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Fig. 1 Ear development in wild-type zebrafish. (A) At 30 hpf the zebrafish ear is an epithelial vesicle containing two otoliths. (Arrowhead indicates the midbrainhindbrain boundary.) (B) Appearance of the zebrafish ear at approximately 60 hpf. Development of the semicircular canals is initiated by the appearance of epithelial protrusions (arrow) extending into the lumen of the otocyst. Protrusions growing from opposing walls of the otocyst fuse together forming columns surrounded by the lumen of semicircular canals. Formation of columns delimiting the anterior and posterior semicircular canals is well advanced at this stage. (C) At 5 dpf the semicircular canals are well formed and easily recognizable in a living embryo (arrows). (D) A schematic representation of the major morphological elements of the zebrafish ear accessible to visual inspection at 5 dpf (compare with photograph in C). The anterior (ac), posterior (pc) and ventral (vc) columns delimit the lumen of semicircular canals (arrows). The posterior otolith (po) is located behind the translucent, ventral column. ao, anterior otolith; asc, anterior semicircular canal; psc, posterior semicircular canal; lsc, lateral semicircular canal. Scale bar, 100 μm.