© Cincinnati Zoo
Homeostasis
Maintaining a body in a “steady
state”
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 44-5
Water
balance in a
kangaroo rat
(2 mL/day)
Ingested
in food (0.2 mL)
Water
balance in
a human
(2,500 mL/day)
Ingested
in liquid
(1,500 mL)
Ingested
in food
(750 mL)
Water
gain
Derived from
metabolism (1.8 mL)
Feces (0.09 mL)
Urine
(0.45 mL)
Derived from
metabolism (250 mL)
Feces (100 mL)
Urine
(1,500 mL)
Water
loss
Evaporation (1.46 mL)
Evaporation (900 mL)
Adaptations for osmoregulation
(water balance)
• ↓ Water Loss
–
–
–
–
Conservation
Utilization (↑Efficiency)
↑ Storage capacity
↕ Solute/waste excretion
LE 44-8
Proteins
Nucleic acids
Amino acids
Nitrogenous bases
—NH2
Amino groups
Most aquatic
animals, including
most bony fishes
Ammonia
Mammals, most
amphibians, sharks,
some bony fishes
Urea
Many reptiles
(including birds),
insects, land
snails
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
Adaptations for osmoregulation
(water balance)
• ↓ Water Loss
–
–
–
–
Conservation
Utilization (↑Efficiency)
↑ Storage capacity
↕ Solute/waste excretion
• ↓Metabolic Requirements
• Unique physiologic structures
– Renal structure
– Salt Glands
Reduce Metabolic Requirements
© Cincinnati Zoo
– Reduce metabolic rate
• Slow heart, blood flow
• Reduces O2 consumption
• Reduces body temp
– Reduce activity
100 µm
100 µm
Hydrated tardigrade
Dehydrated
tardigrade
• 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, Longnecked Turtles
Basic concept review:
Diffusion
Osmosis
• Solutes move from
greater solute
concentration to lower
conc.
• Diffusion of water
through a selectively
permeable membrane
Surface area to volume (SA:V)
d=2
3:2
3:1
Chptr 40: Animal Form & Function, pp. 820-821
d=1
Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata
Mammalia
Order Artiodactyla
Family Camelidae
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
Class
Water lost per day
(L/100 kg body mass)
LE 44-6
4
3
2
1
0
Control group
(Unclipped fur)
Experimental group
(Clipped fur)
Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata
Class
Mammalia
Order Carnivora
Suborder Caniformia
Family Canidae
Fennec Fox
(Fennecus zerda [=Volpes zerda])
Sahara Desert
© Cincinnati Zoo
• Anatomy
– Small body size
– Large ears
– Furred foot pads
• Behavior
– Burrowing (↑ Humidity)
– Nocturnal
• Physiology (↓Water Loss)
– Reduced heart rate
– Reduced metabolic rate
85 - 95 F
Banholzer, U. 1976. Water balance, metabolism, and heart rate in the Fennec.
Naturwissenschaften 63 (4): 202-203.
Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata
Class
Mammalia
Infraclass Marsupialia Order Dasyuromorphia
Suborder Dasyuridae
Family Dasyurinae
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
Bannertail kangaroo rat
(Dipodomys spectabilis)
–Torpor bouts 3 to 12 hr
thus reduce metabolism to
<12% of normal rate**
*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.
**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.
LE 44-18c
Roadrunner
(Geococcyx californianus)
Desert iguana
(Dipsosaurus dorsalis)
Marine Environment
“Water, water everywhere, nor any drop to drink”
- Coleridge
• 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
Marine Invertebrates
Polyclad Flatworm
• 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
Filtration
Metanephridia: most annelids
Malpighian tubules: insects
Freshwater vs. Marine Fish
Osmotic water gain
through gills and body surface
Gain of water and
salt ions from food
and seawater
Osmotic water loss
through gills and body surface
water and some
ions in food
salt ions
by gills
Excrete
large amounts of
Dilute urine
Freshwater animals are hyperosmotic to
their environment
They lose salts by diffusion and maintain
water balance by excreting large amounts
of dilute urine
Salts lost by diffusion are replaced by
foods and uptake across the gills
Excretion of
salt ions
from gills
Excretion of salt ions
and small amounts
of water in scanty
urine from kidneys
Marine bony fishes are hypoosmotic
to sea water
They lose water by osmosis and gain
salt by diffusion and from food
They balance water loss by drinking
seawater
Kingdom Animalia
Phylum Chordata Subphylum Vertebrata Class
Reptilia
Order Testudines
Family Cheloniidae
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 Dermocheliidae
• Salt glands secrete monovalent ions (Na+),
which is the main constituent of seawater,
while renal system processes bivalent ions
(Mg++)
Leatherback Sea • Sea turtles, marine reptiles & marine birds:
super-saline secretions from salt glands
Turtle
(Dermochelys coriacea)
– Lacrymal (turtles) – eye secretions
– Nasal (lizards)
– Post-orbital (birds)
– Sublingual or premaxillary (snakes)
– Lingual (crocodiles)
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
Nasal salt gland
Nostril
with salt
secretions
Pink-footed Shearwater (P. Hodum)
Puffinus cretapus
• 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
Lumen of
secretory tubule
Vein
Capillary
Artery
Secretory
tubule
NaCl
Transport
epithelium
Direction
of salt
movement
Blood
flow Secretory cell
of transport
epithelium
Central
duct
Structure of Kidney
Kidney
Renal
medulla
Renal
cortex
Ureter
Urinary bladder
Urethra
Ureter
Kidney structure
Section of kidney from a rat
Afferent
arteriole
Glomerulus
from renal
Bowman’s capsule
artery
Proximal tubule
Peritubular capillaries
Renal
cortex
SEM
Collecting
duct
20 µm
Renal
medulla
Distal
tubule
Collecting
duct
Descending
limb
Nephron
Loop
of
Henle Ascending
limb
Filtrate and blood flow
LE 44-13
Vasa
recta
LE 44-14
Proximal tubule
NaCl Nutrients
HCO3–
K+
H2O
H+
NH3
Distal tubule
H2O
NaCl
K+
HCO3–
H+
CORTEX
Descending limb
of loop of
Henle
Filtrate
H2O
Salts (NaCl and others)
HCO3–
H+
Urea
Glucose; amino acids
Some drugs
Thick segment
of ascending
limb
NaCl
H2O
OUTER
MEDULLA
NaCl
Thin segment
of ascending
limb
Key
Collecting
duct
Urea
NaCl
Active transport
Passive transport
INNER
MEDULLA
H2O
Kidney: Nephron
Kingdom Animalia
Phylum Chordata
Subphylum Vertebrata
Class
Mammalia
Order Carnivora
Suborder Pinnipedia
Family Otariidae
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 beanshaped kidneys, each kidney
is instead made up of
grapelike clusters of smaller,
independent kidney units, or
renicles, as shown
Cross-section
Marine Wildlife Veterinary Care & Research Center
ADH: Anti-diuretic Hormone
Hypersaline
Environments
Mono Lake, CA (HN)
Often very simple food web & trophic
level structure
– Hypersaline lakes:
– e.g. Mono Lake, Great Salt Lake
American Avocet
Great Salt Lake, Utah (photo: NASA)
• Lower trophic level, low diversity: Brine
shrimp (Artemia spp.)
• Higher trophic level, great diversity:
shorebirds, gulls & grebes
http://ut.water.usgs.gov/shrimp/index.html "Brine
Shrimp and Ecology of Great Salt Lake", United
States Geological Survey
Hypersaline
Environments
Avocets feeding in hypersaline Mono Lake, Lee County, CA 2007 © H. Nevins
Hypersaline
Environments
Laysan Is., Hawaii (photo: USFWS)
Laysan Ducks (photo: USFWS)
– High level of endemism
– Hypersaline lagoons:
– e.g. Laysan Is., NW Hawaiian
Islands
• Brine flies (Ephydra spp.)
• Laysan Duck (Anas laysanensis)
READY FOR
a QUIZ ???
California Gull, Mono Lake, CA 2007 © H. Nevins
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 freshwaterscarce 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
Questions?
Avocets feeding in hypersaline Mono Lake, Lee County, CA 2007 © H. Nevins