Reinterpretation of some tentacular structures in actinodendronid and thalassianthid sea anemones (Cnidaria: Actiniaria)

The oral disc of an actinodendronid sea anemone is drawn out into a variable number of highly branched tentacular structures that make the anemone resemble a tree. These tentacular structures have been considered either lobes or branched tentacles. The term lobe has been applied to various structures of the oral disc in sea anemones; I distinguish between temporary lobes, permanent marginal lobes, and permanent tentacular lobes. I use the number of mesenterial pairs involved in a tentacular structure as evidence that tentacular structures in Actinodendronidae should be considered tentacles, not lobes. According to this interpretation, actinodendronids have only one tentacle communicating with each intermesenterial space, both endocoels and exocoels. The similarity between tentacular structures in members of Actinodendronidae and Thalassianthidae is only superficial; the tentacular structures in these families are not homologues as they have been previously considered.