a–c, Ventral-anterior views of 24 h.p.f. Platynereis trochophora larvae with microRNA expression (red) in prototroch cells and apical organ (arrowheads) (blue, DAPI; green, acTub). d, Ventral view of 72 h.p.f. Platynereis with expression in ciliated cells and midline (arrow). e, 72 h.p.f. Platynereis; expression in ciliated cells of trunk and prototroch (arrow). f, g, 72 h.p.f. Platynereis; expression in ciliated cells of the trunk. h, Lateral view of Capitella stage 6 larva; expression in ciliated bands. i, Ventral-lateral view of Strongylocentrotus pluteus larva with expression in ciliated cells lining the foregut and arms.