Résumé
Parasites with simple life-cycles (SLC) require a single host individual in their development, whereas complex life-cycle (CLC) parasites need several hosts. Several groups of parasites are composed entirely of complex life-cycle species (CLC) with at least one intermediate host and one definitive host, as in the case of digenous trematodes, cestodes and acanthocephalans. Although the intermediate host can serve as the site of parasite reproduction, it can also shelter infesting stages and be a prey for the definitive host, with the parasite then becoming an integral part of a predator-prey network.
Few studies have tried to understand the evolution and maintenance of complex life-cycles (Dobson 1989; Dobson and Merenlender 1991; Esch and Fernandez 1993), or the influence of CLC parasites on the dynamics of a multi-species system. Recently, Freeland and Boulton (1992) argued that CLC parasites may predominate parasitic associations and that they may stabilize multi-species systems.