Ecological study of some parasitic helminths of aquatic organisms

Except for Monogenea, most other helminth parasites (Digenea, Cestoda, Nematoda and Acanthocephala) of aquatic organisms have a rather complex life cycle, which includes one or more intermediate hosts. Studies have been carried out on the elucidation of helminth life cycles and on parasite-host relationships. Knowledge of the feeding behaviour of the host is a very useful starting-point for elucidation of the life cycles of its' parasites. Asymphylodora demeli, a trematode of two sympatric gobies (Pomatoschistus minutus and P. lozanoi) of the Belgian coastal waters, has been studied. Although very abundant, the life cycle of this parasite remains unsolved. During the summer, the percentage of infection is the same for both Pomatoschistus populations, but the infection level is remarkably higher for P. minutus. Some invertebrates, which are important food items for the Pomatoschistus species, are proposed as potential intermediate hosts. It has become clear that special attention has to be paid on the role of Mollusca in the life cycle of A. demeli. The impact of parasites on lenght-weight relationship, gonadosomatic and hepatosomatic index of their hosts is studied