Dissociation of membrane-cortex contacts in the hyalospheres of Amoeba proteus exposed to light-shade differences.

The hyalospheres produced by a heat shock spontaneously separated successive sheets of the cortical actin layer from the plasma membrane and retracted them inward. This phenomenon was hampered or completely inhibited by 10(4) lux white light and restored in shade. The frequency of detaching the consecutive submembrane sheets was much higher in the shade than in full light. If the light-shade difference has been applied across a single hyalosphere, the detachment of cortical layer was initiated and continued in the shaded cell part. Sometimes it was followed by translocation of the hyaloplasm into the dark zone and a compensatory shift of the granuloplasmic core toward the bright area. Probably, the actin sheets which are detached in the frontal caps of normal locomoting amoebae react in the same way to positive or negative photic stimuli.