Biology:Chordotonal organ

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Short description: Stretch receptor organs

Chordotonal organs are stretch receptor organs found only in insects and crustaceans.[1][2][3] They are located at most joints[2] and are made up of clusters of scolopidia that either directly or indirectly connect two joints and sense their movements relative to one another. They can have both extero- and proprioceptive functions, for example sensing auditory stimuli or leg movement.[4] The word was coined by Vitus Graber in 1882, though he interpreted them as being stretched between two points like a string, sensing vibrations through resonance.[5]

Structure

Diagram of the primary components of a chordotonal organ scolopidium

Chordotonal organs can be composed of a single scolopidium with only a single sensory, bipolar neuron (such as the tympanal ear of a notodontid moth), or up to several thousand scolopidia, each equipped with up to four sensory neurons (as in the mosquito Johnston's organ).[6] The bipolar sensory neurons each have an apical dendritic structure with a cilium densely packed with microtubules and surrounded by two specialized cells, the scolopale cell and the attachment (cap) cell, plus a glial cell.[2] Mechanically gated ion channels are located distal to the ciliary dilation, a characteristic part of the upper dendritic cilium. The cavity between the scolopale cell and the sensory neuron is filled with a specialized receptor lymph similar to the endolymph that surrounds the mechanosensory hair bundles of cochlear hair cells (high in potassium and low in sodium).[6] The dendritic cilia can have one of two major forms: in the mononematic form, the major connection between the attachment site and the cilium is a microtubule-rich attachment cell. The electron-dense extracellular material is small and localized mainly to the junction between the cilia and the attachment cell. The femoral chordotonal organ is mononematic. In contrast, in the amphinematic form, the extracellular material of the cap forms a dense, tubular sheath that surrounds the sensory cilium and extends all the way to the cuticle at the attachment site. In this form, the attachment cell contains both microtubules and actin-rich scolopale rods similar to those present in the scolopale cell. The Johnston's organ is an example of an amphinematic chordotonal organ. The functional significance of the morphological differences of the two forms is unknown, but may confer different viscoelastic properties on the sensory units.[7]

Functional diversity

In a chordotonal organ, individual sensory neurons can respond to different types of mechanosensory stimuli (for example, sound vs gravity), and those that respond to a particular stimulus can have different tuning properties (for example, tuned to different position of a joint).[2] One way to generate these functional diversity is by having sensory neurons with different types of mechanosensory channels or intrinsic properties. For example, in Johnston's organ of Drosophila melanogaster, sensory neurons that detect sound may express nompC, an ion channel that belongs to the transient receptor potential (TRP) superfamily, while those that detect gravity may express another member of the TRP channel, painless.[8] Another way to generate functional diversity is by having sensory neurons that are attached to the joint through different types of connections. For example, in the femoral chordotonal organ of the locust, the ligament in which sensory neurons are embedded is divided into several strands that are sequentially pulled as the joint is flexed, providing a mechanism for differential activation of the sensory neurons at different position of the joint.[9]

Major chordotonal organs

Insects

Femoral chordotonal organ

The femoral chordotonal organ is located in the femur of the insect leg and it detects position, speed, acceleration, and vibration of the tibia relative to the femur.[10][11][12][13][14] In Drosophila melanogaster, where it is possible to systematically analyze neuronal populations using genetic tools, the sensory neurons of the femoral chordotonal organ can be separated into at least 3 functionally and genetically distinct populations: the club, claw, and hook.[14] The club neurons encode bi-directional movements and vibrations of the tibia, the claw neurons encode position of the tibia, and the hook neurons encode directional movements of the tibia.[14] Information encoded by the femoral chordotonal organ is thought to be used during behaviors that require precise control of leg movements, such as walking [15] and target reaching.[16] The femoral chordotonal organ is thought to be functionally homologous to muscle spindles.[17]

In the femoral chordotonal organ, the scolopidia are organized into groups called scoloparia. Scoloparia may be functionally distinct from one another, with separate scoloparia containing vibration-sensitive or position-sensitive sensory neurons.[18][19] Drosophila melanogaster has three scoloparia.[20]

Johnston's organ

The Johnston's organ is located in the pedicel (the second segment) of the insect antennae, and it detects the position and the movement of the flagellum (the third segment of the antennae) relative to the pedicel.[21] Johnston's organ exists in nearly all orders of insects.[2] In Drosophila melanogaster, in most mosquito species and some midge species, different subsets of Johnston's organ neurons are tuned to different amplitude and frequency of the movements allowing them to detect various stimuli including, sound, wind, gravity, wing beats, and touch.[22][23][24][25][26]

In several species of Diptera, the Johnston's organ is sexually dimorphic. Males possess both greater numbers, greater diversity, and a more highly organized distribution of scolopidia.[4] Some species of mosquitoes may possess as many as several thousand scolopidia.[6] Males of these species likely use the Johnston's organ to identify potential mates.

Janet's organ

In addition to the Johnston's organ, antennae of Hymenoptera possess a second chordotonal organ, the Janet's organ, which detects flexion of the antennal joints, somewhat like the femoral chordotonal organ.[4]

Subgenual organ

The subgenual organ is found in all insects except Diptera and Coleoptera. It is located in the proximal part of the tibia and detects high-frequency acoustic vibrations transmitted through the substrate as well as sound through air.[27]

Tympanal organ

Tympanal organs are specialized hearing organs that have evolved in at least seven different orders of insects. They consist of a tympanal membrane backed by an air-filled space and are innervated by a chordotonal organ. Tympanal organs detect air-borne vibrations and are used to detect predators, prey, and potential mates and rivals. They can be found in a variety of locations on the body, including the abdomen, wing base, metathorax, and ventral prosternum.[28]

in Drosophila melanogaster, the Wheeler's organ[29][30] is a type of tympanal organs in the first two abdominal sternites. It is named after the American entomologist William Morton Wheeler, who first described it in 1917.[31]

Wheeler's organ is composed of about 20 scolopidia, which are sensory structures that are sensitive to movement and vibration. The scolopidia are innervated by a single neuron, which sends signals to the fly's brain.

The function of Wheeler's organ is not fully understood, but it is thought to be involved in sensing the position of the abdomen and the distension of the abdomen. It may also play a role in the fly's courtship behavior.

Wing and halteres

There is a chordotonal organ located at the base of the wings in many insect orders, and, in Dipterans, there are also two chordotonal organs found at the base of the haltere. Their function is currently not well understood. In lacewings, a tympanal organ is located in the radius vein of the forewing and is thought to monitor ultrasound.[2]

Crustaceans

Myochordotonal Organ

In the order Decapoda, there are chordotonal organs located in the legs, antennules, antenna, chelipeds, and mandibles.[32][33] Each leg joint also contains a chordotonal organ.[34] Similar to the antennal and leg chordotonal organs in insects, the leg chordotonal organs in crustaceans are sensitive to both proprioceptive and auditory information, including airborne and substrate-borne vibrations.[35][36][37] Myochordotonal organs are also called Barth's Myochordotonal Organs and were first studied by Barth in 1934.[32]

See also

References

  1. ↑ Methods in Insect Sensory Neuroscience. CRC Press. December 2004. ISBN 978-1-4200-3942-9. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 "Chordotonal organs of insects.". Advances in Insect Physiology 27: 1–228. January 1998. doi:10.1016/S0065-2806(08)60013-2. ISBN 9780120242276. https://www2.le.ac.uk/departments/npb/people/matheson/matheson-neurobiology/images/publications/chordotonal.pdf. 
  3. ↑ "Chordontonal organs in Crustace". Nature 187 (4736): 522–3. August 1960. doi:10.1038/187522a0. PMID 13844417. Bibcode: 1960Natur.187..522W. 
  4. ↑ 4.0 4.1 4.2 "Antennal Mechanosensors and Their Evolutionary Antecedents". Advances in Insect Physiology (Elsevier) 49: 59–99. 2015. doi:10.1016/bs.aiip.2015.06.003. ISBN 978-0-12-802586-4. 
  5. ↑ The Physiology of Insect Senses. London: Methuen & Co. Ltd. 1963. p. 21. https://archive.org/details/physiologyofinse00deth. 
  6. ↑ 6.0 6.1 6.2 "Chordotonal organs". Current Biology 23 (9): R334-5. May 2013. doi:10.1016/j.cub.2013.03.048. PMID 23660347. 
  7. ↑ "Development of Johnston's organ in Drosophila". The International Journal of Developmental Biology 51 (6–7): 679–87. 2007. doi:10.1387/ijdb.072364de. PMID 17891726. 
  8. ↑ "TRPA channels distinguish gravity sensing from hearing in Johnston's organ". Proceedings of the National Academy of Sciences of the United States of America 106 (32): 13606–11. August 2009. doi:10.1073/pnas.0906377106. PMID 19666538. Bibcode: 2009PNAS..10613606S. 
  9. ↑ "Mechanism for range fractionation in chordotonal organs of Locusta migratoria (L) and Valanga sp. (Orthoptera : Acrididae)". International Journal of Insect Morphology and Embryology 20 (1): 25–39. 1991-02-01. doi:10.1016/0020-7322(91)90025-5. ISSN 0020-7322. 
  10. ↑ "Physiology of the femoral chordotonal organ in the stick insect Cuniculina impigra.". J. Exp. Biol. 114: 207–223. 1985. doi:10.1242/jeb.114.1.207. 
  11. ↑ "Acceleration receptors in the femoral chordotonal organ in the stick insect Cuniculina impigra.". J. Exp. Biol. 114: 225–237. 1985. doi:10.1242/jeb.114.1.225. 
  12. ↑ "Plasticity and proprioception in the insects. I. Responses and cellular properties of individual receptors of the locust metathoracic femoral chordotonal organ.". J. Exp. Biol. 116: 435–461. 1985. doi:10.1242/jeb.116.1.435. PMID 4056657. 
  13. ↑ "Responses and locations of neurones in the locust metathoracic femoral chordotonal organ.". J. Comp. Physiol. A 166 (6): 915–927. 1990. doi:10.1007/bf00187338. 
  14. ↑ 14.0 14.1 14.2 "Neural Coding of Leg Proprioception in Drosophila". Neuron 100 (3): 636–650.e6. November 2018. doi:10.1016/j.neuron.2018.09.009. PMID 30293823. 
  15. ↑ "Functional principles of pattern generation for walking movements of stick insect forelegs: the role of the femoral chordotonal organ afferences". J. Exp. Biol. 136: 125–147. 1988. doi:10.1242/jeb.136.1.125. 
  16. ↑ "Functional recovery of aimed scratching movements after a graded proprioceptive manipulation". The Journal of Neuroscience 29 (12): 3897–907. March 2009. doi:10.1523/jneurosci.0089-09.2009. PMID 19321786. 
  17. ↑ "Proprioception". Current Biology 28 (5): R194–R203. March 2018. doi:10.1016/j.cub.2018.01.064. PMID 29510103. 
  18. ↑ "Structure and physiology of the locust femoral chordotonal organ.". J. Insect Physiol. 20 (7): 1319–1339. 1974. doi:10.1016/0022-1910(74)90236-4. PMID 4854433. 
  19. ↑ "The femoral chordotonal organ: a bifunctional orthopteran (Locusta migratoria) sense organ". Comp. Biochem. Physiol. 93A (4): 729–743. 1989. doi:10.1016/0300-9629(89)90494-5. 
  20. ↑ "Ultrastructure of the femoral chordotonal organs and their novel synaptic organization in the legs of Drosophila melanogaster Melgen (Diptera: Drosophilidae).". Int. J. Insect Morphol. Embryol. 21 (4): 311–322. 1992. doi:10.1016/0020-7322(92)90026-j. 
  21. ↑ "Original communications: auditory apparatus of the Culex mosquito.". Journal of Cell Science 1 (10): 97–102. April 1855. 
  22. ↑ "The neural basis of Drosophila gravity-sensing and hearing". Nature 458 (7235): 165–71. March 2009. doi:10.1038/nature07810. PMID 19279630. Bibcode: 2009Natur.458..165K. 
  23. ↑ "Distinct sensory representations of wind and near-field sound in the Drosophila brain". Nature 458 (7235): 201–5. March 2009. doi:10.1038/nature07843. PMID 19279637. Bibcode: 2009Natur.458..201Y. 
  24. ↑ "Identification of novel vibration- and deflection-sensitive neuronal subgroups in Johnston's organ of the fruit fly" (in English). Frontiers in Physiology 5: 179. 2014. doi:10.3389/fphys.2014.00179. PMID 24847281. 
  25. ↑ "Distinct subpopulations of mechanosensory chordotonal organ neurons elicit grooming of the fruit fly antennae". eLife 9: e59976. October 2020. doi:10.7554/eLife.59976. PMID 33103999. 
  26. ↑ "Antennal mechanosensory neurons mediate wing motor reflexes in flying Drosophila". The Journal of Neuroscience 35 (20): 7977–91. May 2015. doi:10.1523/jneurosci.0034-15.2015. PMID 25995481. 
  27. ↑ "Detection Of Airborne Sound By A Cockroach 'Vibration Detector': A Possible Missing Link In Insect Auditory Evolution". The Journal of Experimental Biology 193 (1): 13–47. August 1994. doi:10.1242/jeb.193.1.13. PMID 9317246. 
  28. ↑ "Tympanal hearing in insects". Annual Review of Entomology 41 (1): 433–50. January 1996. doi:10.1146/annurev.en.41.010196.002245. PMID 15012336. 
  29. ↑ BODMER, R (October 1987). "Transformation of sensory organs by Mutations of the cut locus of D. melanogaster". Cell 51 (2): 293–307. doi:10.1016/0092-8674(87)90156-5. ISSN 0092-8674. https://doi.org/10.1016/0092-8674(87)90156-5. 
  30. ↑ Jarman, A. P.; Grau, Y.; Jan, L. Y.; Jan, Y. N. (1993-07-02). "atonal is a proneural gene that directs chordotonal organ formation in the Drosophila peripheral nervous system". Cell 73 (7): 1307–1321. doi:10.1016/0092-8674(93)90358-w. ISSN 0092-8674. PMID 8324823. https://pubmed.ncbi.nlm.nih.gov/8324823/. 
  31. ↑ Miller, A., & Demerec, M. (1950). Biology of Drosophila. The internal anatomy and histology of the imago of Drosophila melanogaster.
  32. ↑ 32.0 32.1 Rydqvist, Bo (1992) (in English). Comparative Aspects of Mechanoreceptor Systems (1 ed.). Heidelberg: Springer. pp. 238. ISBN 978-3-642-76690-9. 
  33. ↑ Vedel, J.-P.; Monnier, Simone (1983). "A New Muscle Receptor Organ in the Antenna of the Rock Lobster Palinurus vulgaris: Mechanical, Muscular and Proprioceptive Organization of the Two Proximal Joints J0 and J1". Proceedings of the Royal Society of London. Series B, Biological Sciences 218 (1210): 95–110. ISSN 0080-4649. https://www.jstor.org/stable/35726. 
  34. ↑ Whitear, Mary (1962-12-20). "The fine structure of crustacean proprioceptors I. The chordotonal organs in the legs of the shore crab, Carcinus maenas" (in en). Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 245 (725): 291–324. doi:10.1098/rstb.1962.0012. ISSN 2054-0280. https://royalsocietypublishing.org/doi/10.1098/rstb.1962.0012. 
  35. ↑ Bush, B.M.H. (1978). "Intersegmental Reflex Actions from A Joint Sensory Organ (Cb) to A Muscle Receptor (Mco) In Decapod Crustacean Limbs". Journal of Experimental Biology 73 (1): 47–63. https://journals.biologists.com/jeb/article/73/1/47/22514/Intersegmental-reflex-actions-from-a-joint-sensory. 
  36. ↑ Popper, A. N.; Salmon, M.; Horch, K. W. (March 2001). "Acoustic detection and communication by decapod crustaceans". Journal of Comparative Physiology. A, Sensory, Neural, and Behavioral Physiology 187 (2): 83–89. doi:10.1007/s003590100184. PMID 15523997. https://pubmed.ncbi.nlm.nih.gov/15523997/. 
  37. ↑ Horch, Kenneth (1975). "The Acoustic Behavior of the Ghost Crab Ocypode cordimana Latreille, 1818 (Decapoda, Brachyura)". Crustaceana 29 (2): 193–205. ISSN 0011-216X. https://www.jstor.org/stable/20102246. 

Further reading



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