RESUMEN
The SSI model describes the relationship between temperature and development rate of insect based on the laws of thermodynamics. The greatest feature of the SSI model curve is that it defines the "Intrinsic optimum temperature for the development of ectotherms". However, this model has 8 parameters, it was extremely difficult to estimate the values of these parameters from experimental data. This is because the curve fitting of experimental data yields multiple curves depending on the initial conditions. In the first epoch of estimating parameter values, the difficulties were overcome by clarifying the model and applying all the knowledge gained about the model, but it took several days to determine the model. In the second epoch, the OptimSSI-program, which incorporates a basic optimization function, was developed, making it possible to obtain parameter values instantaneously after inputting experimental data. Although this program mostly runs automatically on a PC, a manual calculation remains to be carried outs so that the obtained model curves do not deviate from Arrhenius' law. Afterward, a new program was suggested. This new program called DEoptim.sqrt not only incorporates an optimization function available on the internet but also was completely different from OptimSSI-P in terms of the design concept. Users had hoped that this new program would be start of the third epoch; however, when we examined the output values, there were serious problems, and we were back in the state before the first epoch. After all, OptimSSI-P of the second epoch was decided to be more reliable.
Asunto(s)
Insectos , Modelos Biológicos , Animales , Temperatura , TermodinámicaRESUMEN
For ectotherms such as insects, their low- and/or high-temperature tolerance is one of the most important traits not only for their physiological as well as ecological and evolutional processes. Here, we review the temperature tolerance of insects in relation to their development and suggest a novel method of specifying low and high threshold temperatures. To date, the upper and lower critical thermal threshold for development as Tmin and Tmax, respectively, which are derived from nonlinear empirical models, has been extensively used. These indicators, which originated from the artificial empirical models, however, may not be reliable. Consequently, the Sharpe-Schoolfield-Ikemoto (SSI) model which is a nonlinear theoretical model based on thermodynamics, was implemented as an alternative tool to express tolerance temperatures. In the model equation constructed with subunits, when the reversed denominator (P2 function) is maximum (nearly 100% in general), it denotes the probability of an enzyme being in the almost fully-active state of the intrinsic optimum temperature (TΦ). The profile of the P2 function shows a peak at the TΦ temperature and the two temperatures of TL50 and TH50 which indicate the 50% active and 50% inactive state (P2 = 50%), respectively, are given as parameters in the P2 function of the SSI model. Even so, it is possible to select any values within the range of 0Asunto(s)
Insectos
, Modelos Biológicos
, Animales
, Calor
, Temperatura
, Termodinámica
RESUMEN
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.
Asunto(s)
Algoritmos , Insectos/crecimiento & desarrollo , Insectos/fisiología , Modelos Biológicos , Modelos Estadísticos , Temperatura , Animales , Intervalos de Confianza , TermodinámicaRESUMEN
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.