Aedes albopictus (Skuse), a mosquito vector of the dengue fever virus, is prevalent in Japan, distributed widely in Honshu Island with its northern limits between latitude 38 degrees to 40 degrees north. The factors affecting distribution of the species in the northern part of Japan were studied using the geographical information system (GIS). During 1998-2000, larval surveillance was carried out in 26 urban and rural areas in the Tohoku district, in the northern part of Honshu Island, by collecting larvae from artificial and natural habitats. Climatological analysis, using the GIS, showed that the following conditions accounted for the current distribution of Ae. albopictus: an annual mean temperature higher than 11 degrees C and a mean temperature of the coldest month, January, higher than -2 degrees C. A period with temperature above 11 degrees C in the confirmed area of the mosquito successively continues for more than 186 d per year. The accumulated temperature calculated from a temperature of 11 degrees C, which may be close to the developmental zero of Ae. albopictus, was over 1,350 degree-days. The relationship between the beginning of short-daylength, inducing egg diapause, and the monthly mean temperature during September and October necessary for successful larval development in the Tohoku district is also discussed. We also show the relationship between the current distribution of Ae. albopictus and the annual mean temperature in the United States. From these results it is predicted that Ae. albpictus will be established in some cities in northeast United States.
Since the mid-1990s Japanese society has entered a period of major change. The previous patterns of social order and social integration have collapsed, and it has become increasingly difficult to envision a stable life course for oneself. The 'secure' foundation has been weakening and anxiety has spread at an accelerated pace. Japan could enter the age of second modernity, or reflexive modernization. In Japan's first modernity, the mechanism responsible for risk management, an integrated society, and stabilized social order, was, first, private corporations that guaranteed long-term stability for employees and their families (company-centrism) and, second, land development rapidly implemented under the guidance of bureaucrats (developmentalism). From the 1990s, these systems were fundamentally destroyed by globalization and neoliberal policies. Private corporations limited the groups that could benefit from the seniority wage system, undermining in-house welfare benefits. The government abandoned its role of improving the industrial and economic conditions of surrounding areas through offering public works projects. After these risk-stabilizing mechanisms were gone, two problems became conspicuous - poverty among young workers in urban areas and the collapse of the local community in marginal areas. As the seniority wage system and lifetime employment were substitutes for the public social security system, public measures to deal with poverty remain inadequate. Now, the individualization of the family has advanced somewhat under compulsion as the rate of unmarried people and the divorce rate have climbed. The Japanese have a tendency to seek 'self-realization'; at the same time, they also want 'secure employment'. Thus, they are torn between individualization and the desire for security. What is now necessary is a more stable system that will ensure them adequate material and spiritual 'elbowroom' to allow them to make their own choices.
Background Schistosoma japonicum causes major public health problems in China and the Philippines; this parasite, which is transmitted by freshwater snails of the species Oncomelania hupensis, causes the disease intestinal schistosomiasis in humans and cattle. Researchers working on Schistosoma in Africa have described the relationship between the parasites and their snail intermediate hosts as coevolved or even as an evolutionary arms race. In the present study this hypothesis of coevolution is evaluated for S. japonicum and O. hupensis. The origins and radiation of the snails and the parasite across China, and the taxonomic validity of the sub-species of O. hupensis, are also assessed.Methodology/Principal FindingsThe findings provide no evidence for coevolution between S. japonicum and O. hupensis, and the phylogeographical analysis suggests a heterochronous radiation of the parasites and snails in response to different palaeogeographical and climatic triggers. The results are consistent with a hypothesis of East to West colonisation of China by Oncomelania with a re-invasion of Japan by O. hupensis from China. The Taiwan population of S. japonicum appears to be recently established in comparison with mainland Chinese populations.Conclusions/SignificanceThe snail and parasite populations of the western mountain region of China (Yunnan and Sichuan) appear to have been isolated from Southeast Asian populations since the Pleistocene; this has implications for road and rail links being constructed in the region, which will breach biogeographical barriers between China and Southeast Asia. The results also have implications for the spread of S. japonicum. In the absence of coevolution, the parasite may more readily colonise new snail populations to which it is not locally adapted, or even new intermediate host species; this can facilitate its dispersal into new areas. Additional work is required to assess further the risk of spread of S. japonicum.
The dispersal pattern of the widow spider Latrodectus hasseltii (Araneae: Theridiadae), in Osaka Prefecture, Japan, was analyzed from accumulated survey data of spider distribution. All confirmed infested points from 1996 to 2002 were plotted on a map, and infested points in each survey year were connected with the nearest previously confirmed points. Expansion patterns of the confirmed habitats were analyzed by year and dispersion distances were classified by using spider diagram, one of method of geographical information system spatial analysis. L. hasseltii moves by walking step by step on the ground, mainly in coastal areas during early stages of infestation, and also can be conveyed over distances by various vehicles, mainly in inland areas. These analyses show L. hasseltii does not move by ballooning.
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