Louse


Louse
Phthiraptera
Light micrograph of Fahrenholzia pinnata
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Subclass: Pterygota
Infraclass: Neoptera
Order: Phthiraptera
Haeckel, 1896
Suborders

Anoplura
Rhyncophthirina
Ischnocera
Amblycera

Lice (singular: louse) is the common name for over 3,000 species of wingless insects of the order Phthiraptera; three of which are classified as human disease agents. They are obligate ectoparasites of every avian and mammalian order except for monotremes (the platypus and echidnas), bats, whales, dolphins, porpoises and pangolins.

Contents

Biology

Most lice are scavengers, feeding on skin and other debris found on the host's body, but some species feed on sebaceous secretions and blood. Most are found only on specific types of animals, and, in some cases, only to a particular part of the body; some animals are known to host up to fifteen different species, although one to three is typical for mammals, and two to six for birds. For example, in humans, different species of louse inhabit the scalp and pubic hair. Lice generally cannot survive for long if removed from their host.[1]

A louse's color varies from pale beige to dark gray; however, if feeding on blood, it may become considerably darker. Female lice are usually more common than the males, and some species are even known to be parthenogenetic. A louse's egg is commonly called a nit. Many lice attach their eggs to their host's hair with specialized saliva; the saliva/hair bond is very difficult to sever without specialized products. Lice inhabiting birds, however, may simply leave their eggs in parts of the body inaccessible to preening, such as the interior of feather shafts. Living lice eggs tend to be pale white. Dead lice eggs are more yellow.[1]

Lice are exopterygotes, being born as miniature versions of the adult, known as nymphs. The young moult three times before reaching the final adult form, usually within a month of hatching.[1]

Ecology

Lice are optimal model organisms to study the ecology of contagious pathogens since their quantities, sex-ratios etc. are easier to quantify than those of other pathogens. The ecology of avian lice has been studied more intensively than that of mammal lice.

A few major trends

  1. The average number of lice per host tends to be higher in large-bodied bird species than in small ones.[2]
  2. Louse individuals exhibit an aggregated distribution across bird individuals, i.e. most lice live on a few birds, while most birds are relatively free of lice. This pattern is more pronounced in territorial than in colonial—more social—bird species.[3]
  3. Host taxa that dive under the water surface to feed on aquatic prey harbor fewer taxa of lice.[4][5]
  4. Bird taxa that are capable of exerting stronger antiparasitic defense—such as stronger T cell immune response or larger uropygial glands—harbor more taxa of Amblyceran lice than others.[6][7]
  5. Temporal bottlenecks in host population size may cause a long-lasting reduction of louse taxonomic richness.[8] E.g., birds introduced into New Zealand host fewer species of lice there than in Europe.[9][10]
  6. Louse sex ratios are more balanced in more social hosts and more female-biased in less social hosts, presumably due to the stronger isolation among louse subpopulations (living on separate birds) in the latter case.[11]

A few effects of lice infestation upon the host

  1. Lice may reduce host life expectancy.[12]
  2. Lice may transmit microbial diseases or helminth parasites.[13]
  3. Ischnoceran lice may reduce the thermoregulation effect of the plumage, thus heavily infected birds lose more heat than other ones.[14]
  4. Lice infestation is a disadvantage in the context of sexual rivalry.[15][16]

Classification

The order has traditionally been divided into two suborders, the sucking lice (Anoplura) and the chewing lice (Mallophaga); however, recent classifications suggest that the Mallophaga are paraphyletic and four suborders are now recognized:

  • Anoplura: sucking lice, occurring on mammals exclusively
  • Rhyncophthirina: parasites of elephants and warthogs
  • Ischnocera: mostly avian chewing lice, however, one family parasitizes mammals
  • Amblycera: a primitive suborder of chewing lice, widespread on birds, however, also live on South-American and Australian mammals

It has been suggested that the order is contained by the Troctomorpha suborder of Psocoptera.

Lice in humans

Humans host three different kinds of lice: head lice, body lice, and pubic lice. Lice infestations can be controlled with lice combs, and medicated shampoos or washes. Adult and nymphal lice can survive on sheep-shearers' moccasins for up to 10 days, but microwaving the footwear for five minutes in a plastic bag will kill the lice.[17]

Human lice and DNA discoveries

Lice have been the subject of significant DNA research that has led to discoveries on human evolution. For example, recent DNA evidence suggests that pubic lice spread to humans approximately 2,000,000 years ago from gorillas.[18] Additionally, the DNA differences between head lice and body lice provide corroborating evidence that humans started losing body hair, also about 2,000,000 years ago.[19]

Gallery

See also

References

  1. ^ a b c H. V. Hoell, J. T. Doyen & A. H. Purcell (1998). Introduction to Insect Biology and Diversity (2nd ed.). Oxford University Press. pp. 407–409. ISBN 0-19-510033-6. 
  2. ^ Rózsa L 1997. Patterns in the abundance of avian lice (Phthiraptera: Amblycera, Ischnocera). Journal of Avian Biology, 28, 249–254.
  3. ^ Rékási J et al. 1997. Patterns in the distribution of avian lice (Phthiraptera: Amblycera, Ischnocera). Journal of Avian Biology, 28, 150–156.
  4. ^ Felső B et al. 2006. Reduced taxonomic richness of lice (Insecta: Phthiraptera) in diving birds. Journal of Parasitology, 92, 867–869.
  5. ^ Felső B et al. 2007. Diving behaviour reduces genera richness of lice (Insecta: Phthiraptera) of mammals. Acta Parasitologica, 52, 82–85.
  6. ^ Møller AP et al. 2005. Parasite biodiversity and host defenses: Chewing lice and immune response of their avian hosts. Oecologia, 142, 169–176.
  7. ^ Møller AP et al. 2010. Ectoparasites, uropygial glands and hatching success in birds. Oecologia, 163, 303–311.
  8. ^ Rózsa L 1993. Speciation patterns of ectoparasites and "straggling" lice. International Journal for Parasitology, 23, 859–864.
  9. ^ Paterson AM et al. 1999. How Frequently Do Avian Lice Miss the Boat? Implications for Coevolutionary Studies Systematic Biology, 48, 214–223
  10. ^ MacLeod C et al. 2010. Parasites lost – do invaders miss the boat or drown on arrival? Ecology Letters,
  11. ^ Rózsa L et al. 1996. Relationship of host coloniality to the population ecology of avian lice (Insecta: Phthiraptera). Journal of Animal Ecology, 65, 242–248.
  12. ^ Brown CR et al. 1995. Ectoparasites reduce long-term surviviorship of their avian host. Proceedings of the Royal Society of London B 262, 313–319.
  13. ^ Barlett CM 1993. Lice (Amblycera and Ischnocera) as vectors of Eulimdana spp. (Nematoda: Filarioidea) in Charadriiform birds and the necessity of short reproductive periods in adult worms. Journal of Parasitol, 79, 85–91.
  14. ^ Booth DT et al. 1993. Experimental demonstration of the energetic cost of parasitism in free-ranging hosts. Proceedings of the Royal Society of London B, 253, 125–129.
  15. ^ Clayton DH 1990. Mate choice in experimentally parasitized rock doves: lousy males lose. American Zoologist, 30, 251–262.
  16. ^ Garamszegi LZ et al. 2005. Age-dependent health status and song characteristics. Beahvioral Ecology, 16,580–591.
  17. ^ "Sheep parasites". Government of Queensland. http://www2.dpi.qld.gov.au/sheep/10042.html. Retrieved November 10, 2008. 
  18. ^ David L. Reed, Jessica E. Light, Julie M. Allen & Jeremy J. Kirchman (2007). "Pair of lice lost or parasites regained: the evolutionary history of anthropoid primate lice". BMC Biology 5: 7. doi:10.1186/1741-7007-5-7. PMC 1828715. PMID 17343749. http://www.biomedcentral.com/1741-7007/5/7. 
  19. ^ John Travis (August 23, 2003). The naked truth? Lice hint at a recent origin of clothing. 164. Science News. pp. 118. http://findarticles.com/p/articles/mi_m1200/is_8_164/ai_107897267/. 

External links


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Look at other dictionaries:

  • Louse — (lous), n.; pl. {Lice} (l[imac]s). [OE. lous, AS. l[=u]s, pl. l[=y]s; akin to D. luis, G. laus, OHG. l[=u]s, Icel. l[=u]s, Sw. lus, Dan. luus; perh. so named because it is destructive, and akin to E. lose, loose.] (Zo[ o]l.) 1. Any one of… …   The Collaborative International Dictionary of English

  • louse — [lous; ] for v., also [ louz] n. pl. lice and, for LOUSE 4, louses [ME lous < OE lus (pl. lys), akin to Ger laus < IE * lūs > Welsh lleuen, Bret laouen] 1. a) any of an order (Anoplura) of small, flat, wingless insects with sucking… …   English World dictionary

  • LOUSE — (Heb. כִּנָּם ,כִּנִּים in plural. Talmud כִּנָּה, singular), insect; one of the ten plagues with which Egypt was smitten (Ex. 8:13–14; Ps. 105:31) was the plague of lice. The כֵּן in Isaiah (51.6): They that dwell therein shall die kemokhen may… …   Encyclopedia of Judaism

  • louse — (n.) parasitic insect infecting human hair and skin, O.E. lus, from P.Gmc. *lus (Cf. O.N. lus, M.Du. luus, Du. luis, O.H.G. lus, Ger. Laus), from PIE *lus louse (Cf. Welsh lleuen louse ). Slang meaning obnoxious person is from 1630s. The plural …   Etymology dictionary

  • Louse — (louz), v. t. To clean from lice. You sat and loused him. Swift. [1913 Webster] …   The Collaborative International Dictionary of English

  • louse — ► NOUN 1) (pl. lice) a small wingless parasitic insect which infests human skin and hair. 2) (pl. lice) a related insect which lives on the skin of mammals or birds. 3) (pl. louses) informal a contemptible person. ► VERB (louse u …   English terms dictionary

  • louse — n. /lows/; v. /lows, lowz/, n., pl. lice /luys/ for 1 3, louses for 4, v., loused, lousing. n. 1. any small, wingless insect of the order Anoplura (sucking louse), parasitic on humans and other mammals and having mouthparts adapted for sucking,… …   Universalium

  • louse — de·louse; ja·louse; jea·louse; louse·berry; louse; pa·louse; tou·louse; …   English syllables

  • louse — I UK [laʊs] / US noun [countable] Word forms louse : singular louse plural lice 1) Word forms louse : plural lice a small insect that lives on the bodies of animals and people 2) informal an unpleasant person II UK [laʊs] / US verb Word forms… …   English dictionary

  • louse — noun 1》 (plural lice) a small wingless parasitic insect which infests human skin and hair. [Pediculus humanus (see body louse, head louse).]     ↘a related insect which lives on the skin of mammals or birds. [Orders Anoplura (sucking lice) and… …   English new terms dictionary


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