Fig.3. Expression of OnmyGLUT1 in rainbow trout embryos analysed by in situ hybridization. The developmental age of embryos was measured in t_s units (see Materials and methods); the characteristic traits are as follows. (A) Early gastrula (36t_s). The density of cells is highest in the germ ring (gr) and especially in the terminal node (tn). Scale bar, 1mm. (B) 5–7 somites (60–62t_s). A multilayer embryo with the axial organs; h, head; t, tail. Scale bar, 1mm. (C) 14–15 somites (69–70t_s). The length (L) of the embryo is 3mm. The most rostral part of the head (prospective forebrain, fb) expands as a result of the formation of two eye vesicles (ev). The neural crest (nc) is disposed along the borders separating the neural plate (np) from the lateral ectoderm (le). s, somite. Scale bar, 1mm. (D) 60–62 somites (115–117t_s). In these embryos (L=5.8–6.0mm), the heart contracts and blood circulates in the dorsal aorta; the neural folds (nf) and anlagens of gill arches (ga) are visible. Scale bar, 10mm. (E) Early vitelline plexus (130t_s). Somitogenesis has finished, and the development of the cerebral and caudal arteries is in progress; L=7.0–7.2mm. The upper jaw (uj), gill arches and pectoral fins (pf) are evident. Scale bar, 10mm. (F) Middle vitelline plexus (150t_s). Bile fills the gut, and the semicircular canals in the otic vesicles have begun to develop; L=8.5–9.0mm.