THE REPETITION OF PATTERN IN THE RESPIRATION OF UCA PUGNAX

Abstract

Brown respirometers were used to obtain continuous records of O2-consumption of the fiddler crab. Uca pugnax. A solar-day rhythm consisting of a maximum from 2-6 A.M. and a minimum from noon to 7 P.M. was essentially identical in the summers of 1955, 1956, and 1957. A lunar-day rhythm showing 2 equal maxima (1 at lunar zenith, the other at lunar nadir) was also essentially identical during all 3 summers. Both rhythms persisted under laboratory conditions for at least 16 days. The large amplitude of the lunar-day rhythm and the fact that the 2 maxima were of the same height resulted in a pattern of fluctuation in O2 consumption characteristic of each day in a semi-lunar period. Correlation of hourly values of respiration for single days with hourly values for comparable days of successive semi-lumar periods show significant positive coefficients of correlation for all days in 1957 except on the day of new or full moon and on the 8th day after new or full moon. Correlation of simultaneous hourly valuesfor respiration show a general decrease in the coefficient of correlation with time after collection. The significance of the simultaneous presence of solar-day and lunar-day rhythms is considered in relation to the mechanism of biological rhythmicity.