CRITICAL CONCENTRATIONS, PATHWAYS OF DETOXIFICATION AND CELLULAR ECOTOXICOLOGY OF METALS IN TERRESTRIAL ARTHROPODS

A new interpretation is presented of the concept of "critical concentrations' of metal pollutants. Four critical concentrations are proposed for essential metals such as Zn and Cu in the diet (Ca, Cb, Cc, Cd) which separate five "levels of performance'. These range from "deficiency' (level 5) through "homeostasis' (level 4), "low excess' (level 3), "high excess' (level 2) to "lethal' (level 1). Level 5 does not exist for non-essential metals such as Cd and Pb. The values of the critical concentrations for a specific metal and species may fluctuate with time and will depend on the presence or absence of additional stress factors which act on the animal such as other metals in the diet, climatic changes and food availability. Cc may be set at any concentration between Cb and Cd and could represent the maximum "acceptable' level of pollution. Cb, Cc and Cd are defined for Zn in the diet of the isopod Porcellio scaber. The intracellular pathways for the detoxification of metals are compared with those of a predator, the woodlouse-eating spider Dysdera crocata. The difficulties of defining Cc in a "regulator' of metals (D. crocata) in comparison to a metal "accumulator' (P. scaber) are discussed. -from Author