Meeting Abstract
The cosmopolitan sea anemone genus Anthopleura is defined by the presence of acrorhagi and verrucae, specialized structures of the oral margin and the column, respectively. Acrorhagi are inducible structures resembling inflatable bulbs that differ from marginal spherules (or ‘pseudoacrorhagi’) by the presence of holotrichous isorhizae, a type of nematocyst used frequently in intraspecific aggression. Verrucae are hollow outgrowths on the column to which sand and other debris may adhere, providing relief from dessication and ultraviolet radiation exposure during low tides. Verrucae resemble non-adhesive vesicles which are found in other actiniids, except that verrucae are cup-like while vesicles are rounded. Acrorhagi and verrucae may be complex structures that are homologous among their occurrences across taxa, or merely superficially similar structures that are simply the product of coincidence of their constituent parts. Furthermore, acrorhagi and marginal spherules may be unrelated structures with independent evolutionary origins or alternate states of a single complex character. That these features confer taxonomic distinction in Anthopleura and other genera warrants a phylogenetic assessment of their distribution across taxa and an evaluation of their value in defining monophyletic groups. We present a molecular phylogeny which aims to illuminate the evolutionary and taxonomic patterns of these structures under multiple character coding schemes. We find that the genus Anthopleura is not monophyletic with respect to other actiniid genera and that the phylogenetic relationships reflect geographic patterns to a greater extent than taxonomic ones. All analyses of character evolution indicate that the presence of acrorhagi and verrucae are plesiomorphic conditions for the ingroup.
