1. Systematic Adaptations of Phylum Cnideria
The Jellies, Anemone and Corals

2. Objectives (Chapter 13)
1. Identify characteristics distinguishing phylum Cnideria
2. Discuss adaptations characteristic of the phylum Cnideria with regard to
Body form, morphology & embryonic development
Feeding and digestion
Excretion
Movement/locomotion
Reproduction
Sensory/Motor response
3. Define “dimorphism”. Distinguish between the polyp and medusa form of Cniderians

3. Objectives (Chapter 13)
4. Describe structure and function of cnidocytes
5. Distinguish between the taxonomic Classes in the Phylum Cnideria. Give examples
6. Discuss the ecological significance and development of coral reefs
7. Compare & Contrast Ctenophores with Cniderians

4. 1. Identify characteristics distinguishing phylum Cnideria
Radial symmetry
Tissue level of organization
Incomplete gastrulation (one opening to the digestive cavity)
Diploblastic
Endoderm and Ectoderm only – No mesoderm
Tentacles with stinging “cnidocytes”

5. 2. Discuss adaptations characteristic of the phylum Cnideria
Body form, morphology & embryonic development
Feeding and digestion
Excretion
Movement/locomotion
Reproduction
Sensory/Motor response

6. Body Form & Development

7. Body Form and Development
Epidermis
Derived from embryonic ectoderm
Gastrodermis
Derived from embryonic endoderm
Mesoglea
Middle jelly
Tentacle
With cnidocytes

8. Dimorphism Medusae Bell Shaped Motile Usually sexually reproducing
Jellyfish
Polyps
Tube shaped
Sessile
Usually asexually reproducing
Anemone and Corals

9. Integumentary & Muscular
Epidermis is a single cell layer
Muscle fibers associated with the base of the epithelium
True muscle is mesodermal in origin. Cnideria are diploblastic (no mesodermal tissue)
Movements are simple and non-specific

10. Nervous & Sensory No central nervous system
Nerve cells in a diffuse “nerve net” ennervate the epitheliomuscular cells

11. Digestive One opening to the digestive cavity
Digestive enzymes secreted by the gastrodermis (“extracellular” digestion)
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12. Reproduction
Cnideria have a variety of life cycles, from simple to complex.
Generally, the polyp form is used for asexual reproduction.
Sexual reproduction occurs in the medusae
Both monoecious and dioecious forms exist,

13. Characteristic Cniderian Life Cycle

14. Cnidocytes https://www.youtube.com/watch?v=6zJiBc_N1Zk

15. Cniderian Classes Hydrozoa Scyphozoa Cubozoa Anthozoa
Asexual polyps, sexual medusae
Polyp stage reduced or absent
Polyp stage reduced
All polyps, medusae absent
“velum” at the rim of the bell in the medusae to aid propulsion
Medusae lack a velum. Bell margin with sense organs
Cube shaped medusae. No velum, but “vellarium” with similar function
Cnidocytes in the gastrovascular cavity
See the life cycle diagram on page 261 in the textbook
Enlarged mesoglea (the “jelly” in the jellyfish”)
Blade shaped “pedalium” at the base of the tentacles
Septa (mesenteries) separating gastrovascular cavity
Freshwater and marine
All marine
Hydra, Portugese Man of War
What we think of when we think of jellyfish
Very poisonous. Stings may be fatal to humans
Corals and Anemone

16. Hydrozoa https://www.youtube.com/watch?v=yqXkaZwiu6s

17. Scyphozoa

18. Anthozoa https://www.youtube.com/watch?v=a2m59UoTEgs

19. Cubozoa

20. Coral Reefs https://www.youtube.com/watch?v=eIul2ObvKV8

21. Ctenophores (Comb Jellies)
Superficially similar to Cniderian medusae, but:
“Comb plates” for locomotion
No nematocysts
True muscle (derived from mesoderm?)
Complete digestive tract

22. Video Links Great Barrier Reef Documentary (long!) Cniderian Diversity
Cniderian Diversity
Cniderian Movement