Dear Blue Lobster:
I have two electric blue lobsters and when I got them they were blue but now they seem to be brown with a little orange here and there. What would cause this: Could they be molting and how can I tell. How long does it take for them to molt?
Dear Gentle Sir:
Cray color can be influenced by a number of factors, including genetics, environment, breeding, and lighting.
If the cray is genetically blue, it will remain blue for its life, though its shade may vary. As noted in other columns, crays can be bred for different colors and patterns. One notable new color morph in Procambarus clarkii is called the "Ice Morph," where the cray is entirely white save for its eyes and resembles an albino or a cave species. It is rare and goes for hundreds of dollars.
Sometimes crays will change color slightly to match their environment. Again, the Procambarus clarkii is highly adaptable and can be naturally found with red, orange, brown, green, and gray color morphs, all to match their environments. A cray living in dense weeds will tend towards green while one living in a creek with heavy iron deposits will grow orange. You may find a cray that changes from light to dark or vice versa depending on your tank lighting and gravel shade.
During mating season, the cray will molt in anticipation of the coming intercourse and exhibit color changes. This is called the second, or mating, phase of the cray's color patterns. The Orconectes rusticus will change from a dull tan to a dark grey with vivid red, white, and black stripes on its claws. Cambarides coccus, the Peacock Cray, turns from a dark brown color to a motley of yellow, green, red, and blue spots before it sets out to find a mate. The next molt after mating season will put them back into their first color phase.
Lighting can do some spectacular things to your crayfish too. Using fluorescent lights that mimic natural sunlight, the cray is likely to take on stronger hue and vibrancy. Using old incandescent lights can result in more muted tones, and colored incandescence can alter the undertone of the cray. Using Day-Glo lights will result in crays that glow in the dark, giving off an eery psychedelic luminance. One species of cray even phosphoresces due to the deposits of the mineral in the water where it lives, which helps constitute its shell.
To answer your question directly, unless your cray is crawling out of its shell it's not actively molting but color changes can indeed happen directly after molts: The changes have been there all along underneath its old shell waiting to come out. Think of the cray's new colors as the real him opening up to the world saying, "This is just who I am!"