Soft Anatomy

• Alimentary canal

• Gas bladder

Digestive tracts

Spiral valve intestine

• Chondricthyes• Primitive Bony

Fishes– Coelacanthiformes– Dipnoi– Polypteriformes– Acipenseriformes

Diet and intestinal length

herbivorous

piscivorous

planktivorous

Gas Bladder• General form: gas filled sac derived

from the anterior portion of the alimentary tract

• Occurrence of the gas bladder in fishes

• Number of gas bladders-monopneumonan -dipneumonan

• Kind of gas bladder connections-physostomous-physoclistous

monopneumonan

dipneumonan

physoclistous

digestive tract

gas bladder

pneumatic duct

physostomous

Primitive function: air breathing

Gas Bladder Functions

1. buoyancy control2. respiration3. sound production4. sound reception

Structures associated with gas resorption and gas

secretion• Gas gland

– gas secretion

• Oval– gas resorption

• Rete mirabile– Countercurrent gas exchange in blood

physostomous

physoclistous

Addition of gas to the bladder

• Some physostomes are able to gulp air into the gas bladder

Addition of gas to the bladder

• Some physostomes are able to gulp air into the gas bladder

• Gas addition in both physostomes and physoclists via gas gland and rete mirabile– Processes involved are:

• blood acidification (Bohr and Root effects) • “salting-out” effect• countercurrent exchange (at rete

mirabile)

Bhor and Root effects

Hemoglobin

Bhor and Root effects

“Salting out” effect

• Reduced gas solubility with increasing concentration of lactate and H+

[lactate] + [H+] Gas solubility

Countercurrent effect

Countercurrent exchange in the rete mirabile

Gas g

lan

d

Metabolic processes for pumping gas into the gas bladder

Rete mirabile

Gas gland

Some pressure numbers

• Physostomes can use Pneumatic

duct• Physoclists use highly vascularized

Oval area – Oval isolated from main bladder

Resorption of gas from bladder

benthic fishes without a gas bladder

Gobiidae

Percidae

Bothidae

Charcharhinidae Blue sharkPrionace glauca

Pelagic sharks with high oil content

Large livers containing low density lipids & squalene (hydrocarbon d=0.86)

Reduced density of musculature and skeletal tissues.

AstronesthidaeAstronesthes gemmnifer

Many deepsea midwater fishes

MyctophidaeLanterfishGonichthys sp.

Diel Vertical Migrators (DVM)

Degenerate bladder or lipid-filled bladder