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Animal Physiology > Osmoregulation in fish > Flashcards

Osmoregulation in fish Flashcards

1
Q

Are marine fish hyperosmotic or hyposmotic relative to seawater?

A

Hyposmotic

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2
Q

Will marine fish gain or lose salts relative to seawater?

A

Gain

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3
Q

Will marine fish gain or lose water relative to seawater?

A

Lose

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4
Q

Do marine fish drink water?

A

Yes

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5
Q

How do marine fish cope with the the hyperosmolarity of the seawater?

A

They drink seawater and excrete the salt to replenish their internal water

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6
Q

What is the primary organ of salt excretion in marine fish?

A

Gills

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7
Q

Which ions are excreted from the gills in marine fish?

A

Monovalent ions. Na+, K+, Cl-

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8
Q

Which ions are excreted from the urine of marine fish?

A

Divalent atoms. Mg2+ and SO4 2-

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9
Q

Do marine fish still lose water from getting rid of salts?

A

Yes. Water loss across the gills is passive since the water just follows the monovalent ions by osmosis. The fish will also lose a little bit more making urine to get rid of the divalent atoms

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10
Q

What specialized type of cell gets rid of salts in the gills of marine fish?

A

Chloride cells/mitochondrial rich cells

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11
Q

What is the primary osmoregulatory organ in all fish?

A

The gills

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12
Q

Where are chloride cells found?

A

Gill epithelium

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13
Q

What are 2 characteristics of the chloride cells?

A

Have tons of mitochondria and have an extensive intracellular tubular system for movement of molecules around the cell

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14
Q

What do the chloride cells excrete? Is the transport active or passive?

A

Excrete chloride through active transport

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15
Q

Who moved euryhaline pupfish to a saltier environment to determine how their gill structure changed in response to higher salinity?

A

Karl Karnaky

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16
Q

What happened to the chloride cells in fish exposed to higher salinities in Karnaky’s experiment?

A

Number and size of chloride cells increased. They had a larger surface area of the basolateral membrane and more extensive intracellular tubular system

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17
Q

What happened to the structure of the gill filaments in fish exposed to higher salinities in Karnaky’s experiment?

A

Got thicker

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18
Q

Why did Karnaky use radiolabelled ouabain to determine the number of Na+/K+ ATPases in the chloride cells of fish exposed to high salinities?

A

Ouabain binds to the ATPases and can be detected by microscopy to see how many ATPases there were

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19
Q

What happened to the number and location of Na+/K+ ATPases in fish exposed to higher salinities in Karnaky’s experiment?

A

Number increased, but location stayed the same

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20
Q

What were Karnaky’s 3 conclusions after the fish gill salinity experiment?

A
  1. High solute concentration causes a euryhaline fish to change its gill structure
  2. Fish increase the size, number, and complexity of the chloride cells
  3. Increased Na+/K+ ATPase activity and number on the basolateral membrane of the chloride cells
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21
Q

Which transporters are located on the basolateral membrane of chloride cells?

A

Na+/K+ ATPase, NKCC cotransporter, potassium channels

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22
Q

Which transporters are located on the apical membrane of the chloride cells?

A

Chloride channels

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23
Q

How do the chloride cells transport chloride ions out of the cell?

A

The Na+/K+ ATPase establishes a sodium gradient by transporting sodium ions out the cell into the intercellular space. Sodium enters the cell again through the NKCC cotransporter, and the gradient powers the transport of a K+ and 2 Cl- across through secondary active transport. Cl- will leave the cell through the chloride channels on the apical membrane into the water and the K+ diffuses back across the basolateral membrane through the K+ channel through facilitated diffusion. Na+ will then follow the Cl- through the tight junctions between cells or through sodium channels

24
Q

Are freshwater fish hyperosmotic or hyposmotic relative to the freshwater?

A

Hyperosmotic

25
Q

Will freshwater fish gain or lose water relative to freshwater?

A

Gain

26
Q

Will freshwater fish gain or lose ions relative to freshwater?

A

Lose

27
Q

How do freshwater fish cope with the hyposmolarity of freshwater?

A

Active take up salts across their gills

28
Q

Do freshwater fish drink water?

A

No

29
Q

Is freshwater fish urine hyposmotic or hyperosmotic relative to the blood? How much do they produce?

A

Freshwater fish produce high volumes of hyposmotic urine

30
Q

Why do freshwater fish produce high volumes of hyposmotic urine?

A

Keeps the ion balance. They excrete all the extra water and retain the ions to keep their osmolarity in check

31
Q

What are the specialized ion pumping cells found in freshwater fish gills?

A

PNA cells (Peanut lectin agglutinin antibody)

32
Q

What are the 2 types of PNA cells?

A

PNA- cells: acid secreting cells

PNA+ cells: base secreting cells

33
Q

What ions do the PNA- cells take up and secrete?

A

Take up Na+ and secrete H+

34
Q

What ions do the PNA+ cells take up and secrete?

A

Take up Cl- and Ca2+and secrete HCO3-

35
Q

What enzyme do the PNA cells in freshwater fish have to maintain pH balance?

A

Carbonic anhydrase

36
Q

How do animals that migrate between saltwater and freshwater switch their salt transport depending on which environment they’re in?

A

Hormones cause the ion transport cells in the gills to change function

37
Q

Which hormone mediates NaCl transport out of the gills in seawater in animals that migrate between freshwater and seawater?

A

Cortisol

38
Q

Which hormone mediates NaCl transport into the gills in freshwater in animals that migrate between freshwater and seawater?

A

Prolactin

39
Q

What is a diadromous animal?

A

Animal that moves between marine and freshwater environments

40
Q

What is a catadromous animal?

A

An animal that migrates from freshwater to seawater to breed (eels)

41
Q

What is an anadromous animal?

A

An animal that migrates from seawater to freshwater to breed (salmon)

42
Q

How does the osmolarity of elasmobranch blood compare to the osmolarity of seawater?

A

Slightly hyperosmotic and hypoionic

43
Q

How do sharks maintain hyperosmotic and hypoionic blood?

A

Replace NaCl with organic osmolytes

44
Q

What are the osmolytes that sharks use to maintain their hyperosmotic and hypoionic blood?

A

Urea and trimethylamine oxide. Nitrogenous waste products that are reabsorbed from the kidneys by active transport

45
Q

How does having a high amount of urea in shark blood not denature everything?

A

Gets counteracted by TMAO

46
Q

Is there a net influx or efflux of water for sharks?

A

Influx

47
Q

How much osmotic pressure do urea and TMAO contribute to the hyperosmolarity of shark blood?

A

40%

48
Q

How do sharks gain ions?

A

Passive diffusion across the gills

49
Q

How do sharks deal with extra salts?

A

Rectal gland cells produce secretions that are rich in NaCl. Also get rid of salts and water through their feces

50
Q

Is shark urine hyposmotic or hyperosmotic relative to the blood plasma? How much do they produce?

A

Moderate amounts of hyposmotic urine rich in divalent atoms (Mg2+ and SO4 2-)

51
Q

Which hormone signals the rectal glands in sharks to start secreting salts?

A

Vasoactive intestinal peptide

52
Q

What are the transporters in the rectal gland cells? Where are they located?

A

The receptor for VIP is located on the basolateral membrane, and is a GPCR. The pathway activates NKCC on the basolateral, which bring chloride into the cells. The chloride then leaves through chloride channels on the apical membrane

53
Q

What is smoltification?

A

Hormone mediated remodelling of the gills in salmon as part of their development

54
Q

Which hormone mediates smoltification?

A

Cortisol

55
Q

Why is smoltification different from the hormone mediated gill remodelling seen in migratory eels?

A

Smoltification is related to development and not the salt change, since it happens even before the fish reach the saltwater

Animal Physiology (32 decks)

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