Fig. 4. Schematic diagram illustrating the mRNA expression patterns recorded for six MRF genes, s-smlc1 and Pax7 in the most anterior somite of the Atlantic salmon developmental stages numbered 1–6 (shown at the top of the figure). (A) smyoD1a, (B) smyf5, (C) smyoD1b, (D) smyoD1c, (E) smyoG, (F) sMRF4, (G) s-smlc1, (H) Pax7. The left of each box shows an expression field as viewed from either a dorsal of lateral perspective (indicated) of the most anterior somite using DIC optics. The right of each box shows a corresponding cross section through the region of expression in that somite. ad, adaxial cells; ecl, external cell layer; n, notochord; nt, neural tube; spc, spinal cord; So-1, somite 1.