Fig. 6

Compacting of the octopus brain cords. Brain development in the octopus is summarized with DAPI nuclear labeling imaged using UV stereo epifluorescence microscopy and pseudo-colored to indicate the locations of brain primordia. Pseudo-coloring is based on ELAV gene expression patterns and DLL immunocytochemistry studied in multiple embryo specimens from stage 8 to stage 20 (just before hatching). a–f Dorsal (left column) and ventral (right column) views of embryos from stage 8, 10 and 13. g–l Lateral views of embryos photographed from the side (left column) and after mid-sagittal cuts (right column). Outer yolk sacs were removed from the preparations for clarity. In L, only the central brain is shown. ASM, anterior subesophageal mass; ax, axial nerve cord; es, esophagus; MSM, middle subesophageal mass; PSM, posterior subesophageal mass. Other abbreviations as in Figs. 2 and 5. Scale bars: 500 μm (a–l)