Fig. 1

Pharyngula stages did not show the highest rate of lethal phenotypes following transient perturbations. a Representative embryos that showed malformation or lethal phenotype. (I–IV) Zebrafish embryos with (I) curled trunk, (II) bent trunk axis, (III) pericardial edema, and (IV) shortened trunk. (V–VIII) African clawed frog embryos with (V) curled trunk and small eyes, (VI) severely bent trunk, (VII) edema and abnormal head, and (VIII) bent trunk axis. (IX, X) Chicken embryos with (IX) abnormal head and growth arrest, and (X) small eyes. Scale bars represent 1 mm (I–VIII) and 5 mm (IX, X). b–d Rate of lethal phenotypes rate after transient perturbation in b zebrafish, c African clawed frog, and d chicken. Phenotype evaluation was performed at hatch period in zebrafish, st. 45 in African clawed frog, and HH25 in chicken. Blst blastula, Gst gastrula, Pha pharyngula, Lat late embryo, ctrl untreated control group. Data are displayed as means, and error bars denote SD. Only significant differences between each treated group and the control group are shown. *P < 0.05, **P < 0.01, ***P < 0.001 (Tukey–Kramer method)