Effects of temperature on members of the Anopheles gambiae complex (Diptera: Culicidae) in South Africa : implications for malaria transmission and control.
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Date
1996
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Abstract
This study investigated the effects of temperature and relative humidity (both controlled
and natural) on the lifecyle and morphology of adults of members of the Anopheles
gambiae complex in northern KwaZulu-Natal, South Africa.
Laboratory investigations into the effects of simulated temperature and relative humidity
regimes concentrated on seasonal differences in longevity, egg hatchability,
reproductive potential and adult survivorship of An. arabiensis. Differences were found
in the life table parameters when these mosquitoes were reared under conditions of
seasonal temperature and relative humidity. During the cool season the lifespan and
adult survivorship of mosquitoes were greater than those reared during the warm
season. In summer, the egg hatchability and reproductive potential were greatest
whereas in winter An. arabiensis underwent gonotrophic dissociation although these
females were found to take blood meals readily.
The influence of seasonal temperature and relative humidity on the body size of An.
arabiensis was investigated, both in the laboratory and under field conditions. In both
environments, these factors were found to significantly influence body size. In winter,
there was a 13% increase in wing size compared to summer bred mosquitoes. A
comparison of body size of An. arabiensis, An. merus and An. gambiae reared under
laboratory conditions of seasonal temperature and relative humidity showed that the
wing size of An. arabiensis was greater than that of An. merus and An. gambiae. The effect of temperature and relative humidity on morphological criteria used in
species separation was also investigated. Seasonal differences in wing spot size were
compared for An. arabiensis, An. merus and An. gambiae. From this investigation it
was concluded that the pale and dark spots on the wing of Anopheles mosquitoes could
not be used in species identification due to the large degree of inter-species overlap in
the wing spot measurements. The measurement of the pale band at the junction of the
3rd and 4th tarsomere on the hind leg was also investigated for its use in species
separation and were found to be useful within the An. gambiae complex.
The implications of this study on the transmission and control of malaria are discussed
with reference to the late season transmission during March to May that is characteristic
of the region.
Description
Thesis (Ph.D)-University of Natal, Pietermaritzburg, 1996.
Keywords
Mosquitoes--Behaviour--Climatic factors., Mosquitoes--KwaZulu-Natal., Malaria--KwaZulu-Natal--Control., Malaria--Epidemiology., Theses--Zoology.