Pseudunio auricularius (Spengler, 1793) was rediscovered in two river systems in France. The populations are described regarding size, size-range of the animals, length-distribution, age and sexual maturity. At both sites the population consisted of only adult animals. The oldest animal seen was about 43 years old. The animals become mature at an age of about 18 to 22 years having a length of about 10 cm. P. auricularius can stand rather high degrees of eutrophication as an adult. Some remarks are made on biology and shell characters, especially of the umbo. Literature and data on host fishes are presented. The author doubts whether the sturgeon was the only host fish. Some factors responsible for decline and extinction, viz. eutrophication, dredging and draining, are discussed. The author suggests that juveniles after the stage of glochidiosis may be found between Fraxinus and Alnus roots.

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CC BY-NC 4.0 NL ("Naamsvermelding-NietCommercieel")

Nederlandse Malacologische Vereniging

Jozef A.J.H. Nienhuis. (2003). The rediscovery of Spengler’s freshwater pearlmussel Pseudunio auricularius (Spengler, 1793) (Bivalvia, Unionoidea, Margaritiferidae) in two river systems in France, with an analysis of some factors causing its decline. Basteria, 67(1/3), 67–86.