A) Two-channel rendering of a developing zebrafish maxillary barbel; the distal end, which is digitally truncated, points right. mCherry+ cells (red) occupy a cylindrical, mesenchymal sheath surrounding the barbel core. Numerous EdU+ cells (green) are superficial to this layer, indicating maximal cell division in the overlying epithelium. Only two ventral cells are double-labeled (mCherry+/EdU+).
B) mCherry+ cells from a second double-labeled specimen.
C) EdU+ cells (green) from the same region as B.
D) Merged image of B and C. The two yellow nuclei (*) are double-labeled.