The spatial distribution ofDactylogyrus amphibothriumon the gills of ruffeGymnocephalus cernuaand its relation to the relative amounts of water passing over the parts of the gills

Abstract

The spatial distribution of the monogenean Dactylogyrus amphibothrium over the gill apparatus of the ruffe Gymnocephalus cernua was non-random, parasites being aggregated on certain areas of the gills. By plotting the distribution over the gills of the glochidia of Anodonta cygnea, the relative amounts of water passing over the different parts of the gill apparatus was determined experimentally. The observed distribution of D. amphibothrium was then compared with the distribution of the glochidia. The results obtained suggest that the site of attachment of D. amphibothrium is influenced at least in part by the direction and force of the respiratory current over the gills. Most parasites select a site where they are not subjected to its full force.