The slit sensilla, also known as the slit sense organ, is a small mechanoreceptory organ or group of organs in the

exoskeleton An exoskeleton () . is a skeleton that is on the exterior of an animal in the form of hardened integument, which both supports the body's shape and protects the internal organs, in contrast to an internal endoskeleton (e.g. human skeleton, that ...

arachnid Arachnids are arthropods in the Class (biology), class Arachnida () of the subphylum Chelicerata. Arachnida includes, among others, spiders, scorpions, ticks, mites, pseudoscorpions, opiliones, harvestmen, Solifugae, camel spiders, Amblypygi, wh ...

s 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 Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

. The arachnid slit sensilla corresponds to the campaniform sensilla found in insects. Slit sensilla tend to be widely distributed over the arachnid's exoskeleton, but have also been found to be grouped at specific locations and in a bundle of parallel lines; the latter distribution is referred to as a "lyriform organ". The term "lyriform organ" comes from the shape of such grouped slit sensilla, which resembles a

lyre The lyre () (from Greek λύρα and Latin ''lyra)'' is a string instrument, stringed musical instrument that is classified by Hornbostel–Sachs as a member of the History of lute-family instruments, lute family of instruments. In organology, a ...

. Arachnids with lyriform slit sensilla are commonly used as experimental subjects for investigations into

mechanosensation Mechanosensation is the transduction of mechanical stimuli into neural signals. Mechanosensation provides the basis for the senses of light touch, hearing, proprioception, and pain. Mechanoreceptors found in the skin, called cutaneous mechanorecept ...

because the almost 2D structure of their slit sensilla allows for relatively simple understanding of the system; thus, the results of electrostimulation on such arachnids can be easily recorded. Etymologically, "slit sensilla" are so named because they resemble a channel penetrating through the exoskeleton into the animal; despite this appearance, however, investigation has shown that slit sensilla do not actually penetrate the

chitin Chitin (carbon, C8hydrogen, H13oxygen, O5nitrogen, N)n ( ) is a long-chain polymer of N-Acetylglucosamine, ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is the second most abundant polysaccharide in nature (behind only cell ...

of the exoskeleton, but merely represent a thinning of the material.

References

Bibliography

* *{{cite journal, last1=French, first1=Andrew S. , last2=Torkkeli , first2=Päivi H. , last3=Seyfarth , first3=Ernst-August , date=2002, title=From stress and strain to spikes: mechanotransduction in spider slit sensilla, journal=Journal of Comparative Physiology A, publisher=Springer-Verlag, volume=188, issue=10, issn=0340-7594, doi=10.1007/s00359-002-0363-1, pages=739–752, pmid=12466950, s2cid=308783 Spider anatomy Sensory receptors