Growth, developmental, and longevity rhythms in Campanularia flexuosa

Abstract

Endogenous circannual rhythms in growth, development, and longevity of the marine coelenterate Campanularia flexuosa have persisted for over 3 years in the absence of periodic signals from the environment. The periods for the cycles at three constant ambient temperatures, 10, 17 and 24 C, approximated 1 year, but were always more than 365 days. Although uncertainty exists, temperature was implicated as a Zeitgeber.The endogenous circannual rhythms were marked by seasons of luxuriant colony growth that alternated with more sparse growth. During luxuriant growth, development of individual hydranths was initiated regularly in new positions and as replacements at regression sites on uprights. Nearly all hydranth development was normal and adult life spans were long. The profuse growth was interrupted by seasons of sparse growth each summer and punctuated by recurrent, short periods of sharply curtailed growth in mid-winter. During curtailed growth, the rate of hydranth initiation at all sites was depressed, and abnormal development aborted many individuals. Most strikingly, hydranth life spans fell to about half those observed during seasons of luxuriant growth. With the spontaneous return to the luxuriant growth habit, hydranth life spans rose, nearly doubling.The delineation of these endogenous rhythms in C. flexuosa longevity challenges the generally accepted concept of specific age, an age at death which is characteristic of the species. Copyright © 1974 by the American Society of Zoologists.