Desenvolvimento de Eurytrema coelomaticum (Giard & Billet) (Digenea, Dicrocoeliidae) em Bradybaena similaris (Férussac) (Gastropoda, Xanthonychidae)

Abstract

To follow the larval development of Ewytrema coelomaliclIm (Giard & Billel, 1892) in 8radybaena similaris (Férussac, 1821) snails were separaled in three classes using the shell diameter: Class A (14.5-10.2 mm), Class B (10.1-6.9 mm) and Class C (6.8-2.6 mm). Only snails belonging to classes A and B acquired the inteclion. Specimens of E. coelomalicum removed from lhe pancrealic ducts were exposed to lhree physiological solutions: Earle, Locke and saline 0.85%, to obtain eggs for the experimental infections. The Locke solution induced the best egg release. The route ofmigration lhe intramolluscan development of E. coelomalicum was studied with the aid of histology. The minimal period of intramolluscan development, ending at the expelling of daughler sporocysts, was 107 days for the snails intecled in March, and 79 days for lhe snails infecled in November. The Sludenl "t" test and the Chi-square lest showed a significant difterence (u = 5%) between the two periods, although the mean lemperalure regislered during the experiments did not signiticanlly diftered (u = 5%). The eliminalion of daughter sporocysls occurred lhrough lhe snail's pneumostome, and always aI night. Most sporocysts were eliminated aI intervals thal varied between one to three days, without reglllarity. The time ofelimination ofthe dallghter sporocysts was ditlerenl for the two intection period studied: 12 weeks for the snails infecled in March, and llu'ee weeks for lhos e infecled in November. Positive correlalion between the number of sporocysts expelled by the snail hOSI and higher lemperatures registered in the laboratoy was observed. This correlation was more evident in November infection.