Altered liver sinusoid morphology in arnt2-/- larvae at 120 hpf. Photomicrographs of sections of the liver of a representative WT larva (A, C) and arnt2-/- mutant (B, D) are shown. Compared to WT, the arnt2-/- liver is characterized by enlarged sinusoids engorged with blood that have merged to form large labyrinth-like vascular channels. A red arrowhead points to a blood-filled sinusoid in each of the sections. e, Esophagus; l, liver; y, yolk; g, glomerulus; pd, pronephric duct; bd, bile duct.