Dr. Murai Éva szerk.: Parasitologia Hungarica 13. (Budapest, 1980)

MIHAILOVA et al. (1974); KAMBUROV and OSSIKOVSKI (1976); VASSILEV and SAMNALIEV (1974, 1978) is identical with P. daubneyi. While P. daubneyi and P. microbothrium are species having close similarities to each other yet, P. daubneyi possesses well-defined specific features of its own. The morphological differences between them were studied by DINNIK (1962), SEY .(1974); in their intermediate host specificity by DINNIK (1962), SEY and VISHNYAKOV (1976), SEY and ARRU (1977) and in their stages of the ontogenic cycle by SEY (1979). Results obtained after these examinations are highly suggestive of the European occurrence of P. daub neyi and it seems to be well founded to say that P. microbothrium is found in countries only where its intermediate hosts (bulinid snails) are common. The distribution of Bulinus truncatus in Europe is confined to Corsica, Sardinia, the southern parts of France, Spain and Portugal (PAMPIGLIONE and TOFFOLETTO, 1971). Of the countries in which the systematic status of the rumen flukes (

P. daubneyi

, P. microbothrium) is questionable, according to the writer the most detailed examinations have been done in Bulgaria. VASSILEV and SAMNALIEV (1974, 1978) are of the opinion that the species with which they have worked is such a P. microbothrium of which intermediate host, specially in Bulgaria is Lymnaea truncatula. At the same time, the species of the rumen flukes develop in the same intermediate host (L. truncatula) both in Bulgaria and Hungary is regarded by the writer as the same, single species (

P. daubneyi

) while the Bulgarian authors consider it to be P. microbothrium. Our opinion is based on the following considerations. DINNIK (1962) experimentally demonstrated inKenya that L. truncatula did not pick up the miracidium of P. microbothrium (of which regular intermediate hosts are bulinid snails). Infestational experiments carried out in our laboratory, used three hundred young snails of B. truncatus (derived from Sardinia) with miracidia of P. daubneyi .(of which regular intermediate host is mainly L. truncatula) showed that none of them picked up the miracidia. These experiments indicate that P. microbothrium develops, obligatorily, in bulinid while P. daubneyi in lymnaeid -snails. If the ominous Bulgarian rumen fluke would really be P

t micr

obothrium then the picking up of the infestation would have been expected when miracidia of P. daubneyi (= P. microbothrium by Bulgarian authors) were tested with B. truncatus. Considering the above mentioned experimental results on the obligatory property that appeared in the specificity of these flukes/intermediate host interaction, the recent advances on the genetic regulation of the intermediate host specificity (RICHARDS and MERRITT, 1972) and taking the modern concept of the species (MAYR, 1971) into account then VASSILEV and SAMNALIEV s (1974, 1978) argumentation does not seem to be acceptable. Namely, the obligatorily different intermediate hosts of the two rumen flukes in question indicate that they are reproductively isolated from each other and thus they have independent gene pool satisfying the concept of the distinc species. Thus, the Bulgarian species "

P. mic robothrium

" should be regarded as P. daubneyi. • Figs. 1-15: Median sagittal sections of the muscular organs of some amphistomes Figs. 1-2: Pharynx and genital opening of Paramphistomum cervi (Näsmark specimens) Figs. 3-4: Genital opening of Paramphistomum leydeni (Näsmark' s specimens) Figs. 5-6: Genital opening of Paramphistomum cervi, soaked in water Fig. 7: Pharynx of Paramphistomum leydeni (Näsmark' s specimen) Figs. 8-9: Pharynx and genital opening of Paramphistomum cervi, showing typical appearance Figs. 10-11: Genital openings of Paramphistomum hiberniae and Paramphistomum scotiae (Willmott' s specimens) Fig. 12: Genital opening of Paramphistomum epiclitum Fig. 13: Dorsal half of Paramphistomum cervi with three groups of muscular units in d. e. layer Fig, 14: Dorsal half of Paramphistomum scotiae (Willmott' s specimen) Fig. 15: Pharynx of Paramphistomum gotoi (Photo: O. Sey)