Tegumental changes of Alaria marcianae (Trematoda) during migration in the domestic cat.

Mesocercariae of Alaria marcianae were removed from snake paratenic hosts and fed to domestic cats. The cats were necropsied at specified intervals, the parasites recovered, and studied by SEM. During the prepulmonary phase of migration in cats, mesocercariae recovered from the stomach wall, abdominal cavity, diaphragm, liver, and heart underwent no tegumental modification compared to those fixed immediately after removal from the paratenic host. The mesocercaria resembled the body of an enlarged cercaria. The oral sucker was encircled by 14 or 15 rows of simple, posteriorly directed spines. Similar spines were also located along the margins of the venter and equatorially at the level of the acetabulum. This spinal pattern left two regions, one anterior and one posterior to the acetabulum, devoid of spines. Uniciliate papillae were found in a distinct pattern associated with the spined areas. In the pulmonary phase, the mesocercariae transformed into diplostomula. Earlike lappets on either side of the oral sucker developed with subsequent differentiation of microvilliform processes on their ventral sides. Body spines divided to give rise to three-pronged serrations. A depression on the venter between the acetabulum and posterior end of the body gave rise to the tribocytic organ. Stout, densely-clustered spines arose de novo on this organ. A rudimentary cylindrical hindbody gave the diplostomulum a distinct scoop-shaped appearance. Worms coughed up from the lungs and swallowed were later found in the duodenum. This postpulmonary phase of migration was a quick event and young worms in the duodenum were indistinguishable from those in the lungs. Within 4 days, the diplostomula in the duodenum matured to adulthood.(ABSTRACT TRUNCATED AT 250 WORDS)