Effects of TFM and Bayer 73 on in vivo oxygen consumption of the aquatic midge Chironomus tentans

Exposure of fourth instar larvae of Chironomus tentans to 2.0‐8.0 mg/liter of TFM (3‐trifluormethyl‐4‐nitrophenol) for 6 hr at 22 ± 0.5 C in soft water resulted in a significantly increased rate of larval oxygen consumption compared to that of control larvae, as measured with the Warburg respirometer. Maximum stimulation of oxygen consumption occurred with 8.0 mg/liter of TFM, and 1.0 mg/liter of TFM had no measurable effect on basal respiration. When hardness of exposure water was progressively increased, the effect of TFM on oxygen consumption was diminished.

Bayer 73 (5,2′‐dichloro‐4′‐nitrosalicylanilide) stimulated oxygen consumption at 0.75 and 1.0 mg/liter, had no significant effect at concentrations less that 0.75 mg/liter, and inhibited oxygen consumption at concentrations of 1.20 mg/liter or greater.

Mixtures of TFM and Bayer 73, in the ratio of 98:2, had no greater effect on oxygen consumption than TFM alone.