Inverts - Origins of metazoan (sponges)

Question 1

What are Porifera?

Answer 1

Sponges

Question 2

Porifera characteristics

Answer 2

• simple structure
• Most are filter feeders
• Widespread
• Most marine (some freshwater)
• variety of forms depending where found
• Very successful and ancient

Question 3

Porifera (tree of life?)

Answer 3

Split from rest of animal phyla early on

Parazoa (beside animals - cos of early split)

Question 4

Structure of a sponge (pores within surface)

Answer 4

Ostium or ostia: in-current cells

Porocyte: pores

Question 5

Sponge structure (central chamber)

Answer 5

Spongocoel

Question 6

Sponge structure (top hole)

Answer 6

Osculum

Question 7

what cells generate a current that flows through a sponge?

Answer 7

Choanocytes

Can also trap food

Question 8

What cells take up food in a sponge ?

Answer 8

Amoebocytes

can move around the sponge

Question 9

Why are amoebocytes specialized?

Answer 9

They are totipotent - can transform into any other cell within the sponge

Question 10

How is water passed through a sponge ?

Answer 10

• Water enters through pores (ostia, porocyte) into spongocoel
• Choanocytes waft water current through spongocoel
• Water is exits via osculum

Question 11

Skeleton like structure of a sponge?

Answer 11

Spicules

Made of calcium carbonate/silicates/sponging fibres

Provides support and makes sponge less edible

Form of defence

Question 12

‘skin’ layer surrounding the sponge

Answer 12

Pinacocyte / pinacoderm.

Question 13

Quantity of water passing through sponge

Answer 13

20,000 x its body weight in 24 hours

Question 14

Can the rate of flagella beat change?

Answer 14

Yes

Question 15

example of how Osteocytes can detect/repsond to stimuli

Answer 15

When tide retreats closing of osculum is triggered

Question 16

Where are glass sponges found and why are they structurally specialised?

Answer 16

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

Question 17

Glass sponge - electrical impulses

Answer 17

No nerve cells but can conduct electrical impulses

Question 18

Glass sponge - venus flower basket

Answer 18

Shrimp get stuck within the sponge and live, reproduce and die within the sponge

Question 19

Carnivorous sponge

Answer 19

Harp sponge - no choanocytes

Question 20

Why are sponges important for coral reefs?

Answer 20

• 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

Question 21

Structure of sponge (Body layers)

Answer 21

No body layers

Question 22

How does a sponges structure change as it gets bigger?

Answer 22

• Infolding of pinacoderm
• Increases surface area
• Increases complexity

Question 23

Sponges ability to regenerate

Answer 23

Wilson’s sieve experiment shows some form of self-recognition

Question 24

Sponge Reproduction (Asexual)

Answer 24

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

Question 25

Sponge reproduction (sexual)

Answer 25

Most are hermaphrodite (cross fertilise - don’t fertilise themselves)

Sperm expelled via osculum and engulfed by choanocytes - transferred to egg

Question 26

Sponge relationships with other organisms

Answer 26

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