Culex sp.

May 16th, 2018

Introduction
Culex is a genus of mosquitoes, several species of which serve as vectors of one or more important diseases of birds, humans, and other animals. The diseases they vector include arbovirus infections such as West Nile virus, Japanese encephalitis, or St. Louis encephalitis, but also filariasis and avian malaria. They occur worldwide except for the extreme northern parts of the temperate zone, and are the most common form of mosquito encountered in some major US cities such as Los Angeles.

Etymology

Culex is latin term for a midge or gnat: culex [1].

Description

Depending on the species, the adult Culex mosquito may measure from 4–10 mm (0.2–0.4 in). The adult morphology is typical of flies in the suborder Nematocera with the head, thorax, and abdomen clearly defined and the two fore wings held horizontally over the abdomen when at rest. As in all Diptera capable of flight, the second pair of wings is reduced and modified into tiny, inconspicuous halteres.

Culex quinquefasciatus E-A-Goeldi 1905

Culex quinquefasciatus : male on the left and female on the right (source wikimedia)

Formal identification is important in mosquito control, but it is demanding and requires careful measurements of bodily proportions and noting the presence or absence of various bristles or other bodily features [2].

In the field informal identification is more often important, and the first question as a rule is whether the mosquito is anopheline or culicine. Given a specimen in good condition, one of the first things to notice is the length of the maxillary palps. Especially in the female, palps as long as the proboscis are characteristic of anopheline mosquitoes. Culicine females have short palps. Anopheline mosquitoes tend to have dappled or spotted wings, while culicine wings tend to be clear. Anopheline mosquitoes tend to sit with their heads low and their rear ends raised high, especially when feeding, while culicine females keep their bodies horizontal.

Anopheline larvae tend to float horizontal at the surface of the water when not in motion, whereas culicine larvae float with head low and only the siphon at the tail held at the surface.

Vector role

Diseases borne by one or more species of Culex mosquitoes vary in their dependence on the species of vector. Some are rarely and only incidentally transmitted by Culex species, but Culex and closely related genera of culicine mosquitoes readily support perennial epidemics of certain major diseases if they become established in a particular region.

Arbovirus infections transmitted by various species of Culex include West Nile virus, Japanese encephalitis, St. Louis encephalitis, and Western and Eastern equine encephalitis. Brazilian scientists are investigating if Culex species transmit zika virus [3].
Nematode infections, mainly forms of filariasis may be borne by Culex species, as well as by other mosquitoes and blood-sucking flies.
Protist parasites in the phylum Apicomplexa, such as various forms of avian malaria

Nonanal has been identified as a compound that attracts Culex mosquitoes, perhaps pheromonally [4][5][6]. Nonanal acts synergistically with carbon dioxide [7].

Diversity

Culex is a diverse genus. It comprises over 20 subgenera that include a total of well over 1000 species. Descriptions of newly described species are frequent.

(source & for more information : wikipedia)

Bibliographic references

  1. “culex”. dictionary.com. Retrieved 2011-07-06.
  2. Harbach, Ralph. “Culex Mosquito Taxonomic Inventory“
  3. “Brazilian experts investigate if ‘common mosquito’ is transmitting zika virus”. March 27, 2016. Retrieved 2016-03-07.
  4. “UC Davis Researchers Identify Dominant Chemical That Attracts Mosquitoes to Humans”. University of California, Davis. October 26, 2009. Retrieved 2011-07-06.
  5. Syed, Z.; Leal, W. S. (2009). “Acute olfactory response of Culex mosquitoes to a human- and bird-derived attractant”. Proceedings of the National Academy of Sciences. 106 (44): 18803–8. doi:10.1073/pnas.0906932106. PMC 2767364 Freely accessible. PMID 19858490.
  6. Hill, Sharon R.; Hansson, Bill S.; Ignell, Rickard (January 15, 2009). “Characterization of Antennal Trichoid Sensilla from Female Southern House Mosquito, Culex quinquefasciatus Say”. Chemical Senses. Oxford University Press. 34 (3): 231–252. doi:10.1093/chemse/bjn080. PMID 19153252.
  7. “Scientists Identify Key Smell that Attracts Mosquitoes to Humans”. U.S. News & World Report. October 28, 2009. Retrieved 2011-07-06.

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