arid environments

E3176 Erçin Öncel

E3331 Vassilis Bitsikas

E3175 Aslıhan Çoban

School of Sciences Department of BiologyDo Minho University

Animal Physiology

14.01.2010

Water Balance in AnimalsGain

Oxidation waterWater in foodDrink water

Loss

Evaporation from skinEvaporation from lungsWater in faecesWater in urine

Water Balance in AnimalsEvaporation from skin

For mammals, evaporative heat loss includes sweating.

Evaporation from lungs Water loss through the respiratory tractaverages. Exp panting.

Water in feces Normal gastrointestinal loss ofwater in feces is generally quite small.

Water in urine Urea is very toxic compound in the body which is converted from ammonia by some enyzme. It needs to take it away from body. Some water spends during this process couse of that, It easily soluble in water and has a moderately low toxicity

Loss;

Water Balance in AnimalsDrink water

Animals can gain water directly drinking water

Water in foodAnimals can gain water due to foods especially, fruits and vegetables

Oxidation water The water resulting from the oxidation of nutrients such as protein, carbonhydrates and fats.

Gain;

Deserts

A desert is a very dry place. It either receives an average annual rainfall of less than 250 mm or has more water that is lost than falls as rain. A desert can be freezing cold or burning hot. Most of a desert is made up of sand or snow, sand dunes or snowdrifts, and cacti or very small plants. It is a biome, one where there is little rainfall.

Types of DesertsWe can separate the deserts according to rainfall and temperature

Deserts in the World

ESCAPE FROM THE DESERT ENVIRONMENT

•How important the exploitation of favourable micro-climates is within

the desert ecosystem

•How desert organisms avoid the harshness of the desert climate

• AESTIVATION

• SEOSANAL MIGRATION

AESTIVATION

• Estivatition, also known as ‘summer sleep’, is a state of animal dormancy somewhat similar to hibernation

• Estivatition: Sleep during hottest parts of each year( July and August )

GROUND SQUIRRELS

GENUS: Citellus

• They sleep for about seven months a year in burrows when the air temperature gets above 98 degrees Fahrenheit

SPADEFOOT TOADS

GENUS: Scaphiopus

•They spend most of the time during the dry season buried in the ground in estivation

AFRICAN BULLFROG

Pyxicephalus adspersus

•It makes a dry, watertight cocoon for itself, which prevents the evaporation of body fluids; without a cocoon looses it loses Approximately half of the water that a frog

Seasonal Migration

• The periodic movement of a population from one region or climate to another in accordance with the yearly cycle of weather and temperature changes.

THE NAMAQUA SANDGROUSE

• Phainopepla nitens

•This species winters in thedeserts of the South-Western United States and with the advent of hot summer conditions, moves to the more mesic environments surrounding the desert areas.

Physiological and behavioural adaptations

Tolerance of the Arid Environment

• Morphological Adaptations WATER STORAGE ECTOPIC STORAGE OF FAT ANIMAL COLOUR SHAPE AND SIZE

WATER STORAGE

• Both plants and animals employ water storage as a mechanism of defence against prolonged droughts in the desert.

• Henderson and Loveridge have examined the role of hypo-osmotic urine in the water economy of Chersina angulata.

Desert Tortoises

•They established that when these animals were exposed to starvation and desiccation,there was a progressive reduction in urine volume and concluded that ‘Bladder urine’ was potentially an important source of water for this species

Ectopic Storage Of Fat

• Fat storage in animals would be especially important to allow survival during prolonged periods of drought and shortages of food energy

Large desert- adapted mammals show a similar form of adaptation :

• Antelopes

• Camels

• Humbed do zebu cattle

• Fat-tailed sheep

Animal Colour

• Cryptic Coloration is particularly well developed in many desert animals.

• Lizards, snakes, grasshoppers and the precocious chicks of some ground-nesting birds.

• The desert tenebrionid;

Cryptoglossa verrucosa changes from a jet-black to light blue when the relative humidity decreases.

Shape and Size

• Body size and shape are most important considerations in evaluating the adaptation of desert animals.

Oryx

• This species,because of its large size, has a high thermal inertia and will be able to store a large amount of heat in its body tissues during the day without resorting to the evaporation of precious water for cooling purposes.

shelled, amniotic eggtough, dry,

heavily keratinized skin

Adaptations that unshackled reptiles from the aquatic environment.

No more dependence on aquatic or very moist terrestrial environments.

Arthropod cuticle

Lipid-like deposits provide waterproof properties and minimise water losses by reducing the cuticular transpiration

Specialized spiracle structure that minimises water loss

Behavioural thermoregulation

Activity of the antelope ground squirrel Ammospermophilus leucurus during a typical day in the

Nevada desert

Ammospermophilus is an evader but a degree of endurance is indicated too.

Adaptive heterothermyThe ability of an endothermic animal to allow its body temperature to fluctuate in response to some form of environmental stress.

Saving significant amounts of energy and water.

Maximum fluctuation during 1 day: 6,2 °C

Osmoregulation

Period of dehydration: day 4 - 12

Negative feedback control of the secretion of antidiuretic hormone, ADH

Two types of nephron, distinguished by the length

of their loops of Henle

Most mammalian kidneys contain a mixture of the two types but some species have only one or the other

Cortical nephrons have short-reach loops that just penetrate the boundary between the inner and outer zones of the medulla.

Juxtamedullary nephrons have long-reach loops that penetrate deep into the medulla.

The longer the loop of Henle relative to the overall depth of the cortex, the higher is the osmolarity of the fluid in the bend. The kidney thereby retains as much water as possible, minimising loss of water during water shortage.

Most loops of Henle in desert rodents are of the juxtamedullary type and could therefore be viewed as a desert adaptation

Uric acid is highly insoluble and easily precipitates from solution, allowing its removal in almost solid form.

ExcertionThe key feature that seems to determine choice of nitrogenous waste is availability of water in the environment.

Tolerance to Dehydration

• Desert amphibians can tolerate 40-50% losses of body water

• A camel can lose 30% of its body water and retain it back in 10 minutes. For other large mammals a 12-14% weight loss is lethal. [capacious rumen (fore-stomach) protect them from osmotic stress]

• Store water

What is the physiological differences Between desert and arctic fox?

•Its legs, ears and muzzle are long to dissipate heat, and it has a high surface area

•The coat is often a cream color and fluffy, which deflects heat during the day and keeps them warm at night

•Its legs, ears and muzzle are short to dissipate heat its tail like a muffler when cold. The fox has a low surface area

•Its fur changes color with the seasons: in the winter it is white to blend in with snow, while in the summer months it changes to brown.

Adaptations of Desert Animals

• Dromedary Camel (Camelus dromedarius) A camel can last three months without water, a special adaptation for desert living.

Camels store fat in the hump, not water. The fat can be metabolized for energy. Unlike most mammals, a healthy camel's body temperature fluctuates throughout theday from 34°C to 41.7°C (93°F-107°F.) This allows the camel to conserve water bynot sweating as the environmental temperature rises. Camels have nostrils that can open and close, protecting the respiratory tract fromblowing sand.

Adaptations of Desert Animals

• Kangaroo Rat (Dipodomys deserti)

They have large hind feet that keep them from sinking into the sand. Kangaroo rats dig burrows to protect themselves from predators and heat.Kangaroo Rats are nocturnal (avoiding the heat during the day.)Large ears help dissipate heat.Kangaroo rats may obtain their water from the food they eat.

Adaptations of Desert Animals

• Fennec Fox (Vulpes zerda)Their large ears, which are usually 4 to 6 inches long, help dissipate excess bodyheat on hot days in the desert.Their burrowing and nocturnal lifestyle helps restrict water loss.Their thick fur helps insulate them from the cold desert nights.Their sandy coloration helps to reflect heat, and also provides excellent camouflage

Conclusions

The key to the survival in hot, dry environments consists in avoiding climatic extremes as far as possible, by a combination of seekingrefuge from the most adverse conditions, morphologicaladaptations, behaviour and specialized physiology.

Whereas thermal reactions are primarily behavioural, adaptational responses to aridity are mostly physiological.

Exploitation of desert habitats involves a vast complex of adaptive compromises between set of factors.

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