Phylum Porifera – The Sponges

  • Porifera -> “Pore”Bearing”  Latin Name means to bear pores.
  • Appeared ~700 Million years ago (Oldest multicellular animals on Earth)
  • All other animal groups evolved from sponge-like ancestors

Figure 1: Sponge Diversity

A. Evolution of Body Plan

1. First Multicellular animal – basic body plan is just four types of cells arranged around a series of pores/canals.

  • Water is pulled into the spongocoel through pores and leaves out the osculum (top of sponge

Figure 2: Basic Sponge Body Plan

2. Sessile (Immobile/fixed in one place)

3. Sponges are supported by a “skeleton” of spicules.

    1. Spicules are made of calcium carbonate (solid), silica, or spongin (a type of collagen – flexible and soft).
    2. Spicules hold pores open and keep sponge shape.

Figure 3: Spicules

  1. Asymmetrical – No planes of symmetry.

Figure 4: Sponge Body Plan

B. Feeding and Excretion
How Sponges Feed:

  1. Sponges are filter feeders. They pull water into the spongocoel (middle cavity of a sponge) through pores.
  2. The spongocoel and canals are lined with choanocytes which have flagella (whip-like tails) which pull food inward.
  3. Food enters the cell through phagocytosis (Same as many unicellular organisms such as amoebas)

Figure 5: Process of Phagocytosis

Choanocytes (Collar Cells) – Cells surrounding the “collar” that strains food from the water.

Figure 6: Choanocytes

Parasitic Sponges – Boring Sponges!
  • The sponges bore into corals or shelled animals.
  • The sponges grow in these new holes.
  • The host dies from this or becomes more susceptible to predation.

Figure 7: Victims of the boring sponge

 

 

C. Respiration and Circulation

No respiratory or circulatory system! Each cell is responsible for it’s own food/waste etc. Sponges function more like a colony of unicellular organisms.

CO2/O2 enter/exit through simple diffusion (movement of a substance across the cell membrane)

Figure 8: Diffusion – the movement from high concentration to low concentration over a membrane

D. Reproduction

Sponges reproduce asexually and sexually.

Figure 9: Budding in sponges

Figure 10: Fission in sponges

Sexual Reproduction

Hermaphrodites with Internal Fertilization

Sponges are usually both male and female but rarely self-fertilize.

  1. “Male” releases sperm which enters the “female” sponge for internal fertilization.
  2. Larvae are released. These drift until they attach to a rock and grow into an adult sponge.
  3. This is called broadcast spawning.

Figure 11: Sexual Reproduction in Sponges

Phylum Porifera – Who cares?

  • Glass sponge reefs used to be common, but now are only found off of BCs coast. Individuals in BCs glass sponge reefs are 25000 years old!

  • We get various antibiotics from sponges! (and Acyclovir – first antiviral used to fight herpes).
  • Venus Flower Basket Sponge – the strongest “glass” structure in nature. These sponges have spicules that transmit light better than optic fibres.

Environmentally friendly sponges?

Review Questions:

  1. Sponges function more like a colony of unicellular organisms despite being a single organism. Describe why this statement is true.
  2. What three materials could make up the structure/”skeleton” of a sponge? What are these supports called?
  3. Describe the feeding process of a sponge. Make sure to use the following vocabulary in your answer: spongocoel, choanocytes, phagocytosis.
  4. Why is sexual reproduction beneficial for sponges (or other organisms)?
  5. When could asexual reproduction be beneficial?