Paratropis tuxtlensis tarsal trichobothria II

Trichobothria (singular trichobothrium) are elongate

setae In biology, setae (; seta ; ) are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Depending partly on their form and function, protostome setae may be called macrotrichia, chaetae ...

("hairs") present in

arachnids Arachnids are arthropods in the class Arachnida () of the subphylum Chelicerata. Arachnida includes, among others, spiders, scorpions, ticks, mites, pseudoscorpions, harvestmen, camel spiders, whip spiders and vinegaroons. Adult arachnids ...

, various orders of

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

s, and

myriapod Myriapods () are the members of subphylum Myriapoda, containing arthropods such as millipedes and centipedes. The group contains about 13,000 species, all of them terrestrial. Although molecular evidence and similar fossils suggests a diversifi ...

s that function in the detection of airborne vibrations and currents, and electrical charge. In 1883,

Friedrich Dahl Karl Friedrich Theodor Dahl (24 June 1856 in Rosenhofer Brök north of Dahme, Schleswig-Holstein, Dahme, Holstein – 29 June 1929 in Greifswald) was a German zoologist, and in particular an arachnologist. The son of a farmer, Dahl studied at the ...

observed that they were deflected by the sound waves from a violin and labelled them 'hearing hairs'.

Morphology

Unlike the ordinary setae, which are tapered, the trichobothria have the same gauge throughout their length. They fit into the bottom of a broad and deep cup to which connects a membrane with extreme flexibility which adds an extraordinary mobility to them. The least air vibration is able to get them moving and to excite the small group of sensory cells which ensures their innervation.

Distribution

Trichobothria are present in most orders of the

Arachnida Arachnids are arthropods in the class Arachnida () of the subphylum Chelicerata. Arachnida includes, among others, spiders, scorpions, ticks, mites, pseudoscorpions, harvestmen, camel spiders, whip spiders and vinegaroons. Adult arachnids ...

, except in

Solifugae Solifugae is an Order (biology), order of Arachnid, arachnids known variously as solifuges, sun spiders, camel spiders, and wind scorpions. The order includes more than 1,000 described species in about 147 genus, genera. Despite the common names, ...

Ricinulei Ricinulei is a small order of arachnids. Like most arachnids, they are predatory; eating small arthropods. They occur today in west-central Africa ('' Ricinoides'') and the Americas ('' Cryptocellus'' and '' Pseudocellus'') from Brazil to southern ...

and

Opiliones The Opiliones (formerly Phalangida) are an Order (biology), order of arachnids, Common name, colloquially known as harvestmen, harvesters, harvest spiders, or daddy longlegs (see below). , over 6,650 species of harvestmen have been discovered w ...

(Grassé, 1949). Although the distribution of trichobothria on the bodies of

is often used by systematists (especially in Scorpiones and

Pseudoscorpiones Pseudoscorpions, also known as false scorpions or book scorpions, are small, scorpion-like arachnids belonging to the order Pseudoscorpiones, also known as Pseudoscorpionida or Chelonethida. Pseudoscorpions are generally beneficial to humans bec ...

), few interordinal patterns are apparent (Shultz, 1990).

References

* Foelix, R.F., 1982. Biology of Spiders. Harvard University Press. Cambridge, Massachusetts, and London, England. * Grassé, P. (1949). Traité de Zoologie: Anatomie, Systématique, Biologie / publié sous la dir. de M. Pierre-P. Grassé. tome VI, Onychophores - Tardigrades - Arthropodes - Trilobitomorphes - Chélicérates. - Masson et Cie, Paris. * Shultz, J.W. (1990). Evolutionary Morphology And Phylogeny of Arachnida. Cladistics 6: 1-38. Arachnid anatomy Arthropod anatomy Insect anatomy Animal hair Sensory organs in animals {{insect-anatomy-stub