Animal Science

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Unit

• Animal Science

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Problem Area

• Aquaculture

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Lesson

• Effect of Temperature on Cold-Blooded Animals

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Student Learning Objectives

• 1. Define the term poikilotherm.
• 2. Explain how the circulatory system of
  poikilotherms is affected by changes in
  temperature.
• 3. Describe how temperature affects the
  metabolic rate of poikilotherms.
• 4. Describe the effect other factors, beside
  temperature, have on the activity of
  poikilotherms.

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Terms

• Circulatory system
• Dissolved oxygen
• Homeotherm
• Metabolism
• Poikilotherm

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What is a poikilotherm?

• A poikilotherm is an organism whose body
  temperature adjusts to its environment.
• A. Poikilotherms are often referred to as
  cold-blooded or ectotherms. This includes most
  fish and reptiles. For this reason large
  fluctuation in water temperature in an aquatic
  environment can cause the aquacrop to be stressed
  or can effectively kill them.
• B. Homeotherms are organisms whose body
  temperature is relatively constant. They are
  commonly called warm-blooded or endotherms.

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How is the circulatory system of poikilotherms
affected by changes in temperature?

• The general rule is that as temperature increase
  so does bloodflow.
• A. The circulatory system of the fish includes
  the heart, gill blood vessels, cranial veins,
  cardinal veins, aorta, portal vein, hepatic veins
  as well as capillaries. Blood cells move through
  the capillaries one blood cell at a time.
  Capillaries join together to form veins in the
  tail which do not pulsate.

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• B. When the water temperature decreases the blood
  flow decreases. The diameter of the arteries gets
  smaller and less blood gets circulated.
• C. When the water temperature increases the blood
  flow also increases. The increased temperature
  causes the blood vessels to expand and allow more
  blood to flow.

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What effect does temperature have on the
metabolic rate of poikilotherms?

• Metabolism is the process of converting food to
  energy.
• A. Metabolism requires that oxygen and food be
  transported through the fish. When blood flow is
  reduced due to temperature, less oxygen is
  available to cells for respiration so the process
  is slowed. As a result, in fish that are in
  temperatures lower than their desired range,
  activity is reduced.

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What factors, beside temperature, affect the
activity of poikilotherms?

• A. Water quality is of major importance in the
  general health of aquatic organisms. This
  includes nitrogen compounds and dissolved oxygen,
  among others. Nitrogen levels need to be
  carefully monitored to reduce the harmful effects
  of ammonia and nitrite. Generally dissolved
  oxygen, elemental oxygen that remains in solution
  under existing conditions, levels needed to be
  45 ppm at a minimum. Dissolved oxygen depletion
  can result in large fish dying off in a matter of
  a few hours.
• B. Stress levels associated with handling,
  injuries, crowding also reduce the activity of
  fish.
• C. Poor nutrition will also reduce fish activity.

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Review/Summary

• What is a poikilotherm?
• How is the circulatory system of poikilotherms
  affected by changes in temperature?
• What effect does temperature have on the
  metabolic rate of poikilotherms?
• What factors, beside temperature, affect the
  activity of poikilotherms?