Fig. 3

Ultrastructure of the sensory pit. A The optical horizontal section showing the approximate area in panel B. B The ultrathin horizontal section through the widest part of the sensory pit and associated structures. C The optical horizontal section showing the approximate area in panel D. D The ultrathin horizontal section through the fundus of the pit and associated structures. E Details of the pit as visible in panel B. F Details of the fundus as visible in panel D. Longitudinal (G) and cross (H) section through the cellular processes forming fundus of the pit. I Cell bodies of the pit-forming cells as visible in panel D. J Schematic reconstruction of the fundus-forming cell. Cell nuclei stained with DAPI in cyan, a signal from antibodies against tyrosinated tubulin in yellow, and F-actin stained with phalloidin in green. The lettered boxes in panels A, C, D, E, and F indicate regions magnified in the corresponding panels. The arrows in panel E indicate muscle fibers of the sphincter. Abbreviations: ap apical portion of the fundus cell, av apical vesicle, ax axon, bl brain lobe, cp cavity of the pit, f fundus, lbv large basal vesicle, lm longitudinal muscle, mt mitochondrion, mv microvilli, np brain neuropile, nsp nerve of the sensory pit, nt neurite-like process, nu nucleus of the fundus cell, oc outer cell, rm rostral musculature, sbv small basal vesicle