Nestedness in assemblages of gyrodactylids (Monogenea : Gyrodactylidea) parasitising two species of cyprinid - with reference to generalists and specialists

The structure of gyrodactylid assemblages in individual fishes of two speci es of cyprinid was determined. A total of 100 specimens of minnow, Phoxinus phoxinus, and 137 specimens of roach, Rutilus rutilus, were investigated f or presence of gyrodactylids. Host specificity, specialists vs. generalists , was noted in each host fish. A nested pattern was recorded in parasite as semblages of minnow, the host with a dominant number of specialist gyrodact ylids. A non-nested pattern was observed in parasite assemblages of roach, the host with a dominant number of generalist gyrodactylids. The host speci ficity appears to be a meaningful factor that determines the pattern of gyr odactylid assemblages of both fish hosts. (C) 2000 Australian Society for P arasitology Inc. Published by Elsevier Science Ltd. All rights reserved.