Maintaining a body in a “steady state” Homeostasis © Cincinnati Zoo.

Maintaining a body in a “steady state”

Homeostasis

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Environments where freshwater is scarce:

• Desert• Invertebrates• Reptiles• Terrestrial Mammals

• Ocean• Invertebrates• Fish• Marine Mammals, Turtles, & Birds

• Hypersaline Lakes• Invertebrates

World-wide distribution of desert environments

•For example Shahara Desert is 3.5 mil sq. miles

•Less than < 3 in. annual rainfall (6.7 cm)

•Habitat: Rocky Plateaus (15%), Sandy Dunes (15%), Gravel Plains (70%)

Adaptations for osmoregulation (water balance)

• ↓ Water Loss– Conservation– Utilization (↑Efficiency)– ↑ Storage capacity– ↕ Solute/waste excretion

LE 44-5Water

balance in a kangaroo rat(2 mL/day)

Waterbalance ina human

(2,500 mL/day)

Watergain

Waterloss

Derived frommetabolism (1.8 mL)

Ingestedin food (0.2 mL)

Derived frommetabolism (250 mL)

Ingestedin food (750 mL)

Ingestedin liquid (1,500 mL)

Evaporation (900 mL)

Feces (100 mL)Urine(1,500 mL)

Evaporation (1.46 mL)

Feces (0.09 mL)Urine(0.45 mL)

LE 44-8

Nitrogenous bases

Nucleic acids

Amino acids

Proteins

—NH2

Amino groups

Most aquatic animals, including most bony fishes

Mammals, most amphibians, sharks, some bony fishes

Many reptiles (including birds), insects, land snails

Ammonia Urea Uric acid

Waste management varies under different circumstances:

• Habitat– Terrestrial vs. aquatic turtles

• Reproductive strategy– Mammals: maternal transport of waste

– Amphibians: diffuse Ammonia out of egg (lacking shell)

– Birds/Reptiles: store as relatively less toxic uric acid

• Diet– ↑ Animal tissue => ↑ N-Wastes

• Metabolic requirement– ↑ metabolism => ↑ N-Wastes



• ↓Metabolic Requirements

• Unique physiologic structures– Renal structure– Salt Glands

Reduce Metabolic Requirements– Reduce metabolic rate

• Slow heart, blood flow• Reduces O2 consumption• Reduces body temp

– Reduce activity• Seek shelter, such as a burrow,

shade, deeper water– e.g. Fennec, Leatherback

• Enter torpor (or estivation, in summer) – resting state

– e.g. Tarigrade, Mulgara, Long-necked Turtles

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Hydrated tardigrade Dehydrated tardigrade

100 µm

100 µm

Diffusion Osmosis• Solutes move from

greater solute concentration to lower conc.

• Diffusion of water through a selectively permeable membrane

Basic concept review:

3:2

3:1

Surface area to volume (SA:V)

d = 1

d = 2

Chptr 40: Animal Form & Function, pp. 820-821

Dromedary or Arabian Camel(Camelus dromedarius)

Adaptations to ↓ Heat Loss• Anatomy

– Hump (Fat = H20 Storage)– Lips (chewing tough vegetation)– Double eyelashes

• Physiology– Increase body temp to match

ambient temp– Body temp. range: 34 - 42°C (8°C

range)

• Behavior– Huddling– Tracking sun

Kingdom Animalia Phylum Chordata Subphylum Vertebrata Class Mammalia Order Artiodactyla Family Camelidae

http://animaldiversity.ummz.umich.edu/site/accounts/information/Animalia.html

http://animaldiversity.ummz.umich.edu/site/accounts/information/Chordata.html

http://animaldiversity.ummz.umich.edu/site/accounts/information/Vertebrata.html

http://animaldiversity.ummz.umich.edu/site/accounts/information/Mammalia.html

http://animaldiversity.ummz.umich.edu/site/accounts/information/Artiodactyla.html

http://animaldiversity.ummz.umich.edu/site/accounts/information/Camelidae.html

LE 44-6

Control group(Unclipped fur)

Experimental group(Clipped fur)

Wat

er l

ost

per

day

(L/1

00 k

g b

od

y m

ass) 4

3

2

1

0

Fennec Fox (Fennecus zerda [=Volpes zerda])

Sahara Desert• Anatomy

– Small body size– Large ears– Furred foot pads

• Behavior– Burrowing (↑ Humidity)– Nocturnal

• Physiology (↓Water Loss)– Reduced heart rate– Reduced metabolic rate

Kingdom Animalia Phylum Chordata Subphylum Vertebrata Class Mammalia Order Carnivora Suborder Caniformia Family Canidae

Banholzer, U. 1976. Water balance, metabolism, and heart rate in the Fennec. Naturwissenschaften 63 (4): 202-203.

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85 - 95 F






Mulgara(Dasycercus cristicauda)

• Occurs in arid, sandy regions of Australia

• Related to marsupials• Example of convergent

evolution with rodents– Small size, long tail– Fossorial (burrowing)– Nocturnal

*Nocon, W. 1999. "Dasycercus cristicauda" (On-line), Animal Diversity Web. Accessed May 24, 2008 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Dasycercus_cristicauda.html.

Kingdom Animalia Phylum Chordata Subphylum Vertebrata Class Mammalia Infraclass Marsupialia Order Dasyuromorphia Suborder Dasyuridae Family Dasyurinae

–Torpor bouts 3 to 12 hr thus reduce metabolism to <12% of normal rate**

**Geiser, F and P. Masters. 1994. Torpor in relation to reproduction in the mulgara, Dasycercus cristicauda (Dasyuridae: Marsupialia) J. THERM. BIOL. 19 (1) pp. 33-40.

Bannertail kangaroo rat(Dipodomys spectabilis)





http://animaldiversity.ummz.umich.edu/site/accounts/information/Dasyuromorphia.html


LE 44-18c

Roadrunner(Geococcyx californianus)

Desert iguana(Dipsosaurus dorsalis)

Marine Environment

• Ionic gradient set up: organism less salty than environment, salts want to enter body, water to leave (dehydration)

• Most marine invertebrates are osmoconformers• Most marine vertebrates and some invertebrates

are osmoregulators

• Hypotonic – less salty than environment• Hypertonic - saltier than environment

“Water, water everywhere, nor any drop to drink”- Coleridge

Marine Invertebrates• Most inverts are osmo –

isotonic with environment (e.g. sponges)

• Some have specialized protonephridia composed of ciliated flame cells to transport solutes and waste products for elimination

Polyclad Flatworm

Filtration

Metanephridia: most annelids

Malpighian tubules: insects

Freshwater vs. Marine FishGain of water andsalt ions from foodand seawater

Osmotic water lossthrough gills and body surface

Excretion ofsalt ionsfrom gills

Excretion of salt ions and small amountsof water in scantyurine from kidneys

Excretelarge amounts ofDilute urine

Osmotic water gainthrough gills and body surface

salt ionsby gills

water and someions in food

Marine bony fishes are hypoosmotic to sea waterThey lose water by osmosis and gain salt by diffusion and from foodThey balance water loss by drinking seawater

Freshwater animals are hyperosmotic to their environmentThey lose salts by diffusion and maintain water balance by excreting large amounts of dilute urineSalts lost by diffusion are replaced by foods and uptake across the gills

Green Sea Turtle(Chelonia mydas)

• The primary osmo-regulatory mechanism in sea turtles is the salt gland

• The surface area: volume ratio is different for age classes: a 50g immature has greater surface area, and larger relative salt glands (0.3% of body size) than a 50 kg subadult (0.05 –0.1%)– i.e., osmotic challenge varies by age

Kingdom Animalia Phylum Chordata Subphylum Vertebrata Class Reptilia Order Testudines Family Cheloniidae







Leatherback Sea Turtle

(Dermochelys coriacea)

• Salt glands secrete monovalent ions (Na+), which is the main constituent of seawater, while renal system processes bivalent ions (Mg++)

• Sea turtles, marine reptiles & marine birds: super-saline secretions from salt glands– Lacrymal (turtles) – eye secretions– Nasal (lizards)– Post-orbital (birds)– Sublingual or premaxillary (snakes)– Lingual (crocodiles)

Kingdom Animalia Phylum Chordata Subphylum Vertebrata Class Reptilia Order Testudines Family Dermocheliidae

Prange, H.D. 1985. Osmoregulation: water and salt balance in sea turtles Copeia 1985 (3): 771-776.Hudson, D. M. and P. L. Lutz 1986. Salt Gland Function in the Leatherback Sea Turtle, Dermochelys coriacea Copeia, 1986 (1):247-249







Salt glands in marine birds

Nostrilwith saltsecretions

Nasal salt gland

• Salt glands of marine birds remove excess sodium chloride from the blood• Use transport epithelia, which are specialized cells that regulate solute movement arranged in complex tubular networks

Pink-footed Shearwater (P. Hodum)Puffinus cretapus

Vein

Capillary

Secretorytubule

Transportepithelium

Directionof saltmovement

Centralduct

Artery

Bloodflow

Lumen ofsecretory tubule

NaCl

Secretory cellof transportepithelium

LE 44-13

RenalmedullaRenalcortex

Section of kidney from a ratKidney structure

Ureter

Kidney

Glomerulus

Bowman’s capsule

Proximal tubule

Peritubular capillaries

Afferentarteriolefrom renalartery

Distaltubule

Collectingduct

SEM

20 µm

Filtrate and blood flow

Vasarecta

Descendinglimb

Ascendinglimb

LoopofHenle

Renalmedulla

Nephron

Renalcortex

Collectingduct

Ureter

Urinary bladder

Urethra

Structure of Kidney

LE 44-14

Filtrate

H2O

Salts (NaCl and others)

HCO3–

H+

Urea

Glucose; amino acids

Some drugs

Key

Active transport

Passive transportINNERMEDULLA

OUTERMEDULLA

NaCl

H2O

CORTEX

Descending limbof loop ofHenle

Proximal tubule

NaCl Nutrients

HCO3–

H+

K+

NH3

H2O

Distal tubule

NaCl HCO3–

H+K+

H2O

Thick segmentof ascendinglimb

NaCl

NaCl

Thin segmentof ascendinglimb

Collectingduct

Urea

H2O

Kidney: Nephron

California Sea Lion (Zalophus californianus)

• Derive water from food – fish, squid

• All marine mammals have reniculate kidneys

• which means that instead of having two single bean-shaped kidneys, each kidney is instead made up of grapelike clusters of smaller, independent kidney units, or renicles, as shown

Kingdom Animalia Phylum Chordata Subphylum Vertebrata Class Mammalia Order Carnivora Suborder Pinnipedia Family Otariidae

Cross-section

Marine Wildlife Veterinary Care & Research Center






ADH: Anti-diuretic Hormone

Mono Lake, CA (HN)

Hypersaline Environments

Often very simple food web & trophic level structure– Hypersaline lakes: – e.g. Mono Lake, Great Salt Lake

• Lower trophic level, low diversity: Brine shrimp (Artemia spp.)

• Higher trophic level, great diversity: shorebirds, gulls & grebes

Great Salt Lake, Utah (photo: NASA)

American Avocet

http://ut.water.usgs.gov/shrimp/index.html "Brine Shrimp and Ecology of Great Salt Lake", United States Geological Survey

http://ut.water.usgs.gov/shrimp/index.html

http://en.wikipedia.org/wiki/United_States_Geological_Survey


– High level of endemism– Hypersaline lagoons: – e.g. Laysan Is., NW Hawaiian

Islands• Brine flies (Ephydra spp.)• Laysan Duck (Anas laysanensis)

Laysan Is., Hawaii (photo: USFWS)

Laysan Ducks (photo: USFWS)

Quiz:

• Name three taxa which occur in freshwater-scarce environments

• Give a key physiological or behavioral adaptation for each to reduce water loss

• How would you expect the structure of the loop of Henle to differ among a tropical forest and a desert rodent?

Answers:• Name three species which occur in freshwater-scarce

environments – Camelus, Artemia, Zalophus, others…

• Give a key physiological or behavioral adaptation for each to reduce water loss– Camelus: hump - water storage, orient to sun, fur– Mulgara: fossorial, torpor– Zalophus: reticulate liver

• How would you expect the structure of the Loop of Henle to differ among a tropical forest and a desert rodent?– Shorter in tropics, longer in desert to increase water absorption

Maintaining a body in a “steady state” Homeostasis © Cincinnati Zoo.

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