1. Osmoregulation

2. The problem of osmolarity:
salt water
35 ppt
fresh water
0-5 ppt

3. salt water fresh water 35 ppt 0-5 ppt FISHES
The problem of osmolarity:
Hyper-osmotic
salt water
35 ppt
fresh water
0-5 ppt
FISHES
Hypo-osmotic

4. salt water fresh water 35 ppt 0-5 ppt FISHES
The problem of osmolarity:
Hyper-osmotic
salt water
35 ppt
fresh water
0-5 ppt
FISHES
Hypo-osmotic
fishes are either:
stenohaline - tolerant of limited range of osmolarity
euryhaline - tolerant of wide range (where is this useful?)

5. How fish deal with being osmotic misfits
1. osmo-conformers (hagfishes)
maintain isosmotic conditions

6. How fish deal with being osmotic misfits
1. osmo-conformers (hagfishes)
maintain isosmotic conditions
2. salt supplementers (marine elasmobranches and coelacanths)
high urea content and TMAO (trimethylamine oxide)
low permeability to Na+, Cl-
excrete excess Na+, Cl-

7. How fish deal with being osmotic misfits
1. osmo-conformers (hagfishes)
2. salt supplementers (marine elasmobranches and coelacanths)
3. hyposmotics (marine teleosts)
tend to lose water, replace by drinking
gill cells pump in water, not salts

8. How fish deal with being osmotic misfits
1. osmo-conformers (hagfishes)
2. salt supplementers (marine elasmobranches and coelacanths)
3. hyposmotics (marine teleosts)
4. hyperosmotics (freshwater fishes)
excrete large volumes of water
gill chloride cells pump in salts
often euryhaline (striped bass, tilapia, drum)

9. Diadromous fishes fresh water salt water
anadromous - Pacific salmon, lamprey, shad
fresh water
salt water

10. Diadromous fishes fresh water salt water
anadromous - Pacific salmon, lamprey, shad
fresh water
salt water
behavioral change (drinking)
changes in kidney function
metamorphosis – cued to photoperiod,
lunar cycle

11. Diadromous fishes fresh water
anadromous - Pacific salmon, lamprey, shad
landlocked species (potamodromous) - reversion of salt-water tolerance
fresh water

12. Diadromous fishes anadromous - Pacific salmon, lamprey, shad
landlocked species (potamodromous) - reversion of salt-water tolerance
catadromous - eels
salt
water
fresh
water
Credit: ICES

13. The cost of osmoregulation