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April 15, 2012; 215(8)

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Cover: In Amphimedon queenslandica larvae, phototaxis is conferred by posterior, concentric rings of pigmented and ciliated cells. This image is artificially colored to highlight ciliated cells (purple) that act as light-responsive 'rudders' to steer the living larvae. Because sponges are not known to possess nervous systems or opsins, the molecular components of sponge phototaxis must differ from other animals. Rivera et al. (pp. 1278−1286) characterize two cryptochrome genes in A. queenslandica. One is expressed near the pigment ring, and its protein contains a co-factor responsive to wavelengths of light that also mediate photic behavior, suggesting a cryptochome may act in the aneural, opsin-less eye of a sponge. Photo credit: Sally Leys.