Yes, It's a Lobster, and Yes, It's Blue
By KENNETH CHANG
Published: March 15, 2005
ne lobster in a million is blue, and the reason is not that it has been holding its breath.
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.
possibility is that the protein twisted the astaxanthin. Dr. Frank said
that while changing the shape of a molecule can shift its color from
red to orange, for instance, the radical change to blue results from
the protein pulling astaxanthin molecules close to each other.
close proximity of two astaxanthins changes the orbits of the electrons
in the molecules, causing them to absorb red light and thus appear
blue. "The blue shift is one of the largest shifts that's seen in
nature," said Dr. Ronald L. Christensen, a chemistry professor at
Bowdoin and another author of the paper.
In the blue lobsters, a
genetic mutation has caused an overabundance of the
astaxanthin-wrapping proteins, tying up all of the red astaxanthin into
blue crustacyanin. Lobstermen in Maine find a blue lobster every year
or two, and such rarities generally find their way to aquariums.
a blue lobster would make an unremarkable meal. Heat breaks down the
astaxanthin-wrapping protein, destroying the blue pigment. In other
words, on a dinner plate, a blue lobster would probably be just like
any other lobster: red.