On Copepoda associated with Dutch molluscs

It is known for more than a century already that molluscs are appropriate hosts for Copepoda. Since we are in many cases uncertain what relation exactly exists between the mollusc and the copepod, terms like ”parasite”, ”semi-parasite” and ”commensal” can better be avoided and the more neutral term ”associate” used instead. MONOD & DOLLFUS summarized in 1932 all previous literature on copepods associated with molluscs. HUMES estimated in 1958 the number of copepods known to live on or in molluscs, at over 100 species, divided over about 60 genera. These copepods do not form a systematic unity, but belong to different groups; the greater part of them have been classified with the Cyclopoida, although all other copepod orders, with the exception of the Calanoida, include associated forms. In the last few years several dozens of new species have been described, the total number of copepods associated with molluscs being therefore may be 50% higher than HUMES’ estimate. The hosts belong to the classes Gastropoda, Cephalopoda and Lamellibranchia; from the Monoplacophora, Amphineura and Scaphopoda no copepods became known hitherto. All hosts are marine, except for one case of infection of an African brackish water Congeria (cf. HARDING, 1963).