Responses of Asterias Rubens To Gravity

Abstract

[1. The reported negatively geotactic behaviour of Asterias rubens is confirmed. It presumably operates through a proprioceptive response of the tube of the starfish to applied tension exerted on them, directing the movement of the animal against the pull, as shown in Asterina gibbosa by KALMUS (1929) and CROZIER (1935, a, b). 2. The species reacts geotactically to slopes of 7° but does not react significantly to slopes of 5° or less. 3. The threshold force at which an Asterias of 1 g reduced weight under water reacts, assuming a critical slope of 6°, is approximately 100 dynes. 4. It was found that the negatively geotactic response of Asterias can be reversed: (a) by applying a pull on the animal up the inclined plane, and (b) by subjecting the animal to a light from above producing a flux of 87.72 lux down the slope and an intensity gradient down the slope of -0.043 Loge intensity . cm-1 units., 1. The reported negatively geotactic behaviour of Asterias rubens is confirmed. It presumably operates through a proprioceptive response of the tube of the starfish to applied tension exerted on them, directing the movement of the animal against the pull, as shown in Asterina gibbosa by KALMUS (1929) and CROZIER (1935, a, b). 2. The species reacts geotactically to slopes of 7° but does not react significantly to slopes of 5° or less. 3. The threshold force at which an Asterias of 1 g reduced weight under water reacts, assuming a critical slope of 6°, is approximately 100 dynes. 4. It was found that the negatively geotactic response of Asterias can be reversed: (a) by applying a pull on the animal up the inclined plane, and (b) by subjecting the animal to a light from above producing a flux of 87.72 lux down the slope and an intensity gradient down the slope of -0.043 Loge intensity . cm-1 units.]