Urticating hair

Last updated
Young Grammostola rosea showing patch of urticating hairs, reflecting a camera flash Grammostola.rosea.with.hair.patch.jpg
Young Grammostola rosea showing patch of urticating hairs, reflecting a camera flash

Urticating hairs or urticating bristles are one of the primary defense mechanisms used by numerous plants, almost all New World tarantulas, and various lepidopteran caterpillars. Urtica is Latin for "nettle" (stinging nettles are in the genus Urtica ), and bristles that urticate are characteristic of this type of plant, and many other plants in several families. This term also refers to certain types of barbed bristles that cover the dorsal and posterior surface of a tarantula's or caterpillar's abdomen. Many tarantula species eject bristles from their abdomens, directing them toward potential attackers. These bristles can embed themselves in the other animal's skin or eyes, causing physical irritation, usually to great discomfort. The term "hairs" is technically a misnomer, as only mammals possess true hairs. [1] The scientific term for plant hairs is trichomes.

Contents

In plants

Urticating hairs of a stinging nettle Urtica dioica stinging hair.jpg
Urticating hairs of a stinging nettle

The most common form of urticating hairs in plants are typified by nettles, which possess sharp-pointed hollow bristles seated on a gland that secretes an acrid fluid. The points of these bristles usually break off in the wound, and the acrid fluid is pressed into it. Various plants unrelated to true nettles (Urtica species) possess similar defensive bristles, and the common names often reflect this (e.g. "bull nettle").

Many cacti of the sub-family Opuntioideae feature fine, loosely attached short spines called glochids. When the plant is disturbed many of these spines fall off and penetrate the skin, causing irritation. Many glochidia are barbed, complicating their removal and enhancing their persistence in the skin. Exposure to glochidia is an occupational hazard to fruit pickers and other outside workers in areas where Opuntioideae thrive, as the spines can persist in clothing and gloves and can become airborne under the right conditions.

In Lepidoptera

The larvae of Eutricha capensis (family Lasiocampidae) are practically covered with urticating hairs; the most potent are the stiff, short, orange-maroon bands across the thorax. Eutricha capensis Lasiocampidae larval anterior.jpg
The larvae of Eutricha capensis (family Lasiocampidae) are practically covered with urticating hairs; the most potent are the stiff, short, orange-maroon bands across the thorax.
Larva of Lonomia obliqua, the most toxicologically-significant species, to mammals, of its genus; stings are a medical emergency and require treatment with antivenom. Taturana.JPG
Larva of Lonomia obliqua , the most toxicologically-significant species, to mammals, of its genus; stings are a medical emergency and require treatment with antivenom.

Several lepidopteran families include species whose larvae bear urticating hairs. Families prominent in this respect include the following: [2] [3] [4] [5]

Adults of some species also have urticating scales, and some species shed some of their urticating hairs as defense for their pupae and eggs.

The urticating setae, or spines, can cause irritation when they break off and lodge in the skin of larger animals or humans. In some species, the setae are hollow, connecting to venom-producing cells, like a hypodermic needle. Generally, setae are only externally irritating, but may be more dangerous if contact is made with mucous membranes or if ingested; some can cause severe skin necrosis, eczema-like symptoms and shedding. Certain species of Lonomia (family Saturniidae) can inject venom that is life-threatening to humans. [6]

Stings do not often occur as a defense, but are mainly the result of brushing against the spines. However, many species, whose larvae are armed with these bristles, have evolved to utilize them as a defense mechanism against any perceived threat. For example, many larvae in the family Lasiocampidae bear dense bands of short, stinging bristles across their thoracic segments. The bristles are normally retracted into folds in the skin, but, if the caterpillar is disturbed, it will display its bristles, which are usually of contrasting colors; in nature, bright and/or contrasting colors are used by many invertebrates, amphibians, reptiles, fungi and plants as visual warnings for predators, indicating the presence of toxicity, venom or poison. The same defensive adaptation may also be seen as a 'bluff' technique in certain harmless species, in which they mimic the appearance of a similar-looking, toxic, species as a means of protection. For example (in reptiles), the coral snakes (family Elapidae) are well-known as venomous, while the non-venomous milk snakes (Colubridae) appear visually very similar, utilizing mimicry to their advantage.

If roughly stimulated or held, lasiocampid larvae are likely to writhe and lash about, forcing the stinging bristles into any vulnerable surface they can. Many other species of larvae lack any such localized concentrations of bristles and are armed more generally with urticating hairs; even so, they too will lash about frantically if disturbed, making them difficult to handle without suitable equipment. Toxins from the broken bristles may spill out, causing dermatitis on the surface of the skin. [7] For brown-tail moths (Euproctis chrysorrhoea) native to Europe and invasive in other parts of the world, bristles are shed or broken off during molts and can be wind-borne, so that direct contact with live or dead larvae is not required to trigger a rash. [8]

In spite of such defenses, some species of birds feed avidly on "hairy" caterpillars, grabbing them in their beaks and scrubbing them on the ground until the majority of the bristles have been stripped or damaged; at least a few species of cuckoos, apparently, collect the bristles in their digestive tracts until they form 'pellets' to be regurgitated. Examples of predators other than cuckoos that feed on "hairy" caterpillars include several reptiles and insectivorous mammal species, from several continents. [9] [10]

In tarantulas

Urticating hairs (setae) are found in about 90% of the species of tarantula (spiders of the family Theraphosidae) found in the New World. They are not found in tarantulas from other parts of the world. [11]

Development

Urticating hairs do not appear at birth but form with each consecutive molt, widening from molt to molt and outwardly presenting themselves around areas of more dark bristles on the upper back part of the abdomen of juveniles. In elder ages their coloration shifts to match the main tone of abdomen. Despite this shift, urticating hairs nonetheless retain unique characteristics that render them visually distinct from abdominal bristles, such as their tendency to cover only a portion instead of the entirety of the opisthosoma.

Types

There are seven different types of urticating hair known in tarantulas, varying in size and shape, particularly the distribution of barbs. [11]

Each type of urticating hair is believed to target different enemies. Defined targets for some bristle types are unknown.

Type II is usually not kicked off by the tarantula, rather delivered by direct contact. However, there is at least one aviculariine species— Caribena versicolor —which can kick type II urticating hairs off of the abdomen, similarly to species from the subfamily Theraphosinae. [12] Tarantulas from the genera Avicularia , Pachistopelma and Iridopelma possess Type II hairs (Hoover, 1997).

Type III urticating hairs are most efficient for defense against vertebrates and invertebrates. Types III and IV are the most irritating to mammalian predators.

Types particular to species

An adult female of a Brachypelma species, showing a bald patch after kicking bristles off of her abdomen. After molting, the bristles will grow again. Brachypelma smithi, urticating hairs.JPG
An adult female of a Brachypelma species, showing a bald patch after kicking bristles off of her abdomen. After molting, the bristles will grow again.

Not all urticating hair types are exhibited by each species of tarantula. Type II urticating hairs can be found in the genera Avicularia , Iridopelma and Pachistopelma (subfamily Aviculariinae). Type I and III urticating hairs are representative on a wide diversity of large bodied genera in the subfamily Theraphosinae: Lasiodora , Acanthoscurria , Nhandu , Megaphobema , Sericopelma , Eupalaestrus , Proshapalopus , Brachypelma , Cyrtopholis , and others, although some only have Type I in mature males. Unusually, Type III urticating hairs are found only on the species of Theraphosa , but these otherwise are similar to many species that also have Type I hairs.

Type III alone is found in many 'dwarf' new world genera, e.g. Hapalopus . Type IV is found in several South American genera, e.g. Grammostola , Euathlus etc. (exhibits types III and IV). Type V urticating hairs are typical of the species of the genus Ephebopus . They are located on the pedipalps. They are much shorter and lighter in contrast with other types of urticating hair. These are easily thrown by the spider into the air. [13] Type VI urticating hairs are found in the genus Hemirrhagus . [14]

Genera with the most urticating hairs are Lasiodora, Grammostola and Acanthoscurria. [15] [16]

Defensive behavior

New World tarantulas will, at the moment of danger, turn toward the attacker and briskly rub their hind legs against the opisthosoma throwing the urticating hairs in the direction of the enemy. The cloud of small bristles can get into the mucous membrane of small mammals and cause edema, which can be fatal. The bristles cause both mechanical and chemical harm to the skin and membranes.

Humans' reaction and the degree of irritation to a defensive urticating hair barrage can vary tremendously, based on the species in question. Some, such as those of the Chilean rose tarantula (Grammastola rosea) and the pinktoe tarantula (Avicularia avicularia), are fairly mild and innocuous to humans. Others, such as those of the Brazilian giant white knee tarantula (Acanthoscurria geniculata), are moderately irritating. Still others, such as the Goliath birdeater (Theraphosa blondi), are far more severe. These bristles can result in painful rashes, and have been likened to sharp shards of fiberglass.

After kicking urticating hairs, the tarantula will have a bald spot on its abdominal region.

As territorial markings

Urticating hairs are not just thrown at an enemy as a first line defense, but are also used as an indication of territory. They can be found on and around the burrow entrance and in webbing for protection (for example, some subfamily Theraphosinae species include these bristles in cocoon silk).

Urticating hairs protect tarantula egg sacs (Avicularia spp. and Theraphosa blondi, respectively). This is thought to discourage fly larvae from consuming their eggs and young.

Human reactions

Skin rash caused by the exposure to bristles shed by brown-tail moth larvae Euproctis Chrysorrhoea skin rash cutted.png
Skin rash caused by the exposure to bristles shed by brown-tail moth larvae

In humans, urticating hairs can cause allergic skin reactions which can manifest as inflammation, rash and itching. The reactions can last from several hours to weeks. [8] [17] Ophthalmia nodosa , an irritation reaction, can result when the barbed bristles lodge in the cornea. [18] Handlers are advised to wear eye protection. [18]

Notes

  1. ↑ Shultz, Stanley; Shultz, Marguerite (2009). The Tarantula Keeper's Guide. Hauppauge, New York: Barron's. p. 28. ISBN   978-0-7641-3885-0.
  2. ↑ Matheson 1950.
  3. ↑ Riley & Johannsen 1938.
  4. ↑ Roth & Eisner 1962.
  5. ↑ Wirtz 1984.
  6. ↑ Pinto, Antônio F.M.; Berger, Markus; Reck, José, Jr.; Terra, Renata M.S.; Guimarães, Jorge A. Lonomia obliqua venom: In vivo effects and molecular aspects associated with the hemorrhagic syndrome. Toxicon. Volume 56, Issue 7, 15 December 2010, pages 1103–1112
  7. ↑ "Stinging Caterpillars on Shrubs". University of Maryland Extension. 21 April 2021. Retrieved 16 September 2022.
  8. 1 2 "Browntail Moth" (PDF). Maine Department of Agriculture, Conservation & Forestry. Retrieved 16 September 2022.
  9. ↑ Wyllie, Ian (1981). The Cuckoo. Universe Books. ISBN   978-0-87663-371-7.
  10. ↑ McCullough, Deborah G.; Raffa, Kenneth A.; Chris Williamson R.; Natural Enemies of Gypsy Moth: The Good Guys. Michigan State University Extension Bulletin E-2700, April 1999
  11. 1 2 Bertani, Rogério & Guadanucci, José Paulo Leite (2013). "Morphology, evolution and usage of urticating setae by tarantulas (Araneae: Theraphosidae)". Zoologia (Curitiba). 30 (4): 403–418. doi: 10.1590/S1984-46702013000400006 .
  12. ↑ Bertani, R.; Boston, T.; Evenou, Y.; Guadanucci, J.P.L. (2003). "Release of urticating hairs by Avicularia versicolor (Walckenaer, 1837) (Araneae, Theraphosidae)". Bulletin of the British Arachnological Society. 12 (9): 395–398.
  13. ↑ Marshal & Uetz 1990.
  14. ↑ Perez-Miles 1998.
  15. ↑ Vellard 1936.
  16. ↑ Buecherl 1951.
  17. ↑ Hsu, Chao-Kai; Hsu, Mark Ming-Long; West, Rick C.; Chu, Yau-I (September 2007). "Skin Injury Caused by Urticating Hair of Tarantula". Dermatologica Sinica. 25 (3): 232–235. Retrieved 16 September 2022.
  18. 1 2 Norris, J.H.; Carim, Z.I.; Morrell, A.J. (2010). "Spiderman's eye" (PDF). The Lancet. 375 (9708): 92. doi:10.1016/s0140-6736(09)61672-x. PMID   20109868. S2CID   5506819. Archived from the original (PDF) on 25 December 2014. Retrieved 10 April 2013.

Related Research Articles

<span class="mw-page-title-main">Goliath birdeater</span> Species of tarantula from South America

The Goliath birdeater belongs to the tarantula family Theraphosidae. Found in northern South America, it is the largest spider in the world by mass and body length, and second to the giant huntsman spider by leg span. It is also called the Goliath tarantula or Goliath bird-eating spider; the practice of calling theraphosids "bird-eating" derives from an early 18th-century copper engraving by Maria Sibylla Merian that shows one eating a hummingbird. Despite the spider's name, it rarely preys on birds.

<span class="mw-page-title-main">Chilean rose tarantula</span> Species of arachnid

The Chilean rose tarantula, also known as the rose hair tarantula, the Chilean fire tarantula, or the Chilean red-haired tarantula, is probably the most common species of tarantula available in American and European pet stores today, due to the large number of wild-caught specimens exported cheaply from their native Chile into the pet trade. The species is also known from Bolivia and Argentina.

<i>Avicularia</i> Genus of spiders

Avicularia is a genus of the family Theraphosidae containing various species of arboreal tarantulas. The genus is native to Panama, the Caribbean, and tropical South America. Each species in the genus has very distinguishable pink foot pads.

<i>Brachypelma</i> Genus of spiders

Brachypelma is a genus of spiders in the family Theraphosidae (tarantulas). They may have bodies up to 6 cm long with legs of similar or greater lengths. Some species have brightly colored legs, with red or orange marks and rings.

<span class="mw-page-title-main">Brazilian whiteknee tarantula</span> Species of arachnid

The Brazilian whiteknee tarantula is a species of tarantula from Brazil that is commonly kept as a pet.

<span class="mw-page-title-main">Limacodidae</span> Family of moths

The Limacodidae or Eucleidae are a family of moths in the superfamily Zygaenoidea or the Cossoidea; the placement is in dispute. They are often called slug moths because their caterpillars bear a distinct resemblance to slugs. They are also called cup moths because of the shape of their cocoons.

<span class="mw-page-title-main">Saddleback caterpillar</span> Larva of an eastern North American moth

The saddleback caterpillar is the larva of a species of moth native to eastern North America. It is also found in Mexico. The species belongs to the family of slug caterpillars, Limacodidae.

In a zoological context, spines are hard, needle-like anatomical structures found in both vertebrate and invertebrate species. The spines of most spiny mammals are modified hairs, with a spongy center covered in a thick, hard layer of keratin and a sharp, sometimes barbed tip.

<span class="mw-page-title-main">Tarantula</span> Family of spiders

Tarantulas comprise a group of large and often hairy spiders of the family Theraphosidae. As of December 2023, 1,100 species have been identified, with 166 genera. The term "tarantula" is usually used to describe members of the family Theraphosidae, although many other members of the same infraorder (Mygalomorphae) are commonly referred to as "tarantulas" or "false tarantulas". Some of the more common species have become popular in the exotic pet trade. Many New World species kept as pets have setae known as urticating hairs that can cause irritation to the skin, and in extreme cases, cause damage to the eyes.

<i>Ochrogaster lunifer</i> Species of moth

Ochrogaster lunifer, the bag-shelter moth or processionary caterpillar, is a member of the family Notodontidae. The species was first described by Gottlieb August Wilhelm Herrich-Schäffer in 1855. Both the larval and adult forms have hairs that cause irritation of the skin (urticaria). The adult moth has a woolly appearance and its wings can grow to be about 5.5 cm across. The larvae feed on Grevillea striata at night and reside in brown silken bag nest during the day.

<i>Psalmopoeus irminia</i> Species of spider

Psalmopoeus irminia, also known as the Venezuelan suntiger, is a species of tarantula endemic to Venezuela, Guyana and Brazil. They were first described in 1994 by F. Saager.

<i>Ephebopus</i> Genus of spiders

Ephebopus is a genus of northeastern South American tarantulas that was first described by Eugène Louis Simon in 1892. Its relation to other tarantulas is one of the most uncertain in the family, and it has been frequently moved around and has been placed in each of the eight subfamilies at least once.

<i>Bumba</i> (spider) Genus of spiders

Bumba is a genus of tarantula native to the Americas. It is an uncommon genus, comprising eight known species, including one named after John Lennon. Like most related species in the subfamily Theraphosinae, they may flick urticating hairs in response to threats.

<i>Theraphosa stirmi</i> Species of spider

Theraphosa stirmi is a species of tarantula belonging to the family Theraphosidae. It is known as the burgundy goliath bird eater.

<i>Kankuamo marquezi</i> Species of spider

Kankuamo marquezi is the only species within the monotypic spider genus Kankuamo, in the family Theraphosidae. It is found in the Sierra Nevada de Santa Marta, Colombia. This spider has urticating hairs, the first to be classified as type VII. These sword-shaped, bristly hairs are used as a defense mechanism by stinging or stabbing. Most other species of tarantulas attack by throwing their hairs from a distance. Kankuamo hairs cover the entire body and have penetrating tips which will embed themselves into the skin or mucous membranes and cause severe irritation. Humans often experience mild to severe skin irritation or rashes.

<i>Caribena</i> Genus of spiders

Caribena is a genus of spiders in the family Theraphosidae (tarantulas), found in the Antilles. The two species accepted as of March 2017 were formerly placed in Avicularia. Apart from a different distribution – Avicularia species are found in mainland South and Central America – Caribena is distinguished by having longer and thinner type II urticating hairs in a conspicuous patch on the upper surface of the abdomen. Males also have a differently shaped palpal bulb.

<i>Avicularia juruensis</i> Species of spider

Avicularia juruensis is a species of spider in the family Theraphosidae, found in South America. Avicularia urticans was brought into synonymy in 2017. It has been given the English name Amazonian pink toe spider. Under the synonym Avicularia urticans, it is also known as the Peruvian pinktoe tarantula. It is a large mygalomorph spider, with a maximum body length over 30 mm (1.2 in) and the longest fully extended leg about 60 mm (2.4 in). Like other species in the genus Avicularia, specimens under this name are sold as pets, although their identity has not been confirmed by taxonomic studies.

<i>Caribena laeta</i> Species of spider

Caribena laeta is a species of spider in the family Theraphosidae, found in the US Virgin Islands, Puerto Rico, and Cuba, the last dubiously according to Caroline Fukushima and Rogério Bertani in 2017. It was first described by Carl Ludwig Koch in 1842 under the name Mygale laeta.

<i>Tliltocatl</i> Genus of tarantulas

Tliltocatl is a genus of North American tarantulas that was split off from Brachypelma in 2020. They are also large burrowing tarantulas, but don't have the striking red leg markings of Brachypelma species. A female T. vagans can grow up to 50 mm (2.0 in) long and legs can get as long as 55 mm (2.2 in). They are found predominantly in Mexico, with some species native to Central America. The name is derived from two Nahuatl words, "tlil", meaning "black", and "tocatl", meaning "spider". Habitat destruction and collection for the pet trade has led to this and Brachypelma to be protected under International Convention on International Trade of Endangered Species rules, beginning with B. smithi.

Plesiopelma paganoi is a tarantula in the Plesiopelma genus, this tarantula was first described by Nelson Ferretti and Jorge Barneche in 2014. It is named in honor of Luis G. Pagano, Argentinean ornithologist who helped to collect this species. It is found in Argentina, in the Salta province, next to the south Bolivia border.

References

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.