The sexual dimorphic behaviour of adult Drosophila suzukii: elevated female locomotor activity and loss of siesta is a post-mating response

• DOI: 10.1242/jeb.125468
• Publication Date: 2015-10-21T01:10:17Z
• Authors: Calum T.J. Ferguson; Tara L. O'Neill; Neil Audsley; R. Elwyn Isaac
• Keywords: Male; Sex Characteristics; 0303 health sciences; Insecta; Arthropoda; Diptera; Biodiversity; Darkness; Circadian Rhythm; 03 medical and health sciences; fruit flies; flies; Copulation; Animalia; Animals; Drosophila Proteins; Drosophila; Female; Peptides; Sleep; Locomotion; Taxonomy

The polyphagous Drosophila suzukii is a highly invasive species that causes extensive damage to a wide range of berry and stone fruit crops. A better understanding of its biology and especially its behaviour will aid the development of new control strategies. We have investigated the locomotor behaviour of D. suzukii in a semi-natural environment resembling a typical summer in northern England and show that adult female D. suzukii are at least 4-fold more active during day-light hours than adult males. This result was reproduced in several laboratory environments and was shown to be a robust feature of mated, but not virgin, female flies. Both males and virgin females kept in a 12 h light-12 h dark (12LD) cycle and constant temperature display night-time inactivity (sleep) followed by weak activity in the morning, an afternoon period of quiescence (siesta) and then a prominent evening peak of activity. Both the siesta and the sharp evening peak at lights-off are severely reduced in females after mating. Flies of either sex entrained in 12LD display a circadian pattern of activity in constant darkness confirming the importance of an endogenous clock in regulating adult activity. This response of females to mating is similar to that elicited in female D. melanogaster by the male sex peptide (SP). We used mass spectrometry to identify a molecular ion (m/z, 5145), corresponding to the poly-hydroxylated SP of D. suzukii and to show that this molecule is transferred to the female reproductive tract during copulation. We propose that the siesta experienced by male and virgin female D. suzukii is an adaptation to avoid unnecessary exposure to the afternoon sun, but that post-mated females faced with the challenge of obtaining resources for egg production and finding oviposition sites take greater risks and suggest that the change in female behaviour is induced by the male SP.