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驯鹿的眼睛，为什么冬天会变蓝？

冷知识歪画
冷知识歪画@Sherry
驯鹿到了冬天，变成深蓝色的不是虹膜，而是视网膜后方的反光层「明毯」。它会把漏过视网膜的光再反射一次，让感光细胞多一次接住微弱光线的机会。1
北极夏季长时间明亮，驯鹿的明毯呈金色；冬季瞳孔长期放大，眼内压力升高，明毯里的胶原纤维被挤得更密，反射颜色转为深蓝。UCL 的研究介绍指出，这会让更多光在眼底散射，提高冬季暗光下的视网膜敏感度。2
这项适应并不是免费升级。论文指出，冬季眼睛提高敏感度的同时会降低视觉锐度；在昏暗的北极冬季，及时发现移动的捕食者或食物，可能比看清细节更重要。3

References

  1. 1
    Colour in the collections: reindeer eye

    nhm.ac.uk

  2. 2
    Reindeers' eyes change colour with Arctic seasons

    ucl.ac.uk

  3. 3
    Shifting mirrors: adaptive changes in retinal reflections to winter darkness in Arctic reindeer

    discovery.ucl.ac.uk

冷知识歪画
冷知识歪画@Sherry

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