Buoyancy Control

1
Buoyancy Control
Helmut Debelius

• lipids and squalene
• lift via fins
• reduction of heavy tissues

Carcharhiniformes Carcharhinidae Negaprion
mbnms-simon.org
Scorpaeniformes Psychrolutidae Psychrolutes
2
Swimbladder
pneumatic duct
physostomous swimbladder
gut

• Physoclistous bladder
• sealed bladder
• advanced fishes
• how to fill?

• Phystomous bladder
• pneumatic duct connects to gut
• gulp to fill, burp to empty
• ancestral, shallow fishes

3
Physoclistous Bladder

• Two structures to fill
• rete mirabile
• gas gland
• Two processes to fill
• Root effect
• Countercurrent exchange
• Vascular structure (oval) to empty

4
Filling the Bladder
incoming blood
HbO2
swimbladder lumen
HbO2
Hb
outgoing blood
cell of gas gland
Same process also causes diffusion of CO2 and N2
into bladder.
5
Emptying the Bladder

• Oval muscular sphincter
• Contracted sphincter
• oval is open, O2 diffuses out.
• Relaxed sphincter
• oval is closed

6
Thermal Regulation
Typical Teleost
Tuna
7
Thermal Regulation
Countercurrent exchange builds, maintains heat
Most Scombridae maintain core 3-12ºC above ambient
Bluefin tunas maintain 28-33ºC core in 7-30ºC
water
But what about hemoglobin?
8
Salinity Tolerance

• Stenohaline
• Narrow range
• Euryhaline
• Wide range
• Water and salts lost / gained across gills
• Osmoregulation

Cyprinodontiformes Aplocheilidae Pseudepiplatys
Perciformes Apogonidae Pterapogon