molecular Biology and Genetics

Molecular Biology

Barcode data: Limacina helicina

The following is a representative barcode sequence, the centroid of all available sequences for this species.


There are 8 barcode sequences available from BOLD and GenBank.

Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.

See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

ACTTTATATATAATCTTTGCAATATTTATGGGTTTAGTAGGGTTTAGTTATTCAATTATAATTCGTTTAAATTGCATTTGAATA------TTTTTAAGTGGA------CAACTATATAATGTAATTGTAACTAATCATGCATTAATTATAATTTTCTTTTTTATTATACCAATAGTAATTGGAGGATTTGGGAATTGAATATTACCTTTATATTTAAACATCCCAGATATAATTTTTCCTCGTTTAAATAACTTAAGTTTTTGATTGTTACCTTGTTCATTCTTAATACTAGTAATTTCATCTATAATAAGAATAGGCGCAGGATTAGGATGAACTATATACCCACCATTAAGT---AATATAGGTCACATAACTCAAAGAGTAGATTTTTGTATTTTTTCATTACATTTAGCAGGTTTATCATCAATTATTGGGGCAATCAACATAATTACAACAATTATAGTAAGACGTTCAAAAATAATAACACTATCTCGAATAAGATTATATTTATGAAGAATATTAATTACTTTAATTTTATTATTACTATCCTTACCTGTACTTGCAGGTGCTATCACAATACTATTACTAGATCGTAATTTTAACACTACATTTTTTGATCCTGTAGGAGGAGGTGATCCAATCTTATTTCAACATCTATTT
-- end --

Download FASTA File

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Statistics of barcoding coverage: Limacina helicina

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 2
Specimens with Barcodes: 24
Species With Barcodes: 1
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Genomic DNA is available from 1 specimen with morphological vouchers housed at State Herbarium of South Australia
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Wikipedia

Limacina helicina

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).[7][8]

Limacina helicina is a keystone species of mesozooplankton in Arctic pelagic ecosystems.[9][10][11]

The first written record of this species was by Friderich Martens from Spitsbergen in 1675.[12][13] 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.[1]

Limacina helicina is the type species of the genus Limacina.[14]

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.[11][15]

Subspecies[edit]

Limacina helicina has been recognised as a species complex comprising two sub-species and at least five forms.[15] 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).[15] It is also known as Limacina helicina rangii (d'Orbigny, 1835).[16] 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.[15]

However, at the species level the geographical distribution is considered to be bipolar, as it occurs in both the Arctic and Antarctic oceans.[15] Remigio and Hebert (2003)[19] provided initial evidence for the genetic separation of Limacina helicina helicina and Limacina helicina antarctica.[15] Hunt et al. (2010)[15] 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.[15] 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.[15] Subspecies Limacina helicina antarctica Woodward, 1854 can be considered as a separate species Limacina antarctica Woodward, 1854.[16] 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.[15] Also there is different structure of the shell between Limacina helicina and Limacina antarctica.[9]

Distribution[edit]

The type locality of Limacina helicina is "Arctic seas".[1] Limacina helicina is the only thecosome pteropod in Arctic waters.[11]

The distribution of Limacina helicina is arctic and subarctic (subpolarpolar)[20] especially in the Arctic Ocean and countries include:

Description[edit]

Drawing of part of Limacina helicina from ventral view shows parapodia, anterior lobe of the parapodia, lower part of the foot and foldings on the ventral side of the foot.
Detailed drawing of the same ventral view.

Limacina helicina has wing-like parapodia which evolved from the original gastropod foot (as is the case in all other pteropods).[11]

In this species, the color of the soft parts is dark purple or violet, with paler pellucid (translucent) parapodia.[24]

Dorsal view.
Left lateral view.
Frontal view.

The shell is sinistral, subglobose, subdiscoidal,[25] hyaline and very thin. The spire is depressed[25][26] but it can be considered rather high in comparison of other Limacina species.[21] The shell has 5-6 transversally striated whorls.[21][26] The suture is distinct.[21] The last whorl is large and with very obscure keel next to its umbilicus.[21][25] The shell has a wide umbilicus.[21] The aperture is higher than it is wide.[21]

The width of the shell is 5–10 mm[10] or up to 13 mm.[13] The height of the shell is up to 6 mm (when maximum width was 8 mm).[21]

Apical view.
Apertural view.
Umbilical view.

Adult specimens in the genus Limacina have usually lost the operculum.[21]

The radula consist of 10 rows.[24] Each row consist of one central tooth and two lateral teeth.[24] The Digestive system also includes an esophagus, gizzard sac and gut.[13]

Drawing of the whole radula. Magnified 60×.
Detail of radula showing 3 rows of teeth. Magnified 190×.

Ecology[edit]

Habitat[edit]

Live Limacina helicina. The white rectangle shows the shell opening, the area where Comeau et al. (2009)[10] studied the effect of ocean acidification.

Pteropods are strict pelagic mollusks that are highly adapted to life in the open ocean.[11] They are actively swimming in the water. Limacina helicina is a holoplanktonic species. Habitat of Limacina helicina is upper epipelagic and glacial.[16] It lives in temperatures from -0.4 °C to +4.0 °C or rarely up to 7 °C.[27]

Vertical distribution is affected by the size and also by other factors.[28] Limacina helicina of the size from 0.2 to 0.4 mm lives mainly in depths from 0 m to 50 m.[28] Larger pteropods lives from 0 m to 150 m.[28] For example Gilmer & Harbison (1991)[13] have found larger specimen of Limacina helicina to occur mainly in depths 5–25 m with abundance up to 2.5 adults in m3.[13] They do not occur much in upper 4 m probably because of turbulence.[13]

Already Constantine John Phipps mentioned its "innumerable quantities" in arctic seas in 1774.[1] Limacina helicina is a major component of the polar zooplankton.[15] It can comprise >50% of total zooplankton abundance (number of individuals per unit volume).[15]

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.[11] The aragonitic composition of the shell makes it very sensitive to dissolution.[11] Aragonite is a metastable form of calcium carbonate and it is more soluble in seawater than calcite.[10] Because of its highly soluble[11] 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.[15] As a key indicator of the acidification process, and a major component of polar ecosystems, Limacina helicina has become a focus for acidification research.[15] Based on labolatory experiments, they are able to precipitate calcium carbonate at low aragonite saturation state.[11] Limacina helicina seems to be relatively more resilient to elevated concentration of carbon dioxide (CO2) than other aragonitic organisms such as corals.[11] 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.[10][11] A decline of pteropod populations would likely cause dramatic changes to various pelagic ecosystems.[10][11] 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.[10][11][15]

Researchers found 24-53% individuals of Limacina helicina with shells damaged by dissolution off the U.S. West Coast in 2011.[29]

Feeding habits[edit]

They produce large mucus webs to filter-feed on phytoplankton but also small zooplankton.[11] They eat the web with the captured prey and then re-reproduce a web net.[26] The web is large and spherical[30] and it is difficult to see during the day because of diffuse reflection.[13] Webs are easier to see at night.[13] Limacina helicina is easily disturbed (like all other Thecosomata); when disturbed, it retracts into its shell and destroys its web.[13] Gilmer & Harbison (1991)[13] have assumed, that Limacina helicina feeds while motionless (without actively swimming).[13] Its web enables them neutral buoyancy or allow them slow sinking only.[30]

Limacina helicina it plays a significant ecological role as a phytoplankton grazer.[15] Limacina helicina is obligate ciliary feeder.[28] Gilmer & Harbison (1991)[13] hypothetized, that Limacina helicina are "web trappers", who are also chemically attracting its motile prey.[13]

Major parts of the food of Limacina helicina include tintinnid (Tintinnida), small crustaceans - copepods (Copepoda) and juvenile specimen of its own species (cannibalism).[13] Danish zoologist Johan Erik Vesti Boas reported diatoms (Bacillariophyceae), dinoflagellates (Dinoflagellata) and tintinnids in the digestive system of Limacina helicina in 1888 already.[31] Diatoms and dinoflagellates appear to pass the digestive system of adults largely intact.[8][13] 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.[13] All experiments performed on Limacina helicina in the laboratory were done on starved specimens, because they do not feed in unnatural conditions.[13]

Gilmer & Harbison (1991)[13] also suggested that smaller specimens may be herbivores feeding preferentially on phytoplankton and protozoans and that larger specimens became omnivores.[13]

Life cycle[edit]

Limacina helicina is a protandric hermaphrodite.[8][28] Males are smaller, at sizes of 4–5 mm[8] and then they change to females, which are larger than 5 mm.[8] Sperm is transferred by spermatophores during copulation.[32] They lay eggs in ribbon-like clusters[8] mainly in summer, but also a little in winter.[28]

The size of the veliger larvae is about 0.15 mm.[26] When animals reached 0.7 mm in size, gonads have been detected in them.[28] Fully mature individuals are 0.8 mm in size.[28]

The life cycle of Limacina helicina lasts about 1 year[8] or 1.5–2 years.[28]

Predators[edit]

Limacina helicina plays an important role in the marine food web as a major dietary component for predators such as large zooplankton, herring Clupea sp.,[22] chum salmon Oncorhynchus keta,[22] pink salmon Oncorhynchus gorbuscha,[22] rorquals,[22][27] Phoca hispida[27] and other seals[27] and birds.[11]

The pteropod Clione limacina feeds only on the genus Limacina: on Limacina helicina and on Limacina retroversa.[32][33] Also the pteropod Paedoclione doliiformis feeds on those two species only, but solely on juveniles with shells smaller than 1 mm.[32]

See also[edit]

References[edit]

This article incorporates CC-BY-2.5 text from the reference [11][15] and public domain text from the reference [25]

  1. ^ a b c d Phipps C. J. (1774). A Voyage towards the North Pole undertaken by His Majesty's Command 1773. J. Nourse, London, viii + 253 pp. Page 195.
  2. ^ (Latin) Fabricius O. (1780). Fauna Groenlandica systematice sistens animalis Groenlandiae occidentalis hactenus indagata. Hafniae et Lipsiae. J. G. Rothe pp. XVI + 452 + 1 pl. Page 386-388.
  3. ^ (French) Lamarck J.-B. (1819). Histoire naturelle des animaux sans vertèbres. Paris. Volume 6. page 291.
  4. ^ (French) de Blainville H. M. D. (1824). In: Cuvier F. (ed.). (1804-1845). Dictionnaire des Sciences Naturelles dans lequel on traite méthodiquement des différens êtres de la nature. Levrault, Strasbourg & Paris, and Le Normant, Paris, 32: page 284.
  5. ^ a b (German) Meisenheimer J. (1906). Die Pteropoden der deutschen Sud-polar Expedition 1901-1903. In: Deutsche Sudpolar-Expedition 1901-1903. 9 (Zool.), 1(2): 92-152, pl. 5-7. page 96-98. Plate 5, figure 1 a-b, 3.
  6. ^ "Limacina helicina (Phipps, 1774)". CLEMAM, accessed 29 January 2011.
  7. ^ Bouchet P. & Gofas S. (2011). Limacina helicina (Phipps, 1774). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=140223 on 2011-02-07
  8. ^ a b c d e f g Gannefors, C.; Böer, M.; Kattner, G.; Graeve, M.; Eiane, K.; Gulliksen, B. R.; Hop, H.; Falk-Petersen, S. (2005). "The Arctic sea butterfly Limacina helicina: Lipids and life strategy". Marine Biology 147: 169. doi:10.1007/s00227-004-1544-y. 
  9. ^ a b Sato-Okoshi, W.; Okoshi, K.; Sasaki, H.; Akiha, F. (2010). "Shell structure of two polar pelagic molluscs, Arctic Limacina helicina and Antarctic Limacina helicina antarctica forma antarctica". Polar Biology 33 (11): 1577. doi:10.1007/s00300-010-0849-1. 
  10. ^ a b c d e f g h Comeau, S.; Gorsky, G.; Jeffree, R.; Teyssié, J. -L.; Gattuso, J. -P. (2009). "Impact of ocean acidification on a key Arctic pelagic mollusc (Limacina helicina)". Biogeosciences 6 (9): 1877. doi:10.5194/bg-6-1877-2009. 
  11. ^ a b c d e f g h i j k l m n o p Comeau, S.; Jeffree, R.; Teyssié, J. L.; Gattuso, J. P. (2010). Stepanova, Anna, ed. "Response of the Arctic Pteropod Limacina helicina to Projected Future Environmental Conditions". PLoS ONE 5 (6): e11362. doi:10.1371/journal.pone.0011362. PMC 2894046. PMID 20613868. 
  12. ^ (German) Martens F. (1675). Spitzbergische oder Groenlandische Reise Beschreibung gethan im Jahr 1671. Schultzen, Hamburg. page 110
  13. ^ a b c d e f g h i j k l m n o p q r s Gilmer R. W. & Harbison G. R. (1991). "Diet of Limacina helicina (Gastropoda: Thecosomata) in Arctic waters in midsummer". Marine Ecology Progress Series 77: 125-134. PDF.
  14. ^ Janssen A. W. (2007). "Holoplanktonic Mollusca (Gastropoda: Pterotracheoidea, Janthinoidea, Thecosomata and Gymnosomata) from the Pliocene of Pangasinan (Luzon, Philippines)". Scripta Geologica 137 http://www.scriptageologica.nl/07/nr135/a02
  15. ^ a b c d e f g h i j k l m n o p q Hunt, B.; Strugnell, J.; Bednarsek, N.; Linse, K.; Nelson, R. J.; Pakhomov, E.; Seibel, B.; Steinke, D.; Würzberg, L. (2010). Finkel, Zoe, ed. "Poles Apart: The "Bipolar" Pteropod Species Limacina helicina is Genetically Distinct Between the Arctic and Antarctic Oceans". PLoS ONE 5 (3): e9835. doi:10.1371/journal.pone.0009835. PMC 2847597. PMID 20360985. 
  16. ^ a b c d e f g Bouchet, P.; Gofas, S. (2011). Limacina helicina (Phipps, 1774). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=140223 on 2011-01-29
  17. ^ Spoel S. van der (1967). "Euthecosomata, a group with remarkable developmental stages (Gastropoda, Pteropoda)". J. Noorduyn and Zn, Gorinchem, 375 pp.
  18. ^ Dall W. H. (1871). "Descriptions of sixty new forms of mollusks from the west coast of North America and the north Pacific Ocean, with notes on others already described". American Journal of Conchology 7(2): 93-160, plates 13-16. Pages 138-139.
  19. ^ Remigio, E.; Hebert, P. D. (2003). "Testing the utility of partial COI sequences for phylogenetic estimates of gastropod relationships". Molecular Phylogenetics and Evolution 29 (3): 641–647. doi:10.1016/S1055-7903(03)00140-4. PMID 14615199. 
  20. ^ Orr, J. C.; Fabry, V. J.; Aumont, O.; Bopp, L.; Doney, S. C.; Feely, R. A.; Gnanadesikan, A.; Gruber, N.; Ishida, A.; Joos, F.; Key, R. M.; Lindsay, K.; Maier-Reimer, E.; Matear, R.; Monfray, P.; Mouchet, A.; Najjar, R. G.; Plattner, G. K.; Rodgers, K. B.; Sabine, C. L.; Sarmiento, J. L.; Schlitzer, R.; Slater, R. D.; Totterdell, I. J.; Weirig, M. F.; Yamanaka, Y.; Yool, A. (2005). "Anthropogenic ocean acidification over the twenty-first century and its impact on calcifying organisms". Nature 437 (7059): 681–686. doi:10.1038/nature04095. PMID 16193043.  PDF. (author's draft).
  21. ^ a b c d e f g h i j k l m n o p Spoel S. van der (1972). "Pteropoda Thecosomata". Zooplankton, Conseil International Pour L’Exploration de la Mer, sheet 140-142.
  22. ^ a b c d e Wing B. (not dated). "Auke Bay Laboratory (ABL). Ocean Carrying Capacity Program. Unusual Observations of Fish and Invertebrates From the Gulf of Alaska, 2004-05". accessed 29 January 2011.
  23. ^ Hermans C. O. & Satterlie R. A. (1992). "Fast-Strike Feeding Behaviour in a Pteropod Mollusk, Clione limacina Phipps". The Biological bulletin, Marine Biological Laboratory, 182: 1-7.
  24. ^ a b c (Latin) (Norwegian) Sars G. O. (1878). Bidrag til kundskaben om norges arktiske fauna. I. Mollusca regonis arcticae Norwegiae. Oversigt over de i norges arktiske region forekommende bløddyr. Christiania, Brøgger. pages 328-329, Plate 29, figure 1. Plate 16, figure 17.
  25. ^ a b c d Tryon G. W. (1873). American marine conchology: or, Descriptions of the shells of the Atlantic coast of the United States from Maine to Florida. Philadelphia. page 121-122. plate 14, figure 253.
  26. ^ a b c d Hopcroft R. (created 31 January 2009). "Sea Butterfly: Limacina helicina (Phipps, 1774)". Arctic Ocean biodiversity, accessed 30 January 2011.
  27. ^ a b c d "Limacina helicina helicina helicina". Marine Species Identification Portal, accessed 8 February 2011.
  28. ^ a b c d e f g h i Kobayashi, H. A. (1974). "Growth cycle and related vertical distribution of the thecosomatous pteropod Spiratella (?Limacina?) helicina in the central Arctic Ocean". Marine Biology 26 (4): 295–301. doi:10.1007/BF00391513. 
  29. ^ Bednaršek N., Feely R. A., Reum J. C. P., Peterson B., Menkel J., Alin S. R. & Hales B. (2014). "Limacina helicina shell dissolution as an indicator of declining habitat suitability owing to ocean acidification in the California Current Ecosystem". Proceedings of the Royal Society B 281(1785). doi:10.1098/rspb.2014.0123.
  30. ^ a b Gilmer, R. W.; Harbison, G. R. (1986). "Morphology and field behavior of pteropod molluscs: Feeding methods in the families Cavoliniidae, Limacinidae and Peraclididae (Gastropoda: Thecosomata)". Marine Biology 91: 47. doi:10.1007/BF00397570. 
  31. ^ (Danish) Boas J. E. V. (1888). "Spolia Atlantica. Bidrag til Pteropodernes. Morfologi og Systematik samt til Kundskaben om deres geografiski Udbredelse". Det Kongelige Danske videnskabernes selskabs skrifter. København, serie 6, number 4: 1-231. Page 33, 40-43. Plate 5, figure 69-70.
  32. ^ a b c Lalli C. M. & Gilmer R. W. (1989). Pelagic Snails. The biology of holoplanktonic gastropod molluscs. Stanford University Press: Stanford, California. page 185, 188.
  33. ^ Böer, M.; Gannefors, C.; Kattner, G.; Graeve, M.; Hop, H.; Falk-Petersen, S. (2005). "The Arctic pteropod Clione limacina: Seasonal lipid dynamics and life-strategy". Marine Biology 147 (3): 707. doi:10.1007/s00227-005-1607-8. 

Further reading[edit]

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