Uncommon Descent, for some reason, just posted a link to an article about a blue lobster. This isn't the first time that a blue lobster has been found, and there are even rarer yellow and albino variants that are known. Since there is, as the UD article points out, a trade in blue crayfish, it's reasonable to assume that the blue coloration in lobsters is a heritable. All that leaves me wondering something: exactly why did the folks at Uncommon Descent decide to highlight this example?
The UD article contains the following gem:
Apparently, there is a trade in blue crayfish for aquariums, but any similar trade on blue lobsters depends on finding another one, of the opposite sex.
Does it really?
I didn't take a lot of time to research the genetic mechanisms underpinning lobster coloration (frankly, it's not a topic that fascinates me). I did find, however, that there's reason to suspect that the blue coloration is the result of a recessive trait (a paper I found noted that a prior study had found that blue offspring only occur when two blue lobsters mate). If that's the case, does a would-be purveyor of blue lobsters really need two blue lobsters to get the business off the ground?
The answer to that question, of course, is no. That's really, really, really simple genetics. It's middle school science. If that. I made my daughter work the problem and she complained that she was having a hard time because she had to dig way back to remember how to do those problems. She's just finishing 8th grade.
If you have one fertile blue lobster, one fertile normally-colored lobster, time, and patience, you will eventually be able to start your business. The first generation of offspring will be carriers. Breed them, and you can expect that ~25% of the second generation will be blue. Breed only those blue ones, and you're off to the races.
Punnett squares are your friends, when the genetics are simple.
There is no requirement that a new mutation simultaneously appear in two individuals of the opposite sex if the mutation is to spread through the population.