Fig. 5

Spontaneous and experimental fusion of otolith precursor particles. (A) DIC image of a mnl mutant ear at 22 h (26 somites). An untethered otolith-like mass rests on the medial surface (the lowest point) of the vesicle. A tethered posterior otolith is present but is not in focus in the image shown. (B–F) Phase-contrast images of the ear of a wild-type embryo at 21.5 h (25 somites). (B) The medial surface of the vesicle showing numerous small particles. Most particles are in rapid motion but those entering the beam of the laser tweezers are entrapped (arrowhead). Keeping the laser focused in the same spot for approximately 30 s captured additional particles, which fused into a single otolith-like mass. (C) The particle mass (arrowhead) remained whole after removal of the laser. (D and E) Close-ups showing the endogenous anterior and posterior otoliths, respectively. (F) Enhanced posterior otolith generated by using laser tweezers to collect particle masses from the medial surface and bringing them into contact with the endogenous otolith. Images in B–F were captured from a videotape of the tweezing process. Similar results were obtained in experiments performed on 20 wild-type and 15 mnl mutant embryos (not shown). In all panels, anterior is to the left and dorsal is upward. Scale bar, 24 (A), 17 (B and C), and 10 μm (D–F).