Ultrastructural defects of the chordotonal cilia in cby-deficient flies. (top left) Scheme and longitudinal section of a typical leg or antennal CO composed of two neurons ensheathed by a scolopale cell and linked to the cap cell at the tip of the ciliary endings. The cilia are anchored on a distal basal body (DBB) aligned above the proximal basal body (PBB) at the end of the dendrite. (a1–5) Sections at the level of the ciliary axoneme. In control legs (a1), axonemes are composed of nine peripheral microtubule doublets. (a2–5) cby1/1 axonemes show a reduced number of microtubule doublets (a2 and 3), altered symmetry (a4), or extra microtubules (a5). (b1–3) Sections at the distal TZ. (b1) In control samples, a dense ring structure of ninefold symmetry is observed. (b2 and 3) In cby1/1 antennae, interrupted, incomplete, and misformed ring structures are observed. (c1–3) Sections at the proximal TZ level. (c1) In control TZ, decorations connecting the membrane can be seen and likely correspond the Y links. (c2 and 3) In cby1/1 antennae, decoration are interrupted (black arrows; c2), or the ninefold symmetry of the TZ decorations is interrupted (c3). (d1–3) Sections at the level of the proximal basal body. Bars, 0.5 µm. (d1) Basal bodies are anchored to the cell membrane by dense fibers in control flies (black arrow). Tight junctions connect the two dendrites. (d2 and 3) Two examples showing missing basal bodies in cby1/1 flies. (e1–3) Longitudinal sections of cby1/1 ciliary endings. In several cases (e1 and 2), the TZ is discontinuous (white arrows). (e2 and 3) Membrane bulges are observed along the cilia (black arrows). (f1–3) Low magnifications of transverse sections of scolopidia. Bars, 0.5 µm. (f1) Two axonemes are present in control antennae. (f2 and 3) Only one or no axoneme is sometimes observed in cby1/1 antennae.
