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

Abstract

1. The occurrence of a tidal rhythm in the rate of water propulsion in Mytilus californianus, collected from high and low inter-tidal levels and from a depth of 30 ft. off the shore, and also in M. edulis collected from pilings and the underside of floats, has been demonstrated.2. Such a rhythm is independent of temperature (9 to 20° C.) and persists in the laboratory, in phase with the external tidal cycle, for over four weeks, in continuous darkness, or continuous light or the natural day and night environment.3. No indications of a diurnal rhythm in the rate of water propulsion have been observed.4. A rhythm of similar frequency, but out of phase with local tidal cycle by about 6½ hrs., was observed in M. edulis collected from Barnstable Harbor on Cape Cod and studied at Los Angeles, California, after transporting them by air.5. Some of the east coast mussels were secured in the inter-tidal at Corona del Mar, California, for a week. Examination of their activity pattern after this period, revealed a prompt shift in their tidal rhythm to synchronize with the local tidal schedule.6. The intrinsic nature of the rhythm is discussed and the probable inheritable nature of the rhythmic properties of organisms, coupled with the ease with which they could be set in synchrony with natural environmental rhythms, are suggested as likely causes for the widespread occurrence of rhythmic patterns in organisms.7. It is suggested that the degree to which the intrinsic rhythm of the organism becomes marked and measurable depends upon the amplitude of the environmental rhythm.