 Dear students, in this topic we shall discuss osmoregulation in desert living animals. Animals living in hot dry desert environments face the problems of excessive heat, evaporative water loss and absence of free freshwater availability. These animals have special adaptations for survival in harsh conditions. We shall take an example of kangaroo rat which is a small mammal living in some hottest and driest environments of deserts. It presents exemplary survival strategies in such an environment. They live in an environment which has no available drinking water and have only dry seeds to eat. They have a variety of physiological adaptations for osmoregulation. We shall discuss some of their adaptations. First, they are adapted to a nocturnal lifestyle. That is, they live in the desert during the day and only come out at night. By living outside during the day, the evaporative water loss decreases. It also reduces respiratory water loss. They also have a specialized nasal epithelium which has cooling properties and also has a counter-current mechanism to absorb respiratory moisture. This is how they reabsorb the papers that are coming out. They are also adapted to utilize metabolic water in place of water intake through drinking which is not available to them. That is why they utilize the water produced by metabolism in the body to fulfill water requirements. They also excrete highly concentrated urine so that the water loss through urine is minimized. They also produce essentially dry faces because they reabsorb most of the water from the faces in their rectum. All these adaptations ensure their survival in the desert. Dear students, now we shall discuss the adaptations of large desert mammals like camels. These large animals cannot hide themselves in burrows so they face daylight sun in hot and dry deserts. They can go for long periods without drinking water. They have the ability to withstand extreme body dehydration. A camel can lose 40% of its body water but still survive. When they are deprived of drinking water, camels allow their body temperatures to rise. They do not use evaporative cooling methods for temperature regulation because water is produced in that method. That is why no sweating, no evaporative cooling, but let the body to raise its temperature. This is their strategy. However, it happens during the day but when it is night, the cooler nights come in the deserts so their body temperature drops. Body temperatures in a dehydrated camel, which is not doing thermo regulation, vary a lot. Their body temperature goes up to 35 degree centigrade during the night and rises to 41 degree centigrade during the day. This strategy is not possible in small rodents or small mammals because their temperature oscillations are much more rapid than larger animals. So their body is completely dehydrated or dry up if small mammals have such a strategy. Camels like many other desert animals produce dry faces and produce concentrated urine to minimize water loss. When water is not available, camels stop producing urine but they can store urea in their body. They have the capacity to tolerate not only dehydration but they can also tolerate high levels of urea in their body. So these are the strategies in which camels survive in the desert environment. When water is available, they rehydrate their bodies by drinking large amounts of water quickly at a single time.