Invertebrate Osmoregulation

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Invertebrate Osmoregulation

• Comparative Animal Physiology

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Today
I. Mechanisms or water intake conservation II.
Marine and freshwater osmoregulation III.
Malpighian tubule function in insects IV.
Epithelial cells function in concentation V.
Animal of the Day
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Water conservation intake

• Some snails can estivateshell epiphragm of dry
  mucus
• Insect cuticle of chitin and wax cover 900X
  variance in water loss rates in diff. species
• Melts and increases loss
• Abrasives as non-toxic insecticides.
• Dont excrete. Retain uric acid (low toxicity).
• Rectal or oral uptake from air with highly
  concentrated solutions, or by drinking dew at
  night (desert beetles)

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Absorb water from air
If humidity exceeds 70 R.H., then dry house mite
can absorb H2O from the air to nearly double
volume.
Dermatophagoides farinae
0.5 mm
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Marine invertebrates
Many marine inverts osmoconform by increasing
A.A. in cells (70 of barnacle muscle cell
osmolytes). Urine is isoosmotic to blood. Often
regulate types of ions.
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Metabolic cost of osmoregulation in FW

• Freshwater invertebrates are hyperosomotic to
  environment.
• Problem absorption of H2O, loss of solutes.
• Solutions
• Work harder at re-gaining lost solutes. (mitten
  crab)
• Decreased permeability. (crayfish)
• Increased excretion of water. (agecrayfish
  vol.clam)
• Partial conformation. (clam)

Theoretical
M 60 g 6 mmol
recovery
20!
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Antennal gland of crustaceans
Filtration of blood followed by selective
reabsorption. Also done in molluscan
heart/pericardium.
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Malpighian tubules of terrestrial insects
2-250
K /H2O
Familiar?
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Rectal cells in terrestrial insects
4X urine
1X hlymph
up
down
Excretion of H NH4
up
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Curran model of water xport
Basal membrane
Resorb H2O
Hyper excreta
hemolymph
to H2O solute
Cant swell (intercellular spaces in rectal
epithelium)
Apical membrane
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Rectal membrane concentration
B ECF
A
like renal tubule
C
like renal medulla
Resorb water
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Counter-current recycling of water KCl
low
high K
high K
low
high NH4,H,uric
low
active
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Nephron v. Malpighian tubule filtration
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THE ANIMAL OF THE DAY (PhArthropoda, GeAedes)
Larvae in brackish water able to osmoregulate
(lt2X internal) in surrounding water hypo-osmotic
or hyperosmotic to their body fluids (500X
variation). Their major organ of osmoregulation
is the set of anal papillae, which transport NaCl
from hypoosmotic water. Excess salt acquired
from a hyperosmotic environment is excreted via
the rectum. Mosquitoes of the species Aedes
aegypti are vectors for the virus that causes
yellow fever.