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Spengler's freshwater mussel
	A shell of Spengler's freshwater mussel collected by Fritz Haas in Spain
Conservation status
	; Critically Endangered (IUCN 3.1)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Bivalvia
Order:	Unionida
Family:	Margaritiferidae
Genus:	Margaritifera
Species:	M. auricularia
Binomial name
	Margaritifera auricularia; (Spengler, 1793)
Synonyms
	Unio auricularius Spengler, 1793; Pseudunio auricularia (Spengler, 1793); Pseudunio auricularius auricularius (Spengler, 1793); Unio sinuata Lamarck, 1819

Margaritifera auricularia is a species of European freshwater mussel, an aquatic bivalve mollusk in the family Margaritiferidae, the freshwater pearl mussels. Formerly found throughout western and central Europe, the species is now critically endangered and is one of the rarest invertebrates worldwide, being confined to a few rivers in Spain and France.^[1]^[3] M. auricularia is commonly known as Spengler's freshwater mussel in honour of Lorenz Spengler, who first described this species.

Description

Large shells are up to 180 mm in length.

Taxonomy

There are different opinions on the taxonomy of this species.

The species was originally described as Unio auricularius Spengler, 1793.

When it is placed in the genus Margaritifera Schumacher, 1816, it is considered to be:

Margaritifera auricularia (Spengler, 1793)

At other times it is placed in the genus Pseudunio F. Haas, 1910, in which case it is known as:

Pseudunio auricularia (Spengler, 1793)

Sometimes it is given the masculine gender:

Pseudunio auricularius auricularius (Spengler, 1793)

Distribution

It is found in:

France – recent distribution^[2]
Italy – recent
Spain – recent^[4]
Portugal – recent(?) or fossil(?)^{[citation needed]}
maybe in some rivers in north Africa:^[5] Morocco^[6]
Germany – locally extinct from upper Rhine after 1500^[5]
Netherlands – extinct or fossil^{[citation needed]}
Belgium – extinct or fossil^{[citation needed]}
Luxembourg – extinct or fossil^{[citation needed]}
Czech Republic – only fossil records in layers with settlement from neolite: Ďáblice, Kobylisy, Roztoky, Podbaba.^[6]
United Kingdom – ?^{[citation needed]}

Ecology

The fish hosts for the glochidium larvae of this species are: Salaria fluviatilis, Gambusia holbrooki, Acipenser baerii, Acipenser naccarii and Acipenser sturio.^[5]

The hosts for this species were unknown for a long time: as recently as 1998 they were still not known.^[7]

External links

Spengler’s freshwater mussel (Margaritifera auricularia) media from ARKive

Araujo, R & Moreno, R. 1999. Former Iberian Distribution of Margaritifera auricularia (Spengler) (Bivalvia: Margaritiferidae). Iberus, 17(1): 127–136.
Araujo, R., Bragado, D. & Ramos, M. A. 2000. Occurrence of glochidia of the endangered Margaritifera auricularia (Spengler, 1793) and other mussel species (Bivalvia: Unionoida) in drift and on fishes in an ancient channel of the Ebro River, Spain. Archiv für Hydrobiologie, 148(1): 147–160.
Araujo, R. & Ramos, M. A. 2000. A critic revision of the historical distribution of Margaritifera auricularia (Spengler, 1793) (Mollusca: Margaritiferidae) based on museum specimens. Journal of Conchology, 37(1): 49–59.
Araujo, R. & Ramos, M. A. 2000. Status and conservation of the relict giant European freshwater pearl mussel Margaritifera auricularia (Spengler, 1793). Biological Conservation, 96(2): 233–239
Grande, C., Araujo, R. & Ramos, M. A. 2001. The gonads of Margaritifera auricularia (Spengler, 1793) and Margaritifera margaritifera (L. 1758) (Bivalvia: Unionoidea). Journal of Molluscan Studies, 6: 27–35.

Araujo, R., Bragado, D. & Ramos, M. A. 2001. Identification of the river blenny, Salaria fluviatilis, as a host to the glochidia of Margaritifera auricularia. Journal of Molluscan Studies, 67: 128–129.

Araujo, R., Cámara N. & Ramos, M. A. Glochidium metamorphosis in the endangered freshwater mussel Margaritifera auricularia (Spengler, 1793): A histological and scanning electron microscopy study. Journal of Morphology. 254: 259–265.
Araujo, R., Quirós, M. & Ramos, M. A. 2003. Laboratory propagation and culturing of juveniles of the endangered freshwater mussel Margaritifera auricularia (Spengler, 1793). Journal of Conchology. 38(1): 53–60.
Araujo, R. 2004 Two overlooked host fish species of Margaritifera auricularia (Bivalvia, Unionoidea, Margaritiferidae). Basteria, 67: 113.
Vallejo, A., & Araujo, R. The Historical misidentification of Margaritifera auricularia for M. margaritifera (Bivalvia, Unionoidea) explained by their iconography. Malacologia. (in press)
Araujo, R. & Ramos, M. A. 2001. Action Plan for Margaritifera auricularia. Convention on the Conservation of European Wildlife and Natural Habitats (Bern Convention). Council of Europe Publishing. Nature and environment, No. 117. Strasbourg. 28 pp.
Araujo, R. & Ramos, M. A. 2001. Life-History data on the virtually unknown Margaritifera auricularia. En: Ecological Studies, Vol. 145. "Ecology and Evolution of the Freshwater Mussels Unionoida" ed. by G. Bauer and K. Wächtler. Springer-Verlag Berlin Heidelberg. 143–152. Por invitación.
Araujo, R. & Ramos, M. A. 2001. Margaritifera auricularia. En: Los Invertebrados no Insectos de la "Directiva Hábitat" en España. Serie Técnica. Ed. Organismo Autónomo Parques Nacionales (Ministerio de Medio Ambiente). Madrid. 93–101.