ABSTRACT
Noctiluca miliaris, a marine dinoflagellate, exhibits spontaneous flexion of its tentacle. The movement of the tentacle is always accompanied by perturbations of membrane potential, termed the ‘tentacle regulating potentials’ (TRPs) (Eckert and Sibaoka, 1967). Though the waveform of the TRPs is liable to variation, it consists of four successive basic components: (1) a Na+-dependent depolarizing (positive) spike, (2) a depolarizing plateau potential, (3) a Cl−-dependent hyperpolarizing (negative) spike, and (4) a long-lasting hyperpolarization (Eckert and Sibaoka, 1967; Oami et al. 1988). A slow flexion of the tentacle is seen during the plateau, and the flexion is suddenly accelerated when the negative spike occurs. The tentacle then extends during the long-lasting hyperpolarization. There is no correlation between the positive spike and the tentacular movement (Hisada, 1957; Oami et al. 1988).