Student Resources

Porifera -Workbook Questions

What are the different types of cells that you would find in a sponge, and what does each cell type do?  (p. 12) 

Depending on how precisely biologists define the function of a sponge cell, they come up with different names for each of the cells. These can include:

1.      Choanocytes, or collar cells, use their central flagellum to propel water through the aquiferous system while trapping food on their microvillar collar. Eggs and sperm may also form from choanocytes.

2.      Archeocytes, or amoebocytes, wander through the mesohyl using amoeboid movement. They can also change into any of the other cell types found in a sponge. Archeocytes are involved in digestion; nutrient transport and storage; elimination of wastes; and along with choanocytes, can form the eggs and sperm.

3.      Sclerocytes produce spicules made of silica or calcium salts.

4.      Spongocytes produce the proteinaceous spongin spicules.

5.      Pinacocytes cover the outer surface of the sponge to form the outer body covering, the pinacoderm.

6.      Porocytes are found in the pinacoderm of some sponges and have a pore through their center allowing water to enter the aquiferous system. Porocytes are able to regulate water flow in the sponge by increasing and decreasing the diameter of their central pore.

7.      Myocytes are found in the mesohyl of some sponges and surround the canals or oscula. Like the porocytes, they are assumed to regulate the flow of water by increasing or decreasing the diameter of these openings to the aquiferous system. 

How does captured food get from a choanocyte to the other sponge cells?  (p. 12) 

The archeocytes, or amoebocytes, pick up food trapped by the choanocytes and transport it through the sponge to the other sponge cells. The archeocytes can also digest food, either storing the digested nutrients or passing it to nearby cells. 

Use the following terms and place them in the proper order to explain the flow of water through the three different sponge architectures: spongocoel, osculum, radial canal, excurrent canal, prosopyle, apopyle, choanocyte chambers, porocyte. 

In an asconoid sponge, water enters the sponge through the porocytes, passes directly to the choanocyte-lined spongocoel, and then out of the sponge through the osculum. In syconoid sponge, water passes through dermal pores to the incurrent canal and through the prosopyle to the choanocyte-lined radial canal. It leaves the radial canal through the apopyles entering the spongocoel before leaving through the osculum. With a leuconoid sponge, water enters through the dermal pores, passing to the incurrent canals, and through the prosopyles to the choanocyte-lined filter chamber. From there it leaves the chamber through the apopyle to the excurrent canal leading to another flagellated chamber or out of the sponge through the osculum. 

Why do freshwater sponges have gemmules as part of their life cycle?  (p. 14)

Compared to the marine environment, freshwater habitats often fluctuate in temperature to the point of freezing; have variable amounts of oxygen, or none, becoming anoxic; or they may dry up and disappear. Organisms that survive in freshwater environments need some way to survive these adverse conditions and for sponges, gemmules are the solution. Gemmules form from densely packed archeocytes filled with nutrients surrounded by spicules and cells that produce a protective covering. Gemmules survive these severe conditions by being dormant, and only when conditions improve do the archeocytes escape from the protective gemmule to start forming a new sponge.

Protozoa || Porifera || Cnidaria || Platyhelminthes || Nematoda || Annelida || Mollusca || Arthropoda
Echinodermata || Chordate Origins || Jawed Fishes || Amphibia || Mammalia