Cnidarians

1. Phylum Cnidaria
Hydra, jellyfish, coral, & seaHydra, jellyfish, coral, & sea
anemonesanemones

3. • Both phyla Cnidaria andBoth phyla Cnidaria and
Ctenophora make up theCtenophora make up the
radiate animals.radiate animals.
• They don’t have advancedThey don’t have advanced
beyond tissue level ofbeyond tissue level of
organizationorganization although a fewalthough a few
organs are seen.organs are seen.
• No respiratory or excretoryNo respiratory or excretory
system.system.

4. –They have anThey have an internal body cavity: theinternal body cavity: the gastrovascular cavitygastrovascular cavity
in which extracellular digestion occurs.in which extracellular digestion occurs.
–The cavity hasThe cavity has a single openinga single opening (it’s both mouth and anus)(it’s both mouth and anus)
–TentaclesTentacles around the opening.around the opening.

5. SpecialSpecial stinging cellsstinging cells (cnidocytes) that contain a(cnidocytes) that contain a
specialized stinging organelle, thespecialized stinging organelle, the nematocystnematocyst areare
abundant on tentaclesabundant on tentacles. Coiled thread discharges like a. Coiled thread discharges like a
harpoon. It contains neurotoxin that paralyze preysharpoon. It contains neurotoxin that paralyze preys

8. – The simplest animals with nerve cells; there isThe simplest animals with nerve cells; there is
no central nervous system.no central nervous system.
– The simplest animals with sense organsThe simplest animals with sense organs
(statocysts –balance- and ocelli –eyespots-)(statocysts –balance- and ocelli –eyespots-)

10. –They move with the water currents or byThey move with the water currents or by
contracting their bodycontracting their body..

11. –Two typesTwo types according to their body shape:according to their body shape:
–Polips (cylindrical and attached to floor)Polips (cylindrical and attached to floor)
–Medusae. (umbrella-shaped, gelatinous andMedusae. (umbrella-shaped, gelatinous and
free-swimming)free-swimming)

12. - Sea anemones and corals are all polyps with no
medusa stage.
- Some have an exoskeleton or endoskeleton of
chitinous, calcareous or protein components.

13. • CnidariaCnidaria
– All are aquatic and mostly marine.All are aquatic and mostly marine.
– Radial symmetry.Radial symmetry.
– Reproduction is either asexual or sexual; a planulaReproduction is either asexual or sexual; a planula
larva may be present.larva may be present.

14. Class HydrozoaClass Hydrozoa
–HydraHydra are solitary polyps and one of aare solitary polyps and one of a
few cnidarians found in freshwater.few cnidarians found in freshwater.

16. Class AnthozoaClass Anthozoa
• 1.1. Sea AnemonesSea Anemones
– a. They attach to shells, rocks, wood, etc.; some burrow in mud ora. They attach to shells, rocks, wood, etc.; some burrow in mud or
sand.sand.

17. –Some have a mutualistic relationship with hermit crabs.Some have a mutualistic relationship with hermit crabs.

18. Clown fish with sea anemone

20. Class AnthozoaClass Anthozoa
• 2. Corals2. Corals
– They are miniature sea anemones that live in calcareousThey are miniature sea anemones that live in calcareous
cups they have secreted.cups they have secreted.
– Hermatypic corals and coralline algae form most coralHermatypic corals and coralline algae form most coral
reefs. These corals require full salinity of seawater andreefs. These corals require full salinity of seawater and
warmth and light, limiting them to waters between 30warmth and light, limiting them to waters between 30
degrees north and south.degrees north and south.

23. Class Scyphozoa: True Jellyfish
Fried egg jelly

24. Jellyfish