Starfish Dissection Life Science, Mr. Ditolla

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Starfish DissectionLife Science, Mr. Ditolla
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• Examine the top surface of your starfish and find
  the structures labeled below

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Starfish usually have five legs or rays. If a
leg gets cut off they can replace it by
regeneration. In the middle of the legs is the
central disk. The madreporite is used to
absorb water for the water vascular system. The
water vascular system is a network of canals that
the starfish uses for movement. A starfishes
skin is covered with spines. The phylum name for
starfish is Echinoderm, which means spiny skin.
Starfish obtain their oxygen through skin gills
located on the skin between the spines. Turn the
starfish over onto the other side and find the
structures labeled on the next slide.
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• Bottom surface of starfish.

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A starfishes mouth is on the bottom and the anus
is on the top, which is the opposite of most
animals. A star- fish eats clams and uses its
tube feet to open the clam shell. Once the clam
shell is open the starfish inverts its stomach or
turns it inside out. The stomach comes out of
its mouth and surrounds the clam, digests it,
and then is pulled back through the mouth of the
starfish.
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• Cut the skin off the top of one of the legs and
  identify
• the organs labeled below.

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Most of the inside of each leg is filled with the
hepatic caecum which is a digestive organ used to
help digest food. Remove the hepatic caecum
and locate the yellow colored gonads. These
produce egg cells and sperm cells for
reproduction. Remove the gonads and locate the
ampullae which are where the tube feet are
anchored to the leg. Remove the skin from the
central disk and locate the structures labeled on
the following slide.
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Organs of the central disk.
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• Throw away the starfish, wipe off your tools, and
  wash
• your hands with soap and water.
• Now answer the following questions on a separate
  piece
• of paper
• How many legs does a starfish usually have?
• What happens if a starfish loses a leg?
• What structure is in the middle of the legs?
• What is the madreporite used for?
• What is the water vascular system used for?
• What is a starfishes skin covered with?
• What does the word Echinoderm mean?
• What is unusual about the arrangent of the mouth
• and the anus on a starfish?
• What does a starfish use its tube feet for?
• What does a starfish do to its stomach when it
• eats a clam?

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11. What does the hepatic ceacum do? 12. Where
are the gonads located? 13. What are the
ampullae? 14. What three structures are located
in the central disk? 15. How many stomachs does a
starfish have? 16. In what two ways can a
starfish reproduce?