Real animal lice

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Real animal lice
Head louse

Head louse

Systematics
Order : Insects (Insecta)
Flying insects (Pterygota)
Paraneoptera
Superordinate : Psocodea
Order : Animal lice (Phthiraptera)
Subordination : Real animal lice
Scientific name
Anoplura
Leach , 1815

The real animal lice ( Anoplura ), also known as real lice or simply as lice , are a subordination of the animal lice. All species live as blood-sucking ectoparasites on mammalian species , including humans.

etymology

The altgerm. Insect name mhd. , Ahd. Lūs is with the kelt. Phrase of kymr. llau related to "lice"; further relationships are unclear.

features

Lice reach a body length between 0.35 millimeters ( Microphthirus , males) and 8 millimeters ( Pecaroecus ). Like all animal lice, they are dorsoventrally (from top to bottom) flattened, heavily sclerotized and completely wingless insects with a yellow, brown, or almost black color. The head is narrow when viewed from above, it is always narrower than the trunk (in contrast to the sub- orders Amblycera and Ischnocera, which are often summarized as jaw lice ). The freely visible, short antennae have only three to five links, of which the base link is the largest and the others are pearl-shaped. In the males they are transformed in some species. Some species have small, single-lens eyes, but most species are completely eyeless.

The piercing-sucking, stiletto-shaped mouthparts are retracted into the head capsule in the rest position and are only stretched forward during the act of sucking. The proboscis consists of two narrow, interlocked piercing bristles, which consist of the transformed hypopharynx and labium . During the act of piercing, the cone of the mouth is pressed onto the skin and anchored with teeth that can be pushed forward by hemolymph pressure, then the piercing bristles alternately penetrate the skin until a blood vessel is hit. The upper piercing bristle forms a food channel, the lower a saliva channel.

The head capsule is usually pinched back like a neck. The upper sclerites ( tergites ) of the three segments of the trunk ( thorax ) are seamlessly fused to form a continuous plate when viewed from above. Of the three well-developed pairs of legs sitting on the side, the first is the shortest, and usually the third is the longest. The legs are converted to retain in the coat of the host to clamp legs, whose two membered tarsi a single, strong claw ansitzt. As in most animal lice, both tarsal links are fused with the tibia to form an immobile structure, the tibiotarsus. The abdomen consists of ten segments, eight or nine of which are freely visible. The abdomen is heavily sclerotized on the sides, but flexible above and below in order to allow expansion during the blood meal. At the end of the abdomen, between the eighth and ninth (females) or ninth and tenth (males) segments, the mating organs are located in an inverted genital chamber, the opening of which in the males is surrounded by visible appendages (gonapophyses). The genital apparatus of males is large, heavily sclerotized and of complex construction, as in many insects it has essential characteristics for the identification of the species.

The intestine of the lice has an enlargement (goiter) for food storage in the front section. The midgut usually has two large blind sacs (caeca). Lice are dependent on symbiotic types of bacteria living in the intestine for nutrition, which enrich the animal with vitamins that are lacking in the very one-sided food substrate blood. The bacteria are particularly found in differentiated cells (bacteriocytes) of the intestinal and ovarian walls. It is transmitted through infection of the eggs laid by the female, i.e. vertically.

Reproduction

Lice are always bisexual. After the mostly very short copulation on the host, the female usually lays the eggs called "nits" individually, in which each egg is glued to the host's hair with a cement substance (in a few species the egg sits on a stalk). Each female lays around 15 to 100 eggs in the course of her life. The eggs open through a separate lid. The three larval stages (often called nymphs because they resemble the adults in physique and way of life) can be found all year round. As far as is known, the development time to the imago usually takes 2 to 4 weeks under favorable conditions; 3 to 4 generations can be passed through per year.

Hosts

Lice and their hosts are spread around the world, with the African fauna being particularly rich in species. All species of real animal lice are permanent, blood-sucking parasites of mammalian species. Humans are also hosts of two species ( human lice ). Most species are very host-specific, they only occur on one or a few closely related host species. Hosts are known from most orders of higher mammals . Exceptions are the bats (chiroptera), the Russell animals (Proboscidea), the tooth arms (Edentata) and scaled animals (Pholidota) and the aquatic whales (Cetacea) and sea cows (Sirenia) harboring no real louse. They are also absent from most predators (Carnivora) and insectivores (Insectivora). In total, real animal lice are suspected to be found in around 2,600 species of mammals, around two thirds of all species. In fact, they have so far only been proven in a good 800 of them.

Systematics and phylogeny

Antarctophthirus trichechi , parasite of the walrus ( Odobenus rosmarus )

The real animal lice form the suborder Anoplura, one of the four suborders of the animal lice or Phthiraptera. A synonymous name for the Anoplura is Siphunculata Latreille, 1825. About 530 to 540 species are known, so they are a relatively poor group of insects, whereby it is assumed that the actual number of species will be higher, around 1000 species.

There are still scientific controversies about the classification of the anoplura in the insect system. While they were traditionally placed in the order of the Phthiraptera, which was regarded as the sister group of the dust lice (order Psocoptera), alongside the pine lice known as the taxon Mallophaga , there are weighty arguments for a different classification today. The sister group of animal lice is therefore probably not the Psocoptera as a whole, but only a subgroup of what makes the dust lice paraphyletic . Presumably, however, the four subdivisions of animal lice do not form a monophyletic unit either, which is indicated by phylogenomic data and morphological studies. According to all data, the most likely sister group of the Anoplura is the species-poor group of the Rhynchophthirina or "proboscis lice" (with the elephant louse ), whose sister group is the Ischnocera. The Amblycera could, however, be the sister group of the book lice (Liposcelididae) counted among the dust lice or of the order Troctomorpha containing them. Many authors therefore today regard the Psocodea, the common clade of animal lice and the dust lice, as an order.

Today, 15 families of the Anoplura are mostly distinguished, whereby the monophyly of the traditional families Hoplopleuridae and Polyplacidae is doubted according to molecular data.

Individual evidence

  1. ↑ a b c d e f Eberhard Mey: 20th order Phthirapera, animal lice, Lauskerfe. In A. Kaestner & HE Gruner (editor): Textbook of special zoology. Volume 1, Invertebrates, Part 5: Insecta (edited by Holger H. Dathe). 2nd edition, 2003. Spectrum Academic Publishing House (Springer) Berlin / Heidelberg. 978 3827409300. Pages 308-330.
  2. ↑ a b Eberhard Mey: Phthiraptera - animal lice or Lauskerfe. In: Bernhard Klausnitzer (Hrsg.): Stresemann - excursion fauna of Germany. Volume 2: Invertebrates: Insects. Spectrum Akademischer Verlag (Springer), 2011, ISBN 978-3-8274-2452-5 , on pages 156–157.
  3. ^ The dictionary of origin (=  Der Duden in twelve volumes . Volume 7 ). Reprint of the 2nd edition. Dudenverlag, Mannheim 1997 ( p. 408 ). See also DWDS ( "Laus" ) and Friedrich Kluge : Etymological dictionary of the German language . 7th edition. Trübner, Strasbourg 1910 ( p. 280 ).
  4. ^ A b Ke Chung Kim & Herbert W. Ludwig (1978): The family classification of Anoplura. Systematic Entomology 3: 249-284.
  5. ↑ Harald W. Krenn & Horst Aspöck (2012): Form, function and evolution of the mouthparts of blood-feeding Arthropoda. Arthropod Structure & Development 41: 101-118. doi: 10.1016 / j.asd.2011.12.001
  6. ^ A b Lance A. Durden & Guy G. Musser (1994): The sucking lice (Insecta, Anoplura) of the world: a taxonomic checklist with records of mammalian hosts and geographical distributions. Bulletin of the American Museum of Natural History 218. 90 pages.
  7. ↑ Eberhard Mey (2003) provides an overview of the historical classification: On the development of animal louse systematics (Insecta, Phthiraptera) up to the present day. Rudolstädter Naturhistorische Schriften 11: 115-134.
  8. ↑ Kazunori Yoshizawa & Kevin P. Johnson (2010): How stable is the "Polyphyly of Lice" hypothesis (Insecta: Psocodea) ?: A comparison of phylogenetic signal in multiple genes. Molecular Phylogenetics and Evolution 55 (3): 939-951. doi: 10.1016 / j.ympev.2010.02.026
  9. ↑ Kazunori Yoshizawa & Kevin P. Johnson (2006): Morphology of male genitalia in lice and their relatives and phylogenetic implications. Systematic Entomology 31: 350-361 doi: 10.1111 / j.1365-3113.2005.00323.x
  10. ↑ Kevin P. Johnson & Vince S. Smith: Psocodea Species File Online. Version 5.0 / 5.0. , accessed on August 18, 2017.
  11. ↑ Jessica E Light, Vincent S Smith, Julie M Allen, Lance A Durden, David L Reed (2010): Evolutionary history of mammalian sucking lice (Phthiraptera: Anoplura). BMC Evolutionary Biology 2010, 10: 292. doi: 10.1186 / 1471-2148-10-292