ARGENTOPHILIC STRUCTURES OF THE MIRACIDIUM OF ECHINOSTOMA-TRIVOLVIS (CORT, 1914) (TREMATODA, ECHINOSTOMATIDAE)

Argentophilic structures of the miracidium of Echinostoma trivolvis we re described from 80 specimens reared from material originally collect ed in eastern Pennsylvania, U.S.A. Miracidia were impregnated with 0.5 % aqueous silver nitrate solution. The miracidium has 18 epidermal pla tes arranged in 4 rows of 6 + 6 + 4 + 2 = 18. Up to 20 papillalike str uctures on the terebratorium were arranged along 3 axes and in 5 group s. 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 f irst row of plates and 2 excretory pores were located anterior to the last row of plates.