An experimental test of the immunocompetence handicap hypothesis in a teleost fish: 11-ketotestosterone suppresses innate immunity in three-spined sticklebacks

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T1 - An experimental test of the immunocompetence handicap hypothesis in a teleost fish: 11-ketotestosterone suppresses innate immunity in three-spined sticklebacks

AU - Kurtz, Joachim

AU - Kalbe, Martin

AU - Langefors, Åsa

AU - Hasselquist, Dennis

PY - 2007

Y1 - 2007

N2 - 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.

AB - 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.

KW - oxidative stress

KW - innate immunity

KW - immunocompetence handicap

KW - 11‐ketotestosterone

KW - sexual selection

KW - teleost fish.

U2 - 10.1086/521316

DO - 10.1086/521316

M3 - Article

C2 - 17891730

VL - 170

SP - 509

EP - 519

JO - American Naturalist

JF - American Naturalist

SN - 0003-0147

IS - 4

ER -