Radix auricularia

{{Short description|Species of gastropod}} {{Use dmy dates|date=January 2020}} {{Speciesbox | fossil_range= {{fossil range|Pleistocene|Recent}}<ref name="Baker"/> | image = Radix auricularia auricularia 01.JPG | image_caption = A shell of ''Radix auricularia'' | status = LC | status_system = IUCN3.1 | status_ref = <ref>{{cite iucn |last1=Seddon |first1=M. B. |last2=Van Damme |first2=D. |last3=von Proschwitz |first3=T. |last4=Madhyastha |first4=A. |year=2014 |title=''Radix auricularia'' |volume=2014 |article-number=e.T155568A42429613 |doi=10.2305/IUCN.UK.2014-1.RLTS.T155568A42429613.en |access-date=17 January 2015}}</ref> | status2 = G5 | status2_system = TNC | status2_ref = <ref name=NS>{{cite NatureServe |id=2.113646 |title=''Radix auricularia'' |access-date=18 March 2026}}</ref> | taxon = Radix auricularia | authority = (Linnaeus, 1758)<ref>Linnaeus C. (1758). ''Systema Naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis''. 10th edition. Vermes. Testacea: 700–781. Holmiae. (Salvius).</ref> | synonyms = * ''Helix auricularia'' Linnaeus, 1758 * ''Limnaea auricularia'' * ''Lymnaea auricularia'' (Linnaeus, 1758) * ''Radix (Radix) auricularia'' (Linnaeus, 1758) * † ''Radix (Radix) auricularia auricularia'' (Linnaeus, 1758) (subspecies rank sensu Wenz not accepted) * ''Radix auriculatus'' Montfort, 1810 (unnecessary substitute name for ''Helix auricularia'') }}

'''''Radix auricularia''''', the '''big-ear radix''', is a species of medium-sized freshwater snail, an aquatic pulmonate gastropod mollusk in the family Lymnaeidae.<ref name="WoRMS">Neubauer, Thomas A.; Rosenberg, G.; Gofas, S. (2014). Radix auricularia (Linnaeus, 1758). Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=248263 on 2014-11-17</ref>

''Radix auricularia'' is the type species of the genus ''Radix''.

==Forms== Forms of ''Radix auricularia'' include:<ref name="Glöer 2002"/> *''Radix auricularia'' f. ''tumida'' (Held, 1836) *''Radix auricularia'' f. ''subampla'' (Ehrmann, 1933)

==Shell description== left|thumb|Two shells of ''Radix auricularia''

The shell is thin, roundly ovate and very inflated, such that the last whorl comprises 90% of its volume.<ref name="Clarke">Clarke, A.H. 1981. ''The freshwater molluscs of Canada''. National Museum of Natural Sciences, National Museums of Canada, Ottawa, Canada. 447 pp.</ref><ref name="Jokinen"/><ref name="Peckarsky"/>

The shell has a rounded and broad spire that pinches in steeply at the apex. The spire is short and conic, and is very small compared with the body whorl.<ref name="Baker"/>

There are 4–5 whorls with deep sutures between them.<ref name="Clarke"/><ref name="Jokinen"/> The whorls are convex, inflated, smooth and rapidly increasing. The body whorl is large and spreading. The surface is shining, lines of growth are fine, wavy, crowded, with occasionally a heavy ridge representing a rest period. Sutures are deeply impressed, channeled in some specimens.<ref name="Baker"/>

The color of the shell is yellow, beige or tan.

The ear-shaped aperture, which contains no operculum, is around 5 times higher than the spire.<ref name="Jokinen">Jokinen, E. 1992. ''The Freshwater Snails (Mollusca: Gastropoda) of New York State''. The University of the State of New York, The State Education Department, The New York State Museum, Albany, New York 12230. 112 pp.</ref><ref name="Peckarsky">Peckarsky, B. L., P. R. Fraissinet, M. A. Penton and D. J. Conklin Jr. 1993. ''Freshwater Macroinvertebrates of Northeastern North America''. Cornell University Press, Ithaca, New York State. 442 pp.</ref><ref name="Mackie">Mackie, G. L., D. S. White and T. W. Zdeba. 1980. ''A guide to freshwater mollusks of the Laurentian Great Lakes with special emphasis on the genus Pisidium''. Environmental Research Laboratory, Office of Research and Development, U. S. Environmental Protection Agency, Duluth, Minnesota 55804. 144 pp.</ref> The aperture is very large, ovate, occupying four-fifths of the length of the entire shell. It is rounded above and flaring in old specimens below. The peristome is thin and sharp. The columella is sigmoid with a plait across the middle, which is reflected over the umbilicus.<ref name="Baker"/>

The umbilicus is either wide or covered. Usually the umbilicus is narrow, deep, nearly closed. The epidermis is sometimes marked by light and dark lines of color, alternating.<ref name="Baker"/>

The shell of the species can grow to ~30 mm in height<ref name="Jokinen"/> and 25 mm in width<ref name="Clarke"/> as a full grown adult. However, most individuals in a population only grow to approximately half the maximum size.<ref name="Clarke"/> The width of the shell is from 12 to 18 mm, and the height of the shell is 14–24 mm.<ref name="Glöer 2002">Glöer, P. 2002 ''Die Süßwassergastropoden Nord- und Mitteleuropas''. Die Tierwelt Deutschlands, ConchBooks, Hackenheim, 326 pp., {{ISBN|3-925919-60-0}}, page 213-214.</ref> The shell of ''Radix auricularia'' has a width to length ratio greater than 0.75.

==Anatomy== left|thumb|Drawing of a live ''Radix auricularia'' The body is flecked with small white spots on the back of the head and tentacles, but not on the foot.<ref name="Baker"/> The mantle is pigmented with a line of dark spots along its edge,<ref>Falniowski, A. 1980. ''Pigmentation of the mantle border in Polish representatives of the subgenus Radix (Lymnaeidae, Basommatophora, Gastropoda)''. Basteria 44(1–4):3–8.</ref> irregular spots which show through the shell. The foot is roundly elongated, 18 × 11 mm.<ref name="Baker"/><ref>For a detailed description of ''Radix auricularia'', including the radula and reproductive organs, see pages 179–183 in [https://archive.org/details/lymnidofnort00bakerich Baker F. C. ''The Lymnaeidae of North and Middle America, recent and fossil'' (1911). The Chicago Academy of Sciences.]</ref>

The head is broad, auriculated.<ref name="Baker"/> This species also has tentacles that are large, flat, lobate, triangular, fan-shaped and wider than they are high.<ref name="Baker"/><ref name="Jackiewicz">Jackiewicz, M. and R. Buksalewicz. 1998. ''Diversity in tentacle shape of European lymnaeid species (Gastropoda, pulmonata: Basommatophora)''. Biological Bulletin of Poznan 35(2):131–136.</ref>

The blood contains blue hemocyanin.<ref name="Jing">Jing, Z. 1983. ''Anatomy of the circulatory system of Radix auricularia''. Acta Zoologica Sinica 29(2):133–140.</ref> The heart pulsations are slow and regular: thirty-four per minute. The animal is slow and deliberate in its movements.<ref name="Baker"/>

==Distribution== === Indigenous distribution === ''Radix auricularia'' is native to Europe and most of the Palearctic including Oman, Tibet and Vietnam.<ref name="Jokinen"/>

In Europe it occurs in: * Croatia * Finland * Germany * Sweden * British Isles: Great Britain and Ireland * Netherlands * Poland * Czech Republic<ref name="Horsák 2010">{{in lang|cs}} Horsák M., Juřičková L., Beran L., Čejka T. & Dvořák L. (2010). "Komentovaný seznam měkkýšů zjištěných ve volné přírodě České a Slovenské republiky. [Annotated list of mollusc species recorded outdoors in the Czech and Slovak Republics]". ''Malacologica Bohemoslovaca'', Suppl. 1: 1–37. [http://mollusca.sav.sk/pdf/9/Suppl-1-v2.pdf PDF].</ref> * Slovakia<ref name="Horsák 2010"/> * and others

In Asia it occurs across the East Palearctic and in * Oman<ref name="Soliman 2008">Soliman M. F. M. (2008). "Epidemiological review of human and animal fascioliasis in Egypt". ''The Journal of Infection in Developing Countries'' '''2'''(3): 182–189. [http://www.jidc.org/index.php/journal/article/view/19738348 abstract]. [http://www.jidc.org/files/vol02_no03/PDF/jinfectdevelopingcountries-02-182.pdf PDF]{{dead link|date=April 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> * Vietnam – in northern Vietnam<ref name="Dung 2013">Dung B. T., Doanh P. N., The D. T., Loan H. T., Losson B. & Caron Y. (2013). "Morphological and Molecular Characterization of Lymnaeid Snails and Their Potential Role in Transmission of ''Fasciola'' spp. in Vietnam". ''Korean Journal of Parasitology'' '''51'''(6): 657–662. {{doi|10.3347/kjp.2013.51.6.657}}.</ref> * and others

===Nonindigenous distribution=== ''Radix auricularia'' is an introduced species in the United States and New Zealand.<ref name="USGS"/>

In the Mid-Atlantic Region it is found in the Charles River in Massachusetts, Cayuga Lake and the Hudson River in New York State, in various ponds in New Jersey, New York, and Pennsylvania, and in Lake Champlain in Vermont.<ref name="USGS"/>

In the Great Lakes Region: The first record of ''Radix auricularia'' in North America is from the Hudson River (which is connected through the New York Canal System to Lakes Erie and Ontario) near Troy, New York, before 1869.<ref name="Mills">Mills, E. L., J. H. Leach, J. T. Carlton and C. L. Secor. 1993. ''Exotic species in the Great Lakes: a history of biotic crises and anthropogenic introductions''. Journal of Great Lakes Research 19(1):1–54.</ref> The next record is from Lincoln Park, Chicago, beside Lake Michigan in 1901.<ref name="Mills"/> Subsequently, it was found in Lake Erie and a tributary stream in 1911 and in 1948, and in Lake Ontario in 1930.<ref name="Mills"/> It is also reported from Lake Huron.<ref name="Dundee">Dundee, D. S. 1974. ''Catalogue of introduced mollusks of eastern North America (north of Mexico)''. Sterkiana 55:1–37.</ref>

In 2019, ''Radix auricularia'' was recorded in Botswana and South Africa.<ref>{{cite journal |author1=Malatji, M.P.| author2=Lamb, J.| author3=Mukaratirwa, S. | title=Molecular characterization of liver fluke intermediate host lymnaeids (Gastropoda: Pulmonata) snails from selected regions of Okavango Delta of Botswana, KwaZulu-Natal and Mpumalanga provinces of South Africa |journal=Veterinary Parasitology: Regional Studies and Reports |year=2019| volume=17| pages=Art. 100318 |doi=10.1016/j.vprsr.2019.100318}}</ref>

This species has shown a potential to adapt to new environments within large lakes, as indicated by its recent history in Lake Baikal, Russia, where this introduced species was previously restricted to shallow bays and floodplain areas, but has recently been able to colonize the rocky drop-off in the lake.<ref name="Stift">Stift, M., E. Michel, T. Y. Sitnikova, E. Y. Mamonova and D. Y. Sherbakov. 2004. ''Palaearctic gastropod gains a foothold in the dominion of endemics: range expansion and morphological change of Lymnaea (Radix) auricularia in Lake Baikal''. Hydrobiologia 513(1–3):101–108.</ref> The shells of those snails in the new habitat have a more inflated aperture and are more compact than those in the shallow zones, indicating that wave action may have selected for snails with a stronger suctioning foot in the newly colonized habitat.<ref name="Stift"/>

==Ecology== === Habitat === This species is found in freshwater lakes, ponds, and slow-moving rivers with mud bottoms. ''Radix auricularia'' can live on boulders or vegetation in low or high-flow environments, and is capable of tolerating anoxic conditions, but it tends to prefer very lentic waters in lakes, bogs or slow rivers where there is a silt substrate.<ref name="Clarke"/><ref name="Jokinen"/><ref name="Sytsma">Sytsma, M. D., J. R. Cordell, J. W. Chapman and R. C. Draheim. 2004. ''Lower Columbia River Aquatic Nonindigenous Species Survey 2001–2004''. Final Technical Report: Appendices. Prepared for the United States Coast Guard and the United States Fish and Wildlife Service. 164 pp.</ref>

It has been found in environments with a pH from 6.0 to 7.1.<ref name="Jokinen"/><ref name="Maqbool">Maqbool, A., C. S. Hayat, T. Akhtar, A. D. Anjum and B. Hayat. 1998. ''Prevalence and ecology of freshwater snails in Punjab''. Malaysian Applied Biology 27(1–2):69–72.</ref> Its average thermal preference is ~19 °C, but there is great fluctuation around this mean, depending on the photoperiod for the time of year.<ref name="Rossetti">Rossetti, Y., L. Rossetti and M. Cabanac. 1989. ''Annual oscillation of preferred temperature in the freshwater snail Lymnaea auricularia; effect of light and temperature''. Animal Behaviour 37(6):897–907.</ref> In Great Britain, the species is restricted to hard water.<ref name="Adam">Adam, M. E. and J. W. Lewis. 1992. ''The lack of co-existence between Lymnaea peregra and Lymnaea auricularia (Gastropoda: Pulmonata)''. Journal of Molluscan Studies 58(2):227–228.</ref> It can tolerate polysaprobic waters, or areas of major pollution and anoxia with high concentrations of organic matter, sulfides and bacteria.<ref name="Goodnight">Goodnight, C. J. 1973. ''The use of aquatic macroinvertebrates as indicators of stream pollution''. Transactions of the American Microscopical Society 92(1):1–13.</ref><ref name="Matuskova">Matuskova, M. 1985. ''The significance of water mollusks in estimating the water pollution stage in the watershed of the Zitava River, Czechoslovakia''. Biologia (Bratislava) 40(10):1021–1030.</ref>

===Feeding habits=== ''Radix auricularia'' is in the family Lymnaeidae, which consists of scrapers and collector-gatherers. This species feeds on such items as detritus, ''Cladophora'' spp. (algae), and sand grains.<ref name="Adam"/>

===Life cycle=== Like almost all pulmonate snails, it is a hermaphrodite. It undergoes oogenesis in spring as the daylight hours increase, and spermatogenesis in late summer and early fall as the daylight hours decrease.<ref name="Berezkina">Berezkina, G. V. 1981. ''Seasonal changes in reproductive system of the Lymnaeidae''. Zoologicheskii Zhurnal 60(7):978–983.</ref> It is iteroparous, breeding biennially.<ref name="Adam"/> It lays its eggs in clumps of 50 to 150 eggs.<ref>Piechocki A. 1979. ''Ślimaki''. Fauna Słodkowodna Polski, Warszawa 1979, {{ISBN|83-01-01143-2}}.</ref> Eggs develop faster as temperature increases from 10 °C upward, but the eggs fail to survive and develop when the water temperature reaches 36 °C.<ref name="Salish">Salish, T., O. Al-Habbib, W. Al-Habbib, S. Al-Zako and T. Ali. 1981. ''The effects of constant and changing temperatures of the development of eggs of the freshwater snail Lymnaea auricularia (L.)''. Journal of Thermal Biology.</ref>

===Parasites=== Various lymnaeid snails, including ''Radix auricularia'', are vectors for a diverse range of parasites, particularly trematodes.<ref name="Boray">Boray, J. C. 1978. ''The potential impact of exotic Lymnaea spp. on fascioliasis in Australia''. Veterinary Parasitology 4(2):127–142.</ref> About 80% specimens of ''Radix auricularia'' from population near Wielkopolska National Park were found to contain trematodes.<ref>Jackiewicz M. 2000. ''Błotniarki Europy (Gastropoda: Pulmonata: Lymnaeidae). ''Wydawnicrwo Kontekst, Poznań, {{ISBN|83-911523-4-0}}, 115 pp., page 45.</ref>

''Radix auricularia'' serves as a host to numerous parasites including:

* As first and as second intermediate host for: ** ''Echinostoma revolutum''<ref>{{cite web |url=http://wildlife1.wildlifeinformation.org/S/0zAPlat_Trematod/Echi_Echi_Echinostoma/Echinostoma_revolutum.htm |title=Echinostomum revolutum (Parasite Species Summary) |accessdate=22 October 2008 |url-status=dead |archiveurl=https://web.archive.org/web/20110723233925/http://wildlife1.wildlifeinformation.org/S/0zAPlat_Trematod/Echi_Echi_Echinostoma/Echinostoma_revolutum.htm |archivedate=23 July 2011 }} accessed 22 October 2008</ref> ** ''Echinoparyphium recurvatum''<ref>Sohn, W.-M., H.-C. Woo and S.-J. Hong. "Tegumental ultrastructures of ''Echinoparyphium recurvatum'' according to developmental stages". ''Korean Journal of Parasitology'' '''40'''(2): 67–73.</ref><ref name="Soldanova 2010"/> ** ''Hypoderaeum conoideum''<ref>http://wildlife1.wildlifeinformation.org/S/0zAPlat_Trematod/Echi_Echi_Hypoderaeum/Hypoderaeum_conoideum.htm {{Webarchive|url=https://web.archive.org/web/20081025094815/http://wildlife1.wildlifeinformation.org/S/0zAPlat_Trematod/Echi_Echi_Hypoderaeum/Hypoderaeum_conoideum.htm |date=25 October 2008 }} accessed 22 October 2008</ref> *As first intermediate host for: ** ''Clinostomum complanatum''<ref>Chung, D.-I., H.-H. Kong and C.-Y. Joo. 1998. ''[http://society.kisti.re.kr/~kspa/kjp/abstracts/1998_1.html Radix auricularia coreana: natural snail host of Clinostomum complanatum in Korea]''. Korean Journal of Parasitology 36(1):1–6.</ref> * As a second intermediate host for: ** ''Apatemon gracilis''<ref>http://wildlife1.wildlifeinformation.org/S/0zAPlat_Trematod/Stri_Stri_Apatemon/Apatemon_gracilis.htm {{Webarchive|url=https://web.archive.org/web/20081025094825/http://wildlife1.wildlifeinformation.org/S/0zAPlat_Trematod/Stri_Stri_Apatemon/Apatemon_gracilis.htm |date=25 October 2008 }} accessed 22 October 2008</ref> *As an intermediate host for: ** ''Radix auricularia'' is the most important intermediate host for ''Fasciola gigantica''.<ref name="Soliman 2008"/> ** as an intermediate host for ''Fasciola hepatica'' in Oman.<ref name="Soliman 2008"/> ** ''Notocotylus attenuatus''<ref>{{cite web |url=http://wildlife1.wildlifeinformation.org/S/0zAPlat_Trematod/Echi_Noto_Notocotylus/Notocotylus_attenuatus.htm |title=Notocotylus attenuatus (Parasite Species Summary) |accessdate=22 October 2008 |url-status=dead |archiveurl=https://web.archive.org/web/20081025094820/http://wildlife1.wildlifeinformation.org/S/0zAPlat_Trematod/Echi_Noto_Notocotylus/Notocotylus_attenuatus.htm |archivedate=25 October 2008 }} 22 October 2008</ref> * As a paratenic host for: ** ''Hymenolepis lanceolata''<ref>{{cite web |url=http://wildlife1.wildlifeinformation.org/S/0zAPlat_Cestod/Cycl_Hyme_Hymenolepis/Hymenolepis_lanceolata.htm |title=Hymenolepis lanceolata (Parasite Species Summary) |accessdate=22 October 2008 |url-status=dead |archiveurl=https://web.archive.org/web/20081025094805/http://wildlife1.wildlifeinformation.org/S/0zAPlat_Cestod/Cycl_Hyme_Hymenolepis/Hymenolepis_lanceolata.htm |archivedate=25 October 2008 }} 22 October 2008</ref>

As a host for: * ''Trichobilharzia franki''<ref name="Soldanova 2010"/><ref>Ferte, H., J. Depaquit, S. Carre, I. Villena and N. Leger. (2005). "Presence of ''Trichobilharzia szidati'' in ''Lymnaea stagnalis'' and ''T-franki'' in ''Radix auricularia'' in northeastern France: molecular evidence". ''Parasitology Research'' '''95'''(2): 150–154.</ref> * ''Trichobilharzia ocellata''<ref>Zbikowska, E. 2004. ''Infection of snails with bird schistosomes and the threat of swimmer’s itch in selected Polish lakes''. Parasitology Research 92(1):30–35.</ref> * ''Trichobilharzia szidati''<ref>Kolarova, L., P. Horak and J. Sitko. 1997. ''Cercarial dermatitis in focus: schistosomes in the Czech Republic''. Helminthologia (Bratislava) 34(3):127–139.</ref> * ''radixi}}''<ref>Boshko, E. G. 1993. ''New species of ciliphoran infusoria genus Mantoscyphidia (Peritricha) from fresh water mollusks''. Vestnik Zoologii 0(6):14–19.</ref> * ''Orientobilharzia turkestanica''<ref>Tang, C., G. Cui, Y. Qian, S. Lu and H. Lu. 1990. ''Structural changes in different aged worms of Orientobilharzia turkestanica of sheep in Horqin pasture of inner Mongolia and the hatching periodicity of the Miracidia''. Acta Zoologica Sinica 36(4):366–376.</ref> * ''Diplostomum spathaceum''<ref name="Soldanova 2010">Soldanova M., Selbach C., Sures B., Kostadinova A. & Perez-del-Olmo A. (2010). "Larval trematode communities in ''Radix auricularia'' and ''Lymnaea stagnalis'' in a reservoir system of the Ruhr River". ''Parasites & Vectors'' 2010, '''3''': 56. {{doi|10.1186/1756-3305-3-56|doi-access=free}}.</ref> * ''Paryphostomum radiatum''<ref name="Soldanova 2010"/> * ''Opisthioglyphe ranae''<ref name="Soldanova 2010"/> * ''Plagiorchis elegans''<ref name="Soldanova 2010"/> * ''Australapatemon burti''<ref name="Soldanova 2010"/>  * ''Hypoderaeum conoideum''<ref name="Soldanova 2010"/> * ''Isthmiophora melis''<ref name="Soldanova 2010"/> * ''Notocotylus attenuatus''<ref name="Soldanova 2010"/> * ''Tylodelphis clavata''<ref name="Soldanova 2010"/>

Some of these parasites may infect humans.

One study found that average shell height and infection severity with ''Trichobilharzia'' spp. are positively related.<ref>Allgoewer, R. 1990. ''The trematode fauna of several Freiburg dredging pools with special regard to the pathogen of cercarial dermatitis in humans''. Mitteilungen des Badischen Landesvereins fuer Naturkunde und Naturschutz E V Freiburg im Breisgau 15(1):59–80.</ref>

In its native habitat, this species preys on eggs of the parasite ''Ascaris suum'', which survive and develop after passage through the gut, and are dispersed widely, due to the activity of the snail.<ref>Asitinskaya, S. E. 1975. ''The role of mollusks as benthos components in purification of water bodies from Ascaris suum eggs''. Paraziologiya 9(5):432–433.</ref>

==References== This article incorporates public domain text from references.<ref name="Baker">Baker F. C. (25 April) 1902. ''[https://archive.org/details/molluscaofchicag02bakeiala The Mollusca of the Chicago Area]. Part II. Gastropoda''. Bulletin No. III. of the Natural History Survey, The Chicago Academy of Sciences, 418 pp. 33 plates. Page [https://archive.org/stream/molluscaofchicag02bakeiala#page/408/mode/2up 408]-409.</ref><ref name="USGS">Rebekah M. Kipp & Amy Benson. 2008. Radix auricularia. USGS Nonindigenous Aquatic Species Database, Gainesville, FL. <https://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=1012> Revision Date: 2/28/2007</ref>

==Further reading== * Pfenninger M., Cordellier M. & Streit B. (2006) "Comparing the efficacy of morphologic and DNA-based taxonomy in the freshwater gastropod genus ''Radix'' (Basommatophora, Pulmonata)". ''BMC Evolutionary Biology'' 2006, '''6''': 100. {{doi|10.1186/1471-2148-6-100|doi-access=free}}.

==External links== {{Commons category|Radix auricularia}} *[http://www.animalbase.uni-goettingen.de/zooweb/servlet/AnimalBase/home/species?id=1881 ''Radix auricularia''] at Animalbase *[http://www.habitas.org.uk/molluscireland/species.asp?ID=151 MolluscIreland] *[http://www.bagniliggia.it/WMSD/HtmSpecies/3631200000.htm Worldwide Mollusca Species Database]

{{DEFAULTSORT:Radix Auricularia}} Category:Lymnaeidae Category:Gastropods described in 1758 Category:Animal taxa named by Carl Linnaeus