Biology/ Aedies Aegypti term paper 18007

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Aedes Aegypti

The mosquito that has attracted the most attention is the mosquito Aedes

aegypti. It belongs to the family Culcidae, consisting of about 2,500 species

(Encyclopedia Britanica 1999), along with other genera of mosquitoes such as

Anopheles, Culex, Orthopodomyia, and the Toxorynchites, to name a few (Womack

1993, E.B. 1999). This mosquito has been known best for transmitting yellow fever and

human dengue throughout the tropic and subtropic of the Americas (Womack, M 1993).

This mosquito along with others are looked upon as pests and nuisances in modern day

society because of their attraction to moisture, lactic acid, carbon dioxide, body heat and

movement (E.B. 1999) but we can not confuse the Aedes aegypti with any other

mosquito for it has a very distinct look to it as well as a specific habitat. It has many

related species and it s geographic distribution is extremely wide and varied.

The Aedes aegypti, with regard to both sexes, are generally similar in coloration

(Womack 1993). The female adult is noticed by it s small dark figure that is colored by

white markings and banded legs. Its proboscis or snout is mostly black with regard to

the white palp tips (Russel 1996). The dorsal pattern of white scales on the scutum is in

the shape of a lyre with two central based stripes that contrast with the dark scales

present on the insect (Womack 1993,

Russel 1996). Its wings are dark scaled and femur and hind legs are pale scaled for

about three-quarters, and dark scaled for about two-thirds (Russel 1996).

The first through the fourth segments of the hind tarsi are characterized by white rings

and the fifth segment is all white.

Adults can be found in abundance in towns and cities near human dwelling

places., living in trees, herbaceous plants, dim closets, cabinets or even old automobile

tires (Womack 1993, Juliano 1998). The species feeds mostly during the day increasing

its feeding rate two hours after sunrise and several hours before sunset ( Womack

1993, Geographical Magazine 1998), while it is not rare for females to feed under

artificial light at night. The above feeding habits of the Aedes aegypti contributes to the

species life span which is dependent on nutrition, temperature and humidity (Womack

1993) as well as its ability to avoid predators such as reptiles or even sometimes other

types of mosquitoes (E.B. 1999). The male mosquito can only live a short time ranging

from a few days to a couple weeks whereas the female can live up to a month which

allows her to reproduce longer (Womack 1993).

They lay their eggs in artificial containers on damp surfaces such as jars, urns,

cans or anything that can contain rain water (Womack 1993, Juliano 1998). The eggs

hatch when they become flooded by deoxygenated water, except during winter(Womack

1993, Juliano 1998) and after which can only survive in temperatures above ten degrees

or below 44 degrees Celsius (Womack 1993). The larvae feed on aquatic microbiota

which develops inside the artificial

containers in which the eggs are laid (Womack 1993). In the pupal stage they are free

swimming and active and breathe by means of tubes on the thorax (E.B.

1999). The limitations of availability of habitat has greatly affected the geographic

distribution of the species.

They have a cosmopolitan range extending from 40 degrees N to 40 degrees S

latitude. says Womack (1993). It is found throughout the world in tropic and subtropic

regions (Womack 1993). The species has been distributed throughout New England

staying close to the marshes and damp areas and away from dry and cold climates. It is

not only the dry and cold climates that threaten the Aedes aegypti but one of its

associated species as well.

The Aedes albopictus is an Asian mosquito that was introduced to North America

in the 1980s (Hawley 1988, OMeara et al. 1992,1993,1995, Juliano 1998). It has spread

throughout the north and now threatens declines in the Aedes aegypti because of its

positive population growth at higher combined density and lower per capita resource

availability (Juliano 1998). The A. albopictus is a successful invader because of its

generalized habitat, its adaptation to many climates, ability to live in human dominated

areas, as well as its food requirements and its desiccation resistant eggs (Hawley 1988,

Focks et al. 1994, Juliano 1998). The primary determinant of success says Juliano

(1998) was survivorship to adulthood. The Aedes aegypti only survived well in it s

environment when it was raised alone at a low density with a high resource availability

(Juliano 1998). Competition for these resources among larvae is what seems to

sufficient in accounting the near replacement of the A. aegypti with the A. albopictus. It

is a species that lives to survive, feed and reproduce and although this may not seem

difficult, Juliano has shown us that Darwin s theory of evolution and natural selection is

one that prevails in all species of organisms and in this battle the A. aegypti is losing to a

fellow, more adapted mosquito the A. abopictus.

Some other related species of the A. aegypti are the A. notoscriptus (Russel

1996), the A. triseriatus, A. atropalupus, Othopodomyia signifera, Toxorhynchites rutilis,

Culex nigripalpus, Culex quinquefasciaus, Culex resuans, and Culex salinarius

(Womack 1993).

The A. aegytpi is a species best known for infecting people with such diseases as

yellow fever and human dengue. Its life cycle is very simple compared to many other

organisms. The female feeds on a blood diet to mature her eggs (E.B. 1999), and she

lays them in a damp artificial container. The time for development of these eggs to

mosquitoes is anywhere from four to ten days depending on the water temperature and

the food supply (Womack 1993). Soon after the organism passes through the pupal

stage they mate and start the cycle over again.

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