The discovery of zebra mussels (Dreissena polymorpha) in Lough Derg and the lower Shannon region in 1997 (McCarthy et al 1997, a & b) has lead to considerable concern about the potential ecological and economic damage that this highly invasive aquatic nuisance species can cause.

This web page serves to disseminate information gathered by researchers at NUI, Galway (Zebra Mussel Survey Group) about the species in Irish waters as well as providing some genral information on the species.

McCarthy, T.K; Fitzgerald, J.; and O'Connor, W. (1997 a) The occurrence of the zebra mussel Dreissena polymorpha (Pallas, 1771), an introduced biofouling freshwater bivalve in Ireland. Ir. Nat. Jr. Vol 25 11/12: 413-416

McCarthy, T. K., Fitzgerald, J., Cullen, P., Doherty, D. & L. Copley. (1997 b). Zebra mussels in the River Shannon. Their present distribution, their probable ecological effect, economic impact and prospects for controlling their spread to other Irish river systems. A report compiled on behalf of Electricity Supply Board (Fisheries Conservation).

What is a Zebra Mussel ?

The zebra mussel, Dreissena polymorpha, Pallas, belongs to the bivalve molluscan family Dreissniidae, which evolved during or prior to the Triassic period (230 million years BP) and which has representatives in Central and South America as well as, in the general Mediterranean region and West Africa, in the Old World. The genus Dreissena includes a large number of described species, many of which are either fossil forms or are of questionable taxonomic status. The diversity of described Dreissena species and the occurrence of numerous relict species populations in the Aegean region and Anatolia reflects in part the considerable geographical range variations experienced by these molluscs during their known geological history. In this regard, the relatively more recent Quaternary glacial transformations of the Eurasian landscape strongly influenced Dreissena taxonomy and species distributions. The best known species, Dreissena polymorpha, was first described by the Russian zoologist Pallas in 1771 from specimens collected in the lower course of the Ural River in 1769.

Above: zebra mussels exhibiting differences in shell colouration

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This page is maintained by P. Cullen (Zoology Dept, NUI, Galway)    Last updated: March 1999