Details are found in reviews by Humphrey and Barth and Barth A simple way to classify spider tactile hairs is the number of sensory cells attached to them. The exceptions to the rule of 3 bipolar cells mentioned above Foelix and Chu-Wang are hairs supplied by only 1 sensory cell, as shown for the short and stout hairs of the coxal hair plates Seyfarth et al.
Another type of tactile hairs with one sensory cell only are the so called long smooth hairs on the coxae as described by Eckweiler et al. When going into more morphological detail like shape of hair socket, hair length, shape of hair shaft , a further classification of tactile hairs turns out to be difficult and its value is still doubtful.
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Intriguingly, the distribution of hair types characterized by a certain combination of these parameters is conservative, possibly indicating a relation to particular stimulus patterns, being kind of templates of them Friedrich ; Barth However, in order to turn this speculation into reliable data it still needs a lot of research. Tactile spider hairs represent both proprioreceptors and exteroreceptors, the difference being that the first ones are stimulated by self-generated stimuli whereas the latter respond to stimuli from an outside source.
Proprioreceptive stimulation amply occurs during locomotion when hairs located at joints are deflected by joint movement or when a joint membrane rolls over a field of coxal hair plate sensilla. The long smooth hairs are stimulated when two neighboring coxae are approaching each other, most likely measuring the distance between them Eckweiler et al.
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A number of electrophysiological experiments as well as computational studies of their micromechanical properties have revealed surprisingly "clever" details of tactile spider hair properties, reflecting the properties of the stimuli they have to cope with. Examples are the following. As it seems the hair base and the inner lever arm of the tactile hairs on the inner side of the axis of rotation likewise are structures favoring a combination of high sensitivity and mechanical protection of the dendritic terminals from being overloaded and damaged Barth The inner lever arm is only ca.
This implies a considerable scaling down of the hair tip movement and a corresponding scaling up of the force close to the dendrites.
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Apart from effects of the asymmetry of the socket structure as clearly seen from above in some tactile spider hairs there are directional dependencies of the torques resisting hair deflection before any contact with the socket. The most pronounced case so far known of such a mechanical directionality are the hairs at the joint between walking leg tibia and metatarsus. For the natural direction of stimulation the torsional restoring constant S is smaller by a factor of about as compared to all other directions Schaber and Barth Dechant et al.
The tactile hairs sticking out of the carpet of hairs dorsally on the walking legs of Cupiennius have also been subjects of electrophysiological experiments Albert et al. Like in Ciniflo Harris and Mill for unknown reasons extracellular recordings were only possible from two of the three sensory cells, one of which is much larger than the others.
Tactile hair sensory cells consistently show phasic response characteristics, answering to the dynamic stimulus phase, that is to the velocity of hair deflection. Using biologically relevant stimulus velocities the maximum response is seen with a latency of 1 to 2 ms only, a very short time typical of many mechanoreceptors and implying high temporal resolution. Adaptation time to static deflection varies; consistently, a "slow" and a "fast" cell were found , the latter being much less sensitive in terms of the deflection velocity threshold than the former ca.
Here y is the impulse rate, t is the time, a a constant representing the amplification, d stimulus amplitude and k a receptor constant describing how quickly the response to a maintained stimulus declines. In the present case k -values are around around 0. The characteristic curves impulse rate vs.
However, the slow cell saturates at much lower velocities than the fast cell Figure 6. For the slow cell threshold deflection angles are independent of deflection velocity, whereas they highly depend on it for the fast cell for which the minima occur at ca. Importantly, the cells do not provide information about the exact time course of hair deflection but only about its presence and onset.
Whereas the "fast" cell is working like a mere quasi-digital "event detector", the "slow" cell is suggested to serve the analysis of the texture and shape of surfaces actively scanned by the spider and to be well adapted to that function, similar to the SAI tactile units in the vertebrate glabrous skin Albert et al. Of particular interest may be the remarkable lack of a standing transepithelial potential in spiders.
A lot still needs to be done to better understand why Cupiennius and other wandering spiders are so extremely well equipped with tactile hairs. A particular research requirement is the analysis of complex stimulus patterns like those seen during active tactile probing in the dark and courtship and copulation Barth Upon simple stimulation like the experimental deflection of a few neighboring or individual tactile hairs the spider withdraws the stimulated body part or turns away from the source of stimulation.
Interestingly, the long tactile hairs forming the outposts of the sense of touch are not only found dorsally on the leg, but also ventrally on the tarsus Figure 4 and among all tactile hairs so far studied they were the ones most easily deflected smallest values for elastic restoring constant S; 5.
They are assumed to provide sensory feedback information during locomotion. A full neuroethological analysis of a tactile behavior comes from the work of E-A Seyfarth and his associates who examined "body raising" behavior in Cupiennius , which is also found in salticid and theraphosid and probably many other spiders Figure 7 see review by Seyfarth This behavior must be very helpful when the spiders walk around on structurally complex terrain and have to avoid and cope with all sorts of mechanical obstacles. Seyfarth and co-workers successfully traced the information flow from the sensory receptors to the central nervous system and the motor output.
The deflection of long tactile hairs on the sternum or ventrally on the proximal leg first activates the coxa levator muscle of the stimulated leg. Thus a primary local response pulls the coxa against the prosoma while the distal leg joints are extended hydraulically. Coxal muscle activity in turn leads to the stimulation of internal joint receptors at the tergo-coxal joint, which triggers a second, the pluri-segmental response: The muscles of the remaining seven legs contract almost simultaneously and the legs are extended.
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By intracellular recording and staining the neuronal correlates of "body raising" behavior could be identified from the stimulated tactile hair and its sensory afferents to inter- and motor neurons Figure 8 , Figure 9. Another, more recent analysis, asked how well adapted tactile hairs ventrally at the tibia-metatarsus joint might be to a proprioreceptive function, monitoring the movement of the joint Schaber and Barth The results are much in favor of such an adaptedness.
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There is much left for future research on the tactile sense of spiders. Do wandering spiders use tactile information on form, size and texture of an object's surface? When watching their smooth and elegant way of moving around on geometrically complex structures like bromeliads or other plants and watching the females producing and manipulating their egg sac one is strongly inclined to assume that they do use it.
The same applies to the capture and handling of their prey. The next question then is: How are they doing it? The active tactile probing of their immediate environment Schmid should be examined in more detail as should be the handling of prey and the sexual partner during precopulatory and copulatory communication Barth , Such knowledge would now allow us to predict the respective stimulation patterns of the sensory periphery and to hypothesize on the information theoretically available to the central nervous system.
What the central nervous system is doing with it still largely is in the dark but the neuroethological analysis of the body raising behavior of Cupiennius Seyfarth nicely shows what can be done and hoped for. Barth , Scholarpedia, 10 3 Jump to: navigation , search. Post-publication activity Curator: Friedrich G. Signposts to the Prey: Airflow Stimuli.
Courtship and Vibratory Communication. Kinesthetic Orientation. Visual Targets. Raising the Body when Walking over an Obstacle. Locomotion and Leg Reflexes. Swinging to a New Plant: the Dispersal of the Spiderlings. From the reviews: "Thanks to Professor Friedrich G. Barth, his numerous co-workers and students we have astonishing details about the sensorial world and behaviour of these large neotropical spiders! The book is richly illustrated with numerous line drawings, diagrams and photographs and also contains 16 magnificent colour plates.
Professor Barth's monograph is a very useful book for all students of arthropod sensory physiology and behaviour. Zd'arek, European Journal of Entomology, Vol. The book is very well produced, with a well laid-out text supported by numerous figures and photographs! One of this great book's many attractions is the way that the text involves the reader!
This highly readable and informative book will provide a valuable reference for researchers, students and teachers! Newsletter Google 4. Help pages. Prothero Michael J. Benton Richard Fortey View All. Go to British Wildlife. Conservation Land Management. Go to Conservation Land Management. Publisher: Springer Nature. Click to have a closer look.
Select version. About this book Contents Customer reviews Related titles. Images Additional images. About this book Spiders are wonderful creatures. Customer Reviews Review this book. By: Friedrich G Barth. Media reviews. Current promotions. Bestsellers in Arachnids. Britain's Spiders. More Info.