Meeting Abstract

30.7  Friday, Jan. 4  Phylogenetic informativeness of nematocyst ultrastructure in Anthozoa REFT, AJ; Ohio State Univ. reft.1@osu.edu

Nematocysts, intracellular stinging capsules, are a strong synapomorphy of phylum Cnidaria. The nematocyst, which consists of a capsule and tubule typically with spines, functions in prey capture, defense, and attachment to substrate. Because nematocysts have considerable morphological variation, they are a potential source of characters to investigate phylogeny of cnidarians. One character inferred to reflect phylogeny is the apical structure, which allows for the tubule to emerge from the apex of the capsule. The apical structure is known to occur in two forms, operculum or three flaps. Medusozoan nematocysts are understood to have opercula whereas Anthozoan nematocysts have three flaps. However the apical structure of nematocysts are not well understood for many Anthozoa. To clarify the phylogenetic utility of this character, I used Scanning and Transmission Electron Microscopy to determine the apical structure in several exemplar anthozoans, with particular attention to members of Hexacorallia. This character exhibits more variability in the Anthozoa than expected, and thus its phylogenetic significance needs to be reevaluated.