Biophoton emission fromDaphnia magna: A possible factor in the self-regulation of swarming

Summary The formation of swarms by planktonic organisms was first described almost 100 years ago, but the mechanisms governing the development of patterns in population size and density are still not understood. In this study, we investigated one biophysical factor that may play an important role in swarm-formation. Spontaneous ultraweak photon emission in the visible range has been well documented for living cells, tissues and individuals in the plant and animal kingdom, including humans. We demonstrate here that the intensity of light emitted by the planktonic crustaceanDaphnia magna is a function of population density in relation to body size. The effects are discussed on the basis of the theory of Dicke^1,2, and it is suggested that biophoton emission may be a basic factor in the self-regulation of swarm density.