Published online by Cambridge University Press: 06 April 2009
The relationship between intensity and site of infection of Diorchis brevis, D. inflata and D. ransomi in Fulica atra from central Poland has been analysed; of 173 adult birds 152 (87·9%) were infected with one or more of these three species. From (1) the incidence of the three species (D. brevis, 59·5%; D. inflata, 69·9%; D. ransomi, 61·3%), (2) the high total incidence and high total intensity of infection (118·2 worms/bird) in hosts harbouring the three species concurrently and (3) the frequent co-occurrence of all three species in the same site in the host gut, it is concluded that there are no antagonistic interactions among these species. There are, however, some inter-dependencies between the number of parasites and the site occupied by particular species. In heavy infections there was a tendency to specific segregation and extension of the site of each species. This suggests the existence of inter- and intra-specific competition at higher densities of infection, regulating the spatial distribution of these parasites in the host gut.