Monogenean parasites of introduced pumpkinseed Lepomis gibbosus (Centrarchidae) in the Danube River Basin.

The pumpkinseed, Lepomis gibbosus, a centrarchid fish native to eastern North America, was introduced into Europe at the end of the 19th century. Lepomis gibbosus now represents one of the most successful of introduced fish species, having spread widely throughout many European countries. In this study, we collected monogenean parasites of L. gibbosus from four sites in the Danube River Basin. We recorded four monogenean species: Gyrodactylus sp., probably acquired in the area of introduction, and Onchocleidus similis, O. dispar and Actinocleidus recurvatus, species introduced together with their host. Onchocleidus similis dominated the parasite community at all sampling sites. Actinocleidus recurvatus has only been reported from southern Europe to date and, therefore, this is the first report of A. recurvatus from Central Europe and the Danube River Basin. We observed high morphological variability in both anchor pairs of A. recurvatus. Only in O. similis was there a positive correlation observed between haptor metric traits and fish host length. Differences in metric traits between native and introduced O. similis populations may reflect a difference in fish host size, the introduced fish host achieving a smaller size than fish from native populations. A detailed analysis of microhabitat distribution indicated a preference for the second gill arch for both dominant species O. similis and A. recurvatus, with dissimilar site segregation.

Dactylogyrus species parasitizing European Barbus species: morphometric and molecular variability.

The aims of the study were (1) to describe the Dactylogyrus communities living on selected South European Barbus species, (2) to analyse morphometric variability of their attachment and reproductive organs, and (3) to perform molecular phylogenetic analyses, in order to investigate the mode of speciation in Dactylogyrus species parasitizing congeneric hosts. In Bulgaria, Dactylogyrus crivellius, D. dyki and D. petenyi were found on B. balcanicus, and D. dyki on B. cyclolepis. In Spain, Dactylogyrus carpathicus and D. dyki were detected on B. meridionalis. Morphometric analyses of D. dyki revealed significant differences in the attachment and reproductive organs when individuals from different Barbus species were compared. Two monophyletic groups were recognized from the molecular phylogenetic analyses: the first included D. carpathicus and D. crivellius which have large body size and anchors, with a weakly supported basal position of D. malleus from B. barbus; the second included D. dyki and D. petenyi which have small body and anchor sizes. The comparison of host and parasite phylogenies did not indicate the intrahost speciation. Intraspecific molecular variability was found between individuals of D. dyki and D. carpathicus from different Barbus species, suggesting the need for a taxonomic revision for these species.

Classification and occurrence of abnormally developed Paradiplozoon homoion (Monogenea, Diplozoinae) parasitising gudgeon Gobio gobio.

Morphological analyses of the attachment apparatus (clamps and central hooks) of Paradiplozoon homoion (Bychowsky & Nagibina, 1959) (Diplozoinae, Monogenea) parasitising gills of Gobio gobio (L.) showed a high percentage of abnormally developed parasite specimens. Four different localities in the Vlára River basin, Czech Republic, were investigated for the presence of such abnormal individuals. The highest percentage of abnormalities in the attachment apparatus (over 39%) was recorded in the Vlára River, at Bohuslavice. This study provides a comprehensive classification of these abnormalities with 7 types of abnormalities described and illustrated. Abnormalities of parts of the attachment apparatus that form in the later stage of ontogenetic development were the most frequent, the most frequent types of abnormalities being clamps with abnormal sclerites, and combinations of abnormalities. Abnormalities of the central hooks were also found in our material. The abnormalities found in diplozoids are probably connected with environmental pollution; however, this point requires further investigation.