Smed-meis-like is essential for anterior regeneration.A - WISH reveals that Smed-meis-like is expressed in the cephalic ganglia, the pharynx, the tip of the head (arrowhead) and the parenchyma, from where it is downregulated three days after irradiation. B - Double FISH of Smed-meis-like together with the neoblast marker Smed-h2b, shows that Smed-meis-like is expressed in neoblasts (arrowheads) as well as in differentiated cells (asterisk). DAPI labels the cell nuclei. See Additional file 11A for the separate channels of fluorescence. C - Smed-meis-like(RNAi) produce defects in anterior regeneration, which range from an squared head with elongated eyes, cyclops, to complete loss of anterior regeneration. The marker of brain branches Smed-gpas also shows this different penetrance. D - Double FISH with Smed-opsin and Smed-tph shows aberrant eyes in the less severe phenotype. E - The anterior markers Smed-notum, Smed-sfrp1, Smed-cintillo, and the eye progenitor marker Smed-ovo disappear after Smed-meis-like(RNAi), while the posterior marker Smed-wnt-1 remains. F - Quantification of mitotic cells by α-H3P immunohistochemistry in the whole animal (p < 0.001, t-test). All the experiments are done on bipolar regenerating trunks, at 11 days of regeneration after three rounds of injection.