RESPONSES OF THE WHITE CHROMATOPHORES OF TWO SPECIES OF PRAWNS (PALAEMONETES) TO LIGHT AND TEMPERATURE

Abstract

Responses to light and temperature of the white chromatophores of two species of prawns, Palaemonetes pugio and Palaemonetes paladosus, were studied. The prawns were collected in Lake Pontchartrain at Point Aux Herbes, 15 miles northeast of New Orleans. The white pigment is more dispersed in prawns on a white background than in prawns on an black background at all intensities of illumination due to a specific background (albedo) response. A response to total illumination was also evident. Dispersion of the white pigment increased with increase in total illumination. The white pigment became more concentrated with increased temperature in prawns on both black and white backgrounds. The tendency of the white pigment to disperse in bright light is normally antagonized by the tendency of the pigment to concentrate with increased temperature. Since heat and bright light are usually concomitant in nature, as in sunlight, the antagonistic response to light and temperature has been interpreted as a mechanism to maintain a steady state of the white chromatophores. At all intensities of illumination the white pigment of P. paladosus was more dispersed on a white background than was the white pigment of P. pugio. In distinction to P. pugio the white pigment of P. paladosus on a white background showed no response to illumination between one and 120 ft. c. light intensity.