Estudios morfométricos y biológicos de xifidiocercarias (Trematoda) provenientes de la infección natural de Lymnaea columella Say, 1817 (Basommatophora, Lymaenidae) y Biomphalaria tenagophila Orbigny, 1835 (Basommatophora, Planorbidae) recolectados en Miracatu, Estado S？o Paulo, Brasil

two species of xiphidiocercariae probably belonging to the family haematoloechidae (trematoda) emerging from lymnaea columella (basommatophora, lymnaeidae) and biomphalaria tenagophila (basommatophora, planorbidae) collected in miracatu city, s？o paulo state, brazil, between september 1996 and february 1999 were described. the xiphidiocercariae eliminated by l. columella presented a terminal membrane in the tail that morphologicaly differenciated them from those obtained from b. tenagophila. these late xiphidiocercariae were 1.3 times bigger than the former and with the of that ventral sucker bigger than the oral one, while the former presented a sucker size relation inverse. the stylet observed in the xiphidiocercariae eliminated by b. tenagophila oral sucker was shorter than that observed in xiphidiocercariae obtained from l. columella.