THE EFFECT OF MALEIC HYDRAZIDE ON THE EMBRYONIC AND LARVAL GROWTH OF THREE AMPHIBIANS

¹ Department of Botany and Department of Zoology, University of North Carolina, Chapel Hill, N. C.

1. A 2.0 per cent solution of maleic hydrazide was lethal to all Amblystoma punctatum larvae within 50 hours, but 35 per cent of the larvae survived 10 days in 1.0 per cent MH and 70 per cent in 0.5 per cent MH, while 84 per cent of the controls survived. All concentrations of MH from 0.25 per cent upward killed Daphnia and Cyclops introduced into the Amblystoma cultures as food. A 0.1 per cent solution of MH was slightly toxic to Rana pipiens larvae.

2. MH concentrations ranging from 0.02 per cent to 2.0 per cent had no significant effect on the growth of embryos and larvae of Rana, Bufo and Amblystoma. The full range of concentrations was not used on any one of the three species.

3. The number of mitotic figures in regenerating tail tips of Amblystoma was significantly less in those treated with either 0.25 per cent or 1.0 per cent MH than in the controls. Pyknosis was common in the treated tail tips but was absent in the controls. The writers are of the opinion that these are indirect, rather than direct effects of the MH treatment, and can be attributed to starvation following the death of the Cyclops and Daphnia provided as food for the Amblystoma larvae.