The concept of specificity in the procercoid-copepod system: Bothriocephalus claviceps (Cestoda) a parasite of the eel (Anguilla anguilla).

This paper describes experimental work on parasite specificity in the copepod-procercoid system of Bothriocephalus claviceps. Two criteria were used to characterize five potential host species Macrocyclops albidus, Macrocyclops fuscus, Eucyclops serrulatus, Acanthocyclops robustus and Macrocyclops viridis viridis. The first criterion involves susceptibility of the copepods to infection. The results show random or aggregative distributions and variable susceptibilities according to the species. We observed an ethological barrier to infection in M. viridis viridis and M. fuscus. The second criterion involves the growth and development of the procercoid. Three factors modify the profiles of the growth curves: host species, sex and intensity of infection. The growth of the procercoids is density-dependent, whereas their development is independent of density. This last characteristic is interpreted as a factor favouring the aggregation of procercoid populations. The two most susceptible hosts are M. albidus and A. robustus.