Dr. Kassai Tibor - Dr. Murai Éva szerk.: Parasitologia Hungarica 9. (Budapest, 1976)
to these species and because P. microbothrium was repeatedly reported from Bulgaria special attention should be paid to those characters important in the identification of the species in question. We used the following morphological characters to separate P. daubneyi and P. microbothrium: The terminal parts of the caeca of P. daubneyi turn towards the ventral surface of the body, whereas in P. microbothrium they turn dorsalwards. During our examinations position of the caeca was carefully studied and in 85 of 95 specimens they showed typical position, i. e. turned ventralwards, in 3 specimens the right and in 7 specimens the left terminal parts exhibited discrepancy from the typical position. In these cases the terminal parts of the caeca turned straigh towards the posterior or somewhat to the dorsal or distinctly the dorsal direction. It should be stressed, however, that the terminal parts of the atypical caeca were situated in the lateral region of the body and they did not penetrate into the dorsal part of it. Having made histological sections of those specimens with atypical caeca we could not find any other correlative deviations as compared to specimens having typical ends of the caeca. Therefore we believe that they are individual variations and the position of the terminal parts of the caeca seems to be a valuable and fairly constant character. The structure of the muscular organs, pharynx and acetabulum through histological sections did not display any remarkable deviations from the features described by NASMARK (1937) for these organs under the name Paramphistomum types (Figs. 1, 14-16). The genital atrium, however, deserves more attention since it is of specific importance. It should be remembered that the genital atrium as a muscular organ may exhibit different appearances depending on its physiological state at the moment of fixation. Therefore it can hardly be expected that each specimen should show the same "typical" form described in NASMARK's (1937) or in other's papers. Microphotographs enclosed introduce a series of genital atria, some of them can be called "typical" (Figs. 3-6) whereas others (Figs. 7-10) represent the extreme appearance of this type which can easily give way to misunderstanding (e. g. Fig. 7 and Figs. 8, 9 at first view resemble to Bothriophoron and Calicophoron types, respectively). Although the genital atrium of both P. daubneyi and P. microbothrium are of the Microbothrium type, nevertheless, we have found that the sphincter papillae of P. microbothrium is several times stronger than that of P. daubneyi (Figs. 11 and 12). Apart from the morphological features, the examination of specificity to intermediate hosts can also give us useful help in a correct identification. It is common knowledge that the spectrum of intermediate hosts of flukes is narrower than that of their final hosts. One aspect of the intimate connection between the miracidium and the intermediate host was illustrated by RICHARDS and MERRITT (1972), who experimentally demonstrated that the susceptibility of juvenile Biomphalaria glabrata to Schistosoma mansoni infection is regulated by several genetic factors. Although Figs. 1-11: Median sagittal sections of organs of Paramphistomum daubneyi . 1-2 = pharynx; 3-11 = genital atrium with different appearance. Fig. 12: Genital atrium of a Paramphistomum microbothrium from Egypt. Fig. 13: Genital atrium of Paramphistomum clavula, Näsmark' s material; Figs. 11-13 were taken with the same magnification; compare the measurements of genital sphincter and sphincter papillae. Figs. 14-15: Dorsal half of acetabulum of P. daubneyi . Fig. 16: Ventral half of acetabulum of P. daubneyi. (Photo Sey)
