. The Biological bulletin. Biology; Zoology; Marine biology. 202 HOWARD R. LASKER Reef colonies observed in the field were fully expanded during the night (Table I) and qualitative observations at Galeta Island and at other localities indicate that in the field almost all colonies of 31. cavernosa are fully expanded at night. In the laboratory, however, fewer colonies of both morphs were expanded, and colonies were frequently only partially expanded. In the field there were no nightime dif- ferences between the morphs, but at night in the laboratory the diurnal morph was less frequently expand
. The Biological bulletin. Biology; Zoology; Marine biology. 202 HOWARD R. LASKER Reef colonies observed in the field were fully expanded during the night (Table I) and qualitative observations at Galeta Island and at other localities indicate that in the field almost all colonies of 31. cavernosa are fully expanded at night. In the laboratory, however, fewer colonies of both morphs were expanded, and colonies were frequently only partially expanded. In the field there were no nightime dif- ferences between the morphs, but at night in the laboratory the diurnal morph was less frequently expanded than the nocturnal morph (x2 test. P< ). This indicates that the diurnal morph was more strongly affected by the laboratory environment. The presence of the intermediates and of environmental effects makes it impossible to present a statistically homogeneous characterization of the behaviors of the two morphs. As seen in Figure 3, distributions from different environments differ from each other and in other cases colonies within the same locality and morph can be found to have significantly different expansion patterns. It is pos- sible, however, to describe generalized patterns for the morphs. The frequency dis- tributions of daytime expansion behavior of four representative colonies are pre- sented in Figure 4. Effects of altered light regimes The results of altering the daily light cycle are illustrated in Figures 5 and 6. As can be seen, the experiments demonstrate rather dramatically that the nocturnal morph cues its contraction to the presence of light. In the darkening experiment. EXPANSION STATE Figure 4. Distribution of expansion states occurring within the morphs of .1/. cavernosa. Frequency distributions are presented for the daytime expansion behaviors of colonies repre- sentative of the end member and intermediate conditions of the diurnal (SB-315 and SB-3S3b) and nocturnal (SB-316 and SB-333) Please note that these images are extracted from sca
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