Dr. Murai Éva szerk.: Parasitologia Hungarica 16. (Budapest, 1983)
every subsequent three days up to two months post infection. It was found that neither the cercariae nor the immature worms have had two testes; it was always single. LOOSS' s erroneous observation might be in connection with another frog amphistomes (O. diplodiscoides) which has really two testes. It should be remembered that this species had not yet been discovered at that time. Species of the genus Diplodiscus are predominantly parasites of frogs. There are, however, numerous data in literature on the occurrence of D. subclavatus in other vertebrate hosts: Esox lucius (OSMARIN, 1965), Synodontis membranaceus (1SSA and EBAID, 1969)*, Natrix natrix (PETRIASVILI, 1966; DUBININA, 1953; RADULESCU, 1959), Vipera berus (cit. SHARPILO, 1976), Alopex lagopus (MALCZEWSKI,1962;cit. YAMAGUTI, 1971) and Diplodiscus sp. in Sorex araneus (ELTYSEV, 1975); Megalodiscus temperatus in Coluber constrictor (PARKER, 1941). It is obvious that these accidental hosts were infected through the food-change by these helminths. These findings can throw some light on the real nature of amphistomes recovered in snails. Adult and subadult diplodiscids have been found so far in two species of fresh water snails; in Viviparus (= Paludina) viviparus in Europe (HONER, 1960, 1961) and in India in Pila globosa (ANJANEYULU, 1967 and others, see later). The discovery of amphistomes is snails led to the description of a new subspecies, D. subclavatus paludinae Honer, 1961, and a new genus and species, Pseudodiplodiscus pilai Murty, 197 0; D. anjaneyului Pandey, 197 3 and inspired the speculation (MURTY, 1973) that these cases are instances of reversal to the original mode of employing the mollusk as an adult host (it should be remembered, however, that according to the assumption held by numerous helminthologists, the snails had been intermediate and not definitive hosts in the prevertebrate time while the adults of digeneans were freeliving ones). HONER (1961) found his material to be closely related to D. subclavatus and indicated some minute difference from it; ANJANEYULU (1967) regarded his material as similar to D. meh rai, a common fluke of frogs inlndia. MURTY (1970) worked with the same material as ANJANEYULU (1967) as regards its general topography and inner structure. MURTY (1970), however, was of the opinion that his material represents a new species and genus ( Pseudodiplo- discoides pilai ). Later, PANDEY and.JAIN (1974) raised Diplodiscus sp . of ANJANEYULU (1967) to species level, naming D. anjaneyului. Beside these D. mehrai was also found in Pila globosa by PANDEY (1973) and details of the lifecycle studies of P. pilai were published by MURTY (1973). To the contrary of the notion that the snails in question are normal hosts we can raise the objection that nobody of the abovementioned authors tested the fertility of eggs contained by these flukes. To demonstrate the importance of this circumstance se-veral Viviparus viviparus were infected with metacercariae of D. subclavatus and they were dissected periodically up to months post infection. Flukes were found in snails containing some eggs but they proved to be sterile during incubation. An analogous situation can be imagined in case of Indian amphistomids recovered in snails. Our results show that V. viviparus and probably the other snails in question are accidental ones and they represent a deadline in development of these amphistomes. V, viviparus is a snail characterized by bottom feeding and, as metacercariae of D. subclavatus are often encysted on the bottom, infection can take place in the course of the feeding activity, as it had happened in other, non-amphibian hosts. Their misidentification is evident.
