By Sam Rutka, Aquarist II
The typical American lobster (Homarus americanus) relies on a mottled pattern of greenish brown for an effective camouflage in its seaweed-filled, rocky habitat. On rare occasions, some individuals exhibit vibrant variations in shell color due to genetic mutations. These color deviations are not just striking, they are scientifically intriguing, captivating both biologists and community members with their unusual appearances. Lobster shell color is determined by a complex interplay of three layers of carotenoid pigments that bind with proteins: astaxanthin (reds and yellows), and crustacyanin (blues). In a typical lobster, these stacked pigments combine in the shell to produce the familiar dark camouflage coloration. When genetic mutations alter the expression, or structure, of these pigments, uncommon colors can emerge.
Blue lobsters, for instance, occur due to a mutation that causes an overproduction of crustacyanin, leading to an excess of the blue protein. This results in brilliant blue coloration seen in approximately 1 in 2 million lobsters. On the other hand, red lobsters (approximately 1 in 10 million) and the orange or yellow lobsters (approximately 1 in 30 million) obtain their fiery hue because of mutations wherein the reduced production of crustacyanin allows the predominate pigments of the astaxanthin to dominate the lobster’s appearance.
Albino lobsters result from a complete lack of all pigment-producing proteins, and appear white or translucent, with an estimated occurrence of 1 in over 100 million. A similar condition, known as leucism, results from a partial loss of pigment-producing proteins and shows as very pale or muted tones. For the infamous “cotton candy” lobster (approximately 1 in 100 million), there is an abundance of crustacyanin (blue) adorned with areas containing astaxanthin (red), that when viewed appear to create blends of blue, purple, lavender, and pink resembling the sugary treat.
Calico lobsters, just like calico cats, have a mixture of pigmentation that appear as blotches or spots throughout the body, and occur (in lobsters, not cats) roughly 1 in 40 million. These patchy patterns are caused when the astaxanthin bonds with various proteins in different sections creating a mosaic or “freckled” pattern.
Split lobsters, also called chimera, are specimens that resemble two individual lobsters cut lengthwise and spliced together, can have one half of their body, one color morph (or sex in the case of gynandromorphism) and the other side, a completely different one. These colorful concoctions appear roughly 1 in 50 million and result from two zygotes absorbing one another that develop into an individual with two separate sets of genes.
Environmental factors such as diet can play a role in lobster coloration, albeit to a lesser extent than genetics. Diet can enhance expression of existing pigments in the shell; for example, lobsters that consume a diet rich in carotenoids, which are found in certain algae and shellfish, can exhibit more vibrant red or orange hues, though these dietary influences are generally less pronounced than the effects of genetic mutations.
Since observing and counting every lobster in the ocean to estimate the scarcity of the different color groups is an impossibility, to ascertain the estimated rarity of these magnificent mudbugs, scientists consider the genetic sequences that cause coloration and its deviation in lobsters and calculated the likelihood of the specific gene expression believed to create the different pigmentations. While these rare colored lobsters are particularly vulnerable in the wild, due to their overt lack of camouflage, making them easy targets for predators, it does not impact the math used to determine their frequency.
The study of these rare color morphs provides valuable insights into the genetic and biochemical pathways that govern shell coloration in crustaceans. Understanding these processes can have broader implications for fields such as evolutionary biology, genetics, and even the aquaculture industry, where the potential for cultivating lobsters with specific traits could be of significant interest. Whilst stumbling across a colored lobster is a rare event, it is a potent reminder of the complexity and variability of life. Each colored lobster is not only a biological curiosity but also a window into the intricate genetic mechanisms that drive diversity in the natural world.
For more information and a chance to see these spectacular specimens in person, visit Seacoast Science Center in Rye NH where we have a rotating cast of colorful lobsters on exhibit accompanied by knowledgeable staff ready to answer any questions. Talk to our front desk for up-to-date information on which colors are on display and inquire about times and opportunities to meet a lobster!
