Observations on temnocephalid (Platyhelminthes) ectosymbionts in Australian freshwater crayfish (Cherax destructor Clark) introduced to Northern Italy.

In 1996, freshwater crayfish (Cherax destructor Clark) were imported to Italy from Australia in order to make research and to explore their potential for our national aquaculture. 10 dead specimens were examined at their arrival at the laboratory and 10 live specimens were collected and kept in a suitable tank during the period from June to December. Temnocephalidean platyhelmints were detected on the external surfaces (exoskeleton and gills) of all the crayfish. Strongly adherent temnocephalid eggs were deposited on the cuticle and gills. Morphological features of the specimens of temnocephalan worms were given with electron microscopy. The morphology, the number of tentacles and the size of the sucker indicate that the examined samples belong to the genus Temnocephala. Other crayfish such as Austropotamobius pallipes Lereboullet, Orconectes limosus Say and Procambarus clarkii Girard, placed and exposed in the same tank were infested by the worms The health of the crayfish of all the observed species whether australian or american and european was not significantly affected by the infestation. In native country the effects of these parasites on the well-being of the hosts are unknown, but their translocation might result in a loss of the symbiont flora and fauna associated with the european and american crayfish species.