No abstracts are to be cited without prior reference to the author.Marine ecosystems are collections of abiotic and biotic factors, hierarchically arrayed, and inclined toward interaction. Taking into account that parasites represent far more than half of all animal species (Rohde, 1980) and cephalopods occur in all oceans of the world (Boyle, 1990), the occurrence of a particular marine parasite in any cephalopod species anywhere will depend on the presence of a suitable definitive host(s), suitable intermediate host(s), suitable paratenic host(s) (which help to fill up . the ecological gap in the parasite life cycle), and complex biological factors which afford a strict interdependency on the organisms comprising the host-parasite systems.