The Life Cycle of Cephalogonimus salamandrus sp. n. (Digenea: Cephalogonimidae) from Ambystoma tigrinum (Green) from Eastern Washington

Abstract

Mother and daughter sporocysts and xiphidiocercariae develop in Helisoma trivolvis. Cercariae penetrate tadpoles of Rana pretiosa and small A. tigrinutm larvae in which they encyst. The adult develops in the anterior small intestine of A. tigrilnum after ingestion of an infected 2nd intermediate host. The life cycle of C. salamandrus is compared with C. americanus from Rana clamitans. C. salamandrus is described as a new species on the basis of cercarial and adult morphology, and the failure to achieve cross-infections in the respective definitive hosts for C. americanus and C. salamandrus. Cephalogonimus Poirier, 1886, is the only genus of the family Cephalogonimidae in amphibians. Rai (1961) listed Cephalogonimus brevicirrus (Ingles, 1932), C. amphiumae (Chandler, 1923), C. letusus Dujardin, 1845, and C. am?ericanus (Stafford, 1902) from amphibians of North America. Premvati (1969) described C. sireni from Florida mud eels. The only life cycle reported is for C. americanus from Rana clamitans Latreille (Lang, 1968). This parasite has also been reported from R. catesbeiana Shaw (Rankin, 1945), and R. pipiens Schreber (Brandt, 1936; Najarian, 1955). An undescribed cephalogonimid is a common intestinal parasite of neotenic and adult Ambystoma tigrinum (Green) of eastern Washington. Of the other species of Cephalogonimus, this parasite most closely resembles C. americanus. Comparison of the life cycle stages of this parasite with those of C. americanus and the demonstrated specificity of these two parasites to their respective definitive hosts establishes the validity of this new species to which the name Cephalogonimus salamandrus is assigned. MATERIALS AND METHODS Eggs were teased from adult flukes and stored in filtered spring water at 5 C until used. Fully embryonated eggs were fed to young laboratoryreared Helisoma trivolvis (Say). Exposed snails were crushed and examined at intervals after Received for publication 9 April 1973. *A portion of this study was conducted at the University of Michigan Biological Station. tPresent address: Department of Biology, New Mexico State University, Las Cruces, New Mexico 88003. exposure. Naturally infected H. trivolvis were collected for cercarial study and laboratory infection of the second intermediate host. Cercariae were studied alive with and without vital stains. Cercariae were placed wvith various aquatic invertebrates, small salamander larvae, tadpoles, and small frogs. Penetration and encystment occurred only in amphibian skin. Metacercariae were studied at 2 hr, 1 day, 5 days, 10 days, 12 days, and 21 days after infection. Tadpoles and salamander larvae used as intermediate hosts were laboratory-reared. Large neotenic A. tigrinum for use in laboratory infections were collected from a lake where no trematode or cestode parasites were found in 150 A. tigrinum and no Helisoma spp. have been found in over 6 years of study. Salamanders were maintained in filtered spring wrater on a diet of earthworms. Before exposure 13 neotenic salamanders (20 to 30 cm in length) were starved for 2 weeks. Feeding was resumed the day after exposure. Each of 11 salamanders was permitted to ingest two infected tadpoles, each containing 20 to 30 metacercariae which were 12 days old at exposure. Salamanders were necropsied at 52 hr, 5 days, 10 days, 15 days, 20 days, and 48 days after exposure. Also each of two salamanders was permitted to ingest two infected salamander larvae, each containing 20 to 30 metacercariae which were 12 days old at exposure. These were necropsied at 5 days. Recovered flukes were studied alive, measured, heat-killed, stored in AFA, and stained in Semichon's Carmine. To determine if A. tigrinum and R. pretiosa of eastern Washington could be infected with C. americanus, hosts were transported to the University of Michigan Biological Station. Methods for handling C. americanus and collection of Cephalogonimus-free R. clamitans have been reported (Lang, 1968). Two salamanders were exposed to 10-day-old metacercariae of C. americanus. Each salamander received 50 to 70 metacercariae and was necropsied 10 or 30 days after exposure. During this experiment two A. tigrinum