A quantitative approach to the evaluation of the morphological variability of two echinostomes, Echinostoma miyagawai Ishii, 1932 and E. revolutum (Frolich, 1802), from Europe.

摘要

A morphometric analysis was conducted on 2 European species of Echinostoma to determine the degree of adult variability and to assess the value of morphometric data for discriminating species. Adult E. miyagawai and E. revolutum were compared usingunivariate and multivariate statistical analyses of 35 and 25 metrical characters, respectively. All subsets of worms of different ages represented homogeneous samples with respect to their morphometric characteristics. However, univariate analyses revealed significant differences in 22 and 23 variables between the corresponding age subsets of the 2 species, and it was found that different allometric growth patterns contributed to this. The variables, body width at the posterior border of the ventral sucker, pharynx length and width, ovary length, testes length and width and length of the pre-ovarian region, exhibited isometric or positive allometric growth in E. miyagawai and negative allometry in E. revolutum. A cluster analysis based on 61 specimensand 25 variables separated E. revolutum and E. miyagawai unambiguously, producing an exact ordering of specimens with respect to their identity and age. A forward stepwise discriminant analysis identified 5 variables (body width at the posterior borderof ventral sucker, head collar width, length of oesophagus, width of ventral sucker and length of the pre-ovarian region) which yielded a 100% accurate classification of the 2 species. It is suggested that the morphometric characteristics of adult wormscould be used in the identification of species or isolates of Echinostoma spp., although more comparative data are required in order to define the species boundaries within the 'revolutum' group more accurately.