. The Biological bulletin. Biology; Zoology; Marine biology. COLONY DEVELOPMENT IN HYDROIDS 65 rate and period do not change in P. carnea, although there is a decrease in the variabihty of relative amplitude be- tween stage 1 and 3 (paired comparison ?-test of the stan- dard deviations of relative amplitudes for each colony, ; = , P < ). Because both rate and relative am- plitude are maximal in stage 3, it may be that a constraint is placed on the expansion of the stolonal lumen by the rigid periderm, thus limiting the variability of the ampli- tude and relative amplitude. In gene
. The Biological bulletin. Biology; Zoology; Marine biology. COLONY DEVELOPMENT IN HYDROIDS 65 rate and period do not change in P. carnea, although there is a decrease in the variabihty of relative amplitude be- tween stage 1 and 3 (paired comparison ?-test of the stan- dard deviations of relative amplitudes for each colony, ; = , P < ). Because both rate and relative am- plitude are maximal in stage 3, it may be that a constraint is placed on the expansion of the stolonal lumen by the rigid periderm, thus limiting the variability of the ampli- tude and relative amplitude. In general, the results presented here agree with those reported elsewhere. Other investigators have also reported high rates of expansion and contraction of the stolonal lumen in H. symbiolongicarpus primary polyps {, Buss and Vaisnys, 1993). Further, nine field-collected colonies of each of//, symbiolongicarpus and P. carnea show sim- ilar between-species differences (Blackstone and Buss, 1992). Using replicates of clonally explanted colonies grown to a developmental stage comparable to stage 3, between-species differences in the rate of expansion and contraction of the stolon lumen are very similar to those reported here (see Fig. 6; using the colony-within-species effect as the error variance; F = , df = 1, 16, /" <? ). Note that these studies were carried out under generally similar conditions except (1) colonies from the two species were paired in time so that time effects were expUcitly controlled for, and (2) colonies were grown and filmed at 16°C. Given (2) it is unsurprising that the rates of flow in Figure 6 are generally less than those in Figure 4c, but it is nevertheless notable that the between-species effect remains pronounced in both cases. The measures of periderm-to-periderm stolon width show a consistent between-species effect throughout col- ony development (Fig. 7). At all stages, H. symbiolongi- carpus have wider stolons than P. carnea (te
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