Xenos vesparum
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| Rossi , 1793 |
Xenos vesparum is a parasitoid or endoparasitoid from the order of the fan wing . It only affects wasps . The first description of this species was made by Pietro Rossi (1738-1804) in 1793.
The name is derived from the ancient Greek word ξένος (Xenos), which means foreigner or enemy of war. The second part of the name is derived from the Latin term Vespa ( wasp ). Put together, Xenos vesparum can be translated as "wasp enemy".
features
The female animals reach a body length of about 7.5 millimeters. Due to their permanent parasitic way of life, the female lacks legs and wings. The sense organs such as antennae and eyes are also not developed. They have a mouth that they use to ingest their host's hemolymph , but they have no pronounced mouthparts .
Since the development cycle of Xenos vesparum goes hand in hand with the death of the host , Xenos vesparum is strictly speaking a parasitoid and not a parasite .
Since the only function of the female is reproduction, she has a special strategy of brood care. The chitin shell is not shed completely after moulting, but remains on the animal ( puparium ). The shell forms a brood chamber that is open to the front, in which the female lays up to 1000 eggs. From these larvae hatch , which have a length of about a quarter of a millimeter.
In contrast to the female, the male is significantly smaller ( sexual dimorphism ). Its size is only about 2 mm, and its only work in life is to find and mate a female that is sitting in a wasp. Since it is free living in its last phase of life, unlike the female, it has complete legs, wings and sense organs. The wings are large in relation to the body size and allow a fast flight. They can be folded like a fan . This is also the reason for the name fan-winged wing . The opposite of the two-winged wings, only the rear wing pair is formed. The front pair of wings atrophied in the course of evolution into swinging bulbs . The male has poorly developed mouth parts and does not eat any food during his short life. It only lives a few hours in which it has to find a female to mate.
Host animals
Xenos vesparum feeds as a parasitoid on the hemolymph of the host animal . The main organs of the host are not damaged. Xenos vesparum only attacks field wasps of the genus Polistes :
- Polistes biglumis (mountain field wasp)
- Polistes dominulus (Gallic field wasp)
- Polistes gallicus (outdated: Gallic field wasp)
- Polistes nimpha (heather field wasp)
The infected wasps are also called stylopized wasps. The name comes from the scientific name of the subordination of the great fan wing , Stylopidia , which refers to the genus Stylops with a similar way of life.
Occurrence
The species is restricted to the range of its host. Like its host, it is distributed in North Africa , southern and central Europe and southern Scandinavia , east to the Urals .
Way of life and reproduction
If a larva of Xenos vesparum encounters a wasp, the larva bores into the wasp's abdomen. The females remain in their host until the imago stage, and parts of their bodies are visible between the wasp's abdominal rings.
Here she feeds on her host's hemolymph without killing him. The growth of the Xenos vesparum larva is at the expense of the host. The wasps are weakened by the parasitoid way of life. Stylopized wasps are usually smaller than their uninfected conspecifics. Infestation of many wasps in a colony can kill the entire state .
Control of the host organism
The larva of Xenos vesparum influences the behavior of the host. While uninfected wasps look for food, take care of the brood or defend the nest, the infested insect withdraws more and more and no longer takes part in the tasks within the insect state.
What is remarkable about Xenos vesparum is that the parasitoids gain complete control over the behavior of their host. Exactly how this happens is currently unknown (as of 2014), but the goal of various research projects.
When the infected wasps swarm out, the parasitic fan-winged birds can control them in such a way that several infected wasps can find each other. Because of this 'remote-controlled' behavior, the infested wasp is also referred to as the zombie wasp in popular scientific literature . If several infected wasps meet, controlled in this way, the males of Xenos vesparum drill themselves out of the host's body to mate with one of the females, half of which protrude almost motionless between the abdomen segments of the infected field wasps . The males leave their host completely, while the females only wriggle out as far as is necessary for mating.
pairing
During mating, the male inserts his penis into the female's brood canal. It penetrates the wall of the breeding canal and injects the sperm directly into the female's body cavity.
While the host of the male of Xenos vesparum dies after the adult male has left the wasp body, the host of the female animal continues to live. As with many other insects, the males die soon after mating. The females develop with the fertilized eggs in the host animal.
The eggs initially grow in the female's body cavity. At a certain stage of development they are placed in the brood cavity.
A remarkable change in behavior is now taking place in the stylopized wasps. While uninfected female workers of the wasps do not hibernate and die, the infected wasps behave like queens and hibernate in the burrow .
Development of the larvae
The larvae develop from the eggs in the puparium . When these have reached a size of about 1/4 mm, they leave the host organism. The larvae have point eyes and legs and can move independently. The larvae of Xenos vesparum are released in places where wasps can also be found. These can be feeding places preferred by the wasps, but also the construction of the wasp colony. If the larva encounters a wasp, it bores into it. The larva later sheds its skin and develops into a maggot-like stage. In the following spring, the development cycle of Xenos vesparum is completed. The newly developed larvae are released near the wasp colony.
Diseases
Xenos vesparum can be attacked by molds of the genus Penicillium .
Individual evidence
- ↑ Ragnar K. Kinzelbach: Fungal attack on male puparia from Xenos vesparum Rossi. In: Journal of Parasitic Studies. 30, 2007, pp. 113-116.
literature
- L. Beani: Crazy wasps: when parasites manipulate Polistes phenotype. In: Annales Zoologici Fennici. 43, 2006, pp. 464-574.
- H.-J. Wing: Current records of the fan wing Xenos vesparum Rossi, 1793 from Northern Hesse. In: Communications of the international entomological association. 34, 2009, pp. 143-149.
- H.-W. Pohl: Phylogeny and evolution of the fan-winged (Insecta: Strepsiptera). Habilitation thesis. University of Rostock, 2004.
- H. Pohl, J. Oehlke: Directory of the fan-winged (Strepsiptera) Germany. In: Entomofauna Germanica. 6, (2003), pp. 273-275.
- J. Smit, JT Smit: Xenos vesparum komt hogerop. In: Nieuwsbrief Sectie Hymenoptera. Nederlandse Entomologische Vereniging, 28, 2008, pp. 46-47.
- R. Dallai, L. Beani, J. Kathirithamby, P. Lupetti, BA Afzelius: New findings on sperm ultrastructure of Xenos vesparum. In: Tissue and Cell. 35, 2003, p. 19 ff.
- Fabiola Giusti, Luigi Dallai, Laura Beani, Fabio Manfredini, Romano Dallai: The midgut ultrastructure of the endoparasite Xenos vesparum (Rossi) (Insecta, Strepsiptera) during post-embryonic development and stable carbon isotopic analyzes of the nutrient uptake. In: Arthropod Structure & Development. 36, 2007, p. 183 ff.
