Inverts - Origins of metazoan (sponges) Flashcards
What are Porifera?
Sponges
Porifera characteristics
- simple structure
- Most are filter feeders
- Widespread
- Most marine (some freshwater)
- variety of forms depending where found
- Very successful and ancient
Porifera (tree of life?)
Split from rest of animal phyla early on
Parazoa (beside animals - cos of early split)
Structure of a sponge (pores within surface)
Ostium or ostia: in-current cells
Porocyte: pores
Sponge structure (central chamber)
Spongocoel
Sponge structure (top hole)
Osculum
what cells generate a current that flows through a sponge?
Choanocytes
Can also trap food
What cells take up food in a sponge ?
Amoebocytes
can move around the sponge
Why are amoebocytes specialized?
They are totipotent - can transform into any other cell within the sponge
How is water passed through a sponge ?
- Water enters through pores (ostia, porocyte) into spongocoel
- Choanocytes waft water current through spongocoel
- Water is exits via osculum
Skeleton like structure of a sponge?
Spicules
Made of calcium carbonate/silicates/sponging fibres
Provides support and makes sponge less edible
Form of defence
‘skin’ layer surrounding the sponge
Pinacocyte / pinacoderm.
Quantity of water passing through sponge
20,000 x its body weight in 24 hours
Can the rate of flagella beat change?
Yes
example of how Osteocytes can detect/repsond to stimuli
When tide retreats closing of osculum is triggered
Where are glass sponges found and why are they structurally specialised?
Found in deep sea
Spicules arranged in complex structure
75% tissue syncytial - don’t have any cell walls
Glass sponge structure follows same principles as engineers
Glass sponge - electrical impulses
No nerve cells but can conduct electrical impulses
Glass sponge - venus flower basket
Shrimp get stuck within the sponge and live, reproduce and die within the sponge
Carnivorous sponge
Harp sponge - no choanocytes
Why are sponges important for coral reefs?
- Coral reefs are low in phosphorus and nitrogen
- sponges capture organic material and use for growth
- They shed cells and bits of material in the process
- other organisms feed off bits of sponge or the whole sprong - nutrients recycled
Structure of sponge (Body layers)
No body layers
How does a sponges structure change as it gets bigger?
- Infolding of pinacoderm
- Increases surface area
- Increases complexity
Sponges ability to regenerate
Wilson’s sieve experiment shows some form of self-recognition
Sponge Reproduction (Asexual)
Budding
- Gemmules - small structures (similar to seed) containing amoebocytes with a hole at the top (micropyle)
- When in good conditions amoebocytes crawl out and form new sponges
Sponge reproduction (sexual)
Most are hermaphrodite (cross fertilise - don’t fertilise themselves)
Sperm expelled via osculum and engulfed by choanocytes - transferred to egg
Sponge relationships with other organisms
Symbiotic relationships with:
- Zooanthellae (algae)
- Bacteria (ancient relationships)
- Chemicals within sponges that have antibacterial/antiviral function
- Some produce biotoxins that prevent other organisms growing on them etc defence chemicals
