Homeostasis - part 1

Question 1

What are the 5 basic groups of fish that display the different types of ionic regulation?

Answer 1

Hagfish - osmoconformer
Marine Fish
Freshwater Fish
Migratory Fish
Elasmobranchs

Question 2

What is an osmoconformer?

Answer 2

Blood chemistry matches that of its environment. Narrow range in which it can live.

Question 3

What is an osmoregulator?

Answer 3

Fish that will change blood osmolality/osmolarity to be different from its environment.

Question 4

What is hyperosmoregulation?

Answer 4

Blood osmolarity above environment. (Freshwater)

Question 5

What is hypoosmoregulation?

Answer 5

Blood osmolarity below environment, (Marine)

Question 6

Describe a stenohaline fish.

Answer 6

Narrow range of environmental osmolarity that the fish can withstand.
Poor osmoregulator

Question 7

Describe a euryhaline fish?

Answer 7

Can withstand a broad salinity range.

Good osmoregulator.

Question 8

What is osmosis?

Answer 8

Passive movement of water along its concentration gradient.

Question 9

For salwater fish, what is the direction of water flow?

Freshwater?

Answer 9

Salwater
- more salt in environment so water flows out of fish
Freshwater
- more particles in fish so water flows into the fish

Question 10

What are the different ion exchange surfaces in fish?

What are the most important ones?

Answer 10

Gills
Kidneys
GI tract
Rectal Gland
Skin
Yolk Sac
Urinary bladder

Most important:
Gills
Kidneys
Rectal gland (elasmobranchs)

Question 11

What are the two parts of gills important for ion exchange?

Answer 11

Filaments and lamellae

Question 12

What are lamellae for?

Answer 12

Gas exchange

Question 13

What are filaments for?

Answer 13

Support lamellae and are the site of osmoregulation, especially in teleosts.

Question 14

How are kidneys involved in osmoregulation?

Answer 14

Reuptake water
absorb or secrete ions
get rid of wastes

Question 15

How is the GI tract involved in osmoregulation?

Answer 15

Mostly in water exchange and uptake.

Question 16

How is the Rectal gland involved in osmoregulation?

Answer 16

Location of ion exchange in sharks and rays (only in them).
Site of active excretion of ions (take from blood and excrete them)
Active transport of ions into rectal gland

Question 17

What is the osmolarity of freshwater?

Of seawater?

Answer 17

1

1000 (ish)

Question 18

How does a hagfish compare to osmolarity of a marine environment?

Answer 18

Largely the same for: Na, Cl, Ca, Urea and total.

Question 19

How does the marine shark compare with the marine environment?

Answer 19

Total similar but higher
Urea way higher
sodium lower
Chloride lower

Question 20

How does a marine teleost compare to a marine environment?

Answer 20

Na lower
Cl lower
Ca close but lower
Urea same
Total much lower

Question 21

How does a freshwater shark compare to a freshwater environment?

Answer 21

Na higher
Cl higher
Calcium similar
urea similar
Total higher

Question 22

How does a freshwater teleost compare to its environment?

Answer 22

Na higher
Cl higher
Ca same but higher
Urea same
Total higher

Question 23

Contrast freshwater and marine teleosts for the following conditions:
Drinking water
Peeing a lot
Constantly losing ions
Osmolarity of pee
Hypotonic vs. hypertonic to the environment
Active ion regulation (Y/N)

Answer 23

Marine fish:
Drinks lots of water
Marine fish have a low amount of urine flow
High osmolarity for pee
Hypotonic to environment
Active ion regulation present
Not constantly losing ions

Freshwater fish:
Not drinking water
Constantly peeing
Pee has low osmolarity
Constantly losing ions
Hypertonic to environment
Active ion regulation