Ianowski - theme 6 Flashcards
Protonephridia:
“Kidney” of flatworms and rotifers. A network of closed tubules throughout the body. Interstitial fluid enters the kidney through the flame bulb and is peed out through the skin surface.
Protonephridia function in freshwater flatworms:
Mainly osmoregulation, because waste is excreted into the gastrovascular cavity.
Protonephridia function in parasitic flatworms:
Mainly for excretion of nitrogenous waste, because it’s in an isotonic environment.
Metanephridia:
“Kidney” of annelids, mollusks, and arthropods. Filters coelomic fluid. Actively absorbs NaCl and nitrogenous wastes. Used mostly for osmoreg.
Cryptonephridial complex:
Osmoreg organ in some insects. Excrement is powder. Water is absorbed straight out of the air, using the butt or some specialized organ.
The problem with nitrogenous waste:
When metabolized, they produce toxic ammonia. Ammonia fucks with intracellular pH, uncouples oxidative phosphorylation and kills the proton motive force, and dicks up membrane potential with its charge. It increases glutamate synthesis, which acts as a ntransmitter and fucks with the CNS.
Consequences of NH3 buildup:
Convulsions, coma, death.
Why is NH3 hard to excrete normally?
It’s very water-soluble - would have to be peed out along with a LOT of water.
Strategies for NH3 removal (depending on water availability):
Lots of water - just excrete it.
Not lots of water - urea.
NH3, urea, and uric acid: in order of energy needed to produce and water needed to excrete
NH3
Easy NH3 secreters:
Ammonotelic animals just push ammonia out with water through gills or skin.
Difficult NH3 secreters:
Ureotelic animals use energy to concentrate urea, which is less toxic than ammonia. This sacrifices less water but also takes energy to do.
REALLY difficult NH3 secreters:
Uricotelic animals do the same thing as ureotelic animals, except with uric acid. Uric acid is 1000 times less soluble than ammonia. This is used in shelled eggs, snails, insects, birds, and reptiles.
