R. Toledo et al., Survival and infectivity of Hypoderaeum conoideum and Euparyphium albuferensis cercariae under laboratory conditions, J HELMINTH, 73(2), 1999, pp. 177-182
The survival characteristics of the cercariae of Hypoderaeum conoideum and
Euparyphium albuferensis (Trematoda: Echinostomatidae) at 20 degrees C and
30 degrees C are described, and the age dependency of their infectivity at
20 degrees C is studied to determine their respective transmission efficien
cies. Cercarial survival was found to be age-dependent and was higher at 20
degrees C. For both cercariae, the maximum life-span was 26 h at 20 degree
s C and 16 h at 30 degrees C, and their respective times to 50% mortality w
ere similar at each temperature. Both cercariae seem to be well adapted to
transmission in their natural habitat, though cercarial infectivity of H. c
onoideum was higher than that of E. albuferensis, this being correlated wit
h their prevalences in nature. The age-dependency of cercarial survival may
be related to steadily diminishing endogenous energy levels, though the de
lay in attaining maximum infectivity suggests that other factors not relate
d to energy considerations are involved in the delimitation of the cercaria
l infective period. However, this latter observation may constitute an adap
tative mechanism allowing cercarial dissemination.