The molluscs Heleobia castellanosae and Ampullaria canaliculata and cichlid fishes were collected from an artificial pond at Tres de Febrero Park (Buenos Aires city), between June 1994 and May 1995. One hundred and eighty of 2,467 H. castellanosae examined were infected with pre-adults of Lobatostoma jungwirthi, 112 of them in concurrent infections with digeneans. L. jungwirthi was
significantly more prevalent in larger snails, especially those infected with larval digeneans, but
the prevalence of infection did not fluctuate significantly throughout the year. A.
canaliculata and cichlids smaller than 10 cm were not infected, but larger Cichlasoma
facetum harboured adults of L. jungwirthi in their intestines. Experimental
infections of C. facetum and Gymnogeophagus meridionalis with pre-adult
aspidogastreans obtained from H. castellanosae were successful. The
development of L. jungwirthi in the snail host involves five arbitrary growth
phases.Its life-cycle is heteroxenous, similar to that described for L. manteri,
with H. castellanosae as the intermediate host and cichlid fishes as the definitive host
in this pond.