Scolopidia
Encyclopedia
A scolopidia is the most fundamental unit of a mechanoreceptor
organs in insects. It is a composition of three cells, a scolopale cap cell which caps the scolopale cell, and a bipolar sensory nerve cell. Scolopidia are sensitive to things like sound (vibrations of the air) or substrate vibrations (feeling vibrations on a leaf, for instance) depending on the structure of the overall sense organ in which they reside.
These organs ultimately convert mechanical vibration into a nerve impulse which is sent on to higher ganglion where the information is combined and/or processed into a resultant behavior.
The general term of these overall sense organs is the chordotonal organ
s, with the scolopidia usually lying just under the exoskeleton. A specific example of the chordotonal organ would be the subgenual organ (in the lower part of the legs; senses vibrations in the ground), the crista acustica
(a collection of individually-tuned scolopidiae which can discriminate frequencies
, or Johnston's organ
(in the antennae; senses motion of an antenna relative to the insect's body). There are many types of scolopidia, depending on the sense organ in which they belong, and the terminology among the scolopidia is not always uniform.
There are two types of scolopidia, one whose distal end (the cap end) is contained within the body wall of the insect (subintegumental) or one whose distal end is free (integumental). For example, the integumental type is found in the subguneal organ (also known as the supratypanal organ) while the subintegumental type is found in the crista acustica
and the intermediate organ. Interestingly, the subguneal organ ('organ below the knee') is found in all insects legs, and the probably an evolutionary artifact of prior insect body-types which used their legs to detect vibrations from the substrate (viz., treehoppers). The intermediate organ and the crista acustica, on the other hand, are only found where there is a tympanum, such as on the front legs of insects.
Mechanoreceptor
A mechanoreceptor is a sensory receptor that responds to mechanical pressure or distortion. There are four main types in the glabrous skin of humans: Pacinian corpuscles, Meissner's corpuscles, Merkel's discs, and Ruffini corpuscles...
organs in insects. It is a composition of three cells, a scolopale cap cell which caps the scolopale cell, and a bipolar sensory nerve cell. Scolopidia are sensitive to things like sound (vibrations of the air) or substrate vibrations (feeling vibrations on a leaf, for instance) depending on the structure of the overall sense organ in which they reside.
These organs ultimately convert mechanical vibration into a nerve impulse which is sent on to higher ganglion where the information is combined and/or processed into a resultant behavior.
The general term of these overall sense organs is the chordotonal organ
Chordotonal organ
Chordotonal organs are stretch receptor organs in insects and other arthropods They are used to detect the position of the body segments and appendages, or, in tympanal organs, the vibrations caused by sounds. An example for hearing is the Johnston's organ at the base of the antennae. Sound waves...
s, with the scolopidia usually lying just under the exoskeleton. A specific example of the chordotonal organ would be the subgenual organ (in the lower part of the legs; senses vibrations in the ground), the crista acustica
Crista acustica
Crista acustica is a part of the hearing organ in some insects...
(a collection of individually-tuned scolopidiae which can discriminate frequencies
Tonotopy
In physiology, tonotopy is the spatial arrangement of where sounds of different frequency are processed in the brain. Tones close to each other in terms of frequency are represented in topologically neighbouring regions in the brain...
, or Johnston's organ
Johnston's organ
Johnston's organ is a collection of sensory cells found in the pedicel of the antennae in the Class Insecta. Johnston's organ detects motion in the flagellum . It consists of over 200 scolopidia arrayed in a bowl shape, each of which contains a mechanosensory chordotonal neuron...
(in the antennae; senses motion of an antenna relative to the insect's body). There are many types of scolopidia, depending on the sense organ in which they belong, and the terminology among the scolopidia is not always uniform.
There are two types of scolopidia, one whose distal end (the cap end) is contained within the body wall of the insect (subintegumental) or one whose distal end is free (integumental). For example, the integumental type is found in the subguneal organ (also known as the supratypanal organ) while the subintegumental type is found in the crista acustica
Crista acustica
Crista acustica is a part of the hearing organ in some insects...
and the intermediate organ. Interestingly, the subguneal organ ('organ below the knee') is found in all insects legs, and the probably an evolutionary artifact of prior insect body-types which used their legs to detect vibrations from the substrate (viz., treehoppers). The intermediate organ and the crista acustica, on the other hand, are only found where there is a tympanum, such as on the front legs of insects.