Margaritifera auricularia 

Scope: Global, Europe & Mediterranean
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Mollusca Bivalvia Unionoida Margaritiferidae

Scientific Name: Margaritifera auricularia Spengler, 1793
Common Name(s):
English Spengler's Freshwater Mussel
French Grande Mulette
Pseudunio auricularius (Spengler, 1913)
Unio crassissimus (Ferrussac, 1844)
Unio margaritanopsis Locard, 1889
Unio margaritifera (Draparnaud, 1801)
Unio sinuata Lamarck, 1819
Unio sinuatus (Rossmassler, 1844)
Taxonomic Notes: Haas (1910) has proposed the genus Pseudunio for this species, in order to distinct it from M. margaritifera. Pseudunio was then synonymised by Ortmann (1911). Pseudunio was used again by Haase (1969) to distinguish M. auricularia and M. auricularia marocana (Pallaray 1918) from the other species of the genus Margaritifera. More recently, the genus Pseudunio was used again by Smith (2001), Falkner et al. (2002) and Nienhuis (2003). We now know (Araujo et al. 2009) that M. margaritifera and M. marocana are different species belonging to a same clade (thus monophyletic), but it is still not clear if we should consider different sub-genus within Margaritifera (Huff et al. 2004).

To conclude, we propose not to use the Pseudunio any more, either as a genus or as a sub-genus, as long as no definitive phylogeny recommend it.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered A2ac ver 3.1
Year Published: 2010
Date Assessed: 2010-01-28
Assessor(s): Prie, V.
Reviewer(s): Seddon, M., Gargominy, O. & Cuttelod, A.
Contributor(s): Araujo, R. & Cochet, G.
Over the last three generations (using a 30-year generation estimate), the population size of M. auricularia has decreased by more than 90%, as shown by direct observation and by the drastic reduction in its extent of occurrence. Furthermore, most of the subpopulations are not recruiting any more. It is therefore considered as Critically Endangered A2ac.

This mirrors previous assessment of Critically Endangered, under version 2.3, and whilst there has been progress in finding new populations and managing the habitats for previously known populations, the long generation time of this species means that more time is required to confirm any recovery.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This species was originally known to be widespread in Europe extending in the north to Denmark, east to Italy and to Portugal in the West. Nowadays, it only occurs in France and Spain and is extinct in the rest of Europe (Araujo and Ramos 2001). The current range of this species is recorded from part of the rivers Charente, Vienne and Creuse in France and part of the Ebro river in Spain. Therefore, the species is known from four locations, namely the Charente, Vienne, Creuze and Ebro rivers, with a possible fifth one which has to be confirmed (Dronne river in France). In parts of the range the species has been extinct for hundreds of years (UK), whereas in other regions the decline and disappearance happened in the last century.
Countries occurrence:
France (France (mainland)); Spain (Spain (mainland))
Regionally extinct:
Belgium; Czech Republic; Denmark; Germany; Italy (Italy (mainland)); Luxembourg; Netherlands; Portugal (Portugal (mainland)); United Kingdom (Great Britain - Native)
Additional data:
Estimated area of occupancy (AOO) - km2:2200Continuing decline in area of occupancy (AOO):Yes
Estimated extent of occurrence (EOO) - km2:89700
Continuing decline in extent of occurrence (EOO):Yes
Number of Locations:4
Upper elevation limit (metres):100
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:Currently in France, reproduction is very scarce in the Ebro and Vienne rivers and therefore these subpopulations are decreasing. In the other rivers, no recruitment is observed at all and most of the subpopulations will have disappeared in the next 20-50 years. The subpopulation from the Oise river (France) was probably extirpated in the last few years.
Current Population Trend:Decreasing
Additional data:
Number of mature individuals:20000-25000Continuing decline of mature individuals:Yes
Population severely fragmented:Yes
Continuing decline in subpopulations:Yes
All individuals in one subpopulation:No

Habitat and Ecology [top]

Habitat and Ecology:This species occurs in slow-flowing large rivers. It is dependent on well-oxygenated gravel substrate for juvenile development. It relies on the presence of its fish host (which is believed to be the Common sturgeon Acipenser sturio, nearly extirpated in most western European rivers). Nevertheless, the Mediterranean populations (Ebro river) may reproduce thanks to an other fish host (River Blenny Salaria fluviatillis).
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):30

Use and Trade [top]

Use and Trade: The species' shell has nacre which was used to manufacture knife hilts, especially in the riverside village of Sástago near the Ebro river, where there were abundant M. auricularia populations. Traces exist indicating that this activity probably began two centuries ago. Álvarez (1998a, b) summarized all the available data on this activity. In the Charente River, M. auricularia's nacre was used to make clothes buttons. With regard to freshwater pearl production, it seems that M. auricularia is not a real pearl mussel, as no reference to pearls is available, at least, none comparable with the pearl production reported in M. margaritifera (Hessling, 1859).
Another threat arising directly from people is the possible capture of specimens by poachers, once the risk to the species is known. Collectors may be interested in having specimens of M. auricularia for their value as pretty objects (nacre) and because it is a rare species.

Threats [top]

Major Threat(s): Main threats are/were due to human activities, either by direct killing of individuals or by habitat modification. In particular, dams seriously threat this species, both through habitat modification (siltation) and impeding the migration of the host fish. River regulation, dredging, water pollution and pesticides (there are very large irrigated fields along the banks of the Ebro) and water availability are among the most important reasons for M. auricularia’s decline. Irrational water use in the area is behind all these problems and represents the main threat to the species (Araujo and Ramos 1989).

Conservation Actions [top]

Conservation Actions: This species is protected in France and in Spain. It is listed in the Annex 4 of the Habitat Directive and the Annex II of the Bern Convention. Species Action Plans have been elaborated in France (2009) and Spain (2005).

It is necessary to take major actions if we want to ensure the survival of this species: surveys in southwest France will allow to discover remaining populations, research on the ecology (water quality requirement, host fish, population genetics), management of the habitat, in particular of the dams and water quality, the restoration of host fish populations, designation of special protected areas and captive breeding programmes.

Citation: Prie, V. 2010. Margaritifera auricularia. The IUCN Red List of Threatened Species 2010: e.T12798A3381899. . Downloaded on 19 August 2018.
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