Phenotypic plasticity of adult size and pigmentation in Drosophila:: thermosensitive periods during development in two sibling species

Variation of size-related traits and of abdomen pigmentation was investigated in D. melanogaster and D. simulans by transferring cultures from 25degreesC to 17degreesC at regular daily intervals. In most cases regular sigmoid curves were obtained, which were adjusted to a logistic model. For wing length, the thermosensitive period (TSP) extended during the last larval instar and most of the pupal stage. with an inflection point (LP) at 5.24 +/- 0.24 days. Pigmentation of the last abdomen segments (5-7) in females exhibited a shorter and later TSP (IP at 7.21 +/- 0.13 days) extending in the first day of adult life. In anterior segments (2-4) variations were less regular and our data suggest that TSP might extend during the first two days of adult life, at least in males. Significant differences among species were observed for size and pigmentation, but not for TSPs. (C) 2002 Elsevier Science Ltd. All rights reserved.