Territorial behaviour and immunity are mediated by juvenile hormone: the physiological basis of honest signalling?

Authors

  • Jorge Contreras-Garduño,

    Corresponding author
    1. Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México, Apdo. Postal 70-275, 04510, México, Distrito Federal México
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    • Present address. Unidad de Entomología Aplicada, Instituto de Ecología, A. C., Km. 2.5 Ant. Carr. a Coatepec no. 351, Congregación El Haya, 91070, Xalapa, Veracruz, Mexico

  • Alex Córdoba-Aguilar,

    1. Departamento de Ecología Evolutiva, Instituto de Ecología, Universidad Nacional Autónoma de México, Apdo. Postal 70-275, 04510, México, Distrito Federal México
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  • Humberto Lanz-Mendoza,

    1. Centro de Investigación Sobre Enfermedades Infecciosas, Instituto Nacional de Salud Pública, Avda. Universidad 655. Col. Sta. María Ahuacatitlán, 62508 Cuernavaca, Morelos, México
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  • Adolfo Cordero Rivera

    1. Grupo de Ecoloxía e da Conservación, Departamento de Ecoloxía e Bioloxía Animal, Universidade de Vigo, E. U. E. T. Forestal, Campus Universitario, ES-36005 Pontevedra, Galicia, Spain
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*Correspondence author. E-mail: jcont@ecologia.unam.mx

Summary

  • 1The role of the juvenile hormone (JH) as a potential mediator in the trade-off between male–male competition and immune response has not been tested, but its study could reveal a potential mechanism that mediates resource allocation between these two traits.
  • 2Controlling for body size, we tested whether males of the territorial damselfly Calopteryx virgo administrated with methoprene acid, an analog of the JH (JHa), compared to control males, increased their aggression and occupation time on territories but decreased their phenoloxidase (PO) activity (a key enzyme used during immune response after a bacterial challenge). We found an increase in aggression in JHa treated males compared to control males, but the opposite was found for PO activity.
  • 3As fat load and muscle mass are also important traits during a contest, we tested whether JHa males compared to control males showed more fat and muscle content 2 h after JHa administration. Our results did not show a significant difference between both male groups, suggesting that JHa only increased aggression.
  • 4These results and a review of other published articles, which have documented an effect of JH on a variety of functions in insects, suggest that JH may be a target of sexual selection: this hormone not only promotes the expression of secondary sexual characters but also seems condition-dependent and so its titers may indicate male condition.

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