The sea is host to most of the Earth's biodiversity. However, in the case of parasites and their hosts, little is known of the interactions among the organisms. This important volume covers many aspects of these interactions, including the co-evolution and biogeography of different marine systems, and their applied impact on commercially important host species. Topics discussed include species interactions in such well-studied systems as larval trematodes in gastropods and ectoparasites on fish. The effects of parasites in ecosystems extend to commercial, economic concerns, particularly in aquaculture. The volume presents an easy-to-read account of recent advances in this important topic.