The Mutant Lobster
Last night the BBC had an interesting documentary (Nature’s Weirdest Events) which featured a really bizarre creature; the two-colored lobster, split right down the middle where one half was bright orange, and the other half was muddy brown. How does this work?
✤ To understand this, first we need to go over how lobster pigmentation works. Normal lobsters are colored muddy brown. They get their color from their diet as they grow and develop.
✤ Lobsters feed on a diet of shellfish and other organisms, containing the red pigment astaxanthin, an antioxidant compound. It is also the same pigment that gives salmon and flamingos their pink color. So why are lobsters a muddy brown, instead of pink like a flamingo?
✤ When the red pigment is absorbed from the diet, it is laid down into the muscles that lie beneath the shell. Over a period of time, the pigment migrates into the shell where it is transformed by a protein known as alpha-crustacyanin into a blue color. Later, the pigment migrates even further to the surface of the shell where another protein transforms it again into a yellow color.
✤ It is helpful to think of the lobster shell in terms of three different color filters: first the red muscle, then the blue shell, then the yellow shell. Combining all three forms the typical lobster shell color; the dirty muddy brown. When a lobster is cooked, the yellow and blue proteins degrade while the red astaxanthine is heat-stable, which is why a cooked lobster is bright red.
✤ So how does this explain the mutant two-colored lobster? This lobster was bright orange on one half and normal muddy brown on the other half. Each side of a lobster’s body develops independently of the other half. Once the sperm fertilizes the egg, it grows and splits into two cells. This split is important, because it determines how the lobster will develop for the rest of its life. Sometimes when the fertilized egg makes the split into two cells, very rarely there is a mutation in the gene that codes for protein associated with color. As the lobster grows, each cell replicates, and the genetic abnormality on the mutant side will also replicate. So that is how we end up with a lobster split directly in two, with a color mutation on one side. The chances of this mutation has been estimated at 1 in 50 million!
The American Chemical Society has a really good explainer video on the mechanism of lobster colors:
Unravelling the structural chemistry of the colouration mechanism in lobster shell (unfortunately it’s paywalled)
Be sure to join the discussion on Google+.