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Arion circumscriptus

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Arion circumscriptus
Arion circumscriptus partially retracted
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Mollusca
Class: Gastropoda
Order: Stylommatophora
Family: Arionidae
Genus: Arion
Subgenus: Arion (Carinarion)
Species:
A. circumscriptus
Binomial name
Arion circumscriptus

Arion circumscriptus, common name brown-banded arion, is a species of air-breathing land slug, a terrestrial pulmonate gastropod mollusk in the family Arionidae. It is commonest in woodland, occurring across most of Europe, except for more southern regions, and is also widespread in North America. It has been argued that A. circumscriptus is best considered a colour morph of Arion fasciatus.

Taxonomy

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The subgenus Carinarion Hesse, 1926[2] contains three species—Arion fasciatus, Arion silvaticus and Arion circumscriptus—distinguished on the basis of small differences in pigmentation and in proportions of their genital anatomy.[3][4] Further study of these morphospecies (typological species) revealed that their body colour may be influenced by diet, and that the putative genital differences do not consistently agree with identifications based on pigmentation and allozymes.[5][6] In much of their range these slugs predominantly self-fertilise, leading to distinct genetic strains and thus generating associations between coloration and other phenotypic characters. However, in other regions of Europe where these slugs more often outcross there was evidence of hybridization between strains, contradicting their status as biological species.[7] Moreover, sequencing of mitochondrial DNA revealed that the inferred phylogeny did not match an arrangement in which the three morphologically recognised species form distinct clades.[8]

The suggestion from that work was to treat all three Carinarion taxa as a single species, and this has been followed by recent French literature.[9][10] The name Arion fasciatus then has priority. However, in Britain A. fasciatus s.s. is more distinct than the other two taxa both morphologically and genetically, so that recent British literature considers A. silvaticus as part of A. circumscriptus s.l., but retains A. fasciatus s.s. as distinct even though these taxa may occasionally hybridise.[11] Arion circumscriptus circumscriptus and Arion circumscriptus silvaticus have then been considered as subspecies.[12] Others still consider the situation unresolved and provisionally retain the original three species.[13]

Before the taxonomic work of Lohmander in 1937[14] and Waldén in 1955,[15] and even for some years following, the different species of Carinarion were not distinguished and the name Arion circumscriptus was used to cover all forms.[16][17]

Description and identification

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Like with other Arion species, the pneumostome lies in the anterior half of the mantle, and the back is round in cross-section rather than with a keel.[18][19] However, the subgenus Carinarion is distinguished by a row of paler tubercles along the midline of the back, giving the impression of a keel; this is less prominent in adults.[20] Another feature of Carinarion is that the cross-section is bell-shaped, with splayed-out rather than inward-curving sides.[21] The overall colour of A. circumscriptus is a monochrome dark grey (sometimes with a tinge of blue or brown), with a darker dorsal band and a darker lateral band along each side, the one on the right running above the pneumostome. The flanks below are paler. The sole is white or pale grey, and the mucus colourless, or sometimes pale yellow.[22][23] Length reaches 40 mm, or some say up to 50 mm.[22][20]

Several characters have been proposed to distinguish the species within Carinarion, but note the evidence that they should better all be considered colour morphs of one species (see Taxonomy section). Arion fasciatus is distinguished by reaching a larger size and by the yellow or orange flush below the lateral band (which disappears in alcohol),[6] but the other two Carinarion species may also show faint yellow coloration.[21] Dark flecks on the mantle distinguish A. circumscriptus from A. silvaticus and A. fasciatus, and the flanks of A. silvaticus are brighter but with a slightly broader lateral band.[22] Internally, only A. circumscriptus shows strong pigmentation on the epiphallus.[22][20] Classical morphological distinctions based on size of the atrium, epiphallus and oviduct have not been supported when quantitative measurements are compared against identifications based on pigmentation and allozymes.[6] Since the species are predominantly self-fertilizing, amongst the genetic strains present in a local area certain characters may be consistently associated with one another, yet in another area, with different genetic strains, the same characters may not agree.[6]

Life cycle

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A study in southern England found that adults were present from January to July, with some of these maturing only as late as May; later maturing adults were smaller than those maturing earlier in the year. Few individuals were found above ground over the dry summer months, but otherwise immature animals of a wide range of sizes were present throughout the year. In late summer and autumn many immature animals were already of adult mass. The life cycle was predominantly annual, but some animals may have taken 18 months to mature.[24] The life cycle appears similar in a study in Moscow gardens, although slightly delayed there by the Russian winter.[25] A study in Michigan grassland also found adults most abundant in spring and summer.[26]

Arion circumscriptus reproduces predominantly by self-fertilization, leading to inbred genetic strains, but the presence of rare heterozygotes demonstrates that mating does occasionally result in outcrossing. The incidence of outcrossing is higher in Central Europe than in North-west Europe.[7]

Habitat and distribution

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Arion circumscriptus is most typical of broadleaved woods in temperate climates, occurring in the litter layer, under dead wood and under bark; it sometimes also occurs in other habitats of cultivated land, such as roadsides and waste ground.[27][28] It is only occasional in gardens and not considered a pest.[27][22][29] It occurs up to an altitude of 1300 m in Switzerland.[28]

The species is widespread and common across North-West, Central and Eastern Europe, including southern Scandinavia (naturally to 62° in Sweden, further north still in gardens;[30] also in Iceland).[31] To the east it occurs in Ukraine[32] and as far as the Vyatka river basin and north Caucasus in Russia.[33] But it is absent in southern Europe (e.g. in the Iberian Peninsula[34] and Greece;[35] only present in northern part of Italy).[36] In the Czech Republic re-identifications have led to it being considered much less common than once thought.[20] In contrast, there has been a real decline in Austria, where it has been assessed as vulnerable.[37]

As an introduction, A. circumscriptus is widespread in the U.S.A. and Canada on both sides of the continent, spreading from gardens into natural habitats.[38]

Parasites

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Parasites of Arion circumscriptus include:

References

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  1. ^ Johnston, G. (1828). "A few remarks on the class Mollusca, in Dr Fleming's work of British animals; with descriptions of some new species". Edinburgh New Philosophical Journal. April–September 1828: 74–81.
  2. ^ Hesse, P. (1926). "Die Nacktschnecken der palaearktischen Region". Abhandlungen des Archivs für Molluskenkunde. 2 (1): 1–152.
  3. ^ Kermey, M.P.; Cameron, R.A.D. (1979). A field guide to the landsnails of Britain and North-west Europe. London: Collins.
  4. ^ Backeljau, T.; De Bruyn, L. "Notes on Arion hortensis s.l. and A. faciatus s.l. in Denmark (Gastropoda: Pulmonata)". Apex. 4: 41–48.
  5. ^ Jordaens, K. (1 May 2001). "Food-induced body pigmentation questions the taxonomic value of colour in the self-fertilizing slug Carinarion spp". Journal of Molluscan Studies. 67 (2): 161–167. doi:10.1093/mollus/67.2.161.
  6. ^ a b c d Jordaens, K.; Van Dongen, S.; Van Riel, P.; Geenen, S.; Verhagen, R.; Backeljau, T. (20 April 2002). "Multivariate morphometrics of soft body parts in terrestrial slugs: comparison between two datasets, error assessment and taxonomic implications". Biological Journal of the Linnean Society. 75 (4): 533–542. doi:10.1046/j.1095-8312.2002.00040.x.
  7. ^ a b Jordaens, Kurt; Geenen, Sofie; Reise, Heike; van Riel, Patrick; Verhagen, Ron; Backeljau, Thierry (December 2000). "Is there a geographical pattern in the breeding system of a complex of hermaphroditic slugs (Mollusca: Gastropoda: Carinarion)?". Heredity. 85 (6): 571–579. doi:10.1046/j.1365-2540.2000.00793.x. PMID 11240623. S2CID 30062359.
  8. ^ Geenen, Sofie; Jordaens, Kurt; Backeljau, Thierry (4 December 2006). "Molecular systematics of the Carinarion complex (Mollusca: Gastropoda: Pulmonata): a taxonomic riddle caused by a mixed breeding system". Biological Journal of the Linnean Society. 89 (4): 589–604. doi:10.1111/j.1095-8312.2006.00693.x.
  9. ^ Gargominy, O.; Prie, V.; Bichain, J.-M.; Cucherat, X.; Fontaine, B. (2011). "Liste de référence annotée des mollusques continentaux de France" (PDF). MalaCo. 7: 307–382. Retrieved 2021-03-13.
  10. ^ Audibert, C.; Bertrand, A. (2015). Guide des mollusques terrestres : escargots et limaces. Paris: Belin. ISBN 9782701151649.
  11. ^ Rowson, Ben; Anderson, Roy; Turner, James A.; Symondson, William O. C. (16 April 2014). "The slugs of Britain and Ireland: undetected and undescribed species increase a well-studied, economically important fauna by more han 20%". PLOS ONE. 9 (4): e91907. Bibcode:2014PLoSO...991907R. doi:10.1371/journal.pone.0091907. PMC 3989179. PMID 24740519.
  12. ^ Rowson, B.; Turner, J.; Anderson, R.; Symondson, B. (2014b). Slugs of Britain and Ireland: identification, understanding and control. Telford: Field Studies Council. ISBN 9781908819130.
  13. ^ Welter-Schultes, F.; Audibert, C.; Bertrand, A. (2011). "Liste des mollusques terrestres et dulcicoles de France continentale (excl. hydrobioïdes)". Folia Conchyliologica. 12: 4–44.
  14. ^ Lohmander, H. (1937). "Über die nordischen Formen von Arion circumscriptus Johnston". Acta Societatis Pro Fauna et Flora Fennica. 60: 90–112.
  15. ^ Waldén, H.W. (1955). "The land Gastropoda of the vicinity of Stockholm". Arkiv för Zoologi. 7: 391–448.
  16. ^ Ellis, A.E. (1926). British snails—a guide to the non-marine Gastropoda of Great Britain and Ireland, Pliocene to Recent (with illustrations by R. A. Ellis). Oxford: Clarendon Press.
  17. ^ Quick, H.E. (1949). Synopses of the British fauna. No. 8—Slugs (Mollusca) (Testacellidae, Arionidae, Limacidae). London: The Linnean Society.
  18. ^ "Arion fasciatus group: Arion circumscriptus". Terrestrial Mollusc Tool. University of Florida. Retrieved 20 February 2013.
  19. ^ "Arion circumscriptus Johnston, 1828 Brown-banded Arion". Evergreen State College. Retrieved 20 February 2013.
  20. ^ a b c d Horsák, M.; Juřičková, L.; Picka, J. (2013). Měkkýši České a Slovenské republiky = Molluscs of the Czech and Slovak Republics (1st ed.). Zlín: Nakladatelství Kabourek. ISBN 9788086447155.
  21. ^ a b Cameron, R.A.D.; Eversham, B.; Jackson, N. (1983). "A field key to the slugs of the British Isles". Field Studies. 5: 807–824.
  22. ^ a b c d e Rowson, B.; Turner, J.; Anderson, R.; Symondson, B. (2014). Slugs of Britain & Ireland : identification, understanding and control (First ed.). Telford: Field Studies Council. ISBN 9781908819130.
  23. ^ Anderson, R. "Arion (Carinarion) circumscriptus Johnston 1828 Forest slug". MolluscIreland. National Museums Northern Ireland. Retrieved 20 March 2021.
  24. ^ Hutchinson, John M.C.; Reise, Heike; Skujienė, Grita (2017). "Life cycles and adult sizes of five co-occurring species of Arion slugs". Journal of Molluscan Studies. 83 (1): 88–105. doi:10.1093/mollus/eyw042.
  25. ^ Burenkov, M.S. (1977). "Population age structure of three slug species (Order Stylommatophora, subclass Pulmonata) [In Russian]". Jurnal Obshej Biologii. 38: 296–304.
  26. ^ Getz, L.L. (1959). "Notes on the ecology of slugs: Arion circumscriptus, Deroceras reticulatum, and D. laeve". American Midland Naturalist. 61 (2): 485–498. doi:10.2307/2422516. JSTOR 2422516.
  27. ^ a b Kerney, M. P. (1999). Atlas of the land and freshwater molluscs of Britain and Ireland. Colchester, Essex: Harley Books. ISBN 0946589488.
  28. ^ a b Boschi, Cristina (2011). Die Schneckenfauna der Schweiz ein umfassendes Bild- und Bestimmungsbuch. Bern: Haupt. ISBN 9783258076973.
  29. ^ Ludwig, A.; Reise, H.; Hutchinson, J.M.C. (2015). "Die Nacktschneckenfauna in Gärten der Stadt Görlitz (Sachsen, Deutschland)" (PDF). Berichte der naturforschenden Gesellschaft der Oberlausitz. 23: 43–57.
  30. ^ von Proschwitz, T. "Gråsidig skogssnigel Vetenskapligt artnamn Arion circumscriptus". Artfakta. Sveriges lantbruksuniversitet. Retrieved 19 March 2021.
  31. ^ Ólafsson, E. "Rákasnigill (Arion circumscriptus)". Icelandic Institute of Natural History. Retrieved 19 March 2021.
  32. ^ Gural-Sverlova, N.V.; Gural, R.I. (2016). "New findings of the slugs Arion distinctus and Arion circumscriptus (Arionidae) in the territory of Ukraine". Ruthenica (in Russian). 26 (1): 17–23.
  33. ^ Sysoev, A.; Schileyko, A. (2009). Land snails and slugs of Russia and adjacent countries. Sofia, Bulgaria: Pensoft Publishers. ISBN 9789546424747.
  34. ^ Cadevall, J.; Orozoco, A. (2016). Caracoles y babosas de la Península Ibérica y Baleares. Barcelona: Omega. ISBN 9788428215992.
  35. ^ Wiktor, A. (2001). The slugs of Greece (Arionidae, Milacidae, Limacidae, Agriolimacidae - Gastropoda, Stylommatophora) = Gymnosaligkaria tēs Elladas (Arionidae, Milacidae, Limacidae, Agriolimacidae - Gasteropoda, Pneymonophora. Irakleio, Crete, Greece: Natural History Museum of Crete, University of Crete. ISBN 9603670057.
  36. ^ Manganelli, G.; Bodon, M.; Favilli, L.; Giusti, F. (1995). "Fascicolo 16. Gastropoda Pulmonata". In Minelli, A.; Ruffo, S.; La Posta, S. (eds.). Checklist delle specie della fauna italiana. pp. 1–60. Retrieved 19 March 2021.
  37. ^ Reischütz, A.; Reischütz, P.L. (2007). "Rote Liste der Weichtiere (Mollusca) Österreichs". In Zulka, P. (ed.). Rote Listen gefährdeter Tiere Österreichs. Checklisten, Gefährdungsanalysen, Handlungsbedarf. Teil 2. GrüneReihe des BLFUW. Wien: Böhlauverlag. pp. 363–343.
  38. ^ Grimm, F.W.; Forsyth, R.G.; Schueler, F.W.; Karstad, A. (2009). Identifying land snails and slugs in Canada : introduced species and native genera. Ottawa, Ont.: Canadian Food Inspection Agency. ISBN 9781100124391.
  39. ^ Michigan Department of Natural Resources and Environment. "Brainworm". accessed 14 December 2010.
  40. ^ Blaisdell, K.F. (1950). "Arion circumscriptus, a new intermediate host of the cat lungworm, Aelurostrongylus abstrusus". The Cornell Veterinarian. 40 (2): 197–200. PMID 15411797.
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