An experimental test of the immunocompetence handicap hypothesis in a teleost fish: 11-ketotestosterone suppresses innate immunity in three-spined sticklebacks.
The immunocompetence handicap hypothesis (ICHH) provides a functional explanation for how sexual ornaments can provide honest signals of male quality. A key aspect of this hypothesis is that testosterone (T) has a bimodal effect: a higher T level enhances the expression of ornaments (increasing mating success and, ultimately, fitness); however, at the same time, it suppresses immune function. Tests of the latter assumption, which have focused mainly on aspects of adaptive immunity in birds, led to equivocal results. We performed a hormone-implant experiment in male three-spined sticklebacks (Gasterosteus aculeatus) to test the key assumptions of the ICHH in a fish, where the dominant circulating androgen is 11-ketotestosterone (11kT) rather than T. Males were implanted with 11-ketoandrostenedione, which is a natural precursor of 11kT. Each individual's circulating 11kT level, ornamentation, and immunocompetence were measured 2 weeks later. In addition, we quantified oxidative tissue damage because the ICHH has been hypothesized to work via oxidative stress. We found that the males' 11kT levels correlated positively with ornamentation but negatively with immunocompetence, in particular, measures of innate immunity. Moreover, there was a trend for fish with high 11kT levels to suffer more from oxidative stress. Thus, our data provide support for the ICHH.
Kurtz
Joachim
J
Department of Evolutionary Ecology, Max Planck Institute for Evolutionary Biology, August Thienemann Strasse 2, D-24306 Plon, Germany. joachim.kurtz@uni-muenster.de
Kalbe
Martin
M
Langefors
Asa
A
Mayer
Ian
I
Milinski
Manfred
M
Hasselquist
Dennis
D
D000171:Acrolein / Q000378:metabolism; D000736:Androstenes / Q000493:pharmacokinetics / Q000494:pharmacology*; D000818:Animals; D049628:Body Size / Q000187:drug effects; D007113:Immunity, Innate / Q000187:drug effects*; D007121:Immunocompetence / Q000187:drug effects*; D007958:Leukocyte Count; D007962:Leukocytes / Q000187:drug effects / Q000276:immunology; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D009425:Nesting Behavior / Q000187:drug effects; D009929:Organ Size / Q000187:drug effects; D018384:Oxidative Stress / Q000187:drug effects; D010587:Phagocytosis / Q000187:drug effects; D011485:Protein Binding; D016897:Respiratory Burst / Q000187:drug effects; D012727:Sex Characteristics; D023701:Smegmamorpha; D013154:Spleen / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D013737:Testis / Q000187:drug effects / Q000254:growth & development; D013739:Testosterone / Q000031:analogs & derivatives* / Q000097:blood / Q000378:metabolism
D000736:Androstenes; D013739:Testosterone; D000171:Acrolein; C011657:adrenosterone; C003600:11-ketotestosterone