{{Short description|Species of bivalve}} {{AI-generated|date=January 2026}} {{Speciesbox | image = Naturalis Biodiversity Center - ZMA.MOLL.418104 - Simpsonaias ambigua (Say, 1825) - Unionidae - Mollusc shell.jpeg | status = VU | status_system = IUCN3.1 | status_ref = <ref name="iucn status 16 November 2021">{{cite iucn |author=Bogan, A.E. |author2=Woolnough, D. |author3=Seddon, M.B. |date=2017 |title=''Simpsonaias ambigua'' |volume=2017 |article-number=e.T20247A62905797 |doi=10.2305/IUCN.UK.2017-3.RLTS.T20247A62905797.en |access-date=16 November 2021}}</ref> | status2 = G1 | status2_system = TNC | status2_ref = <ref name=NS>{{cite NatureServe |id=2.114652 |title=''Simpsonaias ambigua'' |access-date=1 January 2026}}</ref> | genus = Simpsonaias | parent_authority = [[Lorraine Screven Frierson|Frierson]], 1914 | display_parents = 2 | species = ambigua | authority = ([[Thomas Say|Say]], 1825) | synonyms = {{Species list |Alasmodonta ambigua|Say, 1825 |Hemilastena ambigua|(Say, 1825) |Simpsoniconcha ambigua|(Say, 1825) |Unio hildrethianus|[[Isaac Lea|Lea]], 1834 |Margarita (Unio) hildrethianus|(Lea, 1834) |Margaron (Margaritana) hildrethiana|(Lea, 1834)}} | synonyms_ref = <ref name=WoRMS>{{cite WoRMS |id=857395 |title=''Simpsonaias ambigua'' (Say, 1825) |db=mollusca |access-date=2 January 2025}}</ref> }}
'''''Simpsonaias ambigua''''', the '''salamander mussel''' or '''mudpuppy mussel''', is a species of [[bivalve]] in the family [[Unionidae]]. It is unique among freshwater mussels in using [[mudpuppies]] as its [[Glochidium|glochidial]] host.<ref>{{Cite web |url=https://mnfi.anr.msu.edu/abstracts/zoology/Simpsonaias_ambigua.pdf |title=''Simpsonaias ambigua'' Michigan Natural Features Inventory |access-date=2016-07-08 |archive-url=https://web.archive.org/web/20190415184421/https://mnfi.anr.msu.edu/abstracts/zoology/Simpsonaias_ambigua.pdf |archive-date=2019-04-15 }}</ref>
== Ecology == Salamander mussels are a unique freshwater mussel species notable for their obligate parasitic relationship with the mudpuppy salamander (''Necturus maculosus'').<ref name="MNDNR">{{cite web | last = Minnesota Department of Natural Resources | title = Rare Species Guide: ''Simpsonaias ambigua'' (Salamander Mussel) | website = Rare Species Guide | publisher = Minnesota Department of Natural Resources | url = https://www.dnr.state.mn.us/rsg/profile.html?action=elementDetail&selectedElement=IMBIV41010 | access-date = 3 November 2025 }}</ref> Its larvae (glochidia) attach to the gills of mudpuppies, where they receive necessary nutrients and dispersal, eventually metamorphosing before dropping off into suitable benthic substrate. The species tends to occur in low-density populations, often associated with mudpuppy parameters such as population size and microhabitats that support them (e.g., refugia such as flat rocks and crevices).<ref name="USFWS2023">{{cite web | author = U.S. Fish and Wildlife Service | date = May 2023 | title = Species Status Assessment Report for the Salamander Mussel (''Simpsonaias ambigua'') Version 1.1 | publisher = U.S. Fish and Wildlife Service — Region 3 | url = https://www.fws.gov/sites/default/files/documents/Salamander%20Mussel%20SSA%20Final%20May%202023_0.pdf | access-date = 7 November 2025 }}</ref> Adult ''S. ambigua'' typically inhabit clean, well-oxygenated, fine-sand or silt substrates in medium- to large-sized rivers with stable flow.<ref name="USFWS2023"/>
Like many freshwater mussels, ''S. ambigua'' contributes to ecosystem processes such as nutrient cycling and substrate stabilization. By filtering suspended particles, individuals improve water clarity and support aquatic food webs.<ref name="PortoHannes2025">{{cite journal | last1 = Porto-Hannes | first1 = I. | last2 = McNichols-O’Rourke | first2 = K. A. | last3 = Gibson | first3 = M. P. | last4 = Morris | first4 = T. J. | year = 2025 | title = Status and Life History Traits of ''Simpsonaias ambigua'' (Salamander Mussel) in Ontario, Canada | journal = Diversity | volume = 17 | issue = 2 | pages = 133 | doi = 10.3390/d17020133 | bibcode = 2025Diver..17..133P | doi-access = free }}</ref>
== Distribution == The historical range of the salamander mussel includes the Mississippi, Ohio, and Great Lakes drainages, spanning 25 U.S. states and parts of southern Ontario, Canada.<ref name="USFWS2023"/> Adult ''S. ambigua'' typically inhabit clean, well-oxygenated, fine-sand or silt substrates in medium- to large-sized rivers with stable flow.<ref name="USFWS2023"/> It has been documented in rivers such as the Wabash, Maumee, Ohio, and Tennessee, though it is now considered rare or extirpated from much of its former range.<ref name="Womble2020">{{cite journal | last1 = Womble | first1 = K. I. | last2 = Dinkins | first2 = G. R. | last3 = Alford | first3 = J. B. | last4 = Harris | first4 = M. H. | year = 2020 | title = New Species Distribution Record for ''Simpsonaias ambigua'' (Say) (Salamander Mussel, Bivalvia: Unionidae) in the Harpeth River, Tennessee | journal = Southeastern Naturalist | volume = 19 | issue = 1 | doi = 10.1656/058.019.0116 | url = https://doi.org/10.1656/058.019.0116 | url-access = subscription }}</ref>
Recent records show persistence in several areas once thought to have lost populations. For example, ''S. ambigua'' was rediscovered in Illinois using environmental DNA (eDNA) analysis,<ref name="Douglass2025">{{cite journal | last1 = Douglass | first1 = S. A. | last2 = Palmer | first2 = S. | last3 = McCallum | first3 = A. R. | last4 = Reves | first4 = O. P. | last5 = Robinson | first5 = H. A. | last6 = Rutledge | first6 = A. J. | last7 = Hartman | first7 = J. H. | last8 = Larson | first8 = E. R. | last9 = Davis | first9 = M. A. | year = 2025 | title = Environmental DNA reveals the Salamander Mussel ''Simpsonaias ambigua'' alive in Illinois, USA, after a century in obscurity | journal = Ecology | volume = 106 | issue = 7 | article-number = e70145 | doi = 10.1002/ecy.70145 | pmid = 40605396 | pmc = 12223466 | bibcode = 2025Ecol..10670145D | url = https://doi.org/10.1002/ecy.70145 }}</ref> and continues to occupy isolated sites in southern Ontario, where populations exhibit small size structure and low density but evidence of continued reproduction.<ref name="PortoHannes2025"/> A 2020 record from the Harpeth River in Tennessee extended the known distribution within the lower Cumberland system.<ref name="Womble2020"/>
Because the species’ occurrence is closely tied to that of the mudpuppy salamander, its range mirrors the distribution of this host. Declines in mudpuppy populations due to habitat degradation and pollution are likely to contribute to the mussel’s reduced distribution.<ref name="McDaniel2009"/>
== Conservation == The Salamander Mussel is considered rare throughout its range, listed as a Special Concern in most U.S. states and Threatened in Canada.<ref name="MNDNR"/><ref name="PortoHannes2025"/> Recovery is limited by the species’ dependence on both pristine benthic habitats and healthy populations of its mudpuppy salamander host.<ref name="USFWS2023"/> Modern molecular and habitat-based tools are increasingly used to aid in the detection and management of the species. Environmental DNA (eDNA) surveys have confirmed its persistence in regions where it was previously thought extirpated, including Illinois and Ontario.<ref name="Douglass2025"/><ref name="PortoHannes2023"/> Research continues to refine methods for identifying suitable habitats and assessing the ecological conditions that support viable populations.<ref name="Womble2020"/><ref name="USFWS2023"/>
== Threats == Major threats to the Salamander Mussel include habitat degradation, pollution, and declines in its amphibian host. Channelization, sedimentation, and dam construction have reduced suitable substrates and altered natural flow regimes, limiting available habitat.<ref name="PortoHannes2025"/> Runoff from agricultural and industrial activities further degrades water quality, negatively affecting both the mussel and the mudpuppy host.<ref name="USFWS2023"/> Declines in mudpuppy populations, linked to pollution and habitat loss, directly limit mussel reproduction and dispersal.<ref name="McDaniel2009">{{cite journal | last1 = McDaniel | first1 = T. V. | last2 = Martin | first2 = P. A. | last3 = Barrett | first3 = G. C. | last4 = Hughes | first4 = K. | last5 = Gendron | first5 = A. D. | last6 = Shirose | first6 = L. | last7 = Bishop | first7 = C. A. | year = 2009 | title = Relative abundance, age structure, and body size in mudpuppy populations in southwestern Ontario | journal = Journal of Great Lakes Research | volume = 35 | issue = 2 | pages = 182–189 | doi = 10.1016/j.jglr.2008.12.009 | bibcode = 2009JGLR...35..182M | url = https://doi.org/10.1016/j.jglr.2008.12.009 | url-access = subscription }}</ref><ref name="USFWS2023"/> Surviving mussel populations are often small and isolated, leaving them vulnerable to stochastic events and local extirpation.<ref name="PortoHannes2023">{{cite journal | last1 = Porto-Hannes | first1 = I. | last2 = Sassoubre | first2 = L. M. | last3 = Sansom | first3 = B. J. | last4 = Morris | first4 = T. J. | year = 2023 | title = Applying Environmental DNA Methods to Inform Detection of ''Simpsonaias ambigua'' under Varying Water Velocities in a River | journal = Freshwater Mollusk Biology and Conservation | volume = 26 | issue = 2 | pages = 54–68 | doi = 10.31931/fmbc-d-21-00013 | url = https://doi.org/10.31931/fmbc-d-21-00013 | doi-access = free }}</ref>
== References == {{Reflist}}
{{Taxonbar|from1=Q599920|from2=Q10371714}} [[Category:Unionidae]] [[Category:Molluscs of the United States]] [[Category:Molluscs of Canada]] [[Category:Bivalves described in 1825]] [[Category:Taxonomy articles created by Polbot]]
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