Complex sentence: Besides the unusually great speed of the mites, the researchers were surprised to find the mites running at such speeds on concrete at temperatures up to, which is significant because this temperature is well above the lethal limit for the majority of animal species.
Split into simpler sentences: Besides the unusually great speed of the mites, the researchers were surprised to find the mites running at such speeds on concrete at temperatures up to. This is significant because that temperature is well above the lethal limit for the majority of animal species.