Crista acustica (also Siebold's organ, or crista acoustica) is a part of the hearing organ (tibial organ) in some insects (e.g. grasshoppers, crickets, katydids). It is a collection of sensory cells that form a crest (hence the name) on top of the hollow tube (the foreleg trachea) behind the hearing membrane (tympanum) on the legs of the insect. The crista acustica is a transition from the

intermedia organ Intermedia is an art theory term coined in the mid-1960s by Fluxus artist Dick Higgins to describe various interdisciplinarity art activities that occur between genres, beginning in the 1960s. It was also used by John Brockman to refer to works ...

(from the midline to the periphery), together which compose the tibial hearing organ (as opposed to the tympanal hearing organ). The crista acustica is one of three fiddle-string-like organs or chordotonal organ in insects: the others are the

intermediate organ Intermediate may refer to: * Intermediate 1 or Intermediate 2, educational qualifications in Scotland * Intermediate (anatomy), the relative location of an anatomical structure lying between two other structures: see Anatomical terms of location ...

and the supratympanal organ/

subgenual organ The subgenual organ is an organ in insects that is involved in the perception of sound. The name ( Latin ''sub: "''below" and ''genus: "''knee") refers to the location of the organ just below the knee in the tibia of all legs in most insects. Th ...

. These chordotonal organs are actually collections of sensory cells sensitive to vibration (these cells are called

scolopidia A scolopidium (historically, scolopophore) is the fundamental unit of a mechanoreceptor organ in insects. It is a composition of three cells: a scolopale cap cell which caps the scolopale cell, and a Bipolar neuron, bipolar sensory nerve cell. Th ...

cells). Their cells are attached to the tube in the legs of the insects (the trachea, "''trah-key-ah''"). So when the tube vibrates, the cells vibrate. In the crista acustica, it turns out that different scolopidia cells are sensitive to different vibrations depending on the frequency of the vibration. Since these organs are sensitive to vibrations (due to changes in pressure.cf. far field pressure gradients, as opposed to pure displacement sensations or near field acoustics It turns out the cells closest to midline are the largest and sensitive to the lowest frequency (low frequencies having the largest wavelength), and the cells further out (distal) are smaller and sensitive to higher frequencies (since high frequencies have shorter wavelengths). This orderly arrangement of sensory cells gives the insect the ability to discriminate frequencies, much like the

inner ear The inner ear (internal ear, auris interna) is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. In mammals, it consists of the bony labyrinth, a hollow cavity in the ...

of mammals.

References

Sensory organs in animals Insect anatomy Auditory system {{insect-anatomy-stub

See also

References