Running title: STRESS EFFECTS OF AMBIENTAL MAGNETIC FIELDS Academy Section: CELLULAR AND MOLECULAR BIOLOGY

In this paper, we analyzed the effects of chronic exposure (5 months) to static magnetic fi eld (110 mT; SMF) and extremely low frequency magnetic fi eld (ELF MF; 10 mT, 50 Hz) on Blaptica dubia nymphs. We have examined acetylcholinesterase (AChE) activity and heat shock protein 70 (HSP70) level, two sensitive biomarkers of stress in terrestrial insects. Relative growth rate (RGR), as a life history trait, was estimated. AChE activity was determined spectrophotometrically and HSP70 levels were quantifi ed using indirect non-competitive ELISA and Western blotting. Calculated RGR was signifi cantly changed upon exposure to both types of ambiental MFs. The effects of chronic exposure of B. dubia nymphs to SMF and ELF MF (50 Hz) were observed as decreased activity of AChE. The increased level of HSP70 was present only after exposure to SMF. The strength of ELF MF was most likely below the energy level needed to induce the expression of this stress protein. Different patterns of the expression of two HSP70 isoforms, where isoform 2 was sensitive only to SMF, are most likely a possibly switch – off in the expression of constitutive and/or inducible HSP70 isoforms.