. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ORCADIAN RHYTHMS IN CORALS 243 LJ LJ §> > PC LJ #28. 0 12 24 12 24 12 24 12 LOCAL TIME 24 24 12 FIGURE 6. The temporal pattern of expansion and contraction of tentacles of Fungia pawnotensis Stutchbury in natural light for one day, then transferred to continuous light of low intensity (100 lux), as shown by the hatched bar on the abscissa. The temperature was kept at 28 ±° C. A circadian rhythm is apparent during the first two days in continuous light. Tentacle stage was scored as in Figure 1. tinuous light, the ten
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ORCADIAN RHYTHMS IN CORALS 243 LJ LJ §> > PC LJ #28. 0 12 24 12 24 12 24 12 LOCAL TIME 24 24 12 FIGURE 6. The temporal pattern of expansion and contraction of tentacles of Fungia pawnotensis Stutchbury in natural light for one day, then transferred to continuous light of low intensity (100 lux), as shown by the hatched bar on the abscissa. The temperature was kept at 28 ±° C. A circadian rhythm is apparent during the first two days in continuous light. Tentacle stage was scored as in Figure 1. tinuous light, the tentacles remained contracted. However, in light of low intensity (100 lux at 28° C), these specimens displayed a clear circadian rhythm (Fig. 6). DISCUSSION The strongly nocturnal behavior of most corals in nature suggests that tentacle expansion might be under the control of a circadian clock, in view of the large number of other nocturnal animals in which such a mechanism has been shown to operate (De Coursey, 1960; Halberg, 1959; Harker, 1954). Among the Coelenterates, however, circadian rhythms have been demonstrated only in the sea-pen, Cavcrnnlaria obesa (Mori, 1960) and the sea-anemone, Metridium senile (Bantham and Pantin, 1950). In both, the rhythmic patterns of body contraction and expansion are somewhat irregular in constant darkness as compared with circadian rhythms in some other organisms under similar conditions, for example in the dinoflagellate polyedra (Sweeney and Hastings, 1957). As in Fungia, some specimens of Metridium clearly display a circadian rhythm while others do not. In Metridium, as in Fungia, rhythmicity may be obscured at the beginning of exposure to continuous darkness, only to become apparent later in a series of measurements (compare Fig. 5 of this paper with Fig. 8 of Bantham and Pantin, 1950). Since single-polyp Fungiidae are essentially calcified sea anemones, this similarity in behavior is perhaps understandable. In the sea pe
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
