Artemia is a tiny marine crustacean, serves as an excellent tool in both basic and applied aspects of stress biology research. In the current manuscript, we report that Artemia parthenogenetica embryos (cysts), in diapause stage, undergo iron transition changes when exposed to chemical diapause deactivation stimulus (hydrogen peroxide). X-ray surface analysis of A. parthenogenetica embryos exposed to H(2)O(2) showed significant transitional changes in iron, as seen in cyst cross-sections. Electron paramagnetic resonance study revealed that upon H(2)O(2) exposure, increased nitric oxide (NO) production was observed in non-decapsulated cysts (ND), but not in decapsulated cysts (DC) (shell-removed cysts). Spin trapping studies also showed an increase in hydroxyl radical formation in NDs exposed to H(2)O(2) through Fenton-like reaction. On the contrary, exposure of DCs to H(2)O(2) did not induce hydroxyl radical formation. Taken together, results from the present study indicate a key role of cyst shell-bound iron and reactive oxygen species on successful diapause termination in eukaryotic extremophile animal model, such as Artemia.