title: Does long term low impact stress cause population extinction?
abstract: This study assessed and monitored 40 consecutive reproduction tests - multigenerational (MG) - of continuous exposure to Cd (at 2 reproduction Effect Concentrations (EC): EC10 and EC50) using the standard soil invertebrate Folsomia candida, in total 3.5 years of data were collected. Endpoints included survival, reproduction, size and metallothionein (MTc) gene expression. Further, to investigate adaptation to the toxicant, additional standard toxicity experiments were performed with the MG organisms of F6, F10, F26, F34and F40generations of exposure. Exposure to Cd EC10 caused population extinction after one year, whereas populations survived exposure to Cd EC50. Cd induced the up-regulation of the MTc gene, this being higher for the higher Cd concentration, which may have promoted the increased tolerance at the EC50. Moreover, EC10 induced a shift towards organisms of smaller size (positive skew), whereas EC50 induced a shift towards larger size (negative skew). Size distribution shifts could be an effect predictor. Sensitivity increased up to F10, but this was reverted to values similar to F0in the next generations. The maximum Cd tolerance limits of F. candida increased for Cd EC50 MG. The consequences for risk assessment are discussed.
authors.affiliation: Department of Biology & CESAM, University of Aveiro, 3810-193 Aveiro, Portugal. Electronic address: mjamorim@ua.pt.
authors.forename: M J B
authors.initials: MJB
authors.lastname: Amorim
authors.affiliation: Department of Biology & CESAM, University of Aveiro, 3810-193 Aveiro, Portugal. Electronic address: CeciliaManuela.Pereira@UGent.be.
authors.forename: C
authors.initials: C
authors.lastname: Pereira
authors.affiliation: Department of Biology & CESAM, University of Aveiro, 3810-193 Aveiro, Portugal. Electronic address: asoares@ua.pt.
authors.forename: A M V M
authors.initials: AMVM
authors.lastname: Soares
authors.affiliation: Department of Bioscience, Aarhus University, Vejlsøvej 25, 8600 Silkeborg, Denmark. Electronic address: jsf@bios.au.dk.
authors.forename: J J
authors.initials: JJ
authors.lastname: Scott-Fordsmand
mesh_terms: D000818:Animals; D001181:Arthropods / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D002104:Cadmium / Q000633:toxicity*; D004781:Environmental Exposure; D053476:Extinction, Biological; D008668:Metallothionein / Q000378:metabolism; D012098:Reproduction / Q000187:drug effects; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000633:toxicity*; D013312:Stress, Physiological; D015854:Up-Regulation
chemical_list: D012987:Soil; D012989:Soil Pollutants; D002104:Cadmium; D008668:Metallothionein
keywords: Kurtosis; Multigenerational; Population size distribution; Skewness; Tolerance