On Lunar Periodicity in Reproduction of Pecten opercularis near Plymouth in 1927–28

Abstract

SUMMARYIt has been shown that there is a lunar periodicity in reproduction of P. opercularis near Plymouth in 1927-28. The ripening of sexual products corresponds with the full phase of the moon.The condition and shape of the gonad changes with the development of the tissues.The colour, too, of the hermaphrodite organ changes with development.Black pigmentation has been observed on the gonad in thin-shelled P. opercularis, a phenomenon apparently due to actinic rays penetrating the thin shell.The breeding season is from January to June inclusive.The gut contents seem to show no appreciable difference either in quantity or in the natureof the food during a lunar month.The moonlight has apparently no effect on the lunar periodicity in reproduction.It is suggested that in the animal there is a physiological rhythm that causes the development of the gonad to coincide with the full moon of each lunar month