Graduate Thesis Or Dissertation
 

Digenetic trematodes of Ascaphus truei in western Oregon

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/g732dd27h

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  • The Tailed Frog Ascaphus truei, the only species in the family Ascaphidae found outside New Zealand, is a common inhabitant of the mountain streams of the Northwestern United States and British Columbia. The anatomical peculiarities of this primitive anuran have been investigated, but no literature is available on the digenetic trematodes it harbors. In Western Oregon, Ascaphus was found to serve as a definitive host for two digenetic trematodes which live in the small intestine, and as a second intermediate host for two digenetic trematodes which live as encysted metacercariae in the subcutaneous connective tissue. Tetracheilos ascaphi Anderson and Pratt, 1964, is a trematode in the family Allocreadiidae, with a life cycle somewhat similar to several species of Crepidostomum. The adult lives in the anterior portion of the small intestine of Ascaphus. Eggs pass with the feces, and the clam Pisidium idahoense becomes infected with the miracidia. The miracidia develop into sporocysts on the gonads and Iiver. The cercariae emerging from the sporocysts enter the caddisfly Rhyacophila grandis and encyst to develop into metacercariae. Ascaphus eat adult Rhyacophila and the excysting metacercariae become adult in the intestine of the frog. Euryhelmis squamula Rudolphi, 1819, (Heterophyidae) is found as encysted metacercariae in the subcutaneous connective tissue of Ascaphus, Metacercariae eaten by golden hamsters become mature in 70 to 92 hours, and eggs pass out with the feces of the host. In the wild, the snail Bythinella hemphilli is infected by the miracidia hatching from the egg. The lophocercous cercariae emerge from the snail and penetrate the frog's skin. Metacercariae become infective in 44 days or less in Rana aurora. Euryhelmis pacificus Senger and Macy, 1952, is also found encysted under the skin of Ascaphus. This trematode has been reported from the salamander Dicamptodon ensatus, and from Mustela vison and Ondatra zibethica in Oregon. It matures in 55 to 72 hours, and lives for more than eight months in the small intestine of the golden hamster. The first intermediate host and early larval stages are unknown, Cephalouterina dicamptodoni Senger and Macy, 1953, (Lecithodendriidae) originally found in the small intestine of Dicamptodon ensatus, also lives in the small intestine of Ascaphus. Metacercariae are found encysted in the Salmonfly Acroneuria californica which is eaten by Ascaphus. The excysted flukes mature in the frog's intestine and eggs are passed with the feces. The first intermediate host and the early larval stages are unknown.
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