PORIFERANS

PORIFERANS

1. Sponges or poriferans ,are either symmetrical or have a radial symmetry .

2. They are aquatic animals (the mojority are marine animals ) that are live attached to a substrate.

3. What their bodies like

   • Poriferans have bodies with perforations called pores.
   • Sponges have bodies that are supported by a skeleton made of tiny needle-like structures called spicules, or spongin fibres.

4. PARTS OF A PORIFERAN

5. The phylum Porifera contains the simplest creatures of the animal kingdom. Sponges are aquatic sessile organisms (they are unable to move by themselves and they remain attached to substrates). They do not have tissue diversity and their bodies have pores (the feature form which their name is derived).

6. How do poriferans live

   • Sponges live exclusively in aquatic environments and are attached by their base to a substrate (fixation ground). Sponges are filtering animals, meaning that they nourish themselves from nutrients that enter their atrium brought in by water.

7. What is the typical shape of poriferans?

   • The shape of sponges is normally that of a tube or a globe with an opening at the top end. They have an internal central cavity and porous walls. The central cavity is called the spongocoel and the opening at the upper extremity is called the osculum.

8. How does water move inside sponges? What is the function of the pores in these animals?

   • Sponges are filtering organisms. They make water enter their bodies through their lateral pores. Water then circulates inside the central cavity and exits through the osculum.

9. How do sponges try to protect themselves against environmental dangers? Is this method efficient or rudimentary?

   • Sponges can close their pores to stop water from entering their body in the presence of stimulus that may may indicate danger. However, this method is rudimentary and is actually a form of protection against harmful agents.

10. What are the main cells that compose poriferans?

    • Sponges contain an outer wall covered by flat cells called pinacocytes as well as pores surrounded by special cells called porocytes. Their internal wall is filled with choanocytes, flagellate cells specialized in the phagocytosis of food brought to the central cavity. The choanocyte flagella also maintain the water flow inside the sponge. Between the outer and the inner sections of the body of a poriferan, there are cells with amoeboid movement (via pseudopods) called amoebocytes. Since they are embedded in connective tissue, amoebocytes move and distribute nutrients to other cells as well as produce spicules that fill the tissue and support the body structure like a primitive skeleton. (Some poriferans have an internal skeleton, which is an endoskeleton, made of spicules and organic fibers.)

11. What is characteristic of poriferan digestion?

    • Sponges are different from other animals in that they can only use intracellular digestion. They do not have a digestive system nor do they release digestive enzymes in the spongocoel to cause the extracellular break down of nutrients.

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