POLAROTAXIS IN COPEPODS. I. AN ENDOGENOUS RHYTHM IN POLAROTAXIS IN CYCLOPS VERNALIS AND ITS RELATION TO VERTICAL MIGRATION

Open Access
Publisher Website
Google Scholar
Abstract
A series of laboratory experiments on the fresh-water copepod, Cyclops vernalis, revealed an endogenous rhythm in its orientation to polarized light. The copepod swam perpendicular to the plane of polarization at the beginning and end of a 12 hr. light period, but swam parallel to the plane of polarization midway through this light period. The rhythm was not present under all experimental conditions, being released only when the intensity of light from above was equal to that from the side. Under other experimental conditions, the copepods swam perpendicular to the plane of polarization at all times during the light period. The diurnal rhythm in polarotaxis, operating only under deep-water intensity ratios of horizontal and vertical light, would serve to orient copepods found in deep water in nature in a horizontal plane at midday. This would inhibit vertical swimming patterns (which occur in deep water at dawn and dusk) that might carry the copepods to the surface at midday. Polaro-tactic behavior is therefore implicated as a factor in the release and control of vertical migrations in nature.

This publication has 0 references indexed in Scilit: