Figure 9. Motor control of the labella.

(A–C) Sagittal schematics of labellar movements controlled by muscles 7 and 6 (colored): abduction (B) and extension (C) of labella (arrows). Muscle origins: dorsal haustellum. Insertions: at labella (asterisks). Proboscis segments (dark gray) pivot around joints (magenta dots). (D–E) Example phenotype: extension of labella in response to CsChrimson activation of mn6 (E), compared to resting proboscis before the stimulus (D). (F–I) % flies showing labellar extension (F,H) or abduction (G,I) in response to CsChrimson activation (F,G) or TNT silencing (H,I) of motor neurons listed, compared to controls. Fisher’s exact test. Biological replicates, n = 16 flies/genotype. (J–N) CsChrimson activation of split GAL4s listed compared to controls (unfilled), quantifying change in proboscis position from rest (J), change in rostrum angle from rest (K), change in haustellum angle from rest (L), change in rostrum angle from a protracted position during feeding (M), and change in haustellum angle from an extended position during feeding (N). (O–S) TNT silencing of split GAL4s listed compared to controls, quantifying proboscis position at rest (O), rostrum angle at rest (P), haustellum angle at rest (Q), change in rostrum angle from rest to feeding position (R), and change in haustellum angle from rest to feeding position (S). Bar: mean. Biological replicates, n = 14–16 flies/genotype. Asterisks: unpaired t-tests, experimental (colored) vs. each control (showing least significant), with multiple testing correction. *p<0.05, **p<0.01, ***p<0.001, no asterisk, not signficant.