Dr. Murai Éva - Gubányi András szerk.: Parasitologia Hungarica 27. (Budapest, 1994)

DISCUSSION Having analyzed the morphometric characters from the descriptions of the different samples of P. sonsinoi presented by Moravec (1986), we assume that in his concept P. sonsinoi is a composite species. There are several grounds for such understanding: 1. The zoogeographical distribution of hosts. Relying on the similarity in the geographical distribution of European capillariid species and the close relationship of their hosts, Moravec (1986) has concluded that there is only one nematode species and that the observed morphological and metricdifferences should be regarded as intraspecific variation. However, the geographical isolation between the type localities of T. sonsinoi and T. mingazzinii, and the localities of the newly described materials should be considered. Moravec (1986) has redescribed P. sonsinoi using materials from Southern France (Bognas-Agde, Hérault) from Natrix maura (L.) and from the USA (Lousiana) from Natrix rombifera. The original description of P. sonsinoi made by Parona (1897) was from Italy (Pisa) from Zamenis viridifiavus Lacepede (=Coluberviridiflavus), and that of Trichosoma mingazzinii was from the island of Sicily from Tropidonotus natrix (L.) (=Natrix natrix). We are not convinced that the entire Southern Europe can be regarded as a geographically homogeneous territory. Between Pisa (Italy) and Southern France lay the mountain ranges of the Northern Apennines and the Western Alps. The island of Sicily is even more isolated. As for the species from North and South America and Eastern Asia, it is obvious that they originate from different zoogeographical regions. The close relations between the host species, put forward by Moravec (1986) to support his views, are in fact reduced to their belonging to one and the same family. However, these hosts belong to different genera (Coluber and Natrix), which have basically different habitats and lifestyles. Furthermore, P. viperae is a parasite of snakes which belong to another family (Viperidae). We consider as quite improbable the existence of only one species of capillariid nematode parasitizing hosts as ecologically diverse as the snakes belonging to the families Colubridae and Viperidae inhabiting, moreover, territories a great distance apart. We believe that there are strong enough reasons to expect that parasite speciation had occurred in these hosts as the result of their geographical and ecological isolation. 2. Localization in the host Capillaria colubra could be hardly synonymized with any of the other known species of the genus because of its specific localization. Pence (1970) stressed the fact that C. colubra was found only in the oviducts of Coluber constrictor and never in the host gut. The parasite has been established only in females and never in male hosts. Collins (1973) confirmed this site specificity of C. colubra in other hosts as well (Natrixspp.). 3. Morphometric characteristics. There are considerable morphological and morphometric differences among the 9 descriptions (Table 1) regarded as synonyms of P. sonsinoi by Moravec (1986). Combinations of the taxonomically significant characteristics of capillariids (e.g. spicule length, length and morphology of spicule sheath, morphology of vulvar lips, egg dimensions, the relations anterior/posterior body length and spicule length/body length) allow a clear differentiation of seven species. The closest similarity was observed between the characteristics of P. xochimilcensis and