Irwin H. Herskowitz

A List of Chemical Substances Studied for Effects on Drosophila, with a Bibliography

It was not until recently that the induction of heritable changes by chemical substances was clearly demonstrated in experiments with Drosophila by Auerbach and her associates. However, earlier work on the genotypic and phenotypic effects of various chemicals on Drosophila contain a wealth of information which may be of use to the investigator. There are several studies on chemically induced mutation which are not widely known, particularly those done in Russia by Rapoport, Gershenson, and others. Therefore, it was felt that a compilation of titles and a list of chemicals studied thus far in Drosophila would be useful The present handlist contains 314 references, including titles through the year 1950. Except for 50 new references, this work is almost identical with the one included by Dr. M. Demerec in Drosophila Information Service, No. 24: 107-122, 1950. In general the bibliography does not list papers concerned solely with ionizing and non-ionizing radiations, temperature, or age. A number of papers dealing with the lethal effect of insecticides on Drosophila have also been omitted. However, a few titles are included that show the variety of methods by which the induction of mutations has been attempted. References to studies on the development of a chemically defined medium for Drosophila are included since it is becoming apparent that more meaningful results will be obtained when the food variable is controlled. The review articles by Timof~eff-Ressovsky (233) and Auerbach (10,11.) have not been cross-indexed with the list of chemical substances. An asterisk in the list of chemical substances means that no test for mutagenicity has yet been made. Numbers following each substance refer to entries in the bibliography. An asterisk in the bibliography indicates that the reference contains no work on chemical mutagens; a question mark means that the paper was not available for checking.

An Estimate of the Number of Loci in the X Chromosome of D. melanogaster

By dividing the total number of viable breaks by the number of mutations occurring at breakage points at a single typical locus, one can obtain an estimate of the number of loci present. Assuming the white locus of D. melanogaster to be a typical one and that all viable breaks involving this locus result in the white phenotype, the number of loci on the X chromosome is calculated to be approximately 726.

The Mutagenicity of Formaldehyde in Different Early Developmental Stages of D. melanogaster Males

The ability of formaldehyde to induce sex-linked recessive lethal mutations in germ cells of male D. melanogaster has been extended, from spermatozoa and the developing germ cells of individuals 36 hours of age and older, to an earlier stage in which treatment was started at 0-12 hours of age and could have lasted until 36 hours of development. The mutation rate of 7.7 per cent obtained for this stage was not significantly below that found for individuals 24-36 (9.2 per cent) or 36-48 (7.6 per cent) hours old at the time formaldehyde was administered, although the 4.2 per cent mutation rate for the 12-24 hours old individuals was significantly lower (P < .01) than the rate of the three other stages when combined and of the rates for the stages just preceding or following when tested separately. The results are interpreted as demonstrating that the mutagen loses a large proportion of its potency within a period of twelve hours.

The Survival and Developmental Rates of D. melanogaster and D. simulans

In laboratory cultures, the number of newly hatched larvae which survive to the adult stage is greater and the time required to complete this development is shorter for D. melanogaster than for D. simulans. These differences are probably important factors in the superiority of D. melanogaster to D. simulans in population cage competition experiments. The data do not support the idea that food in which larvae have previously grown contains a factor biochemically influencing the survival of a succeeding generation of larvae. I wish to thank Miss Julia Colvin and Mr. Seymour Abrahamson for their capable technical assistance.