Culex pipiens molestus

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Culex pipiens molestus
Culex Molestus.jpg

Culex pipiens molestus

Systematics
Order : Fly (Diptera)
Subordination : Mosquitoes (Nematocera)
Family : Mosquitoes (Culicidae)
Genre : Culex
Type : Common mosquito ( Culex pipiens )
Subspecies : Culex pipiens molestus
Scientific name
Culex pipiens molestus
( Forskål , 1775)

Culex pipiens molestus is an independent form of the common mosquito thatlivesexclusively in the immediate vicinity of humans, i.e. synanthropically . Their taxonomic status, whether species, subspecies, shape or biotype, is controversial. In the more northerly parts of its range, such as in Northern and Central Europe , it is strikingly adapted to subterranean habitats. The mosquito is a possible vector of the West Nile virus and, as such, is particularlyfearedin the USA . It was abducted worldwide and occurs today on all continents, it is also very common in Germany.

discovery

The species complex around the common mosquito Culex pipiens is one of the most difficult among the two-winged mosquitoes , but it is intensively researched because of the great annoyance of some of the species and their role as vectors of disease. Already in earlier centuries, researchers noticed that within what had been classified according to morphological criteria (already by Carl von Linné ) as the species Culex pipiens , two types could be distinguished, one of which is preferred in birds , the other in mammals , including the human, sucks. Other differences between them were later discovered. Although the form that suckles on humans has also been described as a species of its own, it was not possible to find reliable distinctive differences in shape; all morphological features used for this are variable and overlap between the populations . Therefore these early descriptions were synonymous with Culex pipiens by later taxonomists . English researchers noticed in the 1990s that the form sucking on humans occurs frequently subterranean, for example in the underground ( London Underground ); In 1999 it was possible for the first time to differentiate them according to genetic characteristics. Thereafter, this form was identified in numerous places around the world.

Morphological features

The form Culex pipiens molestus can not be reliably distinguished from the nominate form Culex pipiens pipiens on the basis of morphological features alone. The expression of features is variable.

  • Length of the piercing proboscis ( Proboscis ) - In f. molestus , the trunk length is shorter to the same length as the first four segments of the maxillary probe , at f. pipiens longer.
  • Coloring - specimens of f. molestus are mostly a little lighter in color, without noticeable light spots on the tips of the thighs and rear rails.

These and some other proposed morphological features overlap, however, in the case of offspring of genetically uniform lines, individual individuals with the features of the “wrong” form also appear again and again.

Genetic traits and hybrids

A differentiation of the forms on the basis of the mitochondrial DNA or on the basis of strains of the parasitic bacterium Wolbachia is also problematic, both are not differentiable in this way from the more warmth-loving, southern subspecies quinquefasciatus (regarded as a species by many taxonomists). This is probably due to the fact that today's populations are influenced by introgression with mating of individuals of the different species / subspecies. A differentiation of the species by means of conventional DNA barcoding (using the mtDNA) should then be impossible. At least one researcher reported in 2007 that they had found a corresponding marker.

Electrophoretic analysis of the DNA showed that the various local populations of the “underground” form molestus show more genetic similarities to one another than to the respective populations of the pipiens form in immediately adjacent aboveground habitats. This finding means that, contrary to earlier assumptions, the molestus form does not represent a local adaptation of pipiens strains to the underground habitat. Rather, the molestus form probably only emerged once and was then carried over to these habitats. Presumably f. molestus from southern Europe or the Mediterranean region , where both forms live side by side ( sympatric ) in above-ground habitats. Here hybrids occur between the forms, but z. B. also in the Netherlands , where such hybrids z. T. next to f. molestus live underground. Due to the differences in the way of life, hybrids in Northern and Central Europe should not be viable above ground, because they do not insert a diapause and would freeze to death in winter.

Features of the way of life

While the two forms are very similar in physique and appearance, they differ markedly in some characteristics of the life cycle and the way of life:

  • Host : While f. pipiens specializes in birds and occurs only in exceptional cases in mammals, preferably f. molestus mammals, especially humans, as hosts.
  • Blood meal: females from f. In order to lay eggs, pipiens are absolutely dependent on having previously sucked blood from a vertebrate , whose nutrients they need for egg maturation. Female of f. Molestus, on the other hand, can produce the first egg clutch without a blood meal. This is known as "autogeny".
  • Mating behavior: The males of Culex pipiens pipiens form the swarms that are typical for mosquitoes , into which the females fly in search of a mating partner. The mating of C. pipiens molestus , on the other hand, can also take place in narrow, restricted spaces, which is called "stenogamy". This behavior makes the permanent colonization of underground habitats possible.
  • Wintering mode: Both forms overwinter as adults. While the adult females of f. pipiens, however, keep a diapause in winter and do not reproduce, is f. molestus is active all year round and continues to reproduce in suitable locations without a break. This is particularly annoying for people who are stung this way even in winter.

The way of life of f. pipiens and f. molestus is otherwise comparable with the exception of the striking preference for underground habitats. Both forms develop as larvae in all types of water, even in the smallest accumulations of water and organically heavily polluted water. Because they breathe oxygen in the air, they do not need oxygen in the water. The molestus form is also dependent on water. It doesn't necessarily have to be underground tunnels: The widespread use of cisterns for the production of process water in residential buildings has meanwhile enabled the form to be widely used in residential areas. In this habitat they are largely protected from conventional measures to combat mosquitoes.

Meaning as a vector

Like many blood-sucking insects , this mosquito can act as a vector of disease. It is particularly feared as a carrier of the West Nile virus. This disease can be transmitted from birds to humans, while human-to-human transmission is considered unlikely. But the mosquito can serve as a "bridge vector" that brings about the transmission. In the USA, the form, which is very likely only recently introduced by humans, occurs in both birds and mammals.

Individual evidence

  1. ↑ a b Ralph E. Harbach, Bruce A. Harrison, Adel M. Gad (1984): Culex (Culex) molestus Forskal (Diptera: Culicidae): neotype designation, description, variation, and taxonomic status. Proceedings of the Entomological Society of Washington 86 (3): pp. 521-542
  2. ^ Katherine Byrne & Richard A. Nicols (1999): Culex pipiens in London Underground tunnels: differentiation between surface and subterranean populations. Heredity 82: pp. 7-15.
  3. ↑ a b c Elena B. Vinogradova (2003): Ecophysiological and morphological variations in mosquitoes of the Culex pipiens complex (Diptera: Culicidae). In: Acta Societatis Zoologicae Bohemicae 67: pp. 41-50.
  4. ↑ Célestine M. Atyame, Frédéric Delsuc, Nicole Pasteur, Mylène Weill, Olivier Duron (2011): Diversification of Wolbachia Endosymbiont in the Culex pipiens Mosquito. Molecular Biology and Evolution Volume 28 Issue 10: pp. 2761-2772. on-line
  5. ↑ EV Shaikevich (2007): PCR-RFLP of the COI gene Reliably differentiates Cx. pipiens, Cx. pipiens f. molestus and Cx. torrentium of the Pipiens Complex. European Mosquito Bulletin 22: pp. 25-30
  6. ↑ Thomas Weitzel, Amandine Collado, Artur Jöst, Kerstin Pietsch, Volker Storch, Norbert Becker (2009): Genetic Differentiation of Populations within the Culex pipiens Complex and Phylogeny of Related Species. Journal of the American Mosquito Control Association 25 (1): pp. 6-17. doi : 10.2987 / 08-5699.1
  7. ↑ a b Dina M. Fonseca, Nusha Keyghobadi, Colin A. Malcolm, Ceylan Mehmet, Francis Schaffner, Motoyoshi Mogi, Robert C. Fleischer, Richard C. Wilkerson (2004): Emerging Vectors in the Culex pipiens Complex. Science 303: pp. 1535-1538
  8. ↑ Bruno Gomes, Carla A. Sousa, Maria T. Novo, Ferdinando B. Freitas, Ricardo Alves, Ana R. Côrte-Real, Patrícia Salgueiro, Martin J Donnelly, António PG Almeida, João Pinto (2009): Asymmetric introgression between sympatric molestus and pipiens forms of Culex pipiens (Diptera: Culicidae) in the Comporta region, Portugal. BMC Evolutionary Biology 2009, 9: p. 262, doi : 10.1186 / 1471-2148-9-262 .
  9. ↑ CBEM Reusken, A. de Vries, J. Buijs, MAH Braks, W. den Hartog, E.-J. Scholte (2010): First evidence for the presence of Culex pipiens biotype molestus in the Netherlands, and of hybrid biotype pipiens and molestus in northern Europe. Journal of Vector Ecology, Vol. 35 no.1: pp. 210-212
  10. ↑ Christine Chevillon, Roger Eritj, Nicole Pasteur, Michel Raymond (1995): Commensalism, adaptation and gene flow: mosquitoes of the Culex pipiens complex in different habitats. Genetical Research, Volume 66 Issue 02: pp. 147-157, doi : 10.1017 / S0016672300034492 .
  11. ↑ N. Becker, A. Jost, V. Storch, T. Weitzel (1999): Exploiting the biology of urban mosquitoes for their control. Proceedings of the 3rd International Conference on Urban Pests: pp. 425-429.

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