Hopkins Marine Station Student Paper

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(full paper is archived in the Miller Library)

Title: An endogenous tidal rhythm of activity in the lined shore crab, Pachygrapsus crassipes in the rocky intertidal at Mussel Point, Pacific Grove, California
Student Author(s): Holdren, Michaela W.
Faculty Advisor(s): Baxter, Chuck
Pages: 32
Location: Final Papers Biology 175H
Date: June 1978
Keywords: biological rhythms in marine and maritime organisms
Abstract: 1. Studies in the field and in the laboratory removed from tidal fluctuation indicate a tidal rhythm of activity in P. crassipes. The crabs are most active at lower low water. 2. The phase advance in LD 12:12 was found to be .9 min per lunar day. In DD the phase advance was found to be 5.5 minutes per lunar day. 3. When the times of lower low water shifted from day to night, crabs showed peaks of activity at both low tides. This suggests that the crabs' activity follows lower low water through the semi-lunar shifts of low tides. 4. A circadian rhythm was not found in this investigation. However, activity after sunset and the effect of light on the activity patterns of crabs in running wheels suggest that light plays an important role in modifying the crabs' behavior.