of Summary problems
Salt and water rela+ons
Homeosta+s
9/29
Freshwater: simple animals
Includes
Protozoans
Simple metazoans (hydra, sponge, ciliates)
Freshwater
Tends to gain water
Tends to lose salt
Marine
Terrestrial
Net loss/gain of salt
depends on diet
Tends to lose water
Tends to lose water
Tends to gain salt
Freshwater: simple animals
Do not have blood
Cells bathed directly by external medium
Problems:
out 0
in > 0 because some solutes are necessary for life
> 0
Which way does water move?
1
Freshwater: simple
Problem
Contrac+le vacuole: Paramecium
large feeder vacuoles
small contractile vacuole
Constant tendency to swell
Solu+ons?
Decrease i somewhat, but not to = o
Pump water out as it comes in: contrac+le
vacuole
1. Feeder vacuoles
accumulate water
2. Transfer water to
contrac+le vacuole
3. Contrac+le vacuole fuses
with cell membrane,
ejects contents
See addi+onal notes under
43 for more informa+on
1
2
large contractile vacuole
small feeder vacuoles
Freshwater: simple
Problem
Constant tendency to swell
Solu+ons?
Decrease i somewhat, but not to = o
Pump water out as it comes in: contrac+le
vacuole
Other possibili+es?
Davenport, Anatomy and Physiology
Freshwater metazoans
Cells bathed in extracellular uid (ECF)
Blood plasma
Lymph
Hemocoel
ECF = cell
Cell is isosmo+c with ECF
2
Freshwater metazoans
Cells bathed in ECF
Cells usually isosmo+c with ECF
No cellular osmo+c problems
Problem transferred: regulate blood (ECF) with
respect to external medium
Freshwater metazoans
Cells bathed in uid
Cells usually isosmo+c with uid
Blood tends to
Gain water
Lose salt
Across skin, gut, gas exchange surface
During excre+on
Freshwater metazoans
Cells bathed in uid
Cells usually isosmo+c with uid
Blood tends to
Gain water
Limit gain: waterproof surfaces
Counteract
Excrete large volumes of urine
Freshwater metazoans
Cells bathed in uid
Cells usually isosmo+c with uid
Blood tends to
Gain water
Lose salt
Minimize loss
Decrease ion permeability of skin
Very dilute urine
3
Freshwater metazoans
Cells bathed in uid
Cells usually isosmo+c with uid
Blood tends to
Gain water
Lose salt
Marine protozoa
Protozoa
Simple metazoa
Corals
Sponges
Cells bathed directly by seawater
Minimize loss
Counteract: Ac+ve uptake of salt: by skin, gas
exchange surfaces, gut
Marine protozoa
out=~1000 mOsmol
Raise i to 1000 mOsmol
Use solute that is not involved in genera+ng
membrane poten+al
Use solute that is not involved in basic metabolism
Not glucose, fructose, pyruvate, etc.
Marine protozoa
Raise i with solutes (osmolytes) not involved in
genera+ng membrane poten+al or basic metabolism
See Table 132, p. 5801, in your text for list.
Does not dis+nguish between intracellular and
extracellular accumula+on
Protozoa: all intracellular
Metazoa may accumulate extra or intracellularly
4
Marine protozoa
(and metazoa)
Typical osmolytes
Polyalcohols*: mannitol, glycerol (sweet taste)
Unusual amino acids or other amines: taurine,
glycinebetaine, methyl amine (shy taste)
Some normal amino acids: proline, glutamate
(umami or delicious taste)
Sulfurcontaining compounds (ocean odor)
*more than 1 COH group; ojen derived from carbohydrates
Marine metazoa
Marine protozoa
in = out: No osmo+c problem
Ccellsalt < CSWsalt (except K+)
Organic solutes contribute to in
Must ac+vely secrete salt
Marine metazoa
Cells bathed in uid (blood)
Two strategies
Cells bathed in uid (blood)
Two strategies
Osmoconformer: blood = SW
Osmoconformer: blood = SW
Osmo+c pressure of blood conforms to that of
seawater
Who are osmoconformers?
Many invertebrates
Some vertebrates
Who are osmoconformers?
Types of osmoconformers
Invertebrates
Cyclostomes
5
Marine metazoa
Cells bathed in uid (blood)
Two strategies
Osmoconformer: blood = SW
Who are osmoconformers?
Types of osmoconformers
Ionoconformers: ion composi+on same as seawater
Ionoregulators
Regulate ionic levels be to constant, dierent from SW
(typically < SW)
Keep blood=SW with organic solute
Marine metazoa
Cells bathed in uid (blood)
Two strategies
Osmoconformer: blood = SW
Advantage: No problems with osmo+c regula+on
Disadvantage
Ojen poorly adapted to changing condi+ons
Excep+ons must regulate cell to match changes in blood with
organic osmolytes
Marine metazoa
Cells bathed in uid (blood)
Two strategies
Osmoconformer: blood = SW
Advantage: No problems with osmo+c regula+on
Disadvantage
Ojen poorly adapted to changing condi+ons
Restricted to limited range of salini+es: stenohaline
Examples: cnidarians, echinoderms, lobster
Excep+ons:
Oysters (cf. p. 582 in text)
Ionoregulators (cf. Rana)
Marine metazoa
Cells bathed in uid (blood)
Two strategies
Osmoconformer: blood = SW
Osmoregulator: Regulate osmo+c pressure so that
it is constant, generally less than sea water
Who? Most vertebrates
Teleosts (except coelocanth)
Rep+les
Mammals
6
Marine metazoa
Cells bathed in uid (blood)
Two strategies
Osmoconformer: blood = SW
Osmoregulator: blood constant, < SW
Advantage: Blood constant, so easier to move between
changing condi+ons
Marine metazoa
Osmoregulators
blood< SW
Tendency to lose water
Prevent: waterproof; small urine volume
Compensa+on: drink
Can adapt to wide range of salini+es: euryhaline
Disadvantage: Always work to maintain blood dierent
from medium
Marine metazoa
Osmoregulators
blood< SW
Csaltin<Csaltout: Same as ionoregula+ng osmoconformers
Marine metazoa
Osmoregulators
blood< SW
Csaltin<Csaltout: Same as ionoregula+ng osmoconformers
Tendency to gain salts
Across skin, gills, gut
Exacerbated by drinking sea water (to compensate for water
loss)
Prevent: decrease Psalts
Compensate: excrete salts
7
Regula+on strategies
Regula+on strategies
Review of stresses and
strategies in dierent
marine vertebrates.
In all strategies, cells and
extracellular uid
(ECF) have same
(=RT Csolutes)
Fig 13-4A; Sherwood Klandorf Yancy, Animal Physiology
Fig 13-9; Sherwood Klandorf Yancy, Animal Physiology
Regula+on strategies
1
1. Osmoconforming
and ionoconforming
Fig 13-4A; Sherwood Klandorf Yancy, Animal Physiology
Salt in extracellular
uid is similar to that
in seawater
Salt in cells much less
Balance of osmo+c
pressure due to
organic osmolytes
Regula+on strategies
1
2
1. Osmoconforming and
ionoconforming
2. Osmoconforming and
ionoregula+ng
ECF = seawater
[salt]ECF < [salt]SW
Osmo+c pressures made
up with organic solutes
Fig 13-4A; Sherwood Klandorf Yancy, Animal Physiology
8
Regula+on strategies
1
2
3
1. Osmoconforming and
ionoconforming
2. Osmoconforming and
ionoregula+ng
3. Osmoregulator
Not all organisms perfect
conformers/regulators
Perfect osmoregulator
of both ECF and cells is
less than SW
Fig 13-4A; Sherwood Klandorf Yancy, Animal Physiology
Regula+on strategies
Not all organisms perfect
conformers/regulators
Perfect osmoregulator
Perfect
osmoconformer
Fig 13-4b; Sherwood Klandorf Yancy, Animal Physiology
Regula+on strategies
Fig 13-4b; Sherwood Klandorf Yancy, Animal Physiology
Regula+on strategies
Not all organisms perfect
conformers/regulators
Some organisms
regulate over a limited
range, and slope may
be >0 even within that
range.
Limits range of salini+es
organism can tolerate
Fig 13-4b; Sherwood Klandorf Yancy, Animal Physiology
9
Regula+on strategies
Organisms with
dierent strategies.
Marine vertebrates:
preqy good osmo
regulators, body uid
~300 mOsm
Fig 13-4c; Sherwood Klandorf Yancy, Animal Physiology
Regula+on strategies
Organisms with
dierent strategies.
Note: inclusion of
terrestrial organisms
Inappropriate: what is
osmolarity of
environment?
Fig 13-4c; Sherwood Klandorf Yancy, Animal Physiology
Terrestrial animals
Strong tendency to lose water to air
Solu+ons
Limit loss
Waterproof where possible (skin, etc.)
Bury gas exchange surfaces (lungs, trachea)
Minimize excretory volume, water content
Replace: eat, drink
10