eggshell

zoology

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June 26, 2026

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In zoology, an eggshell is the hard outer covering of an egg. This shell serves a crucial role in protecting the developing embryo and facilitating gas exchange. While restricting water evaporation, the shell allows oxygen to enter and carbon dioxide to exit, making it vital for terrestrial animals like birds and insects that lay cleidoic eggs. The term "eggshell" can also be used metaphorically to describe something fragile or a yellowish-white color. A "shell egg" specifically refers to an egg that is still in its shell, as opposed to being dried or powdered.123

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coloration
Porphyrins
…the red flecks on the eggshells of some plovers and many other birds. The African turacos (Musophagidae) secrete a copper salt of uroporphyrin III into their wing feathers. This deep-red pigment, turacin, is readily leached from the feathers by water containing even traces of alkali. The green plumes of these…
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…the red flecks on the eggshells of some plovers and many other birds. The African turacos (Musophagidae) secrete a copper salt of uroporphyrin III into their wing feathers. This deep-red pigment, turacin, is readily leached from the feathers by water containing even traces of alkali. The green plumes of these…
Read More

egg tooth
…egg-laying species to break the shell of the egg and so escape from it at hatching. Some lizards and snakes develop a true tooth that projects outside the row of other teeth, helps the young to hatch, and then is shed. Turtles, crocodilians, and birds have an analogous horny structure…
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…egg-laying species to break the shell of the egg and so escape from it at hatching. Some lizards and snakes develop a true tooth that projects outside the row of other teeth, helps the young to hatch, and then is shed. Turtles, crocodilians, and birds have an analogous horny structure…
Read More

Why Are Some Eggs Brown and Some White?
The color of an eggshell is determined primarily by the breed of the hen that laid it. This trait is genetic: hens with white earlobes typically lay white eggs, and those with red earlobes usually produce brown eggs.
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The color of an eggshell is determined primarily by the breed of the hen that laid it. This trait is genetic: hens with white earlobes typically lay white eggs, and those with red earlobes usually produce brown eggs.
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