Color Responses in the Cladocera and Their Ecological Significance

Abstract

Cladocera respond to changes in the wave length of vertical light by swimming up when the energy is shifted toward the long end of the spectrum (over 5000Å), and by swimming down when the energy is shifted toward the short end of the spectrum (under 5000Å). Specific behavior patterns (color dances) are observed under sustained long or short wave lengths. Responses to changes in intensity are described in relation to the two colors. Temperatures less than 10⚬ C. eliminate all aspects of the "blue" response, leaving a "red" response in its place. The color dances are shown to provide a probability mechanism for concentrating populations in areas of dense phytoplankton. Responses to changes in color together with responses to changes in intensity and the effect of temperature, are shown to be intimately associated with diurnal migration.