Colour change: A novel biomarker indicating sublethal stress in the millipede Julus scandinavius (Diplopoda)

Abstract During investigations on the induction of the 70 kD stress protein family (hsp70, stress-70) in Julus scandinavius following exposure to different biohazards, the colour of the supernatant of the homogenate was closely correlated to the hsp70 level. Hsp70 has recently been shown to be a suitable biomarker for sublethal toxicity in soil animals. Control millipedes typically exhibited red or red-orange supernatants whilst the supernatant of starved or toxin-exposed diplopods was orange, orange-yellow, or even bright yellow. Based on these observations, a quantitative colour test was established which was found to be able to indicate the degree of stress situations caused by exposure to heavy metals (cadmium, zinc), organic pollutants (lindane, PCB 52), or by food deprivation in laboratory tests. It is suggested that this is caused by a breakdown of the red-orange bilirubins into orange-yellow urobilins.