Culicoides
| Culicoides | ||||||||||||
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Culicoides imicola , females at different stages of a blood meal |
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| Scientific name | ||||||||||||
| Culicoides | ||||||||||||
| Latreille , 1809 |
Culicoides is a genus of the midges (family Ceratopogonidae) with almost worldwide distribution. With 1343 recent species (plus 44 only fossil found in amber , as of 2014) it is the species-richest genus of midges, which alone contains around a fifth of its species. The species of the genus are difficult to determine, it contains numerous morphologically hardly distinguishable crypto-species and numerous still undescribed species are suspected, especially in tropical latitudes. Females of Culicoides are most commonly bloodsuckers of vertebrates, including humans and their domestic animals. They have received particular attention as the vector of numerous diseases, including bluetongue in sheep.
features
Adults
In Culicoides concerns very small mosquitoes with a body length from 1 to 3 millimeters. The adults are similar in habit to numerous other mosquitoes such as the (very closely related) mosquitoes (Chironomidae). The head of the mosquito has large compound eyes that take up large parts of the head, these are approached or moderately far apart on the top of the head, or they butt directly against one another. As with all culicomorpha, the ocelles are missing . The antennae are relatively long, they consist of the two basic members (whereby the scapus is very small and covered by the pedicellus ) and an antenna whip of 13 segments. The last limb of the flagellum is rounded to pointy, but never has a separate point (in contrast to Forcipomyia ). Only in the males do the whorl-shaped rings of very long hairs (setae) have whorled rings, these are usually located on the whip-hips up to the tenth and are longer than the diameter of the associated antennae, they are usually not vertical, but are directed a little forward. On the first limb of the flagellum there are usually two such rings from Setae. These setae can also be missing in a few species.
In both sexes the head has a proboscis, which is used as a proboscis in the females of most species. The proboscis is formed from the toothed labrum , the mandibles , the hypopharynx , the laciniae of the maxillae and the labium . The saw-shaped mandibles are interlocked and act as piercing bristles when they are moved forward and backward. The upper side of the mandibles and the labium form a tube for the blood, while the lower side with the needle-shaped hypopharynx forms a channel for the flow of saliva. The maxillae and labium serve as covering and supporting structures, with the laciniae being introduced into the wound. To the side of the trunk sit the long, five-limbed maxillary palps that serve as sense organs .
The thorax is arched (hump-shaped) on top and protrudes over the head. He wears the three pairs of legs and the wings. The wings of the genus in almost all species have a conspicuous pattern on light and dark spots, which is formed by sitting, somewhat flaky, widened dark hair. In many cases the determination of the species, and even the subgenera, is based on this wing drawing. For example, a key to identify the Spanish species was created using the wing drawing. The legs have few special features. The tarsi are five-limbed, the claws are only slightly curved (in contrast to Forcipomyia ) and are of the same size among each other, they have no adhesive pad ( empodium ). The tibia of the front legs, as well as the hind legs, have a well-developed spur and also comb-shaped rows of bristles that serve as a cleaning device.
The abdomen consists of ten segments. Usually the dorsal sclerites ( tergites ) are more sclerotized than the ventral sternites , so that the upper side appears dark and the lower side light. The pleurs are membranous, which allows the abdomen to expand when eating. Inside the abdomen there are one to three spermathecae in females, the shape of which is sometimes helpful in determining the species. The males have a copulation apparatus with two gonopods at the end of their abdomen, which has numerous species-specific features.
Larvae
The larvae of Culicoides species reach about 4 to 7 millimeters in length. They live aquatic on the bottom and in the bank zone of bodies of water or semi-aquatic in other, water-saturated substrates such as peat and dung . These are white, yellowish or gray colored, smooth, elongated worm-shaped, mostly relatively hard sclerotized and recognizable segmented animals without extremities or any traces of them. They have no open stigmas . The body consists of the easily recognizable, free head capsule, three trunk and nine abdominal segments. The head is protruding with the mouthparts pointing forward (prognath). Inside there is a large, heavily sclerotized organ called the pharyngeal complex that shows through to the outside; it is used to grind food. The mouthparts are relatively short and work in parallel rather than against each other. The antennas are short and inconspicuous, they are four-segment. On the side of the head there are two dark eye spots that shimmer through the cuticle; there are no pronounced external structures such as lenses. The head is set off from the trunk by a narrowed, neck-shaped sclerite. With the exception of the head capsule, the body only has very short, inconspicuous setae that cannot be seen at all when viewed simply or with a magnifying glass.
The larvae of Culicoides cannot normally be identified right down to the species and can hardly be reliably distinguished from other genera of the Ceratopogoninae. Compared to the larvae of some other genera, they can be distinguished by the fact that the bristles (setae) on the top of the head are simple, not feather-shaped or tufted. The larval stages of a good 10 percent of the species have so far been known and described.
Culicoides has four larval stages.
Dolls
In the aquatic species, the pupae of the genus sit in the bank zone so that they can breathe air with their horns called extensions. They are attached to the hard ground. The pupae of Culicoides sit freely without the abdomen being enveloped in the last larval skin as an exuvia. The tip of the abdomen has two thorn-like appendages (never lengthened like a paddle as in many mosquitos). The third pair of legs is usually tucked under the wing sheaths so that only its tip is visible. The breathing horns of the dolls are undivided and simple, only weakly pigmented, long, and end with a simple row of numerous stigmas. They almost always have a surface sculpture of scales or narrow rings. The abdominal segments have no glandular fields on the abdominal side. Your metathorax is completely divided by a suture on the dorsal side.
Ecology and way of life
The larvae of Culicoides move with characteristic, meandering movements through the inhabited substrate, the aquatic species can swim quite well with similar movement patterns. You are agile and fast. As far as is known, most species live in small, also temporary, pool-like bodies of water and in the banks of rivers. Some species, which are also economically important, prefer special habitats such as salt marshes on the coast of the sea, cesspools or water-filled hollows in tree trunks. Culicoides obsoletus and Culicoides scoticus have been found in maize silage , a number of species including Culicoides dewulfi and Culicoides chiopterus in ruminant dung; these species are able to sting and possibly infect pets even when they are far from water. The development time is, depending on the species and climatic conditions, about two to ten weeks. In the temperate climate of Central Europe, however, the larvae often overwinter, which increases the development time accordingly. For the larvae a predatory way of life is usually indicated, but at least some species obviously also feed on detritus , algae or decomposed plant remains.
The imaginal mosquitoes mostly live in the vicinity of the larval habitats, mostly bodies of water, from which they rarely move further; occasionally, however, they can be blown away over long distances by the wind. Here the females look for hosts to sting. In a few species there is no more food intake in the imaginal stage, the mouthparts are partially receded and can no longer be pricked. Few species sting other insect species and suck up their hemolymph . However, the majority of species suck blood in vertebrates. The hosts are mainly located chemically, with carbon dioxide sensors being of particular importance. The host specificity of almost all species is unknown, since almost only stings are registered in humans and domestic animals and the wider host range is almost never recorded. The blood meal serves almost exclusively for the formation of eggs, it is not necessary for the mosquito's nourishment. Some species can lay at least one clutch without a blood meal. With blood, like the other species, they lay several eggs.
The males are known as flower visitors and feed primarily on nectar. They form swarms over trees and bushes, which help to determine the gender, in which pheromones are also involved.
The mosquitoes are mostly active at dusk, but a few are active throughout the day. In the temperate climate, most adults fly in spring, but adults can be found all year round. Depending on the species, one or more generations are known per year.
Disease transmission
The blood-sucking females of numerous Culicoides species are known as vectors of pathogens, especially from domestic and farm animals. In Central Europe, the bluetongue disease caused by viruses has become particularly well known here because this disease used to occur only further south and only spread to Central Europe since around 2006. Presumably, the infection is not due to gradual spread, for example for climatic reasons, but to the introduction of transport from a distant region. Contrary to false press reports, the genus Culicoides did not immigrate, but has always been native to Central Europe (the species Culicoides imicola has actually immigrated, but is no longer considered an essential vector in Central Europe). The mosquitoes have been shown to transmit more than 50 other pathogens belonging to the arboviruses , of which the so-called Schmallenberg virus, which is closely related to the Akabane virus , made headlines with its sudden new appearance in Central Europe (Sauerland). Other infectious diseases are known both in Europe and worldwide. In addition to viruses, filariae and protozoa (e.g. of the genera Haemoproteus , Hepatocystis and Leucocytozoon ) are also transmitted by Culicoides .
Taxonomy and Distribution
Within the large genus, 31 sub-genera were distinguished, which, however, comprise only two thirds of the known species. For the remaining species, the affiliation to a subgenus is unclear or could not be specified by the descriptor of the species. A catalog of the world's fauna was compiled by Art Borkent of the Royal British Columbia Museum and is regularly updated online. Because of the economic importance of blood-sucking females, the taxonomy of the genus is based almost exclusively on female traits, although in most cases the males are easier to identify. Species identification using molecular methods such as DNA barcoding has begun but is still in its infancy. A major problem here is incorrect reference information. An overview of identification and identification methods in the genus is provided by Culicoides Latreille (Diptera: Ceratopogonidae) taxonomy: Current challenges and future directions by Harrup and colleagues.
Culicoides species live in all climates and on all continents except Antarctica. About 60 species of the genus have been recorded in Germany
Types (selection)
swell
- Ryszard Szadziewski, Jarosław Krzywiński, Wojziech Giłka: Diptera Ceratopogonidae: Biting Midges. In Anders Nilsson (editor): Aquatic Insects of Noth Europe: a taxonomic handbook. Volume 2. Apollo Books, Stenstrup, 1997. ISBN 87-88757-55-2
- Species Borkent: Insecta: Diptera, Ceratopogonidae. In: Catherine Mary Yule, Hoi-Sen Yong (editors): Freshwater Invertebrates of the Malaysian Region. Kuala Lumpur, Academy of Sciences Malaysia, 2004. ISBN 9834193602
- Dustin Swanson (2012): Ecology and Phylogeny of the Biting-Midge Genus Culicoides (Diptera: Ceratopogonidae). Diss., Clemson University, 2002.
- Anja Stephan (2012): Entomological and molecular genetic studies of the midges fauna (Diptera: Ceratopogonidae) in Germany. Diss., Institute for Parasitology and Tropical Veterinary Medicine of the Department of Veterinary Medicine at the Free University of Berlin.
Individual evidence
- ↑ Peter Rawlings (1996): A key, based on wing patterns of Biting Midges (Genus Culicoides Latreille, Diptera, Ceratopogonidae) in the Iberian Peninsula, for the use in epidemiological studies. Graellsia 52: 57-71.
- ↑ Armin RW Elbers, Rudy Meiswinkel, Erik van Weezep, Marianne M. Sloet van Oldruitenborgh-Oosterbaan, Engbert A. Kooi (2013): Schmallenberg Virus in Culicoides spp. Biting Midges, the Netherlands, 2011. Emerging Infectious Diseases 19 (1) doi : 10.3201 / eid1901.121054
- ↑ Simon Carpenter, Martin H. Groschup, Claire Garros, Maria Luiza Felippe-Bauer, Bethan V. Purse (2013): Culicoides biting midges, arboviruses and public health in Europe. Antiviral Research 100 (1): 102-113. doi : 10.1016 / j.antiviral.2013.07.020
- ↑ PS Mellor, J. Boorman, M. Baylis (2000): Culicoides Biting Midges: Their Role as Arbovirus Vectors. Annual Review of Entomology 45: 307-340 doi : 10.1146 / annurev.ento.45.1.307
- ↑ Art Borkent (2014): World Species of Biting Midges (Diptera: Ceratopogonidae). Download PDF
- ↑ LE Harrup, GA Bellis, T. Balenghien, C. Garros (2015): Culicoides Latreille (Diptera: Ceratopogonidae) taxonomy: Current challenges and future directions. Infection, Genetics and Evolution 30: 249-266. doi : 10.1016 / j.meegid.2014.12.018
- ↑ Peter Havelka & Maria Aguilar: Ceratopogonidae. in H. Schuhmann, R. Bährmann, A. Stark (editor): Entomofauna Germanica 2. Checklist of Diptera in Germany. Studia Dipterologica Supplement. Halle (Saale). Pp. 33-38.
- ↑ Doreen Werner: Research project 2808HS007 "Entomological investigations to combat bluetongue disease". Final report for the differentiation of the species (fine determination) and the determination of single dnits in the virus detection of the entomological monitoring including the presentation of the status of the molecular biological work. Research report, Leibniz Center for Agricultural Landscape Research (ZALF) eV, 2010
