The effect of temperature on the photic responses of polyzoan larvae

The rate at which larvae of the polyzoan Cryptosula pallasiana, which display positive phototaxis on liberation, develop a negative response to directional illumination is greatly influenced by temperature. For the series of temperatures investigated, the rate of change varied from 2% per hour at 10°C to 31% per hour at 25°C. Pipetting the newly liberated larvae may prematurely induce negative phototaxis. The results are discussed.