© 1978 by The Society for Integrative and Comparative Biology
Alkylation Treatment of the Mexican Axolotl: An Approach to the Isolation of New Mutations
Department of Biology, University of Ottawa Ottawa, Canada K1N 6N5
SYNOPSIS. Most of the known mutants of the axolotl were uncovered by R. R. Humphrey through inbreeding laboratory stock or wild animals imported from Mexico. All are spontaneous in origin. We believe that chemical mutagenesis may be useful for increasing both the frequency and variety of new mutations. For our experiments, we have chosen the alkylating agent ethyl methanesulfonate (EMS), because its mode of action is reasonably well understood. Though we were unable to establish a lethal dose of EMS by intraperitoneal injection, we were successful when we administered the compound directly in the water. In the weeks immediately after treatment, females administered sublethal doses did not ovulate, except in response to large injections of follicle stimulating hormone. Recovery took several months. Treated males showed more normal performance, in terms of courtship and the number of spermatophores produced. At low doses, and short intervals after treatment, embryos from spawnings with treated males survived nearly as well as controls. Survival reached a minimum about a month after the male had been treated, then improved again. This depression and recovery may be correlated with the stage of sperm maturation at the time of treatment. Treatment of mature sperm from spermatophores affected only their ability to fertilize eggs in an artificial insemination; fertile eggs developed normally. The most promising procedure would, therefore, seem to be treatment of the male. Following mutagenesis, we propose that gynogenesis be used to aid in the rapid identification of new recessive mutations.