Download Ichthyology Fall 2000

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
gills
body
skin
end
Behavioral Thermoregulation
• nearly all fishes
• choose from available temperatures
• concept of temperature preference
end
Temperature Preference:
Preferred Temperature
Frequency
stenotherm
eurytherm
0
20
Temperature C
40
end
Temperature Preference continued:
Preferred Temperature
Frequency
cold adapted
warm adapted
0
20
Temperature C
40
end
Temperature Preference continued:
Preferred Temperature
Frequency
The effect of Acclimation
0
20
Temperature C
40
end
Temperature Preference continued:
The effect of Acclimation
Preferred Temperature C
final preferred temperature
40
bluegill
temperature tolerance
20
0
0
20
40
Acclimation Temperature C
end
Temperature Preference continued:
The effect of Acclimation
Preferred Temperature C
final preferred temperature
40
bluegill
guppy
???
20
chum salmon
0
0
20
40
Acclimation Temperature C
end
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
end
Physiological Thermoregulation
gills
skin
rete mirabile
body
skin
heat
end
Counter-current blood flow
from body
high
Temperature
heat
low
venous blood
arterial blood
from gills
tuna
typical
fish
Distance along capillaries (rete)
end
Counter Current flow:
• fluid flowing in opposite directions
• exchange of heat or gas perpendicular to
flow
• efficiency versus speed
end
Hypothetical Co-current blood flow:
from body
low
venous blood
counter-current
heat
Temperature
high
arterial blood
from gills
Distance along capillaries (rete)
end
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
end
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