Role of the Terminal Pigment Spots of the Starfish, Asterias forbesi, in Light Orientation

Abstract

IT is generally stated in standard reference and text-books of zoology that, in species where such bodies are present, the terminal pigment bodies (or ‘eye spots’) are necessary for light orientation. In two early studies, Romanes¹, in the “starfish”, and Preyer², in Asterina gibbosa and Asterias glacialis, found that these spots were essential in the positive light responses of these starfish and that without these pigment bodies such responses were lacking. On the other hand, several contradictory reports have also appeared^3–5 which emphatically state that positively phototropic responses persist even after the excision of all the eye spots of each ray of Echinaster crassispina, Pentaceros reticulatus and Asterias forbesi. I therefore undertook to check the role of these pigment bodies in light orientation of the common starfish of the North Atlantic coast of North America south of Maine, A. forbesi, as well as to establish a possible chemical basis for light perception.