The Effect of Light On the Shadow Reaction of the Sea Urchin, <i>Diadema Setosum</i> (Leske)

Abstract

ABSTRACT As is mentioned by Mortensen (1940), sea urchins which belong to the genus Diadema react to shadow by spine movements. Since the work of Millott (1954) these responses have been extensively studied on an Atlantic species, D. antillarum. In preliminary experiments on a Japanese species, D. setosum, some of the important findings in the Atlantic species, such as the part played by radial nerves in the reflex (Millott, 1954), the photosensitivity of the nervous elements (Yoshida &amp; Millott, 1959) and the inhibitory effect of light on the reaction (Millott &amp; Yoshida, 1960 a, b), were confirmed. This made it possible to base the work on the Japanese species on what has been found in D. antillarum.