In aphids, reproductive polyphenism (the capacity for one given phenotype to differentiate in parthenogenetic of sexual forms under changing environmental conditions) is triggered by the reduction of both temperatures and photoperiods in autumn. These insects are thus able to detect and integrate modifications in environmental conditions in order to adapt their physiology.
The perception of modifications of the photoperiod is acting in a specialized group of cells located in the protocerebron. These cells could be involved in the synthesis and secretion of signal molecules (neuropeptides, hormones like juvenile hormones) towards target cells of embryogenesis: the oocytes. A high concentration in juvenile hormones near the oocytes might be responsible for the parthenogenetic development (embryogenesis induced from one diploid non-fertilized oocyte) whereas low concentrations might influence the sexual development (embryogenesis from one haploid oocyte after fertilization by one spermatozoid). The molecular mechanisms and the cellular functions involved in the regulation of these reproductive strategies are not known.

The use of functional genomics (like DNA chips) is one of the approaches we develop to study the mechanisms responsible for the switch between parthenogenetic and sexual differentiation. Finally, genes and proteins involved in the regulation of reproductive polyphenisms will be identified and characterized.