title: Bioavailability pathways underlying zinc-induced avoidance behavior and reproduction toxicity in Lumbricus rubellus earthworms.
abstract: We investigated possible bioavailability pathways underlying zinc-induced avoidance behavior and sublethal reproduction impairment in Lumbricus rubellus. Clay-loam (pH 7.3) and sandy soil (three pH values of 4.3-6.0) were amended with zinc sulfate at six soil concentrations of total Zn ranging from 0.1 to 36 mmol/kg dw. Estimated and measured concentrations of free and exchangeable Zn ranged 10(-4) to 7.1 mmol/l. Avoidance behavior responses were fast and could be directly predicted from the activity of free zinc ions without a modifying pH effect. The repellent effect is thus likely mediated by a direct action of Zn(2+) ions on epidermal chemosensitive receptors. Body zinc uptake, however, was determined by proton competition with free Zn(2+) sorption. Excess accumulation of body Zn was a good predictor of reproduction decline, which is indicative of internal zinc poisoning. The results indicated that zinc affects earthworms via both direct and indirect mechanisms of external and internal exposure.
authors.affiliation: Environmental Sciences Group, Alterra, Wageningen University and Research Centre, P.O. Box 47, 6700 AA Wageningen, The Netherlands. wim.ma@wur.nl
authors.forename: Wei-Chun
authors.initials: WC
authors.lastname: Ma
authors.forename: Luc T C
authors.initials: LT
authors.lastname: Bonten
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D000818:Animals; D001362:Avoidance Learning; D002118:Calcium / Q000032:analysis / Q000378:metabolism; D000077215:Clay; D006863:Hydrogen-Ion Concentration; D009835:Oligochaeta / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D012098:Reproduction / Q000187:drug effects; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000378:metabolism / Q000633:toxicity*; D015032:Zinc / Q000378:metabolism / Q000633:toxicity*
chemical_list: D000538:Aluminum Silicates; D012987:Soil; D012989:Soil Pollutants; D015032:Zinc; D002118:Calcium; D000077215:Clay