Effect of DDT on Functional Development of Larvae of Rana pipiens and Fundulus heteroclitus

Abstract

Conclusions

1. A saturated solution of DDT (estimated at 1 ppm) in spring water for Rana pipiens larvae and in distilled water for Fundulus heteroclitus larvae, was sufficiently toxic to produce morphological deformities of a similar nature, the most obvious of which was the sharply bent tail and the very much reduced neuro-muscular response to tactile stimulation.

2. The initial evidence of damage by DDT appeared after 7 days of treatment of Rana pipiens larvae (beginning at stage 11) and after hatching of Fundulus heteroclitus larvae (treatment beginning at stage 8). There was a considerable lag in the effect, due, in all probability, to the (fact that DDT is relatively insoluble and therefore difficult to assimilate by the larvae.

3. In addition to the bent tail, there was a gradual decrease in neuro-muscular responses as determined by the Detwiler racetrack method following tactile stimulation, in both Rana and Fundulus larvae. Ultimately the larvae responded with only muscular tremors.

4. The toxic symptoms were not manifest in Rana larvae if they were returned to the control medium after 6 days of subjection to the DDT or in Fundulus as late as 16 days in the medium if subjected at stage 8.

5. There was no effect of DDT on the growth rate of Fundulus larvae, but after 9 days of exposure of Rana larvae they show a definite inhibition of growth.

6. The older the larvae at the time of DUT exposure, the longer the period before the onset of deleterious symptoms.