Phylum Porifera
I. List the characteristics of Phylum Porifera
1. Multicellular without true tissues
2. Bodies with pores and canals that form a water current system which brings in food
and oxygen
3. Mostly marine, all aquatic
4. Radial symmetry or no symmetry
5. Three types of cells: choanocytes, archaeocytes, pinacocytes
6. Skeletal structure made of spicules and protein
7. No organs or true tissues
8. No nervous system, any response to a stimulus is restricted to the localized area of
the stimulus
9. Adults are sessile (they don’t move)
10. Sexual or asexual reproduction
II. Describe the function of the three main types of cells.
• Choanocytes - also called collar cells because they have a mucus covered collar
around a single flagellum. The flagellum creates the water current that brings food
particles into the sponge. As the water flows through the collar food particles are
trapped in the mucus
•
Archaeocytes - these cells act like amoebas and digest food particles. They also form
spicules and give rise to the other cell types found in sponges
•
Pinacocytes - these cells for a layer that covers the outside surface of a sponge. This
layer of cells is the closest thing sponges have to a true tissue.
III. Diagram a choanocyte and outline the movement of water and food around the cell.
IV. Describe the form and function of spicules.
Spicules are made of silica or calcium carbonate. They form a sort of skeleton for the
sponge and they also help protect a sponge from predators because they irritate the mucus
membranes of the mouth and digestive tract.
V. Diagram and describe the structure of the three types of canal systems found in
sponges.
• Asconoid - The
simplest sponge
body plan where
choanocytes line
the internal cavity
(spongocoel)
•
Syconoid - The
•
Leuconoid - A
sponge body plan
with incurrent
canals and radial
canals. The
choanocytes line
the radial canals
and not the
spongocoel
complex sponge
body plan where
the choanocytes
line the walls of
numerous tiny
chambers
VI. Explain the difference between an ostium and an osculum
Ostia are the numerous tiny holes found all over the surface of the sponge. Water enters
the sponge through an ostium. Oscula are the large openings on sponges. A sponge
typically has only one osculum (leuconoid sponges have a few oscula). Water exits the
sponge through an osculum.
VII. Describe the three Classes of sponges; identify synapomorphies.
• Calcarea - Spicules are made of calcium carbonate and are needle-shaped, three-rayed
or four-rayed. All three body types are found in this class.
•
Hexactinellida - Spicules are made of silica and are six-rayed. Their bodies are
funnel shaped with a syconoid or leuconoid body plan.
•
Demospongiae - Spicules are made of silica and are not six-rayed. Some members
have spongin instead of or in addition to spicules. All have a leuconoid body plan.