Molecular identification of an alien temnocephalan crayfish parasite in Italian freshwaters

Although the symbionts of non-vertebrate metazoans have received scarce attention, scientific interest has recently increased as these symbionts can spread diseases and alter the diversity of the ecosystem where hosts are introduced. We report here a symbiont newly described by molecular markers and observed on the yabby Cherax destructor Clark, 1936, collected in Italian freshwaters. Preliminary morphological observations were performed and a species identification was proposed using molecular techniques. In particular, a 644-bp long 28S rDNA fragment was successfully sequenced and could be aligned for the entire sample set. The minimum spanning network identified two haplotypes clustered into a single haplogroup (H1) together with Temnosewellia minor Haswell, 1888 reference sequences. Considering the introduction of temnocephalans, this represents the third discovery of alien crayfish symbionts in Italian freshwaters, but the first obtained by molecular data. Outside Europe, there are only few records of alien temnocephalans worldwide, introduced with the crayfishes from Australia. The occurrence of this new temnocephalid species and the great number of potential hosts species inhabiting Italian freshwaters suggest that the Italian peninsula might have many undescribed temnocephalid populations/species.