The femoral chordotonal organ is a group of mechanosensory neurons found in an insect leg (Figure 1) that detects the movements and the position of the femur/tibia joint. [1] It is thought to function as a proprioceptor that is critical for precise control of leg position by sending the information regarding the femur/tibia joint to the motor circuits in the ventral nerve cord and the brain [2] [3] [4] [5]
The cell bodies of the femoral chordotonal neurons are generally located in the proximal femur, [1] and their dendrites are mechanically coupled to the tibia through different types of tendons. [6] [7] [8] [9] [10] In Drosophila, where it is possible to genetically identify different subtypes of femoral chordotonal neurons, the neurons can be divided into three subtypes based on their axonal projection pattern into the ventral nerve cord [11] (Figure 2). The axons of the club neurons project to the center of the ventral nerve cord and form a bundle that is shaped like a club. [12] The axons of the claw neurons split into three branches that are shaped like a claw. [12] The axons of the hook neurons are shaped similar to the peavey hook. [11]
The sensory neurons of the femoral chordotonal organ encode various kinematic features of the femur/tibia joint including, position, speed, acceleration, and vibration. [13] [14] [15] [16] [17] [18] [19] In Drosophila , where it is possible to genetically track different subtypes of femoral chordotonal neurons, it is known that these different kinematic features are encoded by anatomically distinct subtypes of neurons mentioned above [11] (Figure 2). The position of the tibia is encoded by the claw neurons, vibrations are encoded by the club neurons, and the direction of the movement is encoded by the hook neurons. [11]
The femoral chordotonal organ is thought to be involved in precise control of leg movements, and the experimental manipulations of the femoral chordotonal organ in stick insects and locusts have shown that they play a critical role during walking. [2] and target reaching [3]
One way in which the femoral chordotonal organ contributes to the control of leg movement is through a resistance reflex, in which a sub-group of femoral chordotonal neurons sense the extension of the tibia and activates the motor neurons that flexes tibia to counteract the movement (Figure 3). [4] During walking, this stabilization reflex is reversed in order to promote the cyclic flexion and extension of the femur-tibia joint necessary for walking (Figure 3). [20] [21]
One possible mechanism for determining the feature selectivity of femoral chordotonal neurons is biomechanical specialization that transmit distinct forces to each type of proprioceptors, or distribute forces differently to proprioceptors in different locations. For position sensing claw cells of Drosophila , it has been shown that biomechanical properties of the tendon, surrounding tissues, and dendrites lead to different amount of strain generated on the dendrite of a claw cell depending on where the cell is located along the femur. [22] This gradient of strain allows claw cells to respond at different tibia angles and generate a topographic map of joint angles in the femoral chordotonal organ. [22]
A rete mirabile is a complex of arteries and veins lying very close to each other, found in some vertebrates, mainly warm-blooded ones. The rete mirabile utilizes countercurrent blood flow within the net to act as a countercurrent exchanger. It exchanges heat, ions, or gases between vessel walls so that the two bloodstreams within the rete maintain a gradient with respect to temperature, or concentration of gases or solutes. This term was coined by Galen.
A mechanoreceptor, also called mechanoceptor, is a sensory receptor that responds to mechanical pressure or distortion. Mechanoreceptors are innervated by sensory neurons that convert mechanical pressure into electrical signals that, in animals, are sent to the central nervous system.
Range fractionation is a term used in biology to describe the way by which a group of sensory neurons are able to encode varying magnitudes of a stimulus. Sense organs are usually composed of many sensory receptors measuring the same property. These sensory receptors show a limited degree of precision due to an upper limit in firing rate. If the receptors are endowed with distinct transfer functions in such a way that the points of highest sensitivity are scattered along the axis of the quality being measured, the precision of the sense organ as a whole can be increased.
Robot locomotion is the collective name for the various methods that robots use to transport themselves from place to place.
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 scolopidia arrayed in a bowl shape, each of which contains a mechanosensory chordotonal neuron. The number of scolopidia varies between species. In homopterans, the Johnston's organs contain 25 - 79 scolopidia. The presence of Johnston's organ is a defining characteristic which separates the class Insecta from the other hexapods belonging to the group Entognatha. Johnston's organ was named after the physician Christopher Johnston, father of the physician and Assyriologist Christopher Johnston.
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, similar to mammalian Golgi tendon organs. Sensory feedback from campaniform sensilla is integrated in the control of posture and locomotion.
The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments are of Latin origin, and may be confused with terms for bones: coxa, trochanter, femur, tibia, tarsus, ischium, metatarsus, carpus, dactylus, patella.
Torkel Weis-Fogh was a Danish zoologist and Professor at the University of Cambridge and the University of Copenhagen. He is best known for his contributions to the understanding of insect flight, especially the clap and fling mechanism used by very small insects. James Lighthill named this "the Weis-Fogh mechanism of lift generation".
Chordotonal organs are stretch receptor organs found only in insects and crustaceans. They are located at most joints 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. 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.
A tympanal organ is a hearing organ in insects, consisting of a membrane (tympanum) stretched across a frame backed by an air sac and associated sensory neurons. Sounds vibrate the membrane, and the vibrations are sensed by a chordotonal organ. Hymenoptera do not have a tympanal organ, but they do have a Johnston's organ.
Journal of Experimental Biology is a peer-reviewed scientific journal in the field of comparative physiology and integrative biology. It is published by The Company of Biologists. The journal is partnered with Publons and has two-way integration with bioRxiv. Journal of Experimental Biology is now a hybrid journal and publishes 24 issues a year. Content over six months old is free to read.
In behavioral biology, the optomotor response is an innate, orienting behavior evoked by whole-field visual motion and is common to fish and insects during locomotion, such as swimming, walking and flying. The optomotor response has algorithmic properties such that the direction of the whole-field coherent motion dictates the direction of the behavioral output. For instance, when zebrafish larvae are presented with a sinusoidal black and white grating pattern, the larvae will turn and swim in the direction of the perceived motion.
Proprioception, also called kinaesthesia, is the sense of self-movement, force, and body position.
The slit sensilla, also known as the slit sense organ, is a small mechanoreceptory organ or group of organs in the exoskeleton of arachnids which detects physical deformation or strain due to forces experienced by the animal. The organ appears in the vast majority of discovered arachnids, and is "remarkably consistent" in location and direction within each order. The arachnid slit sensilla corresponds to the campaniform sensilla found in insects.
A scolopidium 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 sensory nerve cell.
Malcolm Burrows FRS is a British zoologist, and emeritus professor of zoology at the University of Cambridge. His area of research specialization is in the neural control of animal behaviour particularly in those of small invertebrates. Some of his research examines the circuitry of neurons, muscles and the mechanics of joints involved in the rapid movements and leaps of insects.
The subgenual organ is an organ in insects that is involved in the perception of sound. The name refers to the location of the organ just below the knee in the tibia of all legs in most insects.
Hair-plates are a type of proprioceptor found in the folds of insect joints. They consist of a cluster of hairs, in which each hair is innervated by a single mechanosensory neuron. Functionally, hair-plates operate as "limit-detectors" by signaling the extreme ranges of motion of a joint.
The study of animal locomotion is a branch of biology that investigates and quantifies how animals move.