Department of Animal and Plant Sciences, University of Sheffield, Western Bank, Sheffield S10 2TN, UK.
J Exp Biol. 2010 Dec 15;213(Pt 24):4223-31. doi: 10.1242/jeb.045435.
Body temperatures and thus physiological rates of poikilothermic organisms are determined by environmental temperature. The power an organism has available for swimming is largely dependent on physiological rates and thus body temperature. However, retarding forces such as drag are contingent on the temperature-dependent physical properties of water and on an organism's size. Consequently, the swimming ability of poikilotherms is highly temperature dependent. The importance of the temperature-dependent physical properties of water (e.g. viscosity) in determining swimming speed is poorly understood. Here we propose a semi-mechanistic model to describe how biological rates, size and the physics of the environment contribute to the temperature dependency of microbial swimming speed. Data on the swimming speed and size of a predatory protist and its protist prey were collected and used to test our model. Data were collected by manipulating both the temperature and the viscosity (independently of temperature) of the organism's environment. Protists were either cultured in their test environment (for several generations) or rapidly exposed to their test environment to assess their ability to adapt or acclimate to treatments. Both biological rates and the physics of the environment were predicted to and observed to contribute to the swimming speed of protists. Body size was not temperature dependent, and protists expressed some ability to acclimate to changes in either temperature or viscosity. Overall, using our parameter estimates and novel model, we are able to suggest that 30 to 40% (depending on species) of the response in swimming speed associated with a reduction in temperature from 20 to 5°C is due to viscosity. Because encounter rates between protist predators and their prey are determined by swimming speed, temperature- and viscosity-dependent swimming speeds are likely to result in temperature- and viscosity-dependent trophic interactions.
变温动物的体温和生理代谢率取决于环境温度。生物体可用于游泳的能量在很大程度上取决于生理代谢率和体温。然而，阻力等迟滞力取决于水的温度依赖的物理性质和生物体的大小。因此，变温动物的游泳能力对温度高度依赖。水的温度依赖的物理性质（例如粘度）对游泳速度的决定作用尚未得到充分理解。在这里，我们提出了一个半机械模型来描述生物代谢率、大小和环境物理特性如何共同决定微生物的游泳速度的温度依赖性。我们收集了捕食性原生动物及其原生动物猎物的游泳速度和大小的数据，并将其用于测试我们的模型。通过同时操纵生物体环境的温度和粘度（与温度无关）来收集数据。原生动物要么在其测试环境中培养（几代），要么迅速暴露于测试环境中，以评估它们适应或适应处理的能力。生物代谢率和环境物理特性都被预测和观察到对原生动物的游泳速度有贡献。身体大小与温度无关，原生动物表现出一定的适应温度或粘度变化的能力。总的来说，我们使用参数估计和新模型，能够表明，在 20°C 至 5°C 的温度降低过程中，与游泳速度相关的响应的 30%至 40%（取决于物种）归因于粘度。由于原生动物捕食者与其猎物之间的遭遇率取决于游泳速度，因此与温度和粘度相关的游泳速度可能导致与温度和粘度相关的营养相互作用。
