GELLER, Jonathan B.; Moss Landing Marine Laboratories: Clonality and fission in sea anemones: regulation of gene expression underlies transitions in life history.

Clonal growth is widespread in Cnidaria and solitary species are a minority. The prevalence of clonality stands in contrast with the variety of the means by which diverse clonal growth patterns are achieved. Despite this diversity, much of the underlying biology (mechanisms for fission, formation of body axes, body patterning, regeneration, etc…) may be conserved. If so, the evolution of different clonal growth patterns, or the loss of clonality altogether, probably results more from changes in gene regulation rather than from de novo evolution of developmentally regulated genes. For this reason, cnidarians provide an attractive group in which to study the interface between life history evolution and regulation of gene expression. For example, studies on the sea anemone genus Anthopleura have shown multiple and reversible transitions between clonal and solitary phenotypes. Consistent with the hypothesis that changes in gene regulation underlie these transitions, clonality has evolved in A. elegantissima from a solitary ancestor faster than differentiation of nuclear loci shared with its solitary sister species, A. sola. The diversity of clonal morphologies in Cnidaria may similarly depend upon modification of the spatial and ontogenetic patterns of expression of conserved genes.