Morphological variation in Echinorhynchus truttae Schrank, 1788 and the E. bothniensis Zdzitowiecki & Valtonen, 1987 species complex from freshwater fishes of northern Europe

Principal component analysis of the proboscis profiles of female Echinorhynchus bothniensis, E. 'bothniensis', E. leidyi and E. truttae. The first (PC1) and second (PC2) principal components describe 64% and 10% of the variance in the data, respectively. Analysis based on data in Suppl. material 4

Scatterplot of the loadings for the first two principal components. Key: l and b, length and base measurements respectively, from hooks in the 4.5-79.5% region of the proboscis; L and B, length and base measurements respectively, from hooks in the 80.5-95.5% region of the proboscis.