Marine Intermediate Hosts

Marine heteroxenous parasite species face the problem of finding suitable intermediate hosts in a huge three-dimensional diluted environment. Especially in the meso- and bathypelagic layers (200–4000 m depth) of the deep sea the prevalences in evertebrates (Mollusca, Crustacea) and vertebrates (Teleostei) are quite low compared to the benthic realm or shelf areas of the world oceans. Metazoan parasite species, particularly from the groups Digenea, Cestoda, Nematoda, Acanthocephala, with mandatory host changes depend on the availability of proper host organism to maintain their life cycles and reach the final hosts for reproduction. Previous studies and reviews documented that parasite species with a low host specificity are able to maintain their life cycles in the areas of the open ocean and the deep sea, while more specific species are rather distributed in more biomass and consequently more intermediate host-rich regions. In their life cycle, parasitic larvae regularly use the food...