Reading Assignment: Chapter 5: Buoyancy and Thermal Regulation bigeye jack end

Reading Assignment:

Chapter 5: Buoyancy and Thermal

Regulationbigeye jackend

Hemoglobin--molecule of O2 transport

• Structure– protein– monomer in Myxini & Cephalasipdomorphi– tetramer in Gnathostomata (4 polypeptide chains)

chain similar in coelacanth and tadpole

end

Hemoglobin (Hg) cont.• Occurrence: erythrocytes (RBCs)

– up to 4M RBC/mm3 of blood

• RBC’s nucleated in fish• Hg Absent in some species (Channichthyidae)

Antarctic ice fish

endfish human

• Some species have more than one type of hemoglobin

• Catostomus clarki -- desert sucker has an additional form of pH insensitive Hg

end

end

Factors affecting blood oxygen affinity

• pH

• pCO2 (partial pressure of carbon dioxide)

end

0 80 1600

100

50

pO2 mm Mercury

% S

atur

atio

n of

Hg

pH 8.02

pH 7.47

Air saturation

1.affinity

2. capacity

Bohr

Root

Effect of pH on Hg--two components

end

data for winter flounder

• Bohr effect--decrease in affinity of hemoglobin for O2 due to decreasing pH or increasing PCO2

affinity: strength of attraction of Hg for O2

• Root effect--decrease in capacity of Hg for O2 due to decreasing pH or increasing PCO2

(extreme Bohr effect)

capacity: total quantity O2 of that Hg can carry

end

• more active species tend to have greater Bohr & Root effects

• red versus white muscle

• myoglobin

endperciform skipjack tuna lamnid shark

Advantage of Bohr Effect

TissuesGills

blood circulation

pH lowerpH higher

pCO2 higherpCO2 lowerlactic acidno lactic acid

end

pH?

pCO2?

lactic acid?

Teleost Heart:

sinus venosusatrium

ventricle

bulbus arteriosus

end

Teleost Heart:

sinus venosusatrium

ventricle

bulbus arteriosus

endrelax

Teleost Heart:

sinus venosusatrium

ventricle

bulbus arteriosus

endcontract

Conus arteriosus--Myxini, Ceph., elasmobranchs, gar

heartto gills

end

time

Pre

ssur

e (m

m m

erc.

)

0

60

ventricle

bulbus arteriosus

end

end

Buoyancy strategies

1. Low density compounds

2. Lift generated by swimming

3. Reduction of heavy tissues

4. Swim bladder (air bladder)

end

1. Low density compounds:

Advantages/disadvantages

Substance Specific GravityBone 2.0Muscle 1.05Cartilage 1.1Freshwater 1.002 @20CSaltwater 1.072 @20CLipids 0.9-0.92Squalene 0.86

end

2. Lift generated by swimming:

lift

lift

thrust

sharks Advantages/disadvantagesend

hammerhead shark

end

nurse shark

end

sandbar shark

end

3. Reduction of heavy tissues

Eurypharynx pelecanoides

deepwater fishes

Advantages/disadvantagesend

umbrella mouth gulper

end

umbrella mouth gulper

end

4. Swim bladder

• low density

• adjustable

• most osteichthians

• lost secondarily in some species

end

Two types of swim bladders:

• Physostomous– pneumatic duct– soft-rayed teleosts--herrings, salmonids,

catfishes, cyprinids, eels, etc.

• Physoclistous– blood/circulatory system– spiney-rayed teleosts--Acanthopterygii,

sunfishes, perch, most marine fishes

end

Effects of depth on swim bladder volume

• pressure increases 1 ATM/10m

• swim bladder must be adjustable

• Physostomous fishes adjust volume by gulping or spitting air.– mostly shallow water species– gas-spitting reflex– gulp air at surface

end

Physoclistous inflation/deflation

• circulatory system--source of gases

• rete mirabile (wonderful net) --inflation

• oval window--deflation

• Problem: fish need greater pressure in swim bladder than is achieved by equilibrium with blood gases

end

Oxygen equilibrium—swim bladder inflation

water

hemoglobin

plasma swim bladder

gills swim bladder

O2 O2

O2

end

Counter-current multiplication system

afferent blood

efferent blood

O2hemepO2

O2heme pO2

pO2

swim

bla

dder

O2heme pO2

lactic acid

1

Diagram of basic functional unit(inflation)

end

Function of Rete Mirabile

1. Hemoglobin saturated with O2 (O2 heme)

plasma O2 low (p O2)

end

Counter-current multiplication system

afferent blood

efferent blood

O2hemepO2

O2heme pO2

pO2

swim

bla

dder

O2heme pO2

1 2

lactic acid

end

Function of Rete Mirabile

2. Lactic Acid Secretions heme dumps O2 to plasma pO2 diffuses into swim bladder to equil.

end

Counter-current multiplication system

afferent blood

efferent blood

O2hemepO2

O2heme pO2

pO2

swim

bla

dder

O2heme pO2

lactic acid

1 2

3

end

Function of Rete Mirabile

3. Multiplying effect: pO2 diffuses from efferent capillary to afferent cap. Longer capillaries yield more efficient exchange of oxygen, higher pressures

end

Physoclistous swim bladder

• Pressures up to 300 ATM in some deep sea fishes

• Gases mostly O2, some CO2 and N2

• Guanine crystals in SB wall reduce permeability• Deflation occurs at oval window

– dense bed of capillaries on SB wall

– gasses diffuse into blood

– mucus layer covers window during inflation

end

Summary:• Diffusion of O2; controlled by structure & function

• Relationship O2 bound to hemoglobin versus O2 in plasma

• Effect of pH on affinity/capacity of hemoglobin for O2

• Counter-current multiplier– length of capillaries

– counter-current flow of blood

end

• End

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