Anopheles gambiae

The Anopheles gambiae complex consists of at least seven morphologically indistinguishable species of mosquitoes in the genus Anopheles. The complex was recognised in the 1960s and includes the most important vectors of malaria in sub-Saharan Africa, particularly of the most dangerous malaria parasite, Plasmodium falciparum.[2] It is one of the most efficient malaria vectors known. The An. gambiae mosquito additionally transmits Wuchereria bancrofti which causes Lymphatic philariasis, more commonly known as elephantiasis.[3]

Anopheles gambiae
Scientific classification
Kingdom:
Animalia
Phylum:
Arthropoda
Class:
Insecta
Order:
Diptera
Family:
Culicidae
Subfamily:
Anophelinae
Genus:
Anopheles
Species complex:
A. gambiae sensu lato
Species:
A. arabiensis, A. bwambae, A. melas, A. merus, A. quadriannulatus, Anopheles gambiae sensu stricto
Binomial name
Anopheles gambiae
The tube-like heart (green) extends along the body, interlinked with the diamond-shaped alary muscles (also green) and surrounded by pericardial cells (red). Blue depicts cell nuclei.

Discovery and elements

The Anopheles gambiae complex or Anopheles gambiae sensu lato was recognized as a species complex only in the 1960s. The A. gambiae complex consists of:

  • Anopheles arabiensis
  • Anopheles bwambae
  • Anopheles melas
  • Anopheles merus
  • Anopheles quadriannulatus[4]
  • Anopheles gambiae sensu stricto[5]
  • Anopheles coluzzii
  • Anopheles amharicus

The individual species of the complex are morphologically difficult to distinguish from each other, although it is possible for larvae and adult females. The species exhibit different behavioural traits. For example, Anopheles quadriannulatus is both a saltwater and mineralwater species. A. melas and A. merus are saltwater species, while the remainder are freshwater species.[6] Anopheles quadriannulatus generally takes its blood meal from animals (zoophilic), whereas Anopheles gambiae sensu stricto generally feeds on humans, i.e. is considered anthropophilic. Identification to the individual species level using the molecular methods of Scott et al. (1993)[7] can have important implications in subsequent control measures.

Anopheles gambiae in the strict sense

An. gambiae s.s. has been discovered to be currently in a state of diverging into two different species—the Mopti (M) and Savannah (S) strains—though as of 2007, the two strains are still considered to be a single species. The An. gambiae s.s. genome has been sequenced three times, once for the M strain, once for the S strain, and once for a hybrid strain.[8][9] Currently, ~90 miRNA have been predicted in the literature (38 miRNA officially listed in miRBase) for An. gambiae s.s. based upon conserved sequences to miRNA found in Drosophila.

The mechanism of species recognition appears to be sounds emitted by the wings and identified by Johnston's organ.[10]

Fecundity

Fecundity of A. gambiae depends on the detoxification of reactive oxygen species (ROS) by catalase.[11] Reduction in catalase activity significantly reduces reproductive output of female mosquitoes, indicating that catalase plays a central role in protecting oocytes and early embryos from ROS damage.[11]

Historical note

An. gambiae invaded northeastern Brazil in 1930, which led to a malaria epidemic in 1938/1939.[12] The Brazilian government assisted by the Rockefeller Foundation in a programme spearheaded by Fred Soper eradicated these mosquitoes from this area. This effort was modeled on the earlier success in eradication of Aedes aegypti as part of the yellow fever control program. The exact species involved in this epidemic has been identified as An. arabiensis.[13]

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References
  1. Giles, G.M. (1902). A handbook of the gnats or mosquitoes giving the anatomy and life history of the Culicidae together with descriptions of all species noticed up to the present date. John Bale, Sons & Danielsson, Limited. London, United Kingdom. 530pp
  2. "Anopheles gambiae complex". Walter Reed Army Institute of Research. Archived from the original on 2007-09-29.
  3. "Lymphatic filariasis". www.who.int. Retrieved 2020-04-10.
  4. Besansky NJ, Powell JR, Caccone A, Hamm DM, Scott JA, Collins FH (July 1994). "Molecular phylogeny of the Anopheles gambiae complex suggests genetic introgression between principal malaria vectors". Proc. Natl. Acad. Sci. U.S.A. 91 (15): 6885–8. doi:10.1073/pnas.91.15.6885. PMC 44302. PMID 8041714.
    Wilkins EE, Howell PI, Benedict MQ (2006). "IMP PCR primers detect single nucleotide polymorphisms for Anopheles gambiae species identification, Mopti and Savanna rDNA types, and resistance to dieldrin in Anopheles arabiensis". Malar. J. 5 (1): 125. doi:10.1186/1475-2875-5-125. PMC 1769388. PMID 17177993.
  5. Yakob L (2011) Epidemiological consequences of a newly discovered cryptic subgroup of Anopheles gambiae.Biol Lett
  6. G.B. White (1974). "Anopheles gambiae complex and disease transmission in Africa". Trans R Soc Trop Med Hyg. 68 (4): 278–298. doi:10.1016/0035-9203(74)90035-2. PMID 4420769.
  7. C. Fanello; F. Santolamazza; A. Della Torre (2002). "Simultaneous identification of species and molecular forms of the Anopheles gambiae complex by PCR-RFLP". Medical and Veterinary Entomology. 16 (4): 461–4. doi:10.1046/j.1365-2915.2002.00393.x. PMID 12510902.
  8. "Anopheles gambiae: First genome of a vector for a parasitic disease". Genoscope.
  9. Lawniczak, M. K.; et al. (Oct 22, 2010). "Widespread divergence between incipient Anopheles gambiae species revealed by whole genome sequences". Science. 330 (6003): 512–4. doi:10.1126/science.1195755. PMC 3674514. PMID 20966253.
  10. Pennetier C, Warren B, Dabiré KR, Russell IJ, Gibson G (2009) "Singing on the wing" as a mechanism for species recognition in the malarial mosquito Anopheles gambiae. Curr. Biol.
  11. DeJong RJ, Miller LM, Molina-Cruz A, Gupta L, Kumar S, Barillas-Mury C (February 2007). "Reactive oxygen species detoxification by catalase is a major determinant of fecundity in the mosquito Anopheles gambiae". Proc. Natl. Acad. Sci. U.S.A. 104 (7): 2121–6. doi:10.1073/pnas.0608407104. PMC 1892935. PMID 17284604.
  12. Killeen GF (October 2003). "Following in Soper's footsteps: northeast Brazil 63 years after eradication of Anopheles gambiae". Lancet Infect Dis. 3 (10): 663–6. doi:10.1016/S1473-3099(03)00776-X. PMID 14522266.
  13. Parmakelis A, Russello MA, Caccone A, et al. (January 2008). "Historical analysis of a near disaster: Anopheles gambiae in Brazil". Am. J. Trop. Med. Hyg. 78 (1): 176–8. doi:10.4269/ajtmh.2008.78.176. PMID 18187802.
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