The influence of potassium dichromate on growth and survival of the vermicomposting earthworm Eisenia foetida

The present research evaluated the redox ability of Cr6+ in the earthworm Eisenia foetida, and its effects on growth and survival. An assay was conducted with an increasing doses of K2Cr2O7 (0, 200, 400, 800, 1000, and 1200 mg K2Cr2O7 kg-1 substrate) applied to a vermicomposting system which was inoculated with 30 earthworms per chamber. Earthworm growth, estimated by weight, showed a quadratic response (p = 0.03) with the lowest estimated growth at a dose of 435 mg K2Cr2O7 kg-1. Chromium (Cr) concentration increments were positively associated to mortality in adults and cocoons (p < 0.01), and total Cr accumulation in earthworms (p < 0.01). The accumulation of chromium in worms, is an indicator of the capacity of worms to resist different doses of potassium dichromate and, the effect on accumulation of Cr (VI) in vermicomposting was higher (p = 0.11). The difference of potassium dichromate in worms could indicate the oxide reduction in E. fetidae.   Key words: Redox chromium, growth, survival, Eisenia foetida.