zebra mussel; Dreissena polymorpha; spiny-cheek crayfish; Orconectes limosus; body colonisation; epibiosis; Czech Republic

An interaction between two invasive aquatic invertebrates, the American spiny-cheek crayfish, Orconectes limosus, and the Ponto-Caspian zebra mussel, Dreissena polymorpha, was studied in Czechia. At the flooded sandpit Lhota, the crayfish were regularly colonised by mussels. 108 crayfish specimens collected by scuba divers were examined in 2004 and 2005. The frequency of colonised crayfish was consistently over 75 % in spring and the beginning of summer. Afterwards, crayfish lost the bivalves by moulting but new mussels settled by late summer and early autumn. We suggest 3 main ways of colonisation: (1) a settlement of the pediveliger larvae; (2) secondary settlement of plantigrade mussels and juveniles; and (3) active movement of grown mussels from a substrate to crayfish.

An interaction between two invasive aquatic invertebrates, the American spiny-cheek crayfish, Orconectes limosus, and the Ponto-Caspian zebra mussel, Dreissena polymorpha, was studied in Czechia. At the flooded sandpit Lhota, the crayfish were regularly colonised by mussels. 108 crayfish specimens collected by scuba divers were examined in 2004 and 2005. The frequency of colonised crayfish was consistently over 75 % in spring and the beginning of summer. Afterwards, crayfish lost the bivalves by moulting but new mussels settled by late summer and early autumn. We suggest 3 main ways of colonisation: (1) a settlement of the pediveliger larvae; (2) secondary settlement of plantigrade mussels and juveniles; and (3) active movement of grown mussels from a substrate to crayfish.