THE RHYTHMIC ACTIVITY OF THE QUAHOG, VENUS MERCENARIA, AND ITS MODIFICATION BY LIGHT ,

Abstract

Continuous kymograph recordings of the opening and closing of the valves of quahogs, Venus mercenaria, secured from the Virginia coast and from Woods Hole, Mass. were made during 5 months of 1953. The activity records of these clams maintained under constant conditions show a persisting diurnal rhythm with maxima and minima occurring in the afternoon and morning, respectively. A persisiting tidal rhythm, in which times of minimal activity correspond closely with times of low tide in the area of collection, is also evident. The summation of these 2 cycles appears to be responsible for an observed lunar cycle of about 30 days'' duration. It was seen that the character, or phase relationships to time of day, of these rhythms could be shifted by exposing the quahogs to an illumination of 100 ft. c. by night (8 p. m. - 8 a. m.) and to darkness by day for 5 consecutive 24-hour periods. The manner in which these shifts of the phases of the cycles are related is discussed and illustrated.