The American lobster, typically a mottled greenish-brown color, occasionally presents a striking variation. The existence of a lobster with a shell of vivid, uniform sapphire blue is a biological reality. This remarkable coloration is an extremely rare natural phenomenon. The unusual hue is caused by a single genetic anomaly that transforms the animal into a brilliant blue specimen.
The Rarity and Appearance of Blue Lobsters
The blue lobster is a color variant of the American lobster, Homarus americanus, found in the North Atlantic waters. The striking blue coloration is exceptionally uncommon, with estimates suggesting that only about one in every two million lobsters exhibits this trait. The blue variant is distinguished by a deep, almost iridescent hue that covers the entire carapace and claws. This vibrant appearance is a dramatic departure from the lobster’s typical dark, mottled shell, which normally provides effective camouflage. Despite its unusual color, the blue lobster is anatomically identical to its common counterparts.
The Chemical Basis of Lobster Color
The typical coloration of a lobster is determined by astaxanthin, a carotenoid pigment. The animal cannot produce astaxanthin itself and must obtain it through its diet, such as by eating algae and small crustaceans. Astaxanthin is naturally a reddish-orange molecule, the same pigment responsible for the color of cooked lobsters. When the lobster is alive, this pigment is stored within the shell and bound to a large protein complex known as crustacyanin. The binding causes a physical and chemical change in the pigment’s structure.
This structural alteration shifts the light absorption properties of the pigment, known as a bathochromic shift. Instead of reflecting red light, the bound astaxanthin reflects blue light. In a normal lobster, the shell contains multiple layers of this bound blue pigment, which combine with other pigments to create the complex, dark, mottled greenish-brown color.
The Genetic Mutation for Blue
The appearance of a blue lobster stems from a specific genetic mutation that affects the production of the crustacyanin protein. The mutation results in an excessive production of this protein, the component that binds to the red astaxanthin pigment. Because the lobster produces an overabundance of the protein, the shell becomes saturated with the blue-reflecting astaxanthin-crustacyanin complex. This excess overwhelms the other pigments and layers that normally contribute to the mottled brown camouflage.
The blue trait is inherited through a recessive gene, meaning a lobster must inherit the specific mutated gene from both parents to express the pure blue color. This recessive inheritance pattern contributes to the extreme rarity of the blue lobster in the wild population. When the blue lobster is cooked, the heat denatures the crustacyanin protein, causing the astaxanthin to release and revert to its natural reddish-orange hue, just like any other lobster.