No abstract

No abstract

No abstract

If global warming progresses, many consider that malaria in presently malaria-endemic areas will become more serious, with increasing development rates of the vector mosquito and malaria parasites. However, the correlation coefficients between the monthly malaria cases and the monthly mean of daily maximum temperature were negative, showing that the number of malaria cases in tropical areas of Africa decreases during the season when temperature was higher than normal. Moreover, an analysis of temperature and development rate using a thermodynamic model showed that the estimated intrinsic optimum temperatures for the development of the malaria parasites, Plasmodium falciparum and P. vivax, in the adult mosquito stage and that of the vector mosquito Anopheles gambiae s.s. were all approximately 23-24 degrees C. Here, the intrinsic optimum temperature is defined in the thermodynamic model as the temperature at which it is assumed that there are no or negligible adverse effects for development. Therefore, this study indicates that the development of malaria parasites in their mosquito hosts and the development of their vector mosquitoes are inhibited at temperatures higher than 23-24 degrees C. If global warming progresses further, the present center of malarial endemicity in sub-Saharan Africa will move to an area with an optimum temperature for both the vector and the parasite, migrating to avoid the hot environment.

It was found that Oscillatoria agardhii strain 27 produced compounds toxic against mosquito larvae (Aedes albopictus), therefore, these compounds were extracted and separated for insecticide development. Structural characterization of the toxic fraction by 1H‐NMR and GC‐MS showed that these compounds are not the neurotoxins or hepatotoxins conventionally produced by Oscillatoria, but it contained a mixture of unsaturated fatty acids, oleic, linoleic, and γ‐linolenic acids, as well as saturated fatty acids, myristic, palmitic, and stearic acids. In a bioassay developed for these hydrophobic compounds using mosquito larvae, authentic unsaturated fatty acids were shown to be toxic, whereas saturated ones were not active. The results suggested that it might be possible to use unsaturated fatty acids as environmentally safe and effective insecticides without the side effects of the chemically synthesized insecticides. © 2000 John Wiley & Sons, Inc. Environ Toxicol 15: 114–119, 2000

Data sources. To examine the linearity between t and k, data for the temperature-dependent larval development of six groups, i.e., the family Tenebrionidae (10 species(s)/strains(s)), the family Pyralidae (8 s/s), the family Aphididae (13 s/s), the genus Periplaneta (4 s/s) and the genus Aedes (13 s/s) of insects, and the family Tetranychidae (12 s/s) of mites, were selected (see Table 1 and Appendix 1). The data on temperatures related to the induction of diapause (e.g., 20°C for Periplaneta fuliginosa reported by Tsuji, 1975) and the data on "slow stocks", which have the delayed type of development (e.g., Ephestia kuhniella shown by Ahmad, 1936;and Jacob and Cox, 1977) were excluded. Appl. Entomol. Zool. 38 (4): 487-492 (2003) 487 Possible existence of a common temperature and a common duration of development among members of a taxonomic group of arthropods that underwent speciational adaptation to temperature Takaya AbstractThe parameters in the law of total effective temperature, the developmental zero temperature (t) and the effective cumulative temperature (k), were estimated in several species or strains of the family Tenebrionidae. It was shown that the relationship between t and k is linear; k decreases with increasing t. Similar relationships were noted among members of the genus Periplaneta in the family Blattidae, the genus Aedes in the family Culicidae, the family Pyralidae, the family Aphididae and the family Tetranychidae. Based on analysis among groups of orders or higher categories, several researchers have found a similar relationship. The current study on a family or a genus revealed a more rigorous linearity. However, the focus of this study was the linear relationship itself and it was discovered that the t-k relationships of members within each taxonomic group of arthropods determines a common temperature (Tc) and a common duration of development (Dc). This phenomenon was mathematically deducible as a consequence of the t-k linear relation. Biologically, Tc and Dc are probably the optimum temperature and duration of development, respectively, that a group of organisms possess in common.

The intrinsic optimum temperature for the development of ectotherms is one of the most important factors not only for their physiological processes but also for ecological and evolutional processes. The Sharpe–Schoolfield–Ikemoto (SSI) model succeeded in defining the temperature that can thermodynamically meet the condition that at a particular temperature the probability of an active enzyme reaching its maximum activity is realized. Previously, an algorithm was developed by Ikemoto (Tropical malaria does not mean hot environments. Journal of Medical Entomology, 45, 963–969) to estimate model parameters, but that program was computationally very time consuming. Now, investigators can use the SSI model more easily because a full automatic computer program was designed by Shi et al. (A modified program for estimating the parameters of the SSI model. Environmental Entomology, 40, 462–469). However, the statistical significance of the point estimate of the intrinsic optimum temperature for each ectotherm has not yet been determined. Here, we provided a new method for calculating the confidence interval of the estimated intrinsic optimum temperature by modifying the approximate bootstrap confidence intervals method. For this purpose, it was necessary to develop a new program for a faster estimation of the parameters in the SSI model, which we have also done.

If global warming progresses, many consider that malaria in presently malaria-endemic areas will become more serious, with increasing development rates of the vector mosquito and malaria parasites. However, the correlation coefficients between the monthly malaria cases and the monthly mean of daily maximum temperature were negative, showing that the number of malaria cases in tropical areas of Africa decreases during the season when temperature was higher than normal. Moreover, an analysis of temperature and development rate using a thermodynamic model showed that the estimated intrinsic optimum temperatures for the development of the malaria parasites, Plasmodium falciparum and P. vivax, in the adult mosquito stage and that of the vector mosquito Anopheles gambiae s.s. were all approximately 23-24 degrees C. Here, the intrinsic optimum temperature is defined in the thermodynamic model as the temperature at which it is assumed that there are no or negligible adverse effects for development. Therefore, this study indicates that the development of malaria parasites in their mosquito hosts and the development of their vector mosquitoes are inhibited at temperatures higher than 23-24 degrees C. If global warming progresses further, the present center of malarial endemicity in sub-Saharan Africa will move to an area with an optimum temperature for both the vector and the parasite, migrating to avoid the hot environment.