Sponges

1
Sponges Phylum Porifera (Pore-bearing)

• Section 28.1

2
Basic Characteristics

• Asymmetrical
• Bodies do not have tissues or organs just
  specialized cells embedded in a gel-like
  substance called mesohyl
• Cells demonstrate cell recognition

3
Body Plan

• Body is sessile remains attached to solid
  surface their whole lives
• Body wall surrounds a large central cavity
• Body wall is full of holes ostia ? water in and
  oscula ? water out

4
Structure of a Sponge
5
Feeding

• The lining of the body cavity has cells with
  flagella choanocytes (collar cells)
• The flagella move and create a current for water
  to enter the ostia
• Choanocytes filter food from the moving water
• Food is digested intracellularly
• Oxygen diffuses into the cells from the water,
  wastes diffuse from the cells into water
• Choanocytes release nutrients from digested food
  into mesohyl and amoebocytes carry it to all the
  other cells

6
Sponge Skeletons

• Most sponges have an internal skeleton made of
  spicules needles composed of silica (glass) or
  calcium carbonate (rock)
• Some have a flexible protein called spongin
• Some contain both
• Three types
• Calcareous sponges calcium carbonate
• Glass sponges silica
• Demosponge sponges silica and spongin

7
Sponge Reproduction

• Asexual reproduction
• Regeneration broken pieces can form new sponges
  this is called fragmentation
• Budding a small section grows and breaks off,
  forming a new sponge
• Gemmules amoebocytes in protective coats with
  food freshwater sponges do this when conditions
  are too dry or too cold
• Sexual reproduction
• Hermaphrodites sponges make both eggs and
  sperm, but at different times in their life cycle
  to prevent self-fertilization
• Sperm are released into the water and fuse with
  egg cells in another sponge free-living larva
  swim in the water for a time before landing on an
  object and growing into adults

8
Sexual Reproduction in Sponges