导读
来自厄瓜多尔的动画创作者Gino Imagino常常围绕梦境般的非凡世界进行 创作，作品充满想象力。这支短小的动画就在有限的时间里，展现了一个神奇的异想世界。而且其中的主角也绝非寻常动物,他正是今天经济学人文中提到的拥有蓝色脚丫的蓝脚鲣鸟，英文为生活在Blue-footed Booby，是一种生活在美洲西海岸的热带海鸟。它外貌上最大的特点是亮蓝色的脚。它们会通过跳舞来展示蓝色的脚趾，以此吸引异性。这样一种造型独特的生物放在本片的魔幻世界中，可谓“画风”贴合了。
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Mate choice
择偶
本文英文部分选自经济学人Science-and-technology板块
A healthy glow
荣光焕发
Birds with poor digestion are literally off colour.
消化不良的鸟类几乎没有颜色。
THE vibrant hues of beautiful plumage areoften borrowed.Flamingos, for example, owe their pinkness to chemicals called carotenoids that are made by bacteriaknown (confusingly) as blue-green algae. The birds, when feeding, both ingest these bacteria directly and consume small crustaceans that themselves subsist on such bacteria. Blue-footed boobiesobtain their eponymous colour similarly, via the fish they eat.
鸟类羽毛上鲜艳的色彩往往不是先天形成的。例如，火烈鸟的粉红色羽毛，主要是由一种叫做类胡萝卜素的化学物质引起的，这种化学物质由大家熟知的蓝藻（细菌域，类细菌）生物合成的。鸟类在进食时，既会直接摄入这些类细菌，也会吃掉以这些类细菌为食的小甲壳类动物。相似地，蓝脚鲣鸟通过它们觅食的鱼类，获得了与其名称相同的颜色。
1.鸟类羽毛的颜色是由色素或羽毛的显微结构通过反射、干涉、散射自然光决定的，也有两者共同作用的情况。前者称为色素成色，后者成为结构成色。
2.Bacteria：细菌，细菌域，球菌，菌域。细菌域包括细菌、放线菌、蓝细菌和各种除古菌以外的其他原核生物。
3.blue-green algae：蓝绿藻，又称蓝藻或蓝细菌，蓝藻是原核生物（不属于细菌），大多数蓝藻的细胞壁外面有胶质衣，又叫粘藻。在藻类中，蓝藻是最简单、最原始的单细胞生物，如微囊藻、念珠藻、鱼腥藻等。
4.Blue-footed boobies：蓝脚鲣鸟。许多鱼类肌肉中富含类胡萝卜素——比如虾青素，那么这些类胡萝卜素会不会和蓝脚鲣鸟独特的体色有关呢？研究人员使用不含类胡萝卜素的人工饲料饲养蓝脚鲣鸟，仅仅一个月之后，脚蹼的颜色就出现了明显的退化。果然，来自沙丁鱼体内的类胡萝卜素在进入蓝脚鲣鸟体内后，与一些特殊的蛋白质结合，才形成了它们独特的蔚蓝色的脚蹼。也就是说，蓝脚鲣鸟的脚蹼颜色，实际上与它们的摄食情况息息相关。一只雄性蓝脚鲣鸟的脚蹼颜色越蓝，就越能代表它吃的很好、营养很充足，相应的体格也自然会更强健，而它娴熟的捕猎技巧，自然也会给后代提供源源不断的充足的食物，这样的汉子当然能赢得美人心了。具体参考
Carotenoids, though, are dual-use molecules. Besides being pigments, they also help to stimulate the immune system. If a bird is troubled by parasites or pathogens its immune system will thus use up some of its carotenoid stock defending against these interlopers, and its colour will suffer. If it is parasite-free, by contrast, most of the carotenoids it consumes will be used to create colour. This is a difference that potential mates notice and act on, as dozens of experiments have proved.But a study just published in Naturwissenschaften has gone beyond these observations and shown that bright plumage is also an indicator of a healthy digestive system.
类胡萝卜素是一种双重用途的分子。除了是色素，它们还能刺激免疫系统。如果一只鸟受到寄生虫或病原体的困扰，它的免疫系统将会消耗一些体内的类胡萝卜素以抵御这些入侵者，因此它的颜色也会受到影响。相比之下，如果鸟类体内没有寄生虫，那么它所消耗的大部分类胡萝卜素将被用来创造颜色。正如几十个实验证明的那样，潜在的伴侣会注意到这些区别并按此采取行动（雌鸟在选择配偶时会选择羽毛颜色亮丽的雄鸟）。但在《自然科学》杂志上刚刚发表的一项研究已经超出了这些观察结果的范围，指出明亮的羽毛也是消化系统健康的一个指标。
Wild animals live in a world of constant food scarcity. Squeezing every last calorie and nutrient molecule from what they eat is crucial to their survival. Since carotenoids are obtained as part of this digestive process, Tuul Seppof Arizona State University and her colleagues wondered if plumage brilliance might therefore be a reliable signal of the efficiency with which a bird extracts goodness from its food.
“粮荒”是动物世界里常有的事，为了生存，动物们就得拼命汲取食物中的每一丝热量和养分。由于类胡萝卜的吸收是消化过程的一部分，亚利桑那州州立大学的图尔赛普博士（Tuul Sepp）和同事们就想知道鸟类羽毛的成色是否可以作为一个可靠的信号，反映鸟类是否能够从食物中汲取精华。
To assess that she turned to a test called the “acid steatocrit”. This involves collecting an animal’s faeces, mixing them with perchloric acid to liberate the fat molecules within, centrifuging the mixture and then measuring the thickness of the fatty layer which has accumulated at the top. The thinner this layer, the more efficiently the animal in question has been digesting any fats it has eaten. Since most carotenoids are bound to fatty molecules called lipo-proteins, Dr. Sepp reasoned that those birds which the test suggests are collecting fats efficiently from their food will also be brightly colored.
为了验证这个想法，她进行了名为“acid steatocrit”的试验，试验包括收集动物的粪便，将其与高氯酸混合来分离脂质分子，再将上述混合物进行离心后，测量累积在混合物上层的脂肪层厚度。脂肪层越薄，试验对象的脂肪消化效率则越高。因为大部分类胡萝卜素会跟一种名为“脂蛋白”的脂肪分子结合在一起，塞普博士（ Dr. Sepp）由此推测脂肪吸收率高的鸟类，其羽毛的色泽也更加明亮。
Acid steatocrit: a simple, rapid gravimetric method to determine steatorrhea. 参考文章：
To investigate this idea, she and her col- leagues collected 36 male house finches— birds known for having brilliant red breasts. They photographed their captives and held them in cages for a short time, in order to collect some faeces from each. They then ran the images of the birds’ breasts through a computer to analyse how red they were, and studied a sample of each bird’s faeces using the acid steatocrit test.
为了验证上述想法，图尔塞普博士（Tuul Sepp）和同事们搜集36只雄性家朱雀，它们以红胸著称。团队给家朱雀拍照，并将其关在笼子里一小段时间， 以便收集他们的粪便。然后，团队通过电脑播放这些鸟的胸脯照片，来分析它们的红色深浅，并用“acid steatocrit”测试方法对每只燕雀的粪便样本进行了研究。
The result was thatthere is indeed a correlationbetween the brilliance of a bird’s breast and the efficiency of its fat digestion. If Dr Sepp’s computer can see this, it seems likely female house finches can, too—and will thus have yet another reason to pick the mates with the prettiest plumage.
结论是，燕雀胸脯颜色的鲜艳程度与它的脂肪消化效率之间确实存在相关性。如果塞普博士（Dr Sepp）的电脑能看到这点，那么雌性家朱雀很可能也能明白。因此，这也将成为雌性家朱雀选择具有漂亮的羽毛的雄性家朱雀的另一个原因。
翻译组：
Joel，男，产品运营，科技类外刊爱好者
Cyrus，男， 口译民工，经济学人爱好者
Aileen，女，大四数学狗 经济学人粉丝
Coco，男，物流民工，经济学人铁粉
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Xingyi，男，小硕，经济学人爱好者
Damon，男，建筑民工 ，经济学人铁粉
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