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J Insect Physiol. 2014 Jun;65:9-26. doi: 10.1016/j.jinsphys.2014.04.004. Epub 2014 Apr 21.

Rapid behavioural gregarization in the desert locust, Schistocerca gregaria entails synchronous changes in both activity and attraction to conspecifics.

Author information

1
School of Biological Sciences, A08 - Heydon-Laurence Building, and the Charles Perkins Centre, University of Sydney, NSW 2006, Australia. Electronic address: Stephen.rogers@sydney.edu.au.
2
Department of Zoology, University of Cambridge, Downing St, Cambridge CB2 3EJ, UK; Department of Biology, University of Leicester, University Road, Leicester LE1 7RH, UK.
3
School of Biological Sciences, A08 - Heydon-Laurence Building, and the Charles Perkins Centre, University of Sydney, NSW 2006, Australia.
4
Department of Zoology, University of Cambridge, Downing St, Cambridge CB2 3EJ, UK.
5
Concordia University, 7141 Sherbrooke St. West, SP-375-09, Montreal H4B 1R6, QC, Canada.
6
Department of Biology, University of Leicester, University Road, Leicester LE1 7RH, UK.
7
Department of Entomology, Texas A&M University, TAMU 2475, College Station, TX 77843-2475, USA.

Abstract

Desert Locusts can change reversibly between solitarious and gregarious phases, which differ considerably in behaviour, morphology and physiology. The two phases show many behavioural differences including both overall levels of activity and the degree to which they are attracted or repulsed by conspecifics. Solitarious locusts perform infrequent bouts of locomotion characterised by a slow walking pace, groom infrequently and actively avoid other locusts. Gregarious locusts are highly active with a rapid walking pace, groom frequently and are attracted to conspecifics forming cohesive migratory bands as nymphs and/or flying swarms as adults. The sole factor driving the onset of gregarization is the presence of conspecifics. In several previous studies concerned with the mechanism underlying this transformation we have used an aggregate measure of behavioural phase state, Pgreg, derived from logistic regression analysis, which combines and weights several behavioural variables to characterise solitarious and gregarious behaviour. Using this approach we have analysed the time course of behavioural change, the stimuli that induce gregarization and the key role of serotonin in mediating the transformation. Following a recent critique that suggested that using Pgreg may confound changes in general activity with genuine gregarization we have performed a meta-analysis examining the time course of change in the individual behaviours that we use to generate Pgreg. We show that the forced crowding of solitarious locusts, tactile stimulation of the hind femora, and the short-term application of serotonin each induce concerted changes in not only locomotion-related variables but also grooming frequency and attraction to other locusts towards those characteristic of long-term gregarious locusts. This extensive meta-analysis supports and extends our previous conclusions that solitarious locusts undergo a rapid behavioural gregarization upon receiving appropriate stimulation for a few hours that is mediated by serotonin, at the end of which their behaviour is largely indistinguishable from locusts that have been in the gregarious phase their entire lives.

KEYWORDS:

Behavioural plasticity; Density dependent polyphenism; Group attraction; Phase change; Phenotypic plasticity; Serotonin

PMID:
24768842
PMCID:
PMC4062946
DOI:
10.1016/j.jinsphys.2014.04.004
[Indexed for MEDLINE]
Free PMC Article

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