title: Toxicity of cadmium and zinc to encystment and in vitro excystment of Parorchis acanthus (Digenea: Philophthalmidae).
abstract: The toxicity of cadmium, zinc and cadmium/zinc mixtures at concentrations ranging from 1000 to 50000 microg/l were investigated against cercariae and metacercariae of Parorchis acanthus obtained from the dog whelk Nucella lapillus. Cercarial encystment at concentrations of 25000 microg/l or higher was significantly impaired by all test metals; however, at lower concentrations only zinc demonstrated toxicity. Mixtures of cadmium and zinc had a synergistic effect compared with single metal toxicity but only at 50000 microg/l. Excystment in vitro was only significantly affected by cercariae exposed to cadmium/zinc mixtures whilst encysting. Twenty-four h exposures of fully formed cysts had no effect on excystment in vitro. Effects on in vitro excystment rates over a 2 h period demonstrated widespread effects for cercariae-exposed P. acanthus. No effects were evident on excystment rates of cyst-exposed parasites.
authors.affiliation: School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey, UK. n.morley@rhbnc.ac.uk
authors.forename: N J
authors.initials: NJ
authors.lastname: Morley
authors.forename: M
authors.initials: M
authors.lastname: Crane
authors.forename: J W
authors.initials: JW
authors.lastname: Lewis
mesh_terms: D000818:Animals; D002104:Cadmium / Q000633:toxicity*; D004347:Drug Interactions; D006790:Host-Parasite Interactions; D012908:Snails / Q000469:parasitology; D014200:Trematoda / Q000187:drug effects*; D015032:Zinc / Q000633:toxicity*
chemical_list: D002104:Cadmium; D015032:Zinc