MORPHOMETRIC DISCRIMINANT-ANALYSIS OF 3 SPECIES OF PETASIGER DIETZ, 1909 (DIGENEA, ECHINOSTOMATIDAE)

The morphology of three Palaearctic species of the genus Petasiger Die tz, 1909, parasitizing grebes and exhibiting a significant degree of o verlap, was studied. Ninety-three specimens belonging to P. grandivesi cularis, P. neocomense and P. pungens were compared using univariate a nd multivariate statistical analyses of 17 metrical characters. A step wise discriminant analysis run in three variants and based on seven va riables (body length, body width, oral sucker diameter, pharynx diamet er, ventral sucker diameter. posterior testis diameter and oesophagus length) yielded a 100 % accurate classification. The first canonical d iscriminant function separated specimens belonging io P. grandivesicul aris and P. pungens, and the second function effectively differentiate d the P. neocomense sample. Two variables (pharynx diameter and oesoph agus length) were strongly correlated with the canonical functions and , when used alone, discriminated the three Petasiger spp. A simple key based on two variables used in the discriminant analyses and a table of the qualitative and quantitative characters used for the identifica tion of the three species are presented.