Locomotion Induced by Spatial Restriction in Adult Drosophila.

Chengfeng Xiao,R Meldrum Robertson,Efthimios M C Skoulakis

doi:10.1371/journal.pone.0135825

Abstract

Drosophila adults display an unwillingness to enter confined spaces but the behaviors induced by spatial restriction in Drosophila are largely unknown. We developed a protocol for high-throughput analysis of locomotion and characterized features of locomotion in a restricted space. We observed intense and persistent locomotion of flies in small circular arenas (diameter 1.27 cm), whereas locomotion was greatly reduced in large circular arenas (diameter 3.81 cm). The increased locomotion induced by spatial restriction was seen in male flies but not female flies, indicating sexual dimorphism of the response to spatial restriction. In large arenas, male flies increased locomotion in arenas previously occupied by male but not female individuals. In small arenas, such pre-conditioning had no effect on male flies, which showed intense and persistent locomotion similar to that seen in fresh arenas. During locomotion with spatial restriction, wildtype Canton-S males traveled slower and with less variation in speed than the mutant w1118 carrying a null allele of white gene. In addition, wildtype flies showed a stronger preference for the boundary than the mutant in small arenas. Genetic analysis with a series of crosses revealed that the white gene was not associated with the phenotype of boundary preference in wildtype flies.

Highlights

Drosophila adults display an unwillingness to enter confined spaces, which has been described as a claustrophobic effect [1]
Spatial restriction induced intense and persistent locomotion in male flies Following a 5 min acclimation period, most CS male flies became inactive in the large circular arenas
Drosophila adults had sexually dimorphic locomotor strategies in our experiments but it was clear that, independently of sex, confinement in a small arena promoted continuous rapid locomotion largely around the perimeter that lasted for the duration of the assay (>1 h)

Summary

Introduction

Drosophila adults display an unwillingness to enter confined spaces, which has been described as a claustrophobic effect [1]. When individual flies are restrained in a small rectangular arena (1.0 cm × 0.6 cm), locomotion is characterized by relentless or unabated activity for several hours, interspersed with a few short episodes of inactivity [2]. The change from reactivity to spontaneous activity can be observed in relatively large but not small arenas, indicating that flies respond to arena size with different styles of locomotion. Spatial restriction has diverse behavioral consequences in other animals. Confinement imposes movement limitations in egg-laying hens [6,7,8], and induces behavioral and psychological disorders in captive animals [9,10,11,12].

Methods

Results

Discussion

Conclusion