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Learn about the characteristics and body forms of Porifera (sponges), including their specialized cells, reproductive methods, and role in filtering water. Discover how sponges help clear water and reproduce both sexually and asexually.
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1. Phylum Porifera (sponges) Characteristics • Asymmetrical • They have three types of cells. • a. pinococytes • b. mesenchyme • c. choanocytes
2. Central cavity or a series of branching cavities. 3. No tissue or organs. Sponges show division of labor – certain cells are specialized to do certain jobs.
4. Pinacocytes – thin, flat cells, line the outside of the sponge, can be used to help the sponge change shape. Sometimes they are shaped like tubes and are called porocytes. Water can pass through these porocytes into the spongocoel.
5. Moving past the pinococyte layer we get to the mesophyl. Within this jelly-like material there are mesenchyme cells.
6. These cells are specialized for reproduction, making skeleton, transporting and storing food, controlling the opening and closing of pores in the cell wall.
7. Under the mesophyl we find choanocytes. These cells line the inner cavity. These have a flagellum surrounded by a “collar” of microvilli. (very small, finger-like projections)
8. The collar of a choanocyte filters food from the water. The flagella move water around the sponge and the microvilli catch particles in the water.
9. The skeletons of sponges consists of microscopic needle-like projections called spicules.
10.They are made of either calcium carbonate or silica. Some sponges have skeletons made of spongin which is made of collagen.
11.There are three types of body forms found in sponges. Sponge taxonomy is determined by their shape.
12. ascon – shaped like a vase, has porocytes with openings called ostia which lead to the spongocoel.
13. The spongocoel is lined with choanocytes which draw water through though the ostia into the spongocoel.
14. They usually have a large opening at the top where water exits. This is called the osculum. The ascon is the simplest, but least common body form of sponges.
15. The sycon body form has folded walls. Water enters this type sponge through a dermal pore.
16. Incurrent canals, formed by infoldings of the body wall, are connected to radial canals which are lined with choanocytes.
17. The water passes down the radial canal into the spongocoel and out through the osculum.
18. Leucon sponges have an extensive canal system with many branches. Water enters through dermal pores into incurrent canals to choanocyte chambers.
19. From these chambers out through excurrent canals and out one of the many osculum. There is no spongocoel present in leucon sponges. Leucon sponges have the most complex body form.
20. Sponge food includes bacteria, algae, protists, other microscopic organic material.
21. Sponges help clear water. A small sponge can filter 20 liters of water per day.
22. Food is caught on the collar and moved down the microvilli to its base where it is put into a food vacuole.
23. Here it is digested and the nutrients are distributed to other cells. Wastes are removed by diffusion across cell walls.
24. Most are monoecious (both sexes on one individual) but because they release the eggs and sperm at different times there is no self-fertilization.
25. Typically, sperm and egg are released through the osculum. Fertilization occurs in the open ocean resulting in a planktonic larvae.
26. In some sponges the egg is retained and the sperm enter the sponge where fertilization takes place.
27. After the larvae develops it is released. It floats around until it attaches to a substrate where it lives the rest of its life.
28. Another form of asexual reproduction occurs when the sponge forms gemmules.
29. These are protective capsules that keep the cells inside from freezing or drying out until favorable conditions return.
