Experimental evidence of asymmetrical competition between two species of parasitic copepods

Lepeophtheirus thompsoni and Lepeophtheirus europaensis are two parasitic c opepods naturally isolated on their sympatric hosts, i.e. turbot (Psetta ma xima L.) and brill (Scophthalmus rhombus L), respectively. They are able to meet, mate and hybridize on turbot experimentally, but they are naturally prevented from doing so by a strong host preference when given a choice. Th eory suggests that such a pattern is possible, but only under conditions of competition for the resource. In the present study, the attachment rates o f the two copepods were studied experimentally under various conditions of competition, infectious dose and number of available hosts. The results sug gest a greater sensitivity to competition for the generalist species L. eur opaensis than for the specialist L. thompsoni, which is in agreement with t heoretical predictions.