| Aedes albopictus (Skuse) and Ae. aegypti (Linnaeus), are both important vectors of dengue fever in China. Ae. aegypti, a house mosquito, with aggressive human-biting and more transmission ability of dengue virus, is the most dangerous dengue vectors in the tropics. Ae. albopictus can establish both indoor and outdoor even non-urbanized areas, it is an important vector of subtropical region. In China, the distribution of Ae. aegypti was restricted in the coastal areas of Guangdong, Hainan, Guangxi province. Recently it is also found in southern part of Yunnan province. However, Ae. albopictus has a wider-ranging distribution, the known distribution in China was described from southern of Hainan island to northern of Liaoning Province, with western of Baoji in Shanxi province. It is the main mosquito vector in southeast coastal areas of China. Since the 1950’s, the distribution of Ae. albopictus expands unceasingly because of several factors. One aspect is by the process of globalization, the increasingly frequent and developed transport. Eggs are carried to the places where there none exists. So we can see invasion into Europe, Africa and Americas from the origin of eastern Asia, and Ae. albopictus become the vectors of dengue fever in these areas; Another aspect is the climate change. Under the trend of global warming, some regions become suitable for it’s growth and reproduction now, which originally not. Phenomenon exists that expansion of Ae. albopictus from lower latitudes to higher latitudes in China. This research focuses on the differences of distribution and dispersal potential between Ae. albopictus and Ae. aegypti, it is organized with a series of experiments to find out their reactions to different temperatures and light cycles in the processes of growth,development and reproduction. The aim of study is to provide ecological information about potential distribution and diffusion trend of two specieses by further analysis. Also in some sense, by conducting the experimental studies, it may give guidelines for surveillance and control of dengue vectors, and helpful for prevention and early warming of dengue fever.This experimental study was conducted from aspects of the process of egg hatching, the growth and development of larva, the eclosion of pupa and the reproduction of adults of these two species. It is considered the relationship between these processes and temperature and photoperiod, clarified the temperature threshold which is necessary for two species of aedes to complete their life cycle and growth characteristics under different temperature and photoperiod conditions. It is discussed the influences of temperature and photoperiod on the geographical distribution and diffusion of Aedes on this basis. The main contents were as follows:1.The observation of growth of premature aedes including incubation, eclosion, larval survival and the whole generation life cycle in the temperature regime(11±0.1℃,16 ±0.1℃,21±0.1℃,26±0.1℃,31±0.1℃ and 36±0.1℃); 2. The comparison of the number of eggs laid by aedes under different photoperiod conditions (L0:D24, L4:D20, L12:D12, L20:D4, L24:D0).3. By simulating natural high temperature stress, to investigate the effects of high-temperature water treatment in different larval stages on the body size, body weight, and sex ratio of adult Ae. aegypti and to determine the critical stages when high water temperature exerts significant effects on the above indices.Result showed that no adults emerged at 11℃ and 36℃ for both species. Most of Ae. aegypti larvae died at about 10 days while Ae. albopictus prolonged life more than 20 days at 11℃. All of Ae. albopictus larvae ceased at the fourth instar or prior to it at 36℃, but 60.3% of Ae. aegypti larvae had development of pupa. Majority of deaths have occurred in pupa stage and the following process of eclosion. More emergents of Ae.albopictus were observed at 16℃. Rate of development for larvae increased with range of 16～31℃ and then declined for both species. The relation between development rate and temperature is statistically linear, being y=0.00597x-0.0618 (Ae. aegypti) and y=0.00526x-0.0476 (Ae. albopictus), with r=0.966,0.961 respectively. The developmental threshold temperature of Ae. aegypti and Ae. albopictus was 11.0±0.6℃,10.1±0.9℃ respectively, and the effective accumulated temperatures was 150.9±5.6,176.5±7.3 according to the law of effective accumulation temperature and least squares method. Although both species experienced shortest development time at 31℃ adults, the actual numbers of adults produced at this temperature was lower compared to 26℃. The sex ratio of Ae. aegypti was influenced by temperature,which yielding statistically more female at 31℃ compared to 21℃ and 26℃.Ae. aegypti laid no eggs when the photoperiod is L:D=0:24, little at L:D=24:0. The difference of eggs laying and hatching rate between other condition of photoperiod is not significant. With light hours increasing, Ae.albopictus laid more eggs, better uniformity degree of hatching and increased hatching rate. The number of laid eggs, rate of hatching were enhanced at photoperiod L:D=20:4 than that of 4:20. It proved that Ae. albopictus was better adapted to long light hours, compared with Ae. aegypti. Ae. albopictus can not only lay eggs, but also the number of eggs is large at 0:24, further research is still needed to find out the reason.The high-temperature water treatment showed significant influence with different larval stages. The female wing-lengths were significantly smaller for larva of L2, L3 and L4 exposed to high temperature compared to the standard value. The female weight decreased for L2 and L4 under higher temperature. More females emerged when L3 and L4 were exposed to high temperature, than males. The M/F ratio was 0.88 and 0.95 respectively. In contrast, when L2 were cultured in high temperature water, more males emerged in adults stage (M/F=2.43). It concluded that he effect of high water temperature to Ae. aegypti immatures is stage dependent. Egg stage and L1 were less sensitive to the high water temperature, than L2, L3 and L4. L2 is likely a critical period for female development to Ae. aegypti, and L3 is likely the key period for the development of male.The study can partly explain the influence of meteorological factors on geographic distribution of two species, and revealing the spread of the trend in our country under the global warming.It may also evaluate effect of global climate changes on environmental risk problems of dengue transmission, and provides fundamental ecological information for monitoring the population dynamics and early warming of mosquito vectors. |
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