Location of Rediae of Proterometra macrostoma (Trematoda: Azygiidae) in the Snail Elimia semicarinata (Gastropoda: Pleuroceridae), and Daily Emergence of its Cercaria

Abstract

The objectives of this study were to describe the (1) location of Proterometra macrostoma rediae in the snail intermediate host, Elimia semicarinata, and (2) daily emergence of cercariae from individual snails over 3 weeks. Decalcification and histological sections of infected snails revealed rediae restricted to the bottom whorl within the mantle cavity in close association with the host gills. A continuous, low-level emergence of cercariae (0.25–0.833 larvae/snail/day) was observed over 21 days. Both moderately frequent (7–12 days) and infrequent (2–6 days) shedding of cercariae were observed (i.e., mean ± SE = 7.3 ± 0.4 days; range = 2–12 days), but no consistent pattern was apparent. The average ± SE number of rediae was significantly smaller in snails shedding only 2–6 days (11.9 ± 2.9) than snails shedding between 7–12 days (35.2 ± 8.5) at the termination of the experiment.