Abstract: By the method of individual culture, this paper studied the effects of temperature (10 ℃, 15 ℃, 20 ℃, and 25 ℃) on the life table demography (net reproductive rate, intrinsic rate of population increase, generation time, average lifespan, and proportion of mictic offspring) and the offspring morphometric characteristics (body length, body width, antero-median spine length, left and right antero-lateral spine lengths, left and right posterior-spine lengths, and posterior spine number) of two posterior-spined, single posterior-spined, and zero posterior-spined morphotypes of Keratella quadrata. All the test life table demographic parameters and offspring morphometric parameters differed with morphotype and temperature, and their responses to elevated temperature differed with morphotype. Temperature had significant effects on the intrinsic rate of population increase, generation time, average lifespan, and the offspring morphometric parameters (P<0.05); morphotype had significant effects on the offspring body length, antero-median spine length, and left and right posterior-spine lengths (P<0.05) but less effects on the life table demography (P<0.05); and the interaction of temperature and morphotype had significant effects on the generation time and all the offspring morphometric parameters (P<0.05). Among the three morphotypes, the two posterior-spined morphotype had shorter offspring body length (122.1±0.6 μm) than the zero and single posterior-spined morphotypes (126.3±0.7 μm and 125.1±0.7 μm, respectively). The offspring antero-median spine length (32.5±0.3 μm) of the two posterior-spined
morphotype was longer than that of the zero and single posterior-spined morphotypes (31.1±0.3 μm and 30.8±0.3 μm, respectively). The offspring left and right posterior-spine lengths of the two posterior-spined morphotype (31.2±1.0μm and 32.3±0.9μm, respectivedy) were similar to those of the single posterior-spined morphotype（29.5±0.8 μm and 31.5±0.6 μm, respectively), but shorter than those of the zero posterior-spined morphotype (36.7±1.5 μm and 37.3±1.6 μm, respectively). The relationships between the offspring spine length, body width, and body length were also affected by temperature and morphotype.

Key words: Keratella quadrata, morphotype, life table demography, morphometric characteristics, temperature