Experimental evidence of asymmetrical competition between two species of parasitic copepods.

Lepeophtheirus thompsoni and Lepeophtheirus europaensis are two parasitic copepods naturally isolated on their sympatric hosts, i.e. turbot (Psetta maxima 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. Theory suggests that such a pattern is possible, but only under conditions of competition for the resource. In the present study the attachment rates of the two copepods were studied experimentally under various conditions of competition, infectious dose and number of available hosts. The results suggest a greater sensitivity to competition for the generalist species L. europaensis than for the specialist L. thompsoni, which is in agreement with theoretical predictions.