the chromatophores grow longer and longer as they get older, so that makes sense. for it to be that dark they have to have some seriously thick/long branches. cool!
from looking at my shrimp and their molts, i believe that the "racing stripe" is crystallized quanine in the shell. in other crustaceans, it is produced to help reflect UV. since it gets concentrated under the shell, it goes away with each molt.