Vernal Changes in the Behavioral and Endocrine Responses to GnRH Application in Male European Ground Squirrels

Millesi, Eva; Hoffmann, Ilse E.; Steurer, Sabine; Metwaly, Mohammed; Dittami, John

doi:10.1006/hbeh.2001.1735

Cited by 25 publications

(15 citation statements)

References 23 publications

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“…[15,17,19,20,[27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46]). However, such GnRH injections have been rarely used as a means to test the effect of brief elevations in testosterone on the behavior of free-living animals (but see [47]). …”

Section: Introductionmentioning

confidence: 99%

Does a short-term increase in testosterone affect the intensity or persistence of territorial aggression? — An approach using an individual's hormonal reactive scope to study hormonal effects on behavior

Goymann

Villavicencio

Apfelbeck

2015

Physiology & Behavior

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Section: Introductionmentioning

confidence: 99%

Does a short-term increase in testosterone affect the intensity or persistence of territorial aggression? — An approach using an individual's hormonal reactive scope to study hormonal effects on behavior

Goymann

Villavicencio

Apfelbeck

2015

Physiology & Behavior

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“…Testosterone was measured at multiple points in the breeding season in order to assess a male's average testosterone production. Short-term testosterone increases were measured using standardized injections of gonadotropinreleasing hormone (GnRH challenges; Wingfield and Farner 1993;Meddle et al 2002;Millesi et al 2002;Moore et al 2002;Jawor et al 2006). In vivo, GnRH is produced by the hypothalamus and regulates testosterone production by stimulating the hypothalamo-pituitary-gonadal (HPG) axis.…”

Section: Introductionmentioning

confidence: 99%

Natural Selection on Testosterone Production in a Wild Songbird Population

McGlothlin¹,

Whittaker²,

Schrock³

et al. 2010

The American Naturalist

104

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. abstract: Because of their role in mediating life-history trade-offs, hormones are expected to be strongly associated with components of fitness; however, few studies have examined how natural selection acts on hormonal variation in the wild. In a songbird, the dark-eyed junco (Junco hyemalis), field experiments have shown that exogenous testosterone alters individuals' resolution of the survival-reproduction trade-off, enhancing reproduction at the expense of survival.Here we used standardized injections of gonadotropin-releasing hormone (GnRH) to assay variation in the testosterone production of males. Using measurements of annual survival and reproduction, we found evidence of strong natural selection acting on GnRH-induced increases in testosterone. Opposite to what would be predicted from the survival-reproduction trade-off, patterns of selection via survival and reproduction were remarkably similar. Males with GnRHinduced testosterone production levels that were slightly above the population mean were more likely to survive and also produced more offspring, leading to strong stabilizing selection. Partitioning reproduction into separate components revealed positive directional selection via within-pair siring success and stabilizing selection via extrapair mating success. Our data represent the most complete demonstration of natural selection on hormones via multiple fitness components, and they complement previous experiments to illuminate testosterone's role in the evolution of life-history trade-offs.

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“…Both experimental and semi-free living males exhibited elevated testosterone levels at the end of heterothermy and at spring emergence, respectively. Similarly, testosterone concentrations were high at the beginning of surface activity also in field data, and did not change significantly with mating (Millesi et al 1998(Millesi et al , 2002.…”

Section: Experimental Males (N = 4)mentioning

confidence: 84%

“…Plasma was stored at -20°C until analysis. Testosterone levels were analyzed in duplicate after diethylether extraction (85% recovery rates, Millesi et al 2002) with a biotin-streptavidin enzyme immunoassay. Using testosterone as standard, the assay showed cross-reactions with testosterone (100%), 5a-dihydrotestosterone (24%), 5b-dihydrotestosterone (12%), 4-androsten-3b, 17b-diol (8%), 5a-androstan-3a, 17b-diol (5%), 5a-androstan-3b, 17b-diol (1%), and 5b-androstan-3a, 17b-diol (1%, Palme and Möstl 1994).…”

Section: Blood Sampling and Testosterone Assaymentioning

confidence: 99%

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Testis development and testosterone secretion in captive European ground squirrels before, during, and after hibernation

Strauss

Hoffmann

Vielgrader³

et al. 2008

Acta Theriol

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Timing of reproduction constitutes a major decision in life history delimited by resource availability and mortality risk. Hibernating species are subject to additional temporal constraints. Both sexes have to cope with a short active season in completing gonadal development, reproduction, and prehibernatory fattening. Males have to adapt to the strict seasonality and must be reproductively competent [47] Acta Theriologica 53 (1): 47-56, 2008. . 2008. Testis development and testosterone secretion in captive European ground squirrels before, during, and after hibernation. Acta Theriologica 53: 47-56.In some hibernating species, an extended euthermic period before spring emergence has been reported during which testicular maturation occurred. In this study, we investigated whether male European ground squirrels Spermophilus citellus (Linnaeus, 1766) develop scrotal testes before or after the termination of hibernation. The course of testis development and testosterone concentrations were examined in young-of-year male ground squirrels (n = 4) before, during, and after their first hibernation. In the environmental chamber, all animals showed regular hibernation patterns with decreasing torpor bout lengths prior to the end of hibernation. Four weeks before hibernation ended, testosterone levels were elevated during spontaneous arousals. Testosterone concentrations peaked during the first 2 months post heterothermy and decreased thereafter. In 2 experimental males, testes descended from the inguinal region into the scrotum shortly before the end of heterothermy. The state of testis development and testosterone secretion corresponded to that found in semi-free-living males at spring emergence. Testis size increased in active animals to maximum widths during weeks 3 and 4 post heterothermy. Scrotal skin pigmentation was absent until heterothermy ended and developed during the first month thereafter. The data suggest that male S. citellus do not need a pre-emergence euthermic period for reproductive development.

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Vernal Changes in the Behavioral and Endocrine Responses to GnRH Application in Male European Ground Squirrels

Cited by 25 publications

References 23 publications

Does a short-term increase in testosterone affect the intensity or persistence of territorial aggression? — An approach using an individual's hormonal reactive scope to study hormonal effects on behavior

Does a short-term increase in testosterone affect the intensity or persistence of territorial aggression? — An approach using an individual's hormonal reactive scope to study hormonal effects on behavior

Natural Selection on Testosterone Production in a Wild Songbird Population

Testis development and testosterone secretion in captive European ground squirrels before, during, and after hibernation

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