Osmoregulation

salt water35 ppt

fresh water0-5 ppt

The problem of osmolarity:

salt water35 ppt

fresh water0-5 ppt FISHES

The problem of osmolarity:

Hyper-osmotic

Hypo-osmotic

salt water35 ppt

fishes are either:stenohaline - tolerant of limited range of osmolarityeuryhaline - tolerant of wide range (where is this useful?)

fresh water0-5 ppt FISHES

The problem of osmolarity:

Hyper-osmotic

Hypo-osmotic

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+, Cl-excrete 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 drinkinggill 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 watergill chloride cells pump in salts often euryhaline (striped bass, tilapia, drum)

How fish deal with being osmotic misfits

anadromous - Pacific salmon, lamprey, shad

Diadromous fishes

fresh water

salt water

anadromous - Pacific salmon, lamprey, shad

Diadromous fishes

fresh water

salt watermetamorphosis – cued to photoperiod, lunar cycle

behavioral change (drinking)changes in kidney function

anadromous - Pacific salmon, lamprey, shadlandlocked species (potamodromous) - reversion of salt-water tolerance

Diadromous fishes

fresh water

fresh water

anadromous - Pacific salmon, lamprey, shadlandlocked species (potamodromous) - reversion of salt-water tolerancecatadromous - eels

Diadromous fishes

Credit: ICES

saltwater

freshwater

The cost of osmoregulation