1. Kingdom Animalia
Phylum Cnidaria

2. Characteristics Radial or biradial symmetry Diploblastic organization
Mesoglea between epidermis and gastrodermis
Gastrovascular cavity
Nerve net
Cnidocytes – used in defense and feeding

3. Reproduction/Life Cycle
Can be monoecious or dioecious
Alternate generations between polyp and medusa form
Polyp – asexual and sessile
Medusa – dioecious and free swimming

4. Reproduction Cont’d Planula – Cnidaria larvae
Polyps are produced by budding or planula
Medusae formed by budding from a polyp body wall

5. Feeding Use cnidocytes to stun or kill prey
Tentacles contract to bring food to mouth
Food is digested in gastrovascular cavity

6. Support and Locomotion
Hydrostatic Skeleton
Some classes have longitudinal muscles that aid in movement
Polyps – somersault, inchworm, glide on base, and walk on their tentacles
Medusae – swim and float

7. Classification Class Hydrozoa Class Scyphozoa Class Cubozoa
Class Anthozoa

8. Class Hydrozoa
Mostly marine, but the only class with freshwater members!
Alternate generations
Mostly colonial polyps

9. Obelia Gastrozooid – feeding polyp formed from planula larvae
Grows through budding into more gastrozooids
Gonozooid – reproductive polyp that forms medusa by budding
Medusae then reproduce sexually

10. Gastrozooid
Gonozooid

11. Gonionemus Medusa predominant
Has a velum (shelf-like lip that projects inward)
Velum creates jet propulsion
Mouth at end of a manubrium
Nerve ring that coordinates swimming movements
Statocyst – responds to gravity

13. Hydra Freshwater Polyps only, no medusae Testes form sperm by meiosis
Ovaries form one egg each

14. Physalia Portuguese man-of-war Colonial Cannot swim
Cnidocytes in tentacles are lethal to small vertebrates and dangerous to humans

15. Class Scyphozoa
All marine
“True Jellyfish” – medusa dominant

16. Stinging Nettle, Mastigias

17. Aurelia Gastrodermal cells have cilia to circulate food
Feeds on plankton
Rhopalia – chemoreceptors
Lappets – touch receptors
Statocysts – gravity sensors
Ocelli - photoreceptors

18. Class Cubozoa Medusae are cuboidal Polyps are reduced or absent
Tentacles hang from corners

19. Class Anthozoa Polyps only, no medusae Mouth has a pharynx
Gastrovascular cavity is divided into sections
Sexual and asexual reproduction

20. Sea Anemones

21. Corals