A xerocole (from the Greek x> Ros , which means 'dry', and Latin col (ere) , meaning 'to inhabit'), commonly referred to as desert animals, are animals adapted to live in the desert. The main challenge they have to overcome is the lack of water and excessive heat. To conserve water, they avoid evaporation and concentration of excretion (ie urine and faeces). Some are very good at conserving water or getting it from food so they do not need to drink at all. To escape from the heat of the desert, xerocoles tend to be active at night or crepuscular, most active at dawn and dusk.
Video Xerocole
Water preservation
Evading evaporation
Xerocoles has developed various mechanisms to reduce water loss through evaporation. Xerocoles mammals sweat much less than their non-desert counterparts. For example, camels can withstand temperatures of about 49 ° C (120 ° F) without sweating, and kangaroo rats do not have full sweat glands. Both birds and mammals in the desert have oil on the surface of their skin to "waterproof" and inhibit evaporation.
Desert insects use the same method, because their cuticles are waxy to keep water out; However, at critical temperatures (eg, 30 Â ° C (86 Â ° F) for cockroaches), wax molecules in the cuticle reset to permeable and allow for evaporative cooling.
Xerocoles amphibians, like the species of the frog genus Phyllomedusa , have a waxy coating on their skin to reduce water loss. Frogs emit lipids from glands in their skin: when their skin begins to dry out, they move their limbs over the glands on their backs, and wipe the lipids above their bodies. Other desert amphibians, such as the Cyclorana frog genus, avoid drought by digging underground soil during dry periods and forming cocoons from the shed skin: instead of peeling, the skin remains attached to create a cocoon. When the skin layer collects, water impermeability increases.
During evaporation
Although desert birds do not have sweat glands, they can still utilize evaporative cooling with panting, which cools the trachea and lungs, and the gum flap, which consists of rapidly moving the gum to move air above the inner mouth and throat. Kangaroo rats and other small mammals use evaporative cooling in the same way. When the air is inhaled, water evaporates from the nose, cooling the surface of the nasal passage to about 24 ° C (75 ° F). Low temperatures cause moisture to condense, partially fabricated for lost water. The process, called the exchange of breathing heat, works best when the nasal funnel wall has a large surface area.
Some animals pour bodily fluids on themselves to take advantage of evaporative cooling. Xerocole birds like cranes, New World vultures, and ibis urinate on their feet, while desert turtles sometimes salivate around the neck and forelegs to keep them cool. Likewise, many rodents and marsupials lick themselves to spread saliva, although this is only effective for a short time, and requires feathers to get very damp.
Excression
Urine
To remove nitrogen waste products, mammals (and most amphibians) secrete diluted urea in water. The Xerocoles have adapted to make their urine concentrated as possible (ie using the least amount of water) to dissolve urea. Desert mammals have longer and deeper inset nephrons, as well as smaller and less cortical and juxtamedulla glomeruli (glomeruli into capillary tissue where fluids and wastes are extracted from the blood). This in turn leads to a smaller level of glomerular filtration, and overall, less water is transferred from the blood to the kidneys. The kidney of desert mammals is also better adapted to the reabsorption of water from the tubular fluid: although there are fewer glomeruli, xerocole has a larger juxtamedulla glomeruli than the cortical glomeruli (the former plays an important role in urine concentration), whereas the opposite is true for non-xerocoles. Desert mammals also have longer Henle arches, whose efficiency structure in concentrating urine is proportional to its length. The efficiency of their loop from Henle coupled with an increase in antidiuretic hormone in their blood.
The amphibians of the desert can store more nitrogen than the aquatic, and do so when not enough water is available to remove nitrogen as urea. The African reed frogs can store excess nitrogen in iridophore, pigmented shells on its skin, by converting nitrogen into guanine, which forms most of the iridophores composition.
Reptiles, birds, insects, and some amphibian species excrete nitrogenous waste as uric acid rather than urea. Because uric acid is less toxic than urea, uric acid does not need to be dissolved in water to be excreted (hence, mostly insoluble).
Stool
Most animal waste is more than 75% water; xerocoles, however, reabsorb the water in the intestine and produce drier feces. For example, kangaroo mouse droppings contain only 1 / 6 as much water as any other non-desert rodent. In insects, the rectal gland also absorbs water, and the insects secrete dry pellets. In birds, along with several other vertebrates, the ureters and rectum lead to the cloaca, whose walls also absorb water.
Other methods
Camels can further save water by closing holes in their stomachs to make two compartments: one for water and another for food.
The seed-eating rod maintains a low metabolic rate to reduce water lost for respiration (and to prevent their burrow from overheating). The rodents produce concentrated milk for their children, and then eat the urine and dirt of their children to regain some of the lost water. Canang deserts and kangaroos eat their own child feces for the same reason.
Australian water catchers conserve water by holding urine in the bladder, swell like a balloon; then use his bladder as a water reserve during the dry season.
Maps Xerocole
Alternative water source
Xerocoles get large amounts of hygroscopic water from their diet. Many eat moisture-filled plants: aardvarks get water from wild cucumbers and camels eat succulents and shrubs in winter, get enough water to go two months without drinking. The oryx eats Acacia leaves late at night, when the water content is highest: during the hot day, and dry leaves only 1% water; but in the cooler and damper nights, the foliage is 40% water. Some xerocoles can obtain water from halophytic plants (sea water), because they can metabolize oxalic acid in large quantities and produce very concentrated urine. The sharply carved kangaroo mouse also reduces the salty taste of the halophyte it eats (shadscale) by using its wide and sharp bottom teeth to scrape the salted outbeayer from the leaves to reach the less salty center.
Carnivores take water from the flesh and blood of its prey. Insectivores, such as aardwolf (a type of hyena) and southern grasshopper, are thus largely free of free water.
Xerocoles obtain a large percentage of their water from the metabolic processes used to break down their food. Water obtained from fat is almost twice the amount obtained from carbohydrates, because the former contains more hydrogen (which determines the amount of water produced). Water obtained from metabolism is more than enough to offset the lost water from evaporation in the lungs (which increases due to the need for oxygen to break food).
Thermal settings
Morphology
Xerocoles such as rabbits have large ears that help them stay calm: when the ears stand up, the blood flow rises to many vessels there and the heat dissipates. However, at 48Ã, Â ° C (118Ã, Â ° F), horn bunnies near Abu Dhabi, the UAE sits in the shade and the curtains of the ears above itself, as setting them up in such weather will absorb more heat.
The desert animals have less fat than their non-desert counterparts, because the fat will act as insulation, thus retaining heat. What fats they have are localized, such as in the hump of a camel or bison's neck. In terms of feathers, however, desert animals have thick insulating coats that block the heat conduction toward the body. The coat is not distributed uniformly, but leaves a rarely closed patch called "thermal window" in the axilla, groin, scrotum, and mammary gland. Heat can be dissipated from the thermal window by convection and conduction.
Similarly, desert birds have less feathers at underwing and pelvic pressures - the heat induce some birds to lift their wings, increasing the surface area of ​​exposed skin. Birds adjust their feathers to create or remove insulating layers, such as those characterized by ostriches. At high temperatures, the ostrich raises its long dorsal fur to create a barrier against solar radiation while allowing air to move across the skin's surface. In the cool night, the feathers are lower and interlocked, trapping the insulating layer above the skin.
Burrows
Most small xerocoles stay in burrows to avoid desert heat. Hallways function as microenvironments: as they deepen from 50-60 cm (20-24 in) below the surface, they keep humidity and temperatures between 30 and 32 Â ° C (86 and 90 Â ° F), regardless of the external weather. Some animals seal their burrows for moisture.
Ectotherms also uses burrows as a means to keep warm in the cold desert nights. Because ectotherms are usually small and can not store their own body heat, they rapidly pick up the external temperature of the environment, which requires the micro-environment to be controlled. For example, while reptiles can operate at temperatures that exceed optima, they become sluggish when cold. Thus, they spend their nights in burrows or crevices, where they create a warm environment by generating rapid metabolic heat. Desert lizards usually use other animal burrows to meet their goals.
Circadian rhythms
All desert rodents except ground squirrels and chipmunks are nocturnal animals. Amphibians are usually active at night, while many other xerocole are diurnal, but decreases activity in the middle of the day and increases in the morning and evening. Some xerocoles change their activity patterns depending on the season: nocturnal ants, for example, become diurnal during cold periods.
Many xerocoles, especially rodents, react in the summer, become more active. Some desert amphibians are recreated underground for more than a year at a time. Unlike hibernation, which leads to suspended animation, estivation induces lethargy, and may escape the attention of some animals if their body temperature is not measured.
Sun protection
Xerocoles are usually light-colored and sandy as a means to reflect solar radiation and reduce heat absorption. Some change color with the season to reflect more sunlight in summer: addaxes change from gray-brown to almost white. The Iguanid lizard may change color on a much smaller time scale by varying the concentration of melanin. They get darker when digging and lighter in the sun - both desert iguanas and zebra-tailed lizards become so pale that they look shining because of the amount of light they reflect.
Most desert lizards also have a layer of black peritoneum in their abdominal cavities to absorb UV radiation and prevent it from damaging internal organs.
The shade under the bush provides a resting place for diurnal lizards, nesting sites for birds, as well as temporary oases for diurnal rodents, which surround shady spots. Large animals such as camels and carnivores also spend the hottest parts of the day in the shade.
Sand protection
Desert animals such as camels, addax, and mouse kangaroos have large legs to prevent them from drowning in the sand. Fox fennec has extra fur on the soles of his feet to give it an appeal and protect it from hot sand. Most animals in arid environments are slender with long legs, giving them speed as they travel long distances for food and water.
The three major vulnerabilities to sand are through the eyes, ears, and nose. To keep the sand from their eyes, xerocoles include reptiles and birds, and some amphibians and mammals have disruptive membranes in their eyes: a third transparent eyelid that protects the cornea from blowing the sand and can remove it from the eye. Reptiles also have small size eye holes or are protected by valves. To keep the sand out of their ears, mammals such as camels and sand cats have long hair protruding from them. Camels and saiga antelope also have adaptations to protect their noses from the sand: the first has narrow nostrils that can close, and the latter has a large nose with its separate nostrils and far back to prevent sand coming in while grazing. The reptile digger has a nose that faces upward rather than forward for the same reason.
Speed ​​
Xerocoles, have to travel long distances for food and water, often adjusted for speed, and have long legs, legs that prevent them from drowning in the sand, and are overall slim in shape. Because there is little protection to protect them from predators, desert animals also use speed as a defense mechanism. For example, a forest rabbit can run faster than a coyote; thus, "ordinary wolves or coyotes will not try to chase after them, because they realize their despair."
Known xerocoles
The following animals are known as xerocoles:
See also
- Arid Forest Research Institute (AFRI)
- Chionophile
- Desert and shrublands xeric
- Xerophile
- Xerophyte
References
Quote
Source
-
Mares, Michael A.; Oklahoma Museum of Natural History, eds. (1999). Desert . University of Oklahoma Press. ISBNÃ, 9780806131467 Ã,
External links
- Desert Wildlife Photo Gallery from National Geographic
- Photo Gallery from Flickr
Source of the article : Wikipedia
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