TIDAL RHYTHMICITY OF RATE OF WATER PROPULSION IN MYTILUS, AND ITS MODIFIABILITY BY TRANSPLANATION ,

Abstract

Mytilus californianus and M.edulis exhibit alternating periods of high and low pumping rate in the laboratory, the highs corresponding to times of high tide, the lows to low tides at the place from which the mussels were taken. The rhythm persists for over 4 weeks in constant light, constant dark or naturally alternating light and dark. No diurnal rhythm was seen. The tidal rhythm is independent of temp. at least between 9[degree] and 20[degree]C. It is shown in specimens from high and low intertidal levels, from floats as well as from pilings and from 30 ft. subtidally. Specimens transported from Massachusetts maintained their rhythm in Los Angeles out of phase with local animals, for 4 wks., showing that a sudden change in cosmic stimuli does not reset the rhythm. Massachusetts specimens suspended in the California intertidal for 1 week exhibit a rhythm in phase with local specimens and maintain this for wks. The rhythmicity is regarded as inherited, the phase as set by adequate stimuli, which are not needed to maintain it. The amplitude of the environmental rhythm may have to exceed a threshold.