STUDIES ON THE LIFE CYCLES AND MORPHOLOGY OF THE LARVAL STAGES OF ALARIA ARISAEMOIDES AUGUSTINE AND URIBE, 1927 AND ALARIA CANIS LARUE AND FALLIS, 1936 (TREMATODA: DIPLOSTOMIDAE)

Abstract

A. arisaemoides and A. canis have three-host life cycles. In both species there is a mesocercarial stage interpolated between the cercarial and the metacercarial stages. The mesocercaria develops in the second intermediate host and is infective for the definitive host. In the lungs of the definitive host the mesocercariae develops into a diplostomulum which in turn develops into an adult in the small intestine. Mesocercariae survive without developing further in a variety of paratenic hosts, for example, certain frogs, snakes, birds, and mammals. The morphology of the larval stages and the intramolluscan generations is described and observations on the following are given: rate of development, hatching of the egg, and swimming of the miracidium of A. arisaemoides; route of emergence from the snail host, variations in emergence, time of emergence and numbers emerging, activity, and penetration of the second intermediate host by the cercariae; and locomotion and the change in distribution of the mesocercariae of A. arisaemoides and A. canis during metamorphosis of the tadpole host; and egg production by the adult of A. canis.