Melatonin, immunity and cost of reproductive state in male European starlings

G. E. Bentley, G. E. Demas, R. J. Nelson, G. F. Ball

Research output: Contribution to journalArticlepeer-review


The effects of reproductive condition and exogenous melatonin on immune function were investigated in castrated European starlings, Sturnus vulgaris. Photorefractory and photostimulated starlings exposed to long days were implanted with melatonin or with blank capsules. Photostimulated starlings with blank capsules exhibited reduced splenocyte proliferation in response to the T-cell mitogen, concanavalin A, compared with the other long-day birds. Exogenous melatonin prevented the suppression of immune function by photostimulation. Photorefractory starlings, with or without melatonin implants, exhibited enhanced immune function compared with photostimulated starlings implanted with blanks. This enhancement was not mediated by endogenous melatonin, but appeared to be related to changes in reproductive state. In addition to the traditional costs of reproduction in birds (e.g. raising of young), there may be a cost of the reproductive state of starlings (i.e. whether they are phororefractory or photostimulated). These data are, we believe, the first to indicate a direct effect of reproductive state on immune function that is independent of both photoperiod (i.e. changes in the duration of melatonin secretion) and gonadal steroids.

Original languageEnglish (US)
Pages (from-to)1191-1195
Number of pages5
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1402
StatePublished - Jul 7 1998
Externally publishedYes


  • Endocrine-immune interactions
  • Photoperiod
  • Photorefractoriness
  • Seasonal breeding
  • Splenocyte proliferation

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)
  • Environmental Science(all)
  • Agricultural and Biological Sciences(all)


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