Concentrations of a metallothionein-like protein (MTLP) in Tubifex tubifex were consistent throughout the various life stages with no significant variation associated with reproductive stage. The mean concentration from cocoon through 10 weeks of age was 2.5 (+/-0.6) nmol MTLP/g. T. tubifex was subjected to a number of potential environmental stressors to determine whether MTLP production could be induced in the absence of metal exposure. There were no significant differences in the concentrations of MTLP between the controls and worms subjected to decreased food supply, increased handling, or reduced dissolved oxygen at a given exposure temperature. However, at 12 degrees C T. tubifex had significantly (P < 0.01) higher MTLP than T. tubifex held at 23 degrees C. There were also significant differences in wet weight and reproduction at the two temperatures, which may have implications for the levels of MTLP.