[The number of larvae and period of its production of Cosmocerca Ornata females (Nematoda: Cosmocercidae)].

The number of larvae in the Cosmocerca ornata (Dujardin, 1845) females from marsh frogs in vivo and period of larvae production of nematodes in vitro was studied. The number of larvae in females of nematodes and quantity of born larvae depend on the size of parasites. The largest C. ornata females had the highest number of larvae and the longest period of larvae production. The nematode sizes in its turn depends on density of infrapopulation of C. ornata and ambient temperature. The dependence of a number of the C. ornata larvae on the host age and sex and on a season of the year was revealed. Different phenotypes of amphibians showed no influence on the number of larvae inside nematode females. In the experiment C. ornata females remained viable up to 8 days, producing larvae up to 7 days. The optimum temperature for the larvae production constituted 24­28 °C. At a temperature of 12 °C and lower the nematode larvae output from females was stopped.

Getting what is served? Feeding ecology influencing parasite-host interactions in invasive round goby Neogobius melanostomus.

Freshwater ecosystems are increasingly impacted by alien invasive species which have the potential to alter various ecological interactions like predator-prey and host-parasite relationships. Here, we simultaneously examined predator-prey interactions and parasitization patterns of the highly invasive round goby (Neogobius melanostomus) in the rivers Rhine and Main in Germany. A total of 350 N. melanostomus were sampled between June and October 2011. Gut content analysis revealed a broad prey spectrum, partly reflecting temporal and local differences in prey availability. For the major food type (amphipods), species compositions were determined. Amphipod fauna consisted entirely of non-native species and was dominated by Dikerogammarus villosus in the Main and Echinogammarus trichiatus in the Rhine. However, the availability of amphipod species in the field did not reflect their relative abundance in gut contents of N. melanostomus. Only two metazoan parasites, the nematode Raphidascaris acus and the acanthocephalan Pomphorhynchus sp., were isolated from N. melanostomus in all months, whereas unionid glochidia were only detected in June and October in fish from the Main. To analyse infection pathways, we examined 17,356 amphipods and found Pomphorhynchus sp. larvae only in D. villosus in the river Rhine at a prevalence of 0.15%. Dikerogammarus villosus represented the most important amphipod prey for N. melanostomus in both rivers but parasite intensities differed between rivers, suggesting that final hosts (large predatory fishes) may influence host-parasite dynamics of N. melanostomus in its introduced range.

The effect of an experimental infection of the nematode Heterakis gallinarum on hand-reared grey partridges Perdix perdix.

We compared 26 hand-reared grey partridges given an experimental infection of the caecal nematode Heterakis gallinarum with 26 uninfected ones. Under laboratory conditions after 91 days, there were no measurable clinical effects of the infection. We found no effect of treatment on the amount of food eaten or on caecal dropping production. However, treated birds, in particular females, developed slightly lower body mass (around 2%) compared to the controls. At post-mortem examination, we found a positive relationship between breast muscle mass and the number of worms collected from the caeca of treated birds. Treated birds with no worms when examined had smaller breast muscle mass (4.6%) compared to the uninfected control birds. These results are largely different to those found in a similar study that documented significant negative impacts on most of these factors in 8 infected birds compared to 6 controls. Its findings were used in a published model to support a hypothesis that H. gallinarum maintained in the environment by common pheasants, the primary host for this worm, could negatively affect wild grey partridge productivity and survival. In the same model our data would not support this hypothesis. Possible explanations for the different results from the 2 experiments are discussed. Together they suggest that only in certain, as yet unidentified circumstances, could experimental H. gallinarum infections have deleterious effects on hand-reared grey partridges.

Observations on the infectivity of Baylisascaris transfuga eggs for mice.

To investigate the potential pathogenicity of Baylisascaris spp. nematodes, mice were experimentally infected with Baylisascaris transfuga eggs, which had been cultured in 0.1 N sulphuric acid, for a period in excess of 1 year. Infectivity for mice appeared after 2 weeks in cultures (2.8%), peaked after 4 weeks (37.4%) and then waned over the next 18 months. The implications of B. transfuga as a possible agent of visceral larva migrans in animals and humans was demonstrated.