Chordotonal organ

Definition

A mechanosensory organ in insects and some other arthropods that detects stretch, vibration, or joint movement, composed of one or more scolopidia—specialized sensory units containing a bipolar neuron and associated accessory cells. Chordotonal organs function in proprioception (monitoring limb position and movement) and exteroception (detecting airborne or substrate-borne sound, such as the vibrations of a host or mate). They occur at nearly all body joints, in the antennae, and in specialized hearing organs like the tympanal organs of moths and grasshoppers.

Etymology

From Greek chorde (string, cord) + tonos (tension, tone), coined by Vitus Graber in 1882 in reference to the stretched, string-like appearance he perceived between attachment points

Example

The subgenual organ in the tibia of a cricket is a chordotonal organ that detects vibrations from the substrate, allowing the insect to sense approaching predators or potential mates through their footsteps.

Synonyms

• scolopophorous organ

Related Terms

• scolopidium
• tympanal organ
• subgenual organ
• Johnston's organ
• proprioceptor
• mechanoreceptor
• stretch receptor

Usage Notes

Chordotonal organs are distinguished from other mechanoreceptors by their scolopidial structure; the term is sometimes used loosely for any stretch-sensitive joint receptor, but specialists reserve it for the scolopidium-based organs of insects and crustaceans. The organ may be single (mononematic) or multiple (polynematic) scolopidia. Contrast with hair sensilla (trichoid sensilla) and campaniform sensilla, which detect cuticular deformation rather than stretch between two points.