UCB Moorea Class: Biology and Geomorphology of Tropical Islands

Color polymorphism has been implicated as an important component of cryptic coloration in organisms inhabiting complex environments. Recent studies have suggested that mantle color variation in Tridacnid clams may serve various functions, including as a mechanism to achieve background matching. The mantle color variation of Tridacna maxima was examined in a series of experiments, including a background-matching photo survey, a predation experiment, and a zooxanthellae count. The results of the photo survey showed a significant correlation between T. maxima mantle and background color. T. maxima which did not match their background experienced a significantly greater rate of predation. Finally, the population of zooxanthellae was seen to increase for the same size of mantle area with age. These results suggest that balancing photosynthetic efficiency and anti-predation needs can be addressed by mantle color variation throughout the lifetime of T. maxima.