Download Starfish Dissection - Parkway C-2

External Anatomy Procedure
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1. Place the starfish with its dorsal or aboral (top) surface upward.
2. Look at the central disc. Locate the small, round hard plate called the madreporite on
top of the central disc. Water enters through this into the water vascular system. Label
the central disc, arms, and madreporite on your diagram.
Also on the central disc is the opening through which the undigested food is expelled
from the body. This is their anus. Find it and label it on your diagram.
Feel the upper surface of the starfish for spines. These spines protect the starfish and
are part of their internal skeleton. Label one on your diagram.
Look at the tip of each arm and find the eyespot. Label one on your diagram.
Turn the starfish over to its ventral or oral surface (underside). Diagram it.
Locate the mouth in the center of the central disc. Find the ring of oral spines
surrounding the mouth. Label these on your diagram.
Find the groove that extends down the underside of each arm. This is called the
ambulacral groove. Label one on your diagram.
Feel the numerous, soft tube feet inside each groove. These are part of the water
vascular system & aid in movement and feeding. Label one on your diagram.
Internal Anatomy Procedure
Digestive System
1. With the starfish's aboral surface
facing you, cut off the tip of a ray.
Cut along lines a, b, and c (See diagram
to the right) and then remove this flap
of skin.
2. Inside each arm, locate two long digestive glands called the pyloric caeca. These make
enzymes to digest food in the stomach. Label this on the internal diagram.
3. Cut a circular flap of skin from the central disc. (You will have to also cut around the
madreporite in order to remove this flap.) Observe the pyloric stomach under the central
disc. Label this on the internal diagram.
4. Gently lift the pyloric stomach. Under this is the sea star’s cardiac stomach. The sea
stars will push this stomach out of its mouth and into the shell of its prey. This is called
an everted stomach. Label this on the internal diagram.
Reproductive System
5. Remove the pyloric caeca from the dissected ray. Find the gonads (testes or ovaries)
underneath. These may be small if the starfish is NOT in breeding season. Label this on
the internal diagram. Remove these to see the rest of the water vascular system.
Water Vascular System
6. A short canal, called the stone canal, leads from the madreporite, where water enters,
the a circular structure called the ring canal. Find and label these canals on your diagram.
7. From the ring canal, and running down the center of each arm, is a radial canal to which
tube feet are attached. Label this on the internal diagram.
8. Look at the end. Locate the bulb-like top of a tube foot called the ampulla. This sac
works like the top of an eyedropper to create suction. The bottom of the tube foot is a
sucker. Label this on the internal diagram.
Support
9. Embedded in the soft body wall are skeletal plates called ossicles. Locate these and label
them on the internal diagram.
Name ___________________________________________________________
Date __________________________________ Per. __________________
Question: How are the anatomy and physiology of a sea star suited for its survival?
Background:
1.
7 Survival Functions
Systems that perform the Function
Importance (1-7)
2. Why are sea stars called echinoderms? ________________________________________________________________
3. What are the characteristics of echinoderms? __________________________________________________________
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Prediction: From what you read and what you know form your best answer to the question above.
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Results
In the space below diagram the external anatomy of the sea star and label the underlined words.
Aboral Surface
Oral Surface
Conclusion
1. What type of symmetry did your starfish have? _________________________________________________________
2. What are the three essential body functions carried out by the water vascular system? (Hint: pg.735-736)____________
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How does this happen?_________________________________________________________________________________________________________
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3. What type of skeleton does the starfish have?__________________________________________________________
4. What can the starfish do with its stomach when feeding on clams & oysters? _________________________________
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5. In what two ways are the embryos of a sea star and the embryos of a frog similar? __________________________________
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6. Using your book or the internet, describe the nervous system of a sea star? ___________________________________________
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7. Re-draw Patrick so that he is more scientifically accurate
8. Color code the systems on the diagram above. Use purple for the respiratory system, yellow for the digestive system,
blue for the excretory system, red for the circulatory system, and green for the reproductive system