Table 2.

Effects of heavy metals at hormetic and toxic doses on invertebrates.

Metal	Concentration	Invertebrata	Hormetic/Toxic Effect	Increase of Parameter in Invertebrata	Decrease of Parameter in Invertebrata	References
Cd	0.0002, 0.00022, 0.0004, 0.0022, 0.0202, 0.2002 ppm CdCl2	Phormia regina Meig. (Class: Insecta)	hormetic effect	mean percent pupation, stage specific death	mean % emergence, pupae death	[81]
	2.0002, 20.0002, 200.0002 ppm CdCl2		toxic effect	pupae death, stage specific death	mean % pupation, mean % emergence,
Cd	10.53, 7.01, 5.84, 5.25, ng·cm−2 Cd2+	Eisenia fetida (Class: Clitellata)	hormetic effect	catalase (CAT), sodium dismutase (SOD)	none	[159]
	0.33, 0.66 and 1.32 ng·m−2 Cd2+		toxic effect	none	CAT, SOD
Cu	0.04 mM, 0.16 mM, 0.63 mM, 2.5 mM, 10 mM, 40 mM and 160 mM, Cu(NO3)2·3 H2O	Folsomia candida (Class: Entognatha)	hormetic effect	survival	none	[82]
MeHg	0,2 mM, 0,4 mM MeHgCl	Caenorhabditis elegans (Class: Chromadorea)	hormetic effect	expression of glutathione S-transferases (gst-4): GFP (green fluorescence protein)	heat shock proteins (hsp-4):GFP, metallothioneins (mtl-1):GFP and mtl-2:GFP	[84]
Ni	50 and 100 mg·kg−1 [Ni(NO3)2 6H2O]	Eisenia fetida (Class: Clitellata)	hormetic effect	microbial biomass carbon, soil basal respiration	dehydrogenase activities	[86]
	300, 500, 800 mg·kg−1 [Ni(NO3)2 6H2O]		toxic effect	none	urease (UA) and dehydrogenase activities
U	1.86, 5.0, 9.3 mg·kg−1 depleted uranium (DU)	Eisenia fetida (Class: Clitellata)	hormetic effect	natural red retention time, DNA breaks	toxicity factor	[83]
	18.6, 50, 93, 150, 186, 300 and 600 mg·kg−1 DU		toxic effect	DNA breaks	toxicity factor