OBSERVATIONS ON THE LIGHT-SENSITIVE TUBE FEET OF THE BURROWING ECHINOID PROTENASTER AUSTRALIS (GRAY, 1851)

WA Museum Records and Supplements | Updated 1 decade ago

Abstract
Observations made on the burrowing spatangoid echinoid Protellaster allstralis (Gray, 1851) have revealed that it possesses light-sensitive tube feet. These have not previously been reported in irregular echinoids. At a white-light intensity of 8500-9000 lux the tube feet in ambulacrum III undergo positive phototaxis. Ambital sensory tube feet and phyllodal feeding tube feet also respond to light at this level of illumination, but undergo negative phototaxis. The same phototactic responses were observed with illumination by blue and green light, but not with red or yellow light in all three types of tube feet. The tube feet in ambulacrum III remain positively phototactic until a level of illumination of about 150- I 5,000 lux, whereupon they become negatively phototactic. It is considered that these tube feet play an important role in ensuring that the echinoid test remains completely covered by sediment during daylight. Night emergence of some spatangoids, such as P. australis, may be due partly to a lack of stimulation of light-sensitive tube feet.