Thermal Physiology of Cicadas and Regulation of Cuticular Permeability in Insects

托尔森博士最近发现，蝉可以通过蒸发水分来降低体温。这种能力只为少数昆虫所知。蝉在除哺乳动物以外的所有动物中的独特之处在于，它们通过一种能量依赖的过程实现蒸发冷却所需的高失水率，这种过程导致水通过大直径的角质层导管挤出。当蝉的体温有超过特定设定点(TSP)的危险时，水的挤出就会触发，因此在功能上相当于哺乳动物的出汗。这项拟议的研究涉及两个不同的主题。首先，延续了PI的发现，即蝉可以通过激活促进跨角质水通量(TWF)的能量依赖过程来蒸发冷却，PI将进行研究，以阐明TWF促进过程的调节所涉及的化学和神经机制。已被证明影响哺乳动物体温调节的化合物，如阿司匹林、乙酰米芬和前列腺素，以及在昆虫中具有已知调节活性的化合物，如章鱼胺，将被测试其对TWF的影响，从而对体温产生影响。角质层的局部区域将被加热，以确定这是否会影响TWF。经典的结扎实验将被用来评估神经系统是否调节TWF，如果是的话，在什么水平上调节神经调节。最后，将对不同生境的蝉进行驯化实验和比较研究，以阐明热状况、大小、颜色/反射率和其他因素在确定TSP方面的相互作用。拟议研究的第二部分包括实验，旨在测试两种替代假设之间的关系，这两种假设旨在解释大多数陆地节肢动物报告的与栖息地相关的角质层渗透性和季节性模式。蟑螂、蟋蟀和蝎子将受到不同的食物和水可获得性组合的影响，以确定响应不断变化的干燥压力而改变角质层渗透性的能力是否反映了保存能量/前体或调节TWF速率的需要。

Dr. Toolson has recently discovered that cicadas can reduce their body temperature by evaporation of water. This ability is known only for a handful of insects. What makes cicadas unique among all animals except mammals is that they achieve the high water loss rates required for evaporative cooling by means of an energy-dependent process that causes extrusion of water through large-diameter cuticular ducts. The extrusion of water is triggered when a cicada's body temperature threatens to go above a specific setpoint (Tsp), and is thus the functional equivalent of sweating in mammals. The proposed research entails two somewhat distinct themes. First, extending the PI's discovery that cicadas can evaporatively cool by activating an energy- dependent process that facilitates transcuticular water flux (TWF) rates, the PI's will conduct studies to elucidate the chemical and neurological mechanisms involved in regulation of the TWF- facilitating process. Compounds, such as aspirin, acetominiphen, and prostaglandins, that have been shown to affect body-temperature regulation in mammals, and compounds with known regulatory activity in insects, e.g., octopamine, will be tested for their effect on TWF and, therefore, on body temperature. Localized regions of the cuticle will be warmed to determine if this affects TWF. Classic ligation experiments will be used to assess whether the nervous system regulates TWF and, if so, at what level neurological regulation is mediated. Finally, acclimation experiments and comparative studies involving cicada species from a variety of habitats will be conducted to elucidate the interaction of thermal regime, size, color/reflectivity, and other factors in determining Tsp. The second part of the proposed research consists of experiments designed to test between two alternative hypotheses proposed to account for the habitat-associated and seasonal patterns of cuticular permeabilities reported for most terrestrial arthropods. Cockroaches, crickets, and scorpions will be subjected to different combinations of food and water availability to determine whether the ability to modify cuticular permeability in response to changing desiccation stress reflects a need to conserve energy/precursors or to regulate rates of TWF.