Campaniform sensilla

Campaniform sensilla are a class of mechanoreceptors found in insects, which respond to local stress and strain within the animal's cuticle.

Campaniform sensilla function as proprioceptors that detect mechanical load as resistance to muscle contraction,[1][2] similar to mammalian Golgi tendon organs.

[5][6] Each campaniform sensillum consists of a flexible dome, which is embedded in a spongy socket within the cuticle and innervated by the dendrites of a single bipolar sensory neuron (see schematic cross-section).

[7] Campaniform sensilla are located in regions where stress is likely to be high, including on the legs, antennae, wings, and halteres.

[14] Pringle also determined that the oval shape of many sensilla makes them directionally selective[15] – they respond best to compression along their short axis.

[1][18] Based on their responses to white noise stimuli, campaniform sensilla may also be described more generally as signaling two features that approximate the derivative of each other.

[33] Feedback from wing and haltere campaniform sensilla is thought to mediate compensatory reflexes to maintain equilibrium during flight.

[34][35] To better understand the function of campaniform sensilla, computational models that mimic their response properties are being developed for use in simulations and robotics.

Cross-section of a campaniform sensillum. Each sensillum is embedded in a cuticular socket and innervated by a single sensory neuron. The neuron is excited when strain in the cuticle deforms the socket edges (collar) and indents the flexible cuticular dome (cap).
Top panel: Scanning electron micrograph (SEM) of campaniform sensilla on the tarsus of Drosophila melanogaster . Bottom panel: SEM of campaniform on the base of the haltere of a sarcophagid fly.
Distribution of groups of campaniform sensilla on a stick insect leg (anterior view). The inset shows a top view of the two groups on the dorsal trochanter (G3 and G4). The sensilla of these groups have mutually perpendicular orientations. Each sensillum is preferentially excited by compression along its short axis (arrows). The proximal group (G3) is oriented perpendicularly to the long axis of the trochanter and excited when the trochanter-femur is bent upwards. The more distal group (G4) is oriented in parallel to the long axis of the trochanter and excited when the trochanter-femur is bent downwards.
Distribution of campaniform sensilla (CS) on the wing and haltere of Drosophila melanogaster . Adapted from Aiello et al. (2021). [ 9 ]