Some aspects of the development of Lobatostoma jungwirth Kritscher, 1974 (Aspidogastrea) in snails and cichlid fishes from Buenos Aires, Argentina

The mollucs 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 eight 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, specially 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.

Life history of Pygidiopsis crassus n. sp. (Trematoda, Digenea, Heterophyidae) in the neotropical region

The life cycle of Pygidiopsis crassus n. sp. was experimentally reproduced, starting from cercariae from naturally infected Littoridina parchappei collected from Lujan River and different ponds in Buenos Aires Province, Argentina. Metacercariae were found encysted in the body cavity of experimentally and naturally infected fishes Cnesterodon decemmaculatus and naturally infected Jenynsia lineata. Adults were obtained experimentally in chicks and mice. The natural host is unknown. The new species is compared with Pygidiopsis macrostomum Travassos 1928, from Rattus norvegicus and from Noctilio leporinus mastivus, differing in body and egg sizes, in the size relation of oral and ventral sucker and the shape of excretory vesicle.

Biologia poblacional de Posthodiplostomum nanum dubois, 1937 (Trematoda, diplostomidae) en Jenynsia lineata y Cnesterodon decemmaculatus (Pisces, atheriniformes), de la laguna de Chi-chis, provincia de Buenos Aires, Argentina / Populational biology of posthodiplostomum nanum Dubois, 1937 (Trematoda, Diplostomidae) in Jenynsia lineata and Cnesterodon decemmaculatus (Pisces, Atheriniformes), of Chis-chis lagoon, province of Buenos Aires, Argentina

As características da dinâmica populacional de Posthodiplostomum nanum em dois dos seus hospedeiros intermediários foram estudadas, utilizando a prevalência, a intensidade de infecçäo e a maturaçäo das metacercárias, considerando a influência da temperatura da água. Além disso, algumas conseqüências ecológicas säo descritas. Foram realizadas 18 coletas mensais ou bimensais, capturando-se 1113 peixes nos quais 956 metacercárias foram obtidas. P. nanum esteve presente durante todo o ano com variaçöes sazonais significativas na prevalência e na intensidade. Observou-se que a temperatura da água é um fator importante na maturaçäo do parasito. Os valores de prevalência e intensidade foram mairoes em Jenynsia lineata. Este fato pode ser o resultado de vários fatores: a) distribuiçäo do primeiro hospedeiro intermediário, b) comportamento do segundo hospedeiro intermediário e c) diferenças fisiológicas particulares de cada hospedeiro, especialmente relacionadas com a reproduçäo. A relaçäo S2/X flutuou no curso do ano, indicando os períodos de recrutamento (outono e primavera) e de näo recrutamento (inverno e veräo) das metacercárias

Life history studies of heterophyid Trematodes in the neotropical region: Ascocotyle (Leighia) hadra sp.n

The life cycle of Ascocotyle (Leighia) hadra n.sp. was experimentally reproduced, starting from cercariae from naturally infected Littoridina parchappei, collected from Los Ranchos stream, near Mercedes city, Buenos Aires Province, Argentina. Metacercariae were found encysted in the liver and mesentery of experimentally and naturally infected fishes Cnesterodon decemmaculatus and Jenynsia lineata. Adults were obtained experimentally in chicks and mice. The natural host is unknown. The new species is compared with Ascocotyle (Leighia) mcintoshi Price 1936 as described by Leigh, 1974, differing in behavior and morphology of cercarial, metacercarial and adult stages