Cover legend: A planarian, Dugesia japonica, and its brain in the background showing serotonergic neurons (white), GABAergic neurons (green), dopaminergic neurons (magenta), and the other neurons (cyan). Planaria, poikilotherms possessing a sophisticated brain, show cryophilic thermotaxis involving brain serotonergic neurons that process thermosensory signals sensed by a member of the TRPM receptor family. For more details, see the article by Inoue et al. (pages 15701–15714).