The role of sex and temperature in melanin-based immune function

Rebecca L. Ehrlich, Marlene Zuk

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Sex differences in immunity have been observed across a wide range of species. Still, it remains unclear how sex-specific interactions with the environment are linked to sex differences in immunity. We studied the plasticity of immunological sex differences by focusing on melanin-based traits in the Pacific field cricket (Teleogryllus oceanicus (Le Guillou, 1841)). Insects rely on the pigment melanin for both immune function and coloration of the cuticle; therefore, changes in melanin production for one of these traits may indirectly affect the other. Male crickets use melanized wing structures to chirp. These cuticular structures are missing in females and a songless male morph. Given that the thermal environment influences cuticle melanization, we investigated the interactive effects of sex and developmental temperature on melanin-based immunity. Both immunity and wing cuticle melanism were reduced in individuals that developed under warmer temperatures. Rearing temperature also mediated the extent to which the sexes differed in immune traits. Males had darker cuticles, whereas females expressed greater immune activity, suggesting that sex-specific investment in melanin corresponds with sex differences in immunity. However, the lack of immunological differences between the two male morphs does not support the hypothesis that investment in cuticle melanism affects investment in immunity.

Original languageEnglish (US)
Pages (from-to)825-832
Number of pages8
JournalCanadian Journal of Zoology
Issue number9
StatePublished - 2019

Bibliographical note

Funding Information:
We thank the members of the Zuk laboratory for their help raising and processing the crickets used in this study, especially G. Narayanan for her assistance with the photo analysis. S. Adamo provided guidance on measuring insect immunity and E. Snell-Rood and M. Sadowsky provided access to critical laboratory equipment. This work was possible thanks to funding from the Orthopterists? Society (to R.L.E.) and the University of Minnesota (to R.L.E.).

Publisher Copyright:
© 2019, Canadian Science Publishing. All rights reserved.


  • Cuticle melanism
  • Ecological immunology
  • Melanin
  • Pacific field cricket
  • Phenoloxidase
  • Sex difference
  • Teleogryllus oceanicus


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