Lafayette College, Department of Biology, Easton, PA, 18042-1778, USA; Arizona State University, School of Life Sciences, Tempe, AZ, 85287-4501, USA.
Comp Biochem Physiol A Mol Integr Physiol. 2013 Nov;166(3):465-9. doi: 10.1016/j.cbpa.2013.07.024. Epub 2013 Jul 31.
Nutritional constraints on reproduction are well-characterized in female animals, but rarely have particular nutrients been linked to male reproductive investments. Carotenoid pigments promote egg-laying and fertility in several animals, and are displayed externally within secondary sex traits by males of many colorful species to attract mates, but it is unclear if or how carotenoids affect male primary sex traits. We manipulated carotenoid availability in the diet of male mallards (Anas platyrhynchos) during both development and adulthood to determine effects on size and carotenoid content of the testes. We found that developmental carotenoid manipulations did not affect testis size or carotenoid concentration, but that increased carotenoid dietary levels at adulthood resulted in more carotenoid-rich, but smaller, testes. This latter result was surprising, given positive correlations in mammals between testicle size and carotenoid concentration. We also found negative correlations between testis size and carotenoid concentration for individual ducks, regardless of dietary treatment. These results suggest that carotenoid deposition into testis tissue can reduce investment in gonad size (and thus overall sperm count), although the functional consequences of this relationship remain to be tested.
营养限制对雌性动物的繁殖有很好的描述，但很少有特定的营养物质与雄性生殖投资有关。类胡萝卜素色素能促进几种动物的产卵和生育能力，并且在许多色彩鲜艳的物种的雄性中通过次级性特征在外部表现出来，以吸引配偶，但目前还不清楚类胡萝卜素是否或如何影响雄性主要性特征。我们在雄性绿头鸭（Anas platyrhynchos）的发育和成年期间操纵饮食中的类胡萝卜素可用性，以确定其对睾丸大小和类胡萝卜素含量的影响。我们发现，发育中的类胡萝卜素处理并没有影响睾丸大小或类胡萝卜素浓度，但成年时增加类胡萝卜素饮食水平会导致睾丸更小但富含类胡萝卜素。鉴于哺乳动物中睾丸大小和类胡萝卜素浓度之间存在正相关关系，这一结果令人惊讶。我们还发现，无论饮食处理如何，个体鸭子的睾丸大小和类胡萝卜素浓度之间都存在负相关关系。这些结果表明，类胡萝卜素沉积到睾丸组织中可能会减少对性腺大小的投资（因此总体精子数量），尽管这种关系的功能后果仍有待测试。
