Argentophilic structures of the miracidium of Echinostoma trivolvis (Cort, 1914) (Trematoda: Echinostomatidae).

Argentophilic structures of the miracidium of Echinostoma trivolvis were described from 80 specimens reared from material originally collected in eastern Pennsylvania, U.S.A. Miracidia were impregnated with 0.5% aqueous silver nitrate solution. The miracidium has 18 epidermal plates arranged in 4 rows of 6 + 6 + 4 + 2 = 18. Up to 20 papillalike structures on the terebratorium were arranged along 3 axes and in 5 groups. A single papilla was located at the base of each of the 6 epidermal plates of the first row. The eyespots were located posterior to the first row of plates and 2 excretory pores were located anterior to the last row of plates.