 Dear students, in this topic we shall discuss the ectotherms living in hot environments. The ectotherms in hot environments may face a daytime summer temperature of 40 degrees centigrade or above. So they are vulnerable to warming. The maximum temperature tolerance of ectotherms that is the critical thermal maximum is below 45 degrees centigrade. Above this temperature, long-term survival is not possible. Dear students, above the critical thermal temperature most tissue functions are affected because there is a decreased oxygen affinity for respiratory pigments. Above this temperature, proteins are denatured and enzymes fail to function. Dear students, ectotherms have evolved and adapted certain strategies to live in hot environments. These ectotherms actively respond to prevent elevation of their body temperatures to the critical thermal maximum. Animals who see the rise of the temperature immediately respond to not let their body temperature go to this level. They tend to eliminate excess heat which is gained from the environment. For this purpose, they use behavioral as well as physiological mechanisms. We shall discuss the physiological mechanisms and adaptations that ectotherms have evolved to dissipate the heat gained from the environment. The first thing is that high heat conductance in ectotherms is caused by which they can radiate heat rapidly. So such animals, even if they move to a less warmer place for a while, it will radiate a lot of heat and this way the body temperature can be cooled or brought to a less warm level. The second method which is adopted by many reptiles is the painting. Above 40 degree centigrade, many reptiles start painting like birds and mammals. Birds and mammals ectotherms have paintings but reptiles also copy and paint them. This increases heat loss through respiratory evaporation which causes cooling. Then another mechanism is to regulate the heart rate and regulate the flow of blood to body surface. Heat can be eliminated from the body surface. This mechanism uses some marine iguanas. Similarly, we get another mechanism in Gila monster which is a lizard and it evaporates water from its colloica to get cooling. This process is similar to sweating in mammals. Dear students, in addition to physiological adaptation, ectotherms which are in hot environments also use some behavioral mechanisms to dissipate extra heat from the body. For example, the most important behavior that is moving to shades or burrows which are the cooler microclimates in hot environments. Similarly, some animals which are forelegged, start bi-pedal locomotion through the hot surface in the hot environment. The lower part of the body which can absorb heat by touching the hot surface, stays away from the hot surface. For example, this method is used by desert iguanas which are bi-pedal. In addition, this is the animal, desert iguanas or some other animals which are living in desert. If they are travelling for a long time, then the rate is higher than the surface. However, they dig in this sand after some time because the sand present deep inside is cool so they can dissipate extra heat to the digged sand.