BACKGROUND: Recently, human intervention enabled the introduction of Barbus barbus from the Rhône River basin into the Barbus meridionalis habitats of the Argens River. After an introduction event, parasite loss and lower infection can be expected in non-native hosts in contrast to native species. Still, native species might be endangered by hybridization with the incomer and the introduction of novel parasite species. In our study, we aimed to examine metazoan parasite communities in Barbus spp. populations in France, with a special emphasis on the potential threat posed by the introduction of novel parasite species by invasive B. barbus to local B. meridionalis. METHODS: Metazoan parasite communities were examined in B. barbus, B. meridionalis and their hybrids in three river basins in France. Microsatellites were used for the species identification of individual fish. Parasite abundance, prevalence, and species richness were compared. Effects of different factors on parasite infection levels and species richness were tested using GLM. RESULTS: Metazoan parasites followed the expansion range of B. barbus and confirmed its introduction into the Argens River. Here, the significantly lower parasite number and lower levels of infection found in B. barbus in contrast to B. barbus from the Rhône River supports the enemy release hypothesis. Barbus barbus × B. meridionalis hybridization in the Argens River basin was confirmed using both microsatellites and metazoan parasites, as hybrids were infected by parasites of both parental taxa. Trend towards higher parasite diversity in hybrids when compared to parental taxa, and similarity between parasite communities from the Barbus hybrid zone suggest that hybrids might represent "bridges" for parasite infection between B. barbus and B. meridionalis. Risk of parasite transmission from less parasitized B. barbus to more parasitized B. meridionalis indicated from our study in the Argens River might be enhanced in time as higher infection levels in B. barbus from the Rhône River were revealed. Hybrid susceptibility to metazoan parasites varied among the populations and is probably driven by host-parasite interactions and environmental forces. CONCLUSIONS: Scientific attention should be paid to the threatened status of the endemic B. meridionalis, which is endangered by hybridization with the invasive B. barbus, i.e. by genetic introgression and parasite transmission.

• Keywords
• Biological invasion, Cyprinid fish, Hybridization, Metazoan parasite communities,
• MeSH
• Biodiversity * MeSH
• Chimera classification   genetics   growth & development   parasitology   MeSH
• Cyprinidae classification   genetics   growth & development   parasitology   MeSH
• Microsatellite Repeats MeSH
• Parasite Load MeSH
• Parasites classification   isolation & purification   MeSH
• Rivers MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• France MeSH

Specimens of the Paradiplozoon homoion-complex were collected from ten species of cyprinid fish in the Czech Republic. A combined molecular and morphometric approach was performed to distinguish Paradiplozoon homoion and P. gracile. The second internal transcribed spacer (ITS2) of the ribosomal RNA genes was amplified and sequences were analysed. No variability in the analysed sequences was detected. Measurements of clamps and the central hooks obtained from specimens from different host species were compared. Great variability was found in the length and width of the third pair of clamps. No significant differences were detected in the measurements of the central hook sickle. A positive relationship was found between host size and each of the following measurements of the third pair clamps: length and width of the whole clamp; and length of the median plate of the third pair of clamps. The length of the median plate of the attachment clamps may be a useful character for species identification of diplozoids. Further molecular and morphometric studies are required to resolve this taxonomic problem and, henceforth, we suggest considering P. gracile as a species inquirenda.

• MeSH
• Cyprinidae parasitology   MeSH
• Species Specificity MeSH
• Phenotype MeSH
• Genetic Variation MeSH
• Trematode Infections veterinary   MeSH
• DNA, Ribosomal Spacer genetics   MeSH
• Fish Diseases parasitology   MeSH
• RNA, Helminth genetics   MeSH
• RNA, Ribosomal genetics   MeSH
• Sequence Analysis, DNA MeSH
• Trematoda anatomy & histology   classification   genetics   MeSH
• Gills parasitology   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Comparative Study MeSH
• Geographicals
• Czech Republic MeSH
• Names of Substances
• DNA, Ribosomal Spacer MeSH
• RNA, Helminth MeSH
• RNA, Ribosomal MeSH