The trematode life cycles involve intricate transmission patterns adapted to the habitat, the abiotic and biotic conditions and especially the different host species present. Other invertebrates and vertebrates may play a role as the second intermediate host, whereas the definitive hosts are often vertebrates, such as various fishes, amphibians, reptiles, birds and mammals.
Details on the associative life-cycle patterns between 1000 digenean species and their mollusc hosts have been recorded. These metazoans utilize multi-host systems to complete their complex life cycles, often with a mollusc as the first intermediate host. Trematodes, dominated by the digeneans, comprise a group of abundant and ubiquitous parasitic metazoans with high diversity and more than 18,000 nominal species. This survey contributes updated information on parasite–host relations and compatibility and may assist in describing the ecological structure of the investigated Danish freshwater ecosystems. The snail host Lymnaea stagnalis showed the highest prevalence and also exhibited the highest diversity, accounting for 47.6% of the species richness. The overall trematode prevalence was 12.6%, but large variations occurred between host species. ResultsĪ total of 5657 snail hosts belonging to ten species were identified, revealing a highly diverse parasite fauna comprising 22 trematode species. Snails were sampled from 21 freshwater lakes in Denmark, following which shedding procedures were performed, cercariae were recoved and the released parasites were identified using molecular tools (PCR and sequencing). Only limited information on the occurrence of trematodes and their link to other trophic levels in the Danish freshwater ecosystems is currently available.Therefore, the main aim of the present study was to increase our knowledge in this field.
Their presence in a habitat will reflect the presence of different host species and, as such, they can serve as ecological indicators. Digenean trematodes are parasitic platyhelminths that use several hosts in their life cycles and are thereby embedded in various ecosystems affected by local environmental conditions.
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