Prevalence and Potential Evolutionary Significance of Color Mutations in Freshwater Crayfish (Decapoda: Astacidea)

Color mutations may lead to the evolution and diversification of color phenotypes in animals. However, much of the research on this topic has been conducted on vertebrates. Here, I compile records of color mutations in freshwater crayfish (Decapoda: Astacidea). I found color mutations to be surprisingly common, with 103 documented occurrences. The overwhelming majority of these mutations resulted in blue coloration (72.81%), although I also documented red and orange mutations, among others. Whether or not these mutations can lead to adaptive evolution in crayfishes is unknown. Naturally, some crayfish species exhibit conspicuous colors like blue, orange, and red. 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, color mutations may be a neutral color trait which faces little to no selection 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.