Buoyancy and respiration

Pelagic

liver makes up 20-30% of the body weight (Elasmobranchs)

Benthic

Liver makes up 5% of body weight (Elasmobranchs, sharks)

How do bony fishes regulate buoyancy?

1. Lipid accumulation

2. Water accumulation in tissues

3. Reduce ossification and muscular tissue

4. Gas bladder

How do sharks regulate buoyancy?

through lipid accumulation and reduction of ossification/ muscular tissue (cartilage)

Gas bladder

This is filled with CO2, oxygen, nitrogen

-saves energy by regulating buoyancy

-plays a role in respiration

-lost in some species

Why do freshwater fishes have a larger gas bladder?

Because freshwater is less dense (no salt) so a larger volume of gas is needed to achieve stable buoyancy

Barotrauma

Sudden change in pressure causes the gas bladder to expand and push against other organs

-bulging eyes

-bloated

Physostomous

Gas bladder is attached to the gut by pneumatic duct

-Sturgeons and primitive fishes

-inflate by gulping air or diffusion of gases from blood into bladder by gas gland

-Release gas through pneumatic duct

Physoclistous

Gas bladder does not have a connection to the gut

- Derived fishes, 2/3 of all fishes

- Increases or decreases by diffusion of gases in and out of blood

Pneumatic duct

a connective pathway between the gut and gas bladder, that allows air gulped in at the surface to enter it.

-ONLY in physostomous fishes.

gas gland

specialized tissue within the bladder responsible for secreting gases into it

rete mirabile

a countercurrent exchange structure of capillaries that allows gas uptake in a fish swim bladder

Bohr effect

As blood pH decreases, oxygen affinity decreases

Root effect

Saturation (carrying capacity)

-low pH means low Saturation

oxygen affinity of hemoglobin

ability of hemoglobin to bind with oxygen molecules.

-measure of how strongly hemoglobin attracts oxygen

salting out

Solutes/ gases cannot be dissolved in plasma so they are released into gas bladder

ram ventilation

Method of forcing water over gills by swimming with mouth open

-little energy usage

-tuna

-paddlefishes

-billfishes

branchial pump

head of a fish contains two cavities separated by the gills: a buccal or mouth cavity and an opercular or gill cavity.

-uses more energy

1. fish sucks in water into buccal cavity, buccal pump inactive

2. mouth closed, buccal pump active and pushes up to force water over gills into opercular cavity w/ inactive opercular pump

3. Opercular valve opens and opercular pump aactive to push water out of opercular cavity through the valve

Gill

-site of CO2 and O2 exchange

-Excretes nitrogenous wastes

-Essential for osmoregulation

Filament

contain lamellae

-can be hemi or holobranch

Lamellae

within filaments that are the side of gas exchange between blood and water

Afferent filament artery

this supplies blood to each lamella

-blood passes through lamellae countercurrent to direction of water flow

countercurrent exchange

the opposite flow of adjacent fluids that maximizes transfer rates

Gill arch

This supports the filaments and rakers

gill rakers

Projections on the gill arch that prevent large objects passing over filaments

-aids in capture of food

hemibranch

gill arch with filaments on only one side

holobranch

Gill arch with filaments on both sides

Solubility of oxygen in water is affected by what?

1. temperature

2. elevation

3. salinity

monomeric

single heme polypeptide characteristic of lampreys and hagfish

Tetrameric

Hemoglobin has four subunits that can bind a single molecule of oxygen

Ways fish breathe (respire)

1. Skin- oxygen diffusion into capillaries (eels, larval fish)

2. Gas bladder- modified physostomous bladders (gars)

3. Lungs- modified gas bladder (lungfish)

4. Mouth- vascularized region roof of mouth (Electric eel, mudsucker)

5. Gut (Armoured catfish, loaches)