Tsetse flies

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Tsetse flies
Fig. From Meyer's Lexicon 1888/90

Fig. From Meyer's Lexicon 1888/90

Systematics
Order : Fly (Diptera)
Subordination : Flies (Brachycera)
Partial order : Muscomorpha
Superfamily : Hippoboscoidea
Family : Tongue flies
Genre : Tsetse flies
Scientific name of the  family
Glossinidae
Theobald , 1903
Scientific name of the  genus
Glossina
Wiedemann , 1830
Preparation of a tsetse fly
The head and mouthparts of Glossina morsitans

As tsetse flies ( Glossina ), probably of Setswana : tsetse = "Fly", also briefly tsetse is called the only kind from the family of the tongue flies (Glossinidae). The flies are common in Africa, feed on human and animal blood and transmit the dreaded African trypanosomiasis, known as sleeping sickness , and the related Nagana disease in animals . A total of over 30 species and subspecies of tsetse flies are distinguished.

features

They are small to medium-sized flies (6-14 mm) with a relatively narrow body. Characteristic is the posture of the wings, which when sitting in the resting position, like with scissors, are exactly laid over one another lengthwise on the abdomen and thereby a tongue shape ("Glossa" from Greek γλῶσσα, glō̂ssa , "tongue, speech, language", over Latin glossa ) form. The generic name is derived from this. This wing position allows the tsetse fly to be easily distinguished from other flies.

The trunk is a fine, stiff hollow bristle the length of the spinal cord, without kinking and with an onion-shaped thickening at the base; the tsetse flies are capillary suckers . The feather bristle (arista) of the antennae is double-pinnate, i. H. every single feather again bears secondary leaflets; besides, only the front of the Arista is feathered.

The genitals of the males show a strong bulge on the lower surface of the last abdominal section ( hypopygium ).

Tsetse flies have specialized cells that bacterial , absolutely necessary in some cases (obligatory) Endo symbionts included that they need for their survival. These are the species Wigglesworthia glossinidia and Sodalis glossinidius . Bacteria of the species Wolbachia pipientis can also be found, which are regarded as not absolutely necessary (facultative) symbionts (here: a bacterium that benefits from a mutual community).

Reproduction and development

The tsetse flies are viviparous ( larviparia ). The larva is housed in the abdomen until birth and, similar to the other Hippoboscoidea - louse flies (Hippoboscidae) and bat flies ( Nycteribiidae with Streblidae ) - is nourished by a "mammary gland" for 10 days (adenotrophic viviparia ). In the rainy season they give birth to only one offspring each time: a larva of yellowish-brown color, which has twelve segments and is almost as big as the fly itself.

Preferred breeding places are shady areas where the larva can be deposited in the ground. After the birth it moves around vigorously, looks for a protective place where it changes its color and turns into a brown-black doll after about 1 to 2 hours. After about 3 to 4 weeks (depending on the climatic conditions) the young fly hatches. The location of the larval deposit is different for the individual species.

Way of life

The tsetse flies are diurnal and live mainly in dense, moist forest areas. Important species such as Glossina morsitans also live independently of larger surface water in the open bush savannah . The tsetse flies sting almost exclusively outdoors. The sting is very painful and therefore cannot go unnoticed. Tsetse flies perceive their host mainly with their compound eyes before they approach it. The sense of smell probably only plays a role when approaching the victim.

Vectors of disease

Tsetse flies transmit trypanosomes , parasitic unicellular organisms that cause various diseases. So the kind transfers Glossina palpalis the sleep illness of humans, Glossina morsitans also the Naganaseuche at various domestic animals, especially in horses . In tsetse flies, both males and females sting, so that both sexes can transmit trypanosomes.

In the flies, the trypanosomes undergo a change in shape and a phase of reproduction. About three weeks after taking blood, the trypanosomes accumulate in the fly's salivary gland . When a new host is attacked, the parasites are then transmitted. The tsetse flies transmit the unicellular parasites to humans as well as to many wild animals and domestic animals, so that there is a wide reservoir for the pathogen and an eradication of the transmitted disease is unlikely. In many regions of tropical Africa, many people are at risk, over 300,000 are already infected and 30,000 new infections are recorded every year. Tsetse flies also cause major economic losses in cattle farming in tropical Africa, as there is a lack of milk to feed the children and cattle as meat suppliers and work animals in the affected areas.

Tsetse flies do not specifically bite a blood vessel like the female Anopheles mosquitoes do. They generate rather with their mouthparts , much like the brakes , a wound from which it blood and lymph absorb (called Telmophagen ). As a result, they are able to use the blood of almost all types of vertebrates while sitting on the skin . In the case of an infection, a doughy, reddish and painful swelling develops at the injection site after 3 to 10 days, which heals by itself after several days or weeks. It is called trypanosome chancre and represents the first stage of sleeping sickness. After a few days or weeks and months it comes to the second stage, which is caused by swelling of the lymph nodes , fever, headache and body aches as well as blotchy, itchy rashes, swellings on the body and Weight loss can be marked. The third stage is reached when, after weeks or more than a year, the central nervous system is affected and severe sleep disorders with insomnia as well as disorders of body coordination, language and food intake occur. There is currently no vaccine against sleeping sickness and if left untreated, the disease is often fatal.

A distinction is made between two pathogens of African sleeping sickness, which are transmitted by different subgroups of tsetse flies: Trypanosoma brucei rhodesiense , the pathogen of East African sleeping sickness, and Trypanosoma brucei gambiense , the pathogen of West African sleeping sickness, which only occurs in humans, named after David (Bruce ) . The carrier of the West African form is the so-called Palpalis group, whose representatives prefer to stay in the riparian forests of lakes and rivers. The East African form of sleeping sickness is transmitted by the Morsitans group, whose representatives live in the dry bush.

Combat

With differently designed special tsetse traps, a certain monitoring and restriction of the tsetse populations is possible . In the tropical belt of Africa, the SIT process ( sterile insect technology , means pest control through sterilization) has now seen the first successes in the fight against tsetse flies. An IAEA project has succeeded in exterminating the tsetse flies on Zanzibar . Sufficient cattle farming for milk and meat production has now become possible there. The successes in the fight against the tsetse flies have also fed the hope that the SIT procedure can also be used successfully for the control of the Anopheles mosquitoes . It should be noted, however, that SIT only makes sense after the fly density has been reduced using insecticides and traps. The success of SIT in Zanzibar is very unlikely to be achievable on the mainland because flies from other areas can immigrate again and again. The extermination of the tsetse flies across Africa would require the continuous cooperation of all affected states and their own stability. Targeted control of tsetse is therefore of an economic and political nature. It should also be examined whether the intentional, total extermination of a species would be ethically justifiable at all , or whether the control of the distribution areas by the affected population with the support of the United Nations would not be more desirable.

species

literature

  • mentioned by Meyers in 1909:
    • Austen: A monograph of the Tsetse flies. London 1903.
    • Sander: The tsetsen. Leipzig 1905.
    • Stuhlmann: Contributions to the knowledge of the tsetse (s). Berlin 1907.
  • Paul de Kruif : David Bruce. On the trail of the tse-tse fly. In: Paul de Kruif: Microbe hunters. (Original edition: Microbe Hunters. Harcourt, Brace & Co., New York 1926) Orell Füssli Verlag, Zurich / Leipzig 1927; 8th edition ibid 1940, pp. 242-267.
  • P. Nagel: A fly in Africa - What role does the tsetse fly play in the balance of nature and what happens when it is exterminated? In: From research and medicine. 3rd year, Issue 1, Schering Aktiengesellschaft, Berlin 1988, S, pp. 91-105.
  • JA Van Vesten: The Tsetse Fly 'Glossina fuscipes fuscipes' Newstead, 1911, in East Africa; some aspects of its biology and its role in the epidemiology of human and animal trypanosomiasis. Doctoral thesis. University of Amsterdam, 1971.
  • AM Jordan: Tsetse-flies (Glossinidae). In: RP Lane, RW Crosskey (Ed.): Medical Insects and Arachnids. Chapman & Hall, London / New York 1993, Chapter 9.
  • S. Aksoy, RV Rio: Interactions among multiple genomes: tsetse, its symbionts and trypanosomes. In: Insect biochemistry and molecular biology. (Insect Biochem Mol Biol) July 2005, Volume 35, No. 7, pp. 691-698; Epub: March 28, 2005, Review PMID 15894186 .

Individual evidence

  1. ↑ Greek alphabet: Ancient Greek transcription
  2. ↑ Fritz Cl. Werner: Word elements of Latin-Greek technical terms in the biological sciences (= Suhrkamp Taschenbuch. Volume 64). 1st edition, Suhrkamp Taschenbuch Verlag, Frankfurt am Main 1972, ISBN 3-518-06564-5 , p. 206.
  3. ↑ Julia Walochnik, Horst Aspöck: Tsetse flies, trypanosomes and sleeping sickness - the deadliest parasitosis. In: Horst Aspöck (ed.): Sick through arthropods (= Denisia. No. 30, ISSN  1608-8700 ). Province of Upper Austria, Biology Center of the Upper Austrian State Museums, Linz 2010, pp. 641–645.
  4. ^ S. Aksoy, RV Rio: Interactions among multiple genomes: tsetse, its symbionts and trypanosomes. In: Insect biochemistry and molecular biology. (Insect Biochem Mol Biol.). July 2005, Vol. 35, No. 7, pp. 691-698; Epub: March 28, 2005, doi: 10.1016 / j.ibmb.2005.02.012 . PMID 15894186 .
  5. ↑ Geoffrey M. Attardoa, Claudia Lohs, Abdelaziz Heddi, Uzma H. ​​Alama, Suleyman Yildirim, SerapAksoy: Analysis of milk gland structure and function in Glossina morsitans : Milk protein production, symbiont populations and fecundity , in: Journal of Insect Physiology, Volume 54, No. 8, August 2008, pp. 1236-1242, doi: 10.1016 / j.jinsphys.2008.06.008
  6. ↑ J. Bouyer et al: The Ethics of Eliminating Harmful Species: The Case of the Tsetse Fly. In: BioScience. 2018, Volume 69, No. 2, pp. 125-135. doi: 10.1093 / biosci / biy155 .

Web links

Commons : Tsetsefliegen  - Collection of pictures, videos and audio files