1. Phylum Cnidaria Anemones, Corals, Hydroids and Jellies

2. Phylum Cnidaria Three classes: Class Anthozoa Class Scyphozoa
Anemones
Corals
Class Scyphozoa
True jellies
Class Hydrozoa
Hydrozoans

3. Same body plan for all classes

4. Differences between Classes
Some spend more time in the medusa or polyp form
Can reproduce differently
Can be colonial or solitary

5. Cnidaria Characteristics
Symmetry: Radial
Level of Organization: Tissue
Two cell layers (epidermis and gastrodermis) around a jelly-like substance (mesoglea)

6. Feeding: Excretion: Suspension feeding
Single opening (mouth/anus) into a gastrovascular cavity
All are carnivores
Have light sensing organs (ocelli)
Excretion:
Wastes diffuse out of the cells into the water

7. Defense / Predation: Stinging Cells
All Cnidarians have stinging cells to protect themselves
A nematocyst is triggered with a hair cell
It ejects a harpoon or string with a toxin

8. Class Anthozoa
Corals and anemones
dominant polyp life stage

9. Anemones Solitary: Usually one large polyp
Some can “swim” away if attacked
Some have symbiotic relationships, e.g. with clownfish or shrimp

10. Corals Corals are colonial animals Hard Corals
Many polyps live on the outside of a calcium carbonate skeleton

11. Soft Corals
Many polyps live together but without the hard skeleton

12. Reproduction Both sexual and asexual reproduction Asexual reproduction
budding or fission (splitting in two)
Sexual reproduction
Spawning
Female eject eggs and males eject sperm into the water
Timed to the phase of the moon!

13. Soft Corals

14. A hard coral close up

15. Hard Coral
Table coral has a large flat top to take advantage of sunlight

16. Purple Stubby Coral
Some grow in small finger-like projections

17. Staghorn Coral

18. Mushroom Coral

19. Brain Coral

20. Special relationships with algae
Coral animals have a symbiotic relationship with a kind of algae called zooxanthellae
Mutualistic relationship – they both benefit one another

21. Zooxanthellae
Does photosynthesis and gives the coral food (90% of the coral’s food is from here!)
Coral
gives the zooxanthellae a stable home
gives the zooxanthellae nutrients from its waste

22. Colourful corals!
The algae are responsible for the beautiful colours we see

23. Coral bleaching
Zooxanthellae are very sensitive to temperature change and pollution
If the temperature becomes too high, they leave the coral
This is coral bleaching.
Without the zooxanthellae, the coral will die.

24. Where would you rather dive? Here…

25. Or here…?

26. Class Scyphozoa Jellies Dominant medusa stage
Some have both polyp and medusa stages

27. Coastal Jelly Life Cycle
An ephyra larva

28. More images of the Jelly Life Cycle...

29. Powerful defenses
Some jellies inject a very painful sting with their nematocysts
Box jellies and sea wasps may be fatal

30. Class Hydrozoa Hydrozoans
Colonial with specialized individuals to float, reproduce, defend or hunt.
Some have both polyp and medusa stages
Some have a skeleton of chitin

31. Portuguese Man O’ War
specialized polyps to float and sting

32. Hydra lives in fresh water has only a polyp stage
can reproduce by budding

33. Other Cnidarians
Gorgonians like sea pens and sea whips are also in Phylum Cnidaria