Transcript Sponges – Phylum Porifera

Sponges – Phylum
Porifera (Pore-bearing)
Section 28.1
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
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
Structure of a Sponge
Feeding
 The lining of the body cavity has cells with flagella –
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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
Sponge Skeletons
 Most sponges have an internal skeleton
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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
Sponge Reproduction
 Asexual reproduction:
1. Regeneration – broken pieces can form new sponges – this is
called fragmentation
2. Budding – a small section grows and breaks off, forming a new
sponge
3. 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
Sexual Reproduction in Sponges