Crustaceans may either eat infective snails or be penetrated by cercariae, which develop into metacercariae
within their viscera, gills, muscles and legs.
Siphons and mantle edges were slide mounted and examined under transmitted light on a compound microscope to count metacercariae
present (1/21/09 collection only counted up to 100).
Digeneana Deropegus aspina 7 2% 3/150 2.3 (1-3) Glypthelmins quieta 16 6% 9/150 1.8 (1-5) Gorgoderina multilobata 82 11% 17/150 7.4 (1-50) Haematoloechus kernensis 121 10% 15/150 8.1 (1-33) Megalodiscus microphagus 16 5% 8/150 2.0 (1-5) Echinostome metacercariae
1000 39% 59/150 -- -- Nematoda Cosmocercoides variabilis 13 6% 9/150 1.4 (1-5) Hedruri.s sp.
Encysted cercariae (metacercariae
) may remain viable for many months unless they become desiccated.
Often, the location of metacercariae
is specific for each species of Ascocotyle, providing a feature that is useful in species identification.
have been shown to be fully infective soon after encystment (Herber, 1942).
Because the infection rate by metacercariae
in the experiment was less than that in the field population, a few metacercariae-infected individuals may have died during the experiment.
Relatively few studies have looked at the effect of trematode metacercariae
on host behavior (Poulin 1994a).
Cattle are infected by eating grass containing metacercariae
. Once in the animal's small intestine, they emerge from cysts and the immature flukes begin to penetrate the intestinal wall and migrate to the liver.
Drawings of life-cycle stages associated with the parasite's intermediate hosts (sporocysts and rediae, cercariae and metacercariae
) are made on the surface of a water-filled tank.
of Cryptogonimids encyst in the tissues of fishes The adults are found in the gut sometimes in the other organs of freshwater and marine fishes, occasionally in amphibians and reptiles (14).