Osmoregulation
The problem of osmolarity:
fresh water
0-5 ppt
salt water
35 ppt
The problem of osmolarity:
Hyper-osmotic
fresh water
0-5 ppt
FISHES
Hypo-osmotic
salt water
35 ppt
The problem of osmolarity:
Hyper-osmotic
fresh water
0-5 ppt
FISHES
salt water
35 ppt
Hypo-osmotic
fishes are either:
stenohaline - tolerant of limited range of osmolarity
euryhaline - tolerant of wide range (where is this useful?)
How fish deal with being osmotic misfits
1. osmo-conformers (hagfishes)
maintain isosmotic conditions
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+, Clexcrete excess Na+, Cl-
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
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)
Diadromous fishes
anadromous - Pacific salmon, lamprey, shad
fresh water
salt water
Diadromous fishes
anadromous - Pacific salmon, lamprey, shad
fresh water
behavioral change (drinking)
changes in kidney function
salt water
metamorphosis – cued to photoperiod,
lunar cycle
Diadromous fishes
anadromous - Pacific salmon, lamprey, shad
landlocked species (potamodromous) - reversion of salt-water tolerance
fresh water
fresh water
Diadromous fishes
anadromous - Pacific salmon, lamprey, shad
landlocked species (potamodromous) - reversion of salt-water tolerance
catadromous - eels
salt
water
fresh
water
Credit: ICES
The cost of osmoregulation