Prevalence and potential evolutionary significance of color variants in freshwater crayfishes (Decapoda: Astacidea)

Abstract Mutations may lead to the evolution and diversification of color phenotypes in animals. Much of the research on this topic, however, has been conducted on vertebrates. I compile here records of color variants in freshwater crayfishes (Decapoda: Astacidea). I found color variants to be surprisingly common, with 115 documented occurrences. The overwhelming majority of these variants were blue-colored (71.3%), although there are records of document red and orange variants, among others. Whether these variants are all due to mutations or can lead to adaptive evolution in crayfishes is unknown. Some crayfish species exhibit conspicuous colors like blue, orange, and red in nature. Many of these conspicuously colored species are also semi-terrestrial burrowers, which have limited migration potential, smaller population sizes, and thus reduced gene flow compared to aquatic burrowing crayfishes. I speculate that in at least some species, conspicuous colors may be a neutral color trait that faces little to no selective pressure. This is one potential explanation as to why semi-terrestrial burrowing species are more likely to be conspicuously colored. Genetic studies and behavioral experiments are required to test this hypothesis.