文章来源:未知 文章作者:enread 发布时间:2018-03-26 00:50 字体: [ ]  进入论坛
Peruse1 the egg section of a grocery store or farmers market, and you'll notice cartons of eggs separated into white and brown, sometimes even green or blue eggs. But once they arrive scrambled2 on a plate, perhaps, or baked into a cake, it's tough to tell the difference. In fact, what is the difference between eggs with shells of different colors? 
This isn't a flour or rice situation. Brown eggs are not more "natural," and white eggs have not been decolored with bleach3. Both varieties occur completely naturally, as do bluish-green chicken eggs. But really, all chicken eggs are the same on the inside. So what causes different egg colors among the same type of bird? 
Dr. Justin Fowler, a professor in the University of Georgia's poultry4 science department, shines a light on things. "The different colors, or the presence of spots or speckling, come down to the genetics of the bird," he says. 
"Leghorn chickens (which make up most of the commercial egg industry in the US) lay white eggs, while Orphingtons or Plymouth Rocks will lay brown eggs," explains Fowler. "The Ameraucana breed has a pigment5 that is able to permeate6 the whole egg shell and make blue-colored eggs that are colored on both the inside and outside of the shell." 
Want to know whether a specific chicken will pop out a white egg or a colored egg? Examine the chicken's earlobe. (Surprise, birds have earlobes!) "Breeds with white earlobes will typically be those that do not put extra pigment on the egg shell before laying," says Fowler. And more often than not, chickens with lighter7 earlobes tend to have white feathers, and thus white eggs, while those with colored feathers and earlobes tend to produce colored eggs. 
Where does this color come from? Here's where understanding how an egg comes to be is important. Chicken yolks, or ova, form in the chicken's ovaries. A fully9 formed ovum will leave the ovary and be deposited into the oviduct. This part of the chicken's reproductive system has five distinct sequential segments which the yolk8 passes through on its way to the outside world, but it's the fourth one -- the shell gland10 -- that affects the color of the egg. This is where the shell forms around the ovum. 
"The shell of all chicken eggs are made of calcium11 carbonate, a crystal that is white in color," says Fowler. "So all eggs are, at least at the start, white. Any that we then see that are other colors have had a pigment deposited on them as they were moving through the oviduct, after the white egg shell had been deposited. You can see this if you open up a brown egg and look at the inside of the shell, it'll be white." 
Two pigments12 are responsible for the spectrum13 of chicken egg color. Shades of greens and blues14 are caused by the pigment biliverdin, while protoporphyrin is responsible for reddish-brown hues15
The same egg-coloring process holds true for all birds with colorful eggs. American robin17 (Turdus migratorius) eggs, for instance, are famously blue. The pear-shaped eggs of a common murre (Uria aalge) can sport a blue hue16, be speckled or feature brown streaks18.


1 peruse HMXxT     
  • We perused the company's financial statements for the past five years.我们翻阅了公司过去5年来的财务报表。
  • Please peruse this report at your leisure.请在空暇时细读这篇报道。
2 scrambled 2e4a1c533c25a82f8e80e696225a73f2     
v.快速爬行( scramble的过去式和过去分词 );攀登;争夺;(军事飞机)紧急起飞
  • Each scrambled for the football at the football ground. 足球场上你争我夺。 来自《现代汉英综合大词典》
  • He scrambled awkwardly to his feet. 他笨拙地爬起身来。 来自《简明英汉词典》
3 bleach Rtpz6     
  • These products don't bleach the hair.这些产品不会使头发变白。
  • Did you bleach this tablecloth?你把这块桌布漂白了吗?
4 poultry GPQxh     
  • There is not much poultry in the shops. 商店里禽肉不太多。
  • What do you feed the poultry on? 你们用什么饲料喂养家禽?
5 pigment gi0yg     
  • The Romans used natural pigments on their fabrics and walls.古罗马人在织物和墙壁上使用天然颜料。
  • Who thought he might know what the skin pigment phenomenon meant.他自认为可能知道皮肤色素出现这种现象到底是怎么回事。
6 permeate 0uWyg     
  • Water will easily permeate a cotton dress.水很容易渗透棉布衣服。
  • After a while it begins to permeate through your skin.过了一会,它会开始渗入你的皮肤。
7 lighter 5pPzPR     
  • The portrait was touched up so as to make it lighter.这张画经过润色,色调明朗了一些。
  • The lighter works off the car battery.引燃器利用汽车蓄电池打火。
8 yolk BVTzt     
  • This dish would be more delicious with some yolk powder.加点蛋黄粉,这道菜就会更好吃。
  • Egg yolk serves as the emulsifying agent in salad dressing.在色拉调味时,蛋黄能作为乳化剂。
9 fully Gfuzd     
  • The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气,然后全部呼出。
  • They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。
10 gland qeGzu     
  • This is a snake's poison gland.这就是蛇的毒腺。
  • Her mother has an underactive adrenal gland.她的母亲肾上腺机能不全。
11 calcium sNdzY     
  • We need calcium to make bones.我们需要钙来壮骨。
  • Calcium is found most abundantly in milk.奶含钙最丰富。
12 pigments 90c719a2ef7a786d9af119297e63a36f     
n.(粉状)颜料( pigment的名词复数 );天然色素
  • The Romans used natural pigments on their fabrics and walls. 古罗马人在织物和墙壁上使用天然颜料。 来自辞典例句
  • The original white lead pigments have oxidized and turned black. 最初的白色铅质颜料氧化后变成了黑色。 来自辞典例句
13 spectrum Trhy6     
  • This is a kind of atomic spectrum.这是一种原子光谱。
  • We have known much of the constitution of the solar spectrum.关于太阳光谱的构成,我们已了解不少。
14 blues blues     
  • She was in the back of a smoky bar singing the blues.她在烟雾弥漫的酒吧深处唱着布鲁斯歌曲。
  • He was in the blues on account of his failure in business.他因事业失败而意志消沉。
15 hues adb36550095392fec301ed06c82f8920     
色彩( hue的名词复数 ); 色调; 信仰; 观点
  • When the sun rose a hundred prismatic hues were reflected from it. 太阳一出,更把它映得千变万化、异彩缤纷。
  • Where maple trees grow, the leaves are often several brilliant hues of red. 在枫树生长的地方,枫叶常常呈现出数种光彩夺目的红色。
16 hue qdszS     
  • The diamond shone with every hue under the sun.金刚石在阳光下放出五颜六色的光芒。
  • The same hue will look different in different light.同一颜色在不同的光线下看起来会有所不同。
17 robin Oj7zme     
  • The robin is the messenger of spring.知更鸟是报春的使者。
  • We knew spring was coming as we had seen a robin.我们看见了一只知更鸟,知道春天要到了。
18 streaks a961fa635c402b4952940a0218464c02     
n.(与周围有所不同的)条纹( streak的名词复数 );(通常指不好的)特征(倾向);(不断经历成功或失败的)一段时期v.快速移动( streak的第三人称单数 );使布满条纹
  • streaks of grey in her hair 她头上的绺绺白发
  • Bacon has streaks of fat and streaks of lean. 咸肉中有几层肥的和几层瘦的。 来自《现代英汉综合大词典》
TAG标签: color eggs shells