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EN
The availability of aquatic insects (Odonata: Coenagrionidae, Libellulidae and Trichoptera: Integripalpia) as potential intermediate hosts for the nematode Contracaecum rudolphii Hartwich, 1964 sensu lato was studied under laboratory conditions. The infective material consisted of nematode eggs, newly hatched larvae, as well as in vitro infected cyclopoid copepods. High prevalence and intensity of infection associated with a low mortality of aquatic insect larvae suggests that they may serve as intermediate hosts for C. rudolphii and constitute a major reservoir of C. rudolphii larvae in aquatic habitats.
EN
Laboratory-reproduced and bred asps were experimentally infected with Contracaecum rudolphii larvae, either directly or with previously infected copepods. In the fish exposed to larval infection, the intensity and prevalence of infection were noticeably higher than in the group exposed to copepods. The course of larvae development was similar in both groups. In the larvae measuring ca. 1000 μm in length, the gastrointestinal tract with a developed ventriculus, ventricular appendix and intestinal caecum was clearly visible. The mouth was surrounded by three lips. Over the 10-week experimental period, slightly-coiled larvae surrounded with a thin theca but no encysted larvae were found in the fish exposed to larvae. On the other hand, spirally-stranded and encysted larvae were observed after the 7th week in the fish exposed to infected copepods. The results demonstrated that in the experimentally infected asps, the intensity and prevalence of infection as well as the location of the larvae in a fish depended on the type of invasive material applied.
EN
Seasonal changes in the intensity and prevalence of infestation of the black cormorants from the colony on Lake Selment Wielki were investigated. In 2006, the cormorants were procured in April, August, and October, while in 2007, they were collected in August and September. The prevalence of the infestation was very high and reached 100%. The highest intensity (mean values of 102.46 and 82.17 nematodes/bird in 2006 and 2007, respectively) was revealed in the cormorants shot in August. Intensity of infestation of those birds procured in autumn 2006 was more than twice that found in spring and one-fourth of that found in summer of that year. Similarly, in autumn of 2007, the birds’ stomachs contained less than half of the number of nematodes recorded in summer of that year.
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