Testosterone, body size, and sexual signals predict parasite load in Yarrow's Spiny Lizards (Sceloporus jarrovii)
Testosterone, body size, and sexual signals predict parasite load in Yarrow's Spiny Lizards (Sceloporus jarrovii)
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DOI：
10.1139/cjz-2014-0256
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发表时间：
2014-12-01
影响因子：
1.4
通讯作者：
Blouin-Demers, G.
中科院分区：
文献类型：
--
作者：
Halliday, W. D.;Paterson, J. E.;Blouin-Demers, G.
寄生虫负载显著影响宿主健康和健身，并且可能在种群内的个体之间存在显著差异。免疫功能障碍假说认为，性信号是男性质量的诚实指标，因为它们是由睾丸激素维持的，睾丸激素是一种免疫抑制剂，产生更高的寄生虫负荷。此外，睾酮可能会通过增加活动水平来影响寄生虫负荷。我们研究了这两个假设，在野生种群的亚罗的刺落叶松（Sceloporus jarrovii科普，1875年）在亚利桑那州。我们（i）粪便睾酮水平相比，体外寄生虫和血液寄生虫负荷，（ii）测试，如果性信号（总着色面积，侵略，和头部大小），运动活动，和身体大小与睾酮水平相关，（iii）比较性信号，运动活动，和身体大小寄生虫负荷。外寄生虫负荷增加总有色区，并倾向于增加睾酮，但后者的关系是只有近显着。寄生虫负荷增加与身体的大小。因此，我们发现一些支持免疫功能障碍假说和活动假说没有。我们的研究结果与另一种假设是一致的，即较大的个体有更多的寄生虫，因为他们有更多的表面积和（或）有更长的时间来积累寄生虫。未来的研究应该检查睾丸激素和糖皮质激素在驱动寄生虫负荷变化中的相对贡献。
Parasite load significantly impacts host health and fitness and may vary substantially among individuals within a population. The immunocompetence handicap hypothesis posits that sexual signals are honest indicators of male quality because they are maintained by testosterone, an immunosuppressant that yields higher parasite loads. Additionally, testosterone may influence parasite load by increasing activity levels. We examined these two hypotheses in a wild population of Yarrow's Spiny Lizards (Sceloporus jarrovii Cope, 1875) in Arizona. We (i) compared fecal testosterone levels to ectoparasite and haemoparasite loads, (ii) tested if sexual signals (total coloured area, aggression, and head size), locomotor activity, and body size correlated with testosterone levels, and (iii) compared sexual signals, locomotor activity, and body size to parasite load. Ectoparasite loads increased with total coloured area and tended to increase with testosterone, but this latter relationship was only nearly significant. Parasite loads increased with body size. Thus, we found some support for the immunocompetence handicap hypothesis and none for the activity hypothesis. Our results are consistent with an alternative hypothesis that larger individuals have more parasites because they have more surface area and (or) have had longer to accumulate parasites. Future studies should examine the relative contributions of testosterone and glucocorticoids in driving variation in parasite loads.