Dr. Murai Éva szerk.: Parasitologia Hungarica 16. (Budapest, 1983)

The structure of the acetabulum is characterized by having a thin acetabular wall (Diplodiscus Nasmark, 1937) with a great number of very small muscle units in the circular layers. Five types were differenciated among the species examined. Beside the Diplodiscus type (hold for D. subclavatus) (Fig. 10), D. mehrai (Fig. 11), M. temparatus (Fig. 12), O. diplo discoides (Fig. 13) which was described by NASMARK (1937) four new ones could be distinguished: Catadiscus (without accessory sucker and with lateral constrictions), Progonimodiscus (with ruffled peduncle) (in case of these genera sections were not available); Megalodiscus and Dermatemytrema. Megalodiscus (Figs 14-15) Well developed acetabulum, 1,7-1.9 mm in diameter; d.i. numerous, 85-88 units; thickness of acetabulum 450 jum, with acetabular prominence. Dermatemytrema (Figs 16-17) Diameter of acetabulum 0.7-0.8 mm, number of units in d.e. and v.e. is about 33-35; thickness of acetabulum 0. 5-0. 8 mm, muscular pad short; without acetabular prominence. Both SKRJABIN (1949) and YAMAGUTI (1971) characterized the oesophagus of Opisthodiscus as having no oesophageal bulb. In fact, it is present (Fig. 18). YAMAGUTI (19 71) reported the presence of a hermaphrodite sac in D. trifoliata. Histological preparations show, however, that a simple cirrus pouch is present in the genital opening (Fig. 8). BIOLOGICAL OBSERVATIONS Examining the life-cycle of Diplodiscus subclavatus Looss (1892) reported that not rarely the testes, unite into a single, conical body. This statement was accepted by the subsequent authors and the involvement of this feature in the diagnosis of the genus Diplodiscus (YAMAGUTI, 1971) and that of the species (SKRJABIN, 1949) is still recognized. As this phenomenon seems to be a unique feature not only among amphistomes but also in trematodes, it was worth re-examining. Some sets of amphistomum-free frogs were infected with ten metacercariae of D. subclavatus each and two specimens of frogs were dissected in Legend to figures Figs. 1-6: Median sagittal sections of pharynxes Fig. 1: Opisthodiscus diplodiscoides Fig. 2: Megalodiscus americanus Fig. 3: Diplodiscus mehrai Fig. 4: Megalodiscus temperatus Fig. 5: Dermatemytrema trifoliata Fig. 6: Diplodiscus subclavatus Figs. 7-9: Median sagittal sections of genital openings Fig. 7: Megalodiscus americanus Fig. 8: Dermatemytrema trifoliata Fig. 9: Diplodiscus subclavatus Figs. 10-17: Median sagittal sections of acetabula Fig. 10: Dorsal half of Diplodiscus subclavatus Fig. 11: Diplodiscus mehrai Fig. 12: Megalodiscus temperatus Fig. 13: Dorsal half of Opisthodiscus diplodiscoides Figs. 14-15: dorsal (14) and central (15) parts of Megalodiscus americanus Figs. 16-17: ventral (16) and dorsal (17) parts of Dermatemytrema trifoliata Fig. 18: Oesophageal-bulb of Opisthodiscus diplodiscoides