Turbidity and the Polarized Light Orientation of the Crustacean Mysidium

Abstract

1. The influence of the turbidity of the medium on the previously reported directional orientation of the littoral mysid, Mysidium gracile, swimming in a vertical beam of linearly polarized light, has been studied. 2. In carefully clarified sea water the slight preference shown for orientation perpendicular to the polarization plane was not statistically significant. 3. In water made turbid with known amounts of suspended yeast a statistically significant preference for swimming perpendicular to the plane of polarization appeared. 4. This response to the pattern of plarized light illumination appears strontger in highly turbid water than it is in water of moderate turbidity. 5. The mechanism of the observed response seems largely depedent upon discrimination of intensity differences in the light scattered horizontally. 6. These results emphasize the need for careful consideration of the scattering and reflexion artifacts almost invariably present with linearly polarized light.