THE EFFECT OF INCREASING TIME OF DEVELOPMENT AT CONSTANT TEMPERATURE ON THE WING SIZE OF VESTIGIAL OF DROSOPHILA MELANOGASTER

¹ From the Department of Biology, Amherst College, Amherst, Massachusetts

The time of development of an isogenic vestigial stock of D. melanogaster was increased by two methods: (1) by adding nipagin (ethyl parahydroxy benzoate) to the food, and (2) by adding only very little yeast to the food. Both methods are essentially the same in that the developing larvae are under starvation conditions. With increasing concentration 0.05, 0.1, 0.2 and 0.4 per cent, there was an increase in the time of development and increase in the size of the wings, males showing a greater effect than females. The large wings resembled those of other vestigial alleles raised under normal conditions.

In another series of experiments 0.1 per cent nipagin and starvation were used. The larvae were removed from the culture as they pupated, to determine the relation between time of pupation and wing size. The first flies to pupate did not differ significantly in wing size from controls at that temperature. With increasing time of development there was an increase in wing size. Larvae which were very much delayed, however, developed into small flies with small wings. These wings, although small, were more differentiated and larger than the control wings.

The "carry-over" effect was studied using normal food. The treated females and males were mated with control males and females respectively. Treated males were also mated with treated females. The wings of flies from the latter mating showed the greatest carry-over effect. Treated females by control males resulted in flies having a significantly larger wing size than flies from the reciprocal cross. These results indicate that there is a definite effect on the germ cells of flies raised under starvation conditions, which effect shows itself in the subsequent development of the zygote.