Reading Assignment:

• Chapter 6--Hydromineral Balance

end

Thermoregulation:

• Cold-blooded -poor descriptor

• Poikilotherm (n); poikilothermic (adj)– variable body temperature– opposite = homeotherm

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

end

Why are fishes ectothermic?Heat generated by metabolism

skin

bodygills

end

Behavioral Thermoregulation

• nearly all fishes

• choose from available temperatures

• concept of temperature preference

end

Temperature Preference:

Temperature C0 4020

Freq

uenc

yPreferred Temperature

eurytherm

stenotherm

end

Temperature Preference continued:

Temperature C0 4020

Freq

uenc

yPreferred Temperature

cold adapted

warm adapted

end

Temperature C0 4020

Freq

uenc

yPreferred Temperature

Temperature Preference continued:

The effect of Acclimation

end

0 4020Acclimation Temperature C

Pref

erre

d Te

mpe

ratu

re C

Temperature Preference continued:The effect of Acclimation

20

0

40final preferred temperature

bluegill

temperature tolerance

end

0 4020Acclimation Temperature C

Pref

erre

d Te

mpe

ratu

re C

Temperature Preference continued:The effect of Acclimation

20

0

40final preferred temperature

chum salmon

bluegill

guppy ???

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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

end

Counter-current blood flow

Distance along capillaries (rete)

Tem

pera

ture

low

high

arterial blood

venous blood

heat

from gills

from body

end

typical

fish

tuna

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

• vessels naturally flow in opposite direction

end

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Hydromineral Balance: Life in a solvent

Environmental forces cause movement of water and dissolved substances

versus

Homeostasis--the need to maintain balance of water and dissolved substances in cells and body fluids of organisms

-constant internal environment

end

Environmental forces:• heat--(movement of molecules) energy for

movement

• diffusion--net movement of molecules

• pressure--density of molecules – difference causes or blocks movement

• osmosis--movement of water

• electrochemical forces--attraction & repulsion of molecules based on charge

end

• Environmental forces work together toward equilibrium

• equilibrium-no net movement of molecules

end

end

Lecture Exam Monday

• 100 point exam

• covers lectures, assigned readings

• 8-12 short answer questions; 4-6 pts ea– complete, concise answer– ex: definition

• 3-5 longer questions; 10-15 pts ea

• Finish by 1:55--budget time

• Power Point lectures at: http://www.und.nodak.edu/instruct/skelsch/425~1.htm