Effects of a textile azo dye on mortality, regeneration, and reproductive performance of the planarian, Girardia tigrina

BACKGROUND Many dyes can be considered emerging contaminants. The most widely used dyes belong to the class of azo compounds, some of which are known to have toxic and genotoxic properties. They are used in great quantities in textile activities and are of environmental concern because of their potential discharge in water. Planarians have been successfully used as test organisms in hazard evaluation of different chemicals, and we demonstrate the suitability of Girardia tigrina for laboratory testing. The aim of this work was to evaluate the suitability of the planarian species G. tigrina to assess the ability of the azo textile dye disperse red 1 to cause acute toxicity and adverse effects in the regeneration and reproduction of newborn and adult specimens. RESULTS Disperse red 1 presented a median LC50 of 75 and 152 mg/L, respectively, for newborns and adults of G. tigrina, showing that newborns are twice as susceptible to the dye. Uncoordinated movements, irregular twists, colored skin, increased mucous production, and regenerative delays were observed after dye exposure at sub-lethal concentrations. CONCLUSIONS A no-observed-adverse-effect concentration (NOAEC) of 0.1 mg/L could be determined for disperse red 1 based on the fecundity test. Zinc seems to be a suitable positive control for monitoring the sensitivity in G. tigrina tests within only 24 h of exposure. This study demonstrates the applicability of G. tigrina tests in the hazard evaluation of water contaminants, such as azo dyes.