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Anopheles gambiae

By Jason Prior

Geographic Range

The Anopheles gambiae complex is widely distributed throughout Africa. (Roberts and Janovy, Jr., 2000)

Habitat

Individuals live throughout Africa, as long as water is readily available. Some species prefer fresh water, while others within the Anopheles gambiae complex live near water with high saline concentrations. (Blackwell and Johnson, June, 2000; Evans, 1938)

  • Aquatic Biomes
  • lakes and ponds
  • rivers and streams
  • temporary pools
  • brackish water

Physical Description

Mosquitoes, like all insects, have three body segments: a head, thorax, and abdomen. The thoracic segment possesses three pairs of legs and a pair of wings used for flight. The hind wings are modified into balancing appendages called halteres. Male antennae have significantly more hair like structures, called setae, which aid in locating females. The general coloration of this species is yellowish brown to brown with the last segment of the body normally all dark. The legs are spotted or speckled as an adult, and females normally have three pale bands on their palpi. The wings have pale scales that are creamy white and tinged with yellow. Anopheles gambiae larvae are 5-6 mm long and they are colored in much the same manner as the muddy water in which they are found. They breathe underwater through posterior spiracular plates on the 8th abdominal segment. (Evans, 1938; Roberts and Janovy, Jr., 2000)

  • Sexual Dimorphism
  • sexes colored or patterned differently

Development

Anopheles gambiae development is holometabolous, with four larval instar stages followed by a non-feeding pupal stage where the organism undergoes complete metamorphosis from the larval form to the adult morphology. All mosquito larvae and pupae are aquatic. The larvae eat small pieces of organic matter, while the pupae eat nothing and do not move. (Comstock, 1920; Roberts and Janovy, Jr., 2000)

Reproduction

Adults mate almost immediately after emerging.

Adults mate soon after emerging from their pupae. Females require blood meals to mature their fertilized eggs. Some species in the Anopheles gambiae complex are freshwater breeders while others prefer saltwater, but mosquito eggs must remain in contact with water to survive. Females lay their eggs singly on the surface of the water, up to 200 eggs at a time. The presence of water is necessary for the development of the eggs and larvae. Some species in the Anopheles gambiae complex prefer small, shaded pools and rice fields to lay their eggs, while others prefer water with a high salinity concentration. Despite the site preference, the pools of water are almost always exposed to direct sunlight. (Comstock, 1920; Roberts and Janovy, Jr., 2000)

Behavior

When at rest, Anopheles gambiae larvae float horizontally beneath the water's surface. The larvae breathe underwater through posterior spiracular plates on the 8th abdominal segment instead of through an air tube. This feature allows larvae to remain submerged underwater with only a small portion of their body exposed to the air.

Anopheles gambiae is especially adept at breeding in areas created by humans. After taking a blood meal, females often rest on nearby walls within the human host's residence. This behavior may provide an opportunity to eradicate this species from villages and homes in Africa through residual insecticide use.

In addition, adults in the genus Anopheles have a distinctive resting and feeding posture. While at rest, the head, mouth and abdomen are nearly in a straight line, but when feeding the body is inclined at a sharp angle to the host's body. (Roberts and Janovy, Jr., 2000)

Communication and Perception

Females locate their hosts using a variety of sensory receptors, but respond to movement, carbon dioxide gradients, and sweat. Also, two odorant-binding proteins (OBP) have been isolated in Anopheles gambiae, which are hypothesized to aid female's search for human hosts. ("World Health Organization", 2004; Konate, et al., September, 1999; Meijerink, et al., June, 2000; Roberts and Janovy, Jr., 2000)

Food Habits

All Anopheles gambiae females are temporary ectoparasites, living in the environment and coming to the host to feed. The females require blood meals to mature their eggs. Males, however, are non-parasitic and feed on plant fluids. Females do not display a tremendous amount of host specificity, but research indicates Anopheles gambiae preferentially feeds on humans. Females locate their hosts using a variety of sensory receptors, but respond to movement, carbon dioxide gradients, and sweat. Also, two odorant-binding proteins (OBP) have been isolated in Anopheles gambiae, which are hypothesized to aid female's search for human hosts. ("World Health Organization", 2004; Konate, et al., September, 1999; Meijerink, et al., June, 2000; Roberts and Janovy, Jr., 2000)

  • Animal Foods
  • blood
  • Plant Foods
  • nectar
  • sap or other plant fluids

Predation

Mosquitos are food for many types of birds, bats, frogs, lizards, and spiders.

Ecosystem Roles

These mosquitoes are disease vectors, and also provide food to predators.

Species Used as Host

Economic Importance for Humans: Positive

Anopheles gambiae have no known positive economic impact on humans.

Economic Importance for Humans: Negative

In the United States, mosquitoes are often thought of as a pest and a nuisance. Anopheles gambiae is much more than a simple pest, it is responsible for the transmission of malaria and other serious diseases throughout Africa. Anopheles gambiae transmits Plasmodium falciparum, which is the most severe of the four malarial agents. Although this disease was wiped out in the United States, it remains a world health hazard. There are an estimated 300 to 500 million cases of malaria each year and as a result, 1.5 to 2.7 million deaths worldwide. Continental sub-Sahara Africa, however, accounts for roughly 90% of all malarial cases worldwide. (Nchinda, 1998)

  • Negative Impacts
  • injures humans
    • bites or stings
    • carries human disease
  • household pest

Conservation Status

Other Comments

Anopheles gambiae is not a single mosquito species, but instead a species complex comprising six species that are morphologically similar but reproductively isolated.

An average person in Africa may experience 50 to 100 Anopheles gambiae bites per night. (Nchinda, 1998; Roberts and Janovy, Jr., 2000)

Contributors

Sara Diamond (editor), Animal Diversity Web.

Matthew Wund (editor), University of Michigan-Ann Arbor.

Jason Prior (author), University of Michigan-Ann Arbor, Solomon David (editor), University of Michigan-Ann Arbor.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

freshwater

mainly lives in water that is not salty.

herbivore

An animal that eats mainly plants or parts of plants.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

internal fertilization

fertilization takes place within the female's body

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nectarivore

an animal that mainly eats nectar from flowers

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

parasite

an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

sanguivore

an animal that mainly eats blood

scrub forest

scrub forests develop in areas that experience dry seasons.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

suburban

living in residential areas on the outskirts of large cities or towns.

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

year-round breeding

breeding takes place throughout the year

References

2004. "World Health Organization" (On-line). Accessed 12/15/04 at http://www.who.int/tdr/research/progress/mal_str/default.htm.

Blackwell, A., S. Johnson. June, 2000. Electrophysiological investigation of larval water and potential oviposition chemo-attractants for Anopheles gambiae s.s.. Annals of Tropical Medicine and Parasitology, 94(4): 389-398.

Comstock, J. 1920. Introduction to Entomology. United States: The Comstock Publishing Company.

Evans, A. 1938. Mosquitoes of the Ethiopian Region. London: Oxford University Press.

Konate, L., O. Faye, O. Gaye, M. Diouf, A. Diop. September, 1999. Observations on the feeding patterns and the alternative hosts selection of the malaria vectors in Senegal. Parasite, 6(3): 257-267.

Meijerink, J., M. Braks, A. Brack, W. Adam, T. Dekker. June, 2000. Identification of olfactory stimulants for Anopheles gambiae from human sweat samples. Journal of Chemical Ecology, 26(6): 1367-1382.

Nchinda, T. 1998. "Centers for Disease Control and Prevention" (On-line). Accessed 12/15/04 at http://www.cdc.gov/ncidod/eid/vol4no3/nchinda.htm.

Roberts, L., J. Janovy, Jr.. 2000. Foundations of Parasitology sixth edition. United States: McGraw-Hill Companies.

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