Easton D M
Department of Biological Science, Florida State University, Tallahassee 32306-3050, USA.
Exp Gerontol. 1997 Nov-Dec;32(6):719-26. doi: 10.1016/s0531-5565(97)00043-0.
A recent report (Easton, 1995) showed that, at least for Mediterranean fruit flies, a Gompertz growth equation based on the increase in number of individuals that die is a better predictor of survival data than is the classical Gompertz survivorship model based on the decrease in number that survive (analysis of medfly data of Carey et al., 1992). In the growth model, the rate of increase of the number dead (i.e., the death rate) decreases exponentially with age. The poor fit of the classical model predicts "excess survival" of older members, but, when the scale of the better-fitting growth model is increased 2400x, such excess is now also evident as a small but distinctly separate cohort of the medfly subjects. The smaller population appears to be about 0.01% of the larger, and the death rate decreases about one-fourth as fast. Survival of the nematode C. elegans (Brooks et al., 1994) is also better predicted by the growth model, which also shows excess survival of the worms at great age.
最近的一份报告（伊斯顿，1995年）表明，至少对于地中海实蝇来说，基于死亡个体数量增加的冈珀茨生长方程比基于存活个体数量减少的经典冈珀茨存活模型能更好地预测存活数据（对凯里等人1992年的地中海实蝇数据进行分析）。在生长模型中，死亡数量的增加速率（即死亡率）随年龄呈指数下降。经典模型拟合不佳预测老年成员存在“过度存活”，但是，当拟合效果更好的生长模型的规模放大2400倍时，这种过度存活现在也表现为地中海实蝇研究对象中一个数量虽少但明显独立的队列。较小的群体似乎约为较大群体的0.01%，且死亡率下降速度约为其四分之一。线虫秀丽隐杆线虫的存活情况（布鲁克斯等人，1994年）同样通过生长模型能得到更好的预测，该模型也显示老龄线虫存在过度存活现象。
