Life Cycle: The first intermediate host are Phsya sp. snails, the second intermediate host are copepods, and the definitive host is a bullfrog, specifically in the eustachian tubes (Thomas, 1939).
Orange-brown worms: body elongate, 6.0-6.5 mm long x 1.8 mm wide as an adult; greatest width just anterior to posterior testis. Cuticula 15 μ. thick, sparsely studded with low, glandular tubercles. Oral sucker subterminal, 455 x 434 μ to 621 x 534 μ. No prepharynx; pharynx 192 x 175 μ to 210 x 210 μ. Esophagus extremely short. Ceca sinuous, narrow, rugose, dorsal to other organs, extending nearly to posterior end of body. Acetabulum thick, muscular, 674 x 621 μ to 700 x 674 μ, near middle of body; acetabular opening anterior, eccentric. Testes extra-cecal, ovoidal, widely separated, oblique; anterior testis 700 x 674 μ to 805 x 796 μ; posterior testis 884 x 796 μ to 892 x 805 μ. Seminal receptacle pyriform, broad, ex-tending dorsoventrally; neck near genital pore, supplied with prostate glands. Ovary nearly median, just anterior to vitellaria, ovoidal, 464 x 437 μ to 490 x 402 μ long, axis at right angles to long axis of body. Oviduct joins Laurer's canal, then common vitelline duct, and continues a short distance to meet oӧtype with well developed Mehlis' gland. Uterus, packed with eggs, mostly in transverse, S-shaped coils extending from vitellaria to bifurcation of ceca. Genital pore ventral, median, near level of pharynx. Vitelline follicles mostly ovoidal average 280 x 192 , in diameter, posterior, in two groups, right and left, 4 to 6 or 4 to 5 on a side. Vitelline ducts from follicles unite in short common duct in region of ovary. Two lateral ciliated excretory canals, united dorsally near posterior margin of oral sucker, dip towards median line at posterior margin of acetabulum to join thick-walled urinary bladder just anterior to ovary. Bladder median, supplied with villi, discharges through terminal pore. Eggs, straw-colored, mitriform, 67 x 26 μ to 67 x 27 μ, broad end operculate; opposite pole, with filament measuring 56-58 μ in length, tapers to fine tenuous recurved tip; fully embryonated when laid. Development in snails Physa gyrina, P. sayii crassa Walker, P. parkeri Currier, and copepods Mesocyclops obsoletus and Cyclops vulgaris; cercaria cystophorous, with two streamers in addi-tion to excretory tubes and bulbus; metacercaria in cyclops with everted urinary villi; young flukes in tadpoles.
Sources: Thomas, L.J. 1939. Life Cycle of a Fluke, Halipegus eccentricus n. sp., Found in the Ears of Frogs. The Journal of Parasitology, Vol. 25, No. 3, p. 207-221. Published by Allen Press on behalf of American Society of Parasitologists.