A DEVELOPMENTAL AND BIOMETRICAL ANALYSIS OF LARVAL PHOTORESPONSE OF DROSOPHILA

Young Drosophila larvae (24-28 and 48-52 h old) show a preference for feeding in dark environments, while older larvae (72-76h post-hatching) prefer more illuminated environments. Changes in the photoresponse during larval development are characteristic of D. melanogaster, D. immigrans, D. hydei and D. virilis. In contrast, larvae of D. simulans, D. gaucha, D. pavani and D. funebris show no change in their response to light during larval development, both dispersing and feeding in dark environments. A biometrical analysis of the development of larval photoresponse of D. melanogaster shows that the genetic structure involved in the expression of this behaviour depends on larval age. At 24-28 h of age, additive, dominant and epistatic components were found. At 48-52 h, dominant and epistatic interactions were significant. At 72-76 and 96-100 h of age only non-allelic interactions were important. Thus, epistasis tends to increase as larval development progresses. The concepts of genetic co-adaptation, developmental homeostasis and heritability are discussed in relation to the development of larval photoresponse in D. melanogaster.