~PHYLUM PORIFERA – THE SPONGES~
Background:
Sponges are the simplest of all multicellular animals. They have no distinct organ systems—no
glands, no digestive tract, no muscles, no nervous system, no sense organs, no excretory system. Their
body wall is perforated by small pores (ostia) through which water enters. The pores are the means by
which sponges capture food particles suspended in water that passes through their body. The water is
drawn from the pores into a central cavity, the spongocoel. Water moves into the sponge because tiny
collar cells (choanocytes) in the body wall have flagella drawing the water inside. Tiny food particles in
the water are engulfed by these collar cells and amoebocytes (archaeocytes) lining the pathway and are
digested in their food vacuoles. Water then flows out of the sponge through a larger opening called the
osculum. Under certain conditions, the cells around the pores and osculum contract closing the openings.
The sponges have an internal skeletal support system of microscopic needles (spicules) composed of
calcium carbonate, silicon, or as in bath sponges, a fibrous protein network called spongin. These skeletal
differences are used to classify sponges. Grantia demonstrates the sycon body plan in which the wall of
the colony is folded into a series of internal and external canals that circulate water to bring in
dissolved oxygen and prey while removing waste products.
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Examination of Grantia, a simple sponge
Materials needed:
 Grantia sample
 Petri dish
 Forceps
 Fine point dissecting needle
 Dissecting scissors
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Dissection pan
Exam gloves
Stereomicroscope
Lab apron (optional)
Procedure:
1) Remove a Grantia from the dish at the station using your forceps. Be gentle so as to not crush the
center of the sponge. Try to grab it at one end and lay it flat in the dissection pan. Observe the outer
characteristics of the animal under the stereomicroscope. The body has several pores perforating the
body called incurrent pores. Water flows in through these pores and into the radial canals, which empty
into the central cavity, the spongocoel and exits though the osculum.
On your lab paper, complete the following:
• Sketch and label the body including the ostia and osculum.
• Describe the function of each the ostia & osculum.
• Describe the type of body symmetry displayed by this specimen.
2) Using your scissors and forceps, CAREFULLY lift the Grantia and make a horizontal cut through the
midsection. If you did not add water to float your specimen before, now would be a good time to do so.
Observe the spongocoel by using your fine point probe and forceps to open the center cavity in the
water. Notice that it is hollow, and that the incurrent pores do indeed penetrate through the body.
On your lab paper, complete the following:
• Sketch and label the body including the spongocoel, ostia and osculum.
• Describe the function of each the ostia & osculum.
3) Clean up your lab area. Dispose of the sponge in the designated disposal bag; wash and dry all lab
materials. Complete the lab questions below.
QUESTIONS: (answer using complete sentences; attach to your lab drawings/descriptions)
1. What are the three types of skeletal material in sponges?
2. Sponges seem to be the earliest of all of the multicellular organisms to evolve. What evidence might
have led to this prediction?
3. How do sponges gain their energy and nutrients?
4. Describe the path of water flowing through Grantia.
5. Name the cells that create the water currents.
6. How do you think that sponges get rid of waste products since they have no digestive tract or kidney?
7. Sponges are capable of sexual reproduction. Since sponges don’t move around, how they accomplish
this?
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