Meeting Abstract

S5.8  Jan. 5  Implications of cnidarian gene expression data for the origins of bilaterality � is the glass half full or half empty? MILLER, David J*; DE JONG, Danielle M; SCHIERWATER, Bernd; HAYWARD, David C; BALL, Eldon E; James Cook University; Australian National University; Tier�rztliche Hochschule Hannover; Australian National University; Australian National University david.miller@jcu.edu.au

The last two years have seen a dramatic increase in the available sequence and gene expression data for cnidarians and other �lower� Metazoa, and a flurry of recent papers has drawn on these to address the origins of bilaterality. Cnidarian homologs of many genes that play key roles in the specification of both the A/P and D/V axes of bilaterians have been characterised, and their expression patterns determined. Some of these expression patterns are consistent with the possibility of conservation of function between Cnidaria and Bilateria, but others clearly differ. Moreover, in some cases very different interpretations have been made on the basis of the same or similar data. In part these differences reflect the inevitable uncertainties associated with the depth of the divergence between cnidarians and bilaterians. In this paper we briefly summarise the cnidarian data on gene expression and organization relevant to axis formation, the varying interpretations of these data, and where they conflict. Our conclusion is that the presently available data do not allow us to unequivocally homologize the single overt axis of cnidarians with either of the bilaterian axes.