Figure 1.
Semicircular canal ducts are absent, but sensory patches are present, in the inner ears of adult rescued swr zebrafish.
(A–F) 10 µm resin parasagittal sections through the inner ears of adult rescued swr zebrafish and age-matched wild-types (anterior to the left, dorsal to the top). Note the absence of semicircular canal ducts in the rescued swr ear (A), which are clearly present in the wild-type ear in an equivalent section (B, showing lumens of anterior and posterior canal ducts). All sensory patches detected in the wild-type ears are also present in the rescued swr ears. Differences in the orientation of the lagenar macula (E, F) reflect a slight difference in the position of the wild-type and swr sections for this pair of panels. (G–J) Higher magnification views of the posterior crista (G, H) and utricular macula (I, J). The structure of the sensory patches is similar in both rescued swr and wild-type ears. Abbreviations: ac, anterior crista; lc, lateral crista; pc, posterior crista; ascc, anterior semicircular canal duct; lscc, lateral semicircular canal duct; cc, crus commune; ut, utricular macula; s, saccular macula; lg, lagenar macula; br, brain; s, somite; gl, gill. Scale bar, (A–F) 400 µm; (G–J) 50 µm.
Figure 2.
Three-dimensional reconstructions of adult rescued swr inner ears.
(A–F) Three-dimensional reconstructions of the inner ears of two adult rescued swr fish (swirl 1 (A, D) and swirl 2 (B, E)) and an age-matched wild-type fish (C, F). Semicircular canals are absent in the rescued swr fish ears, while the ampullae, crus commune, utricle, saccule and lagena are present and appear normal. Note that the pars superior (ampullae, crus commune and utricle) of swirl 1 is twisted relative to the pars inferior (saccule and lagena), about the point marked with the arrow (we are unable to tell whether or not this is an experimental artefact). The kink in the lateral canal of the wild-type ear (C) is an artefact. The asterisk marks the transverse canal that links the two saccules across the midline. (G, H) Sketch of the inner ears of adult rescued swr and wild-type fish. Shading in the wild-type ear indicates the regions missing from rescued swr ears. Abbrevations: a-amp, anterior ampulla; l-amp, lateral ampulla; p-amp, posterior ampulla; a-canal, anterior semicircular canal; l-canal, lateral semicircular canal; p-canal, posterior semicircular canal; cc, crus commune. swirl 1 is a smad5-rescued swrdc24 fish; swirl 2 is a bmp2b-rescued swrta72 fish. A–C, G and H are lateral views of left hand ears, with anterior to the left; D–F are dorsal views. Scale bar, 500 µm.
Figure 3.
Sensory patches and fusion plates are present in the inner ears of 5 dpf rescued swr embryos.
Projected confocal z-stacks through inner ears of 5 dpf embryos stained with FITC-conjugated phalloidin, revealing the actin-rich stereociliary bundles of the sensory hair cells and the cortical actin in every cell. (A–D) Lateral views; anterior to left, dorsal to top. (A, B) Lateral plane of focus, showing the cristae, utricular macula and the fusion plates (arrowheads) between the semicircular canal projections. (C, D) More medial plane of focus showing the saccular macula. (E, F) Dorsal views; anterior to left, medial to top. Images shown are composites of two sets of projected z-stacks as the anterior crista is in a more dorsal plane of focus than the remaining sensory patches. Abbreviations: sm, saccular macula; um, utricular macula. Cristae are indicated with an asterisk. Scale bar, 50 µm.