Lecture Exam Monday• 100 point exam• covers lectures, assigned readings• 8-12 short answer questions; 4-6 pts ea

– complete, concise answer– ex: definition; short description

• 3-5 longer questions; 10-15 pts ea• Finish by 2:55--budget time• Power Point lectures on blackboard• Chapters: 1, 2, 12, 13, 3, 14, 4, 15, 5

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4. Swim bladder

• low density• adjustable• most bony fishes• lost secondarily in some species

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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

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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

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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

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Oxygen equilibrium—swim bladder inflation

DO

hemoglobin

plasma gaseous O2O2 O2

O2

gills

blood

rete

water swim bladder

How are high pressures achieved?

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Counter-current multiplication system

afferent blood

efferent blood

O2hemepO2

O2heme pO2

pO2

swim

bla

dder

O2heme pO2

lactic acidBohr & Root

1

Diagram of basic functional unit of rete(inflation)

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Function of Rete Mirabile

1. Hemoglobin saturated with O2 (O2 heme)

plasma O2 low (p O2)

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Counter-current multiplication system

afferent blood

efferent blood

O2hemepO2

O2heme pO2

pO2

swim

bla

dder

O2heme pO2

1 2

lactic acid

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Function of Rete Mirabile2. Lactic Acid Secretions heme dumps O2 to plasma pO2 diffuses into swim bladder to equil.

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Counter-current multiplication system

afferent blood

efferent blood

O2hemepO2

O2heme pO2

pO2

swim

bla

dder

O2heme pO2

lactic acid

1 2

3

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Function of Rete Mirabile3. Multiplying effect: pO2 diffuses from efferent

capillary to afferent cap. Longer capillaries yield more efficient exchange of oxygen, higher pressures

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O2O2

1. Steady supply of oxygen in2. Little or none leaves3. PO2 accum. in plasma

4. Diffusion into SB

Summary of what happens to O2

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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

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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 (Bohr & Root)

• Counter-current multiplier– length of capillaries– counter-current flow of blood

end

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Thermoregulation:

• Cold-blooded -poor descriptor• Poikilotherm (n); poikilothermic (adj)

– variable body temperature– opposite = homeotherm

• Ectotherm (n); ectothermic (adj)– temp. determined by environment– opposite = endotherm

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Why are fishes ectothermic?Heat generated by metabolism

skin

skin

bodygills

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Behavioral Thermoregulation

• nearly all fishes• choose from available temperatures• concept of temperature preference

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Temperature Preference:

Acclimation temperature C

Pre

ferr

ed te

mpe

ratu

re C

10 4010

40

bluegill

chum salmon

guppy

final preferendum

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Physiological Thermoregulation

• few fishes--tunas & lamnid sharks• fish are active --generate heat• rete mirabile for heat exchange & conserv.• fish are large--low surface area to mass ratio

– body surf. area increases as square of length– body mass increases as cube of length

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Physiological Thermoregulation

body

skin

skingills

heat

rete mirabile

Counter-current blood flow

Distance along capillaries (rete)

Tem

pera

ture

low

high

arterial blood

venous bloodheat

from gills

from body

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Counter Current flow:

• fluid flowing in opposite directions• exchange of heat or gas perpendicular to

flow• efficiency versus speed

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Distance along capillaries (rete)

Tem

pera

ture

low

high

Hypothetical Co-current blood flow:

from gills

from body

arterial blood

venous bloodcounter-current

heat

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Hypothetical Co-Current flow:

• fluid flowing in same direction• exchange of heat or gas perpendicular to

flow• speed versus efficiency

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