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Planorbella trivolvis the snail first intermediate host.
Life cycle stages of Megalodiscus temperatus in snails, tadpoles and adult anurans. A. Comparison of a typical adult gravid worm recovered from an adult anuran and tadpole (black arrow). Scale bar = 0.8 mm. B. Adult gravid worm recovered from a tadpole, note the eggs and eyespots. Scale bar = 0.25 mm. C. Miracidia hatching from an egg released by a gravid worm from a tadpole. Scale bar = 25 µm. D. A three day old Planorbella trivolvis with a M. temperatus miricidium trying to penetrate under the shell (arrow). Scale bar = 0.5 mm. E. A three month old laboratory reared and infected Planorbella trivolvis with shell removed, showing the infected hepatopancreas (Box) with Megalodiscus temperatus rediae. Scale bar = 75 mm. F. Close up of E. Scale bar = 2 mm. G. Megalodiscus temperatus redia removed from the hepatopancreas of an infected snail. Note the round pharynx and developing cercariae. Scale bar = 80 µm. H. Megalodiscus temperatus cercaria from a laboratory infected snail. Scale bar = 180 µm. I. A tadpole of Rana blairi, with a Megalodiscus temperatus metacercaria attached to the skin (arrow). Scale bar = 1 mm. J. Large intestine of a tadpole of Pseudacris triseriata with two attached Megalodiscus temperatus adult worms 10 DPE (arrows). Note the eyespots. Scale bar = 100 µm. K. Sexually mature worm from J. Note the presence of eyespots, and the developed testes (black arrows) and ovary (white arrow). Scale bar = 30 µm. L. Two week old worm from an experimentally infected tadpole of Pseudacris triseriata fed algae. Note the green cecae full of algae. Scale bar = 30 µm. M. Enlarged cecum of L. Scale bar = 5 µm. N. Megalodiscus temperatus metacercaria on the skin of an experimentally infected adult Pseudacris triseriata frog. Scale bar = 150 µm. O. Two week old worm from an experimentally infected adult Pseudacris triseriata fed crickets. Note the red ceacae full of frog blood. Scale bar = 30 µm. P. Enlarged cecum of O. Scale bar = 5 µm.