Fever and phenotype: transgenerational effect of disease on desert locust phase state

Authors

  • Sam L. Elliot,

    Corresponding author
    1. NERC Centre for Population Biology, Imperial College London, Silwood Park Campus, Ascot, Berks, SL5 7PY, UK
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  • Simon Blanford,

    1. NERC Centre for Population Biology, Imperial College London, Silwood Park Campus, Ascot, Berks, SL5 7PY, UK
    2. Institute of Cell, Animal and Population Biology, Ashworth Laboratories, West Mains Road, University of Edinburgh, Edinburgh, EH9 3JT, UK
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  • Charlotte M. Horton,

    1. NERC Centre for Population Biology, Imperial College London, Silwood Park Campus, Ascot, Berks, SL5 7PY, UK
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  • Matthew B. Thomas

    1. NERC Centre for Population Biology, Imperial College London, Silwood Park Campus, Ascot, Berks, SL5 7PY, UK
    2. Department of Agricultural Sciences, Imperial College London, Wye Campus, Ashford, Kent, TN25 5AH, UK
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*E-mail: s.elliot@imperial.ac.uk

Abstract

Natural enemy attack can cause transgenerational shifts in phenotype such that offspring are less vulnerable to future attack. Desert locusts (Schistocerca gregaria) show density-dependent variation in their resistance to pathogens, such that they are less vulnerable to pathogens when in the high-density gregarious phase state (when they would probably be more exposed to pathogens) than when in the solitarious phase state. We therefore hypothesized that infected gregarious parents would maintain this phenotype in their offspring. We infected gregarious desert locust nymphs with the fungal pathogen Metarhizium anisopliae var. acridum, and allowed them to survive to reproduction by means of behavioural fever. The phase state of the locust offspring was assessed by their colouration and behavioural assays. Contrary to our hypothesis, we found an increase in solitarization in the infected population (14.6% solitarious offspring from infected parents, vs. <2% from uninfected counterparts at equivalent density). In a second experiment, we simulated behavioural fever temperatures and obtained a similar result (13.6% solitarious offspring vs. 4.4% from controls), implying that the phenomenon is probably a side-effect of the hosts’ fever response. Identification of this novel environmental factor affecting locust phase state could have important implications for the biological control of these major pests.

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