Tracking Color Change in Individual Green Crabs, Carcinus maenas (L.)

Carcinus maenas (Green Crab) exhibits a color range from green through yellow and orange to red. The change from green to red is hypothesized to signal a change in resource allocation from growth to reproduction. In order to understand color change in individuals, C. maenas were held in captivity or tagged and recaptured in summer 2007 and 2008. Over the course of the study, crabs fell into 4 categories: those which were green and did not change color, those which were red and did not change color, those which became redder, and those which molted, changing from red to green. Crabs did not change from red to green unless they had molted. Our data show that some individual crabs turn progressively redder when they have not molted, and turn green again after molting.