Effects of host habitat quality on the viability of Cryptocotyle lingua (Trematoda: Digenea) cercariae

Abstract

In an earlier study it was shown that Cryptocotyle lingua cercariae, matured in Littorina littorea from a polluted marine lagoon, displayed slower horizontal swimming rates, and reduced longevity compared to cercariae released by periwinkles from a cleaner environment. This work investigated whether the pollution-induced reduction in swimming rates was due to an inefficient swimming action or the adoption of a less direct swimming path. In addition, cercariae from L. littorea that had been transferred from an 'unpolluted' to a 'polluted' site for 1 month provided information on the speed with which pollutants affect cercariae through their intermediate hosts. Results indicated that, in general, horizontal swimming rates were reduced due to slower swimming rather than disorientation and longer swimming pathways. Effects of host transplantation to a polluted site were clearly evident after 1 month. Evidence suggested that the pollutants accumulated by the cercariae via their first intermediate host affected the neuromusculature associated with swimming performance rather than sensory structures. Bearing in mind the reduced viability of C. lingua cercariae in polluted sites it is assumed that high prevalence of this digenean in gastropods (at such sites) must be due to their continual introduction by infected birds attracted to these habitats from other areas.

Diversity of the digenean fauna in sparid fishes from the Lagoon of Bizerte in Tunisia

“…Indeed, Bizerte Lagoon, being a subject to eutrophication, is susceptible also to anthropogenic disturbances of various origins (domestic and industrial wastes released by the neighbouring towns and agricultural waste run-off) (Dellali et al 2001, Ben Said et al 2010. This polluted environment may reduce the lifespan of cercaria (Morley et al 2003) and decrease their success in infecting the second host (Cross et al 2005). Indeed, Cross et al (2001) showed that there is a reduction in the speed of swimming and longevity of the cercaria Cryptocotyle lingua infesting a bivalve, Littorina littorea living in polluted environment.…”

Digenean diversity in labrid fish from the Bay of Bizerte in Tunisia

“…However, in polluted environments, increasing concentrations of pollutants bring about a reduction of cercarial viability and reduce their success in infecting the second host (Evans, 1982; Cross et al , 2001; Morley et al , 2001). Similarly, Cross et al (2005), when examining the swimming behaviour of Cryptocotyle lingua (Creplin, 1825) cercariae living in a polluted environment, found that they displayed a slower horizontal swimming rate and reduced longevity compared to cercariae released in a cleaner environment. Another similar finding was recorded by Morley et al (2003) on the cercariae of Echinoparyphium recurvatum (Digenea: Echinostomatidae) living within rediae parasitizing molluscs having accumulated toxic substances (cadmium and zinc).…”

Cercarial swimming performance and its potential role as a key variable of trematode transmission

“…However, pronounced variations may still remain, even within studies undertaken using the same experimental conditions, e.g. studies undertaken on Cryptocotyle lingua from Northern Ireland (Rea and Irwin, 1992, 1995, 2001; Cross et al ., 2001, 2005).…”