Other reflective regions occur outside of the ring, mostly as contiguous patches of cells rather than as scattered individual cells. Where the dorsal stripe is bilateral, in the posterior trunk and anterior tail, the melanophores now neatly flank reflective iridophores present in the midline. Bilateral patches of reflectivity, the lateral patches , also have formed on the dorsal yolk sac, just to either side of the median black patch marking the location of the developing swim bladder. A few scattered iridophores appear elsewhere on the yolk sac, but only variably in a distinctive ventral median row that accompanies the melanophore yolk stripe at the same location. The heart is prominent, beating strongly, and full of circulating blood.
Blood flows in all of the aortic arches and through the subclavian loop.
The common cardinal vein no longer has a fan-shape, but remains narrow along its length, as it takes a direct course, anterior to most of the yolk, towards the heart. Most dechorionated embryos now rest in a dorsal-up attitude and nearly always finish a bout of swimming in this attitude. The contractions during the escape response occur so rapidly that one cannot resolve them by eye. The mouth is wide open and it protrudes anteriorly just beyond the eye. The primordium of the operculum extends posteriorly to cover the first or even the second branchial arch.