Les Nàiades (Mollusca: Bivalvia: Unionoida) dels Països Catalans

The unionoids of the Catalan Countries have been revised considering characters from the
shell, the glochidium larvae, and the topographical anatomy. Four species are recognized.
Margaritifera auricularia is known from the rivers Ter and Ebre; the latter harbors the last known
living population of the species. Anodonta cygnea is widely distributed in the lowlands. Psilunio
littoralis is subdivided into five subspecies:P. I. Littoralis from the River Ter northwards, P. I.
Subreniformis in Lake Banyoles, P. I. Catalonicus in the small rivers of the Catalan Central Depression, P. I. Umbonatus from the Ebro southwards, and P. I. Gandiensis in the northern slope of the Dianic Ranges. Four subspecies are also recognized of Unio elongatulus: U. e. Aleroni from the
Rosselld Plain to the Tordera River, U. e. Penchinatianus in Lake Banyoles, U. e. ssp. in the River Ebro, and U. e. Valentinus along the Gulf of Valencia. No unionoid lives in the Balearic Islands. The intense differentiation of Catalan naiades appears to be caused by the scarcity of freshwater
environments in a Mediterranean climate, and by the patterns of dispersal of the fishes that are
hosts for the unionoid larvae. All the naiades in the Catalan Countries are at present in regression
due to human activities. M. auricularia and the endemisms of Banyoles are endangered.