A NESTED PARASITE SPECIES SUBSET PATTERN IN TROPICAL FISH - HOST AS MAJOR DETERMINANT OF PARASITE INFRACOMMUNITY STRUCTURE

The number of monogenean gill parasite species associated with fish ho sts of different sizes is evaluated for 35 host individuals of the Wes t African cyprinid Labeo coubie. The length of host individuals explai ns 86% of the total variation in monogenean species richness among ind ividuals. Larger hosts harbour more species than smaller ones. The exi stence of a hierarchical association of parasite species in individual s of L. coubie is demonstrated. Monogenean infracommunities on larger fish hosts consist of all species found on smaller hosts plus those re stricted to the larger size categories, suggesting some degree of comp ositional persistence among host individuals. The findings provide str ong support for an interpretation of the relationship between monogene an parasite species richness and host body size in terms of a nested s pecies subset pattern, thus providing a new record of repetitive struc ture and predictability for parasite infracommunities of hosts.