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This is a fun story:
One lobster in a million is blue, and the reason is not that it has been holding its breath.
A combination of red and blue pigments in the shell of a live lobster creates a mottled camouflage of indeterminate hue that blends in with the ocean floor.
The red comes from the molecule astaxanthin, a cousin of beta carotene, which gives carrots their orange color and is a source of vitamin A. Astaxanthin, which looks red because it absorbs blue light, also colors shrimp shells and salmon flesh. The blue pigment in lobster shells also comes from crustacyanin, which is astaxanthin clumped together with a protein. "It's a gorgeous bluish color, almost an ice blue color," said Dr. Harry A. Frank, a professor of chemistry at the University of Connecticut. In an article that will be published in The Journal of Physical Chemistry, Dr. Frank and colleagues at Connecticut and Bowdoin College report data explaining why astaxanthin is red, but the astaxanthin-protein compound crustacyanin is blue.