egg capsule of Haematoloechus medioplexus from the lungs of Rana
pipiens, the leopard frog. This is the common digenetic trematode that
infects the lungs of frogs. Egg capsules like this one which contains the
miracidium (the cilia can be seen as the small circular bodies inside the
capsule), are coughed up and swallowed by the frog, eventually exiting the body
through the feces. A specific snail such as Planorbula armigera,
ingests the egg capsules, eventually resulting in the production of cercaria
which emerge and enter the cloacal respiratory system of a dragon fly naiad
where they encyst as metacercaria. After completing metamorphosis, the
adult dragon fly may be preyed upon by a frog, completing the life cycle.
4000x.