Abstract
Clonal plants, fungi, and invertebrate animals often display both intra- and interspecific heterochronic variation in the relative proportions of ramets (e.g., polyps, plantlets) and stolons (or rhizomes, hyphae). Treatment of developing colonies of Podocoryne carnea, a hydractiniid hydroid, with dilute solutions of 2,4-dinitrophenol (DNP), an uncoupler of oxidative phosphorylation, accelerates the usual ontogenetic trajectory of polyp and stolon production. This morphological heterochrony can be related to the hydrodynamic behavior of the gastrovascular system under the conditions of "loose-coupling" of oxidative phosphorylation produced by DNP. In its normal ontogeny, Hydractinia symbiolongicarpus, a closely related hydractiniid hydroid, not only shows morphological heterochrony similar to that induced in P. carnea by DNP, but also shows a pattern of gastrovascular flow similar to that observed in P. carnea under treatment with DNP. These results support hypotheses linking metabolic activity to heterochronic variation and provide a potentially widely applicable experimental basis for the study of such variation.