Cnidarians Part Deux

1
CnidariansPart Deux

• HW

2
Reproduction

• Most cnidarians have two forms
• Polyp tube shaped body with a mouth surrounded
  by tentacles
• Medusa umbrella shaped body and tentacles that
  hang down. The mouth is on the ventral side
  between the tentacles.

3
Reproduction

• The two forms of cnidarians can be seen in the
  life cycle of a jellyfish
• The dominant form varies depending on the type of
  cnidarian.

4
(No Transcript)
5
Jellyfish Reproduction

• To reproduce jellyfish (in the medusa stage)
  release egg and sperm into the water.
• When the two meet fertilization occurs in the
  water not internally.
• Resulting zygotes (product of fertilization) will
  develop into free-swimming larvae that will grow
  into polyps.

6
Jellyfish Reproduction

• Jellyfish polyps reproduce asexually to form new
  medusae (plural of medusa).
• So jellyfish alternate generationally from the
  polyp stage and the medusa stage.
• What does this mean???

7
Cnidarian Diversity

• You know that jellyfish and sea anemones are
  cnidarians, but what else is there?
• Hydroids
• Jellyfishes
• Sea Anemone Coral
• How do these three groups consititute 10,000
  species????

8
Hydroids

• Hydroids
• 2700 species
• Have both polyp and medusa stages in their life
  cycles.
• Most form colonies (like the Portugese Man of
  War).
• Another example of hydroids is the hydra which
  we will study.

9
Jellyfishes

• Jellyfishes
• 200 species
• Transparent/transulscent appearance
• Medusa is the dominant form, but there is a polyp
  stage
• One well known example is the box jellyfish.
• Box jellyfish get their name because the medusa
  form has a boxlike structure.
• A sting from a box jellyfish can kill a human.

10
Sea Anemones Corals

• 6200 species (WOW)
• Polyp stage is the dominant stage.
• Recent research suggests bilateral symmetry for
  the polyps, unlike jellyfish and hydroids.

11
Sea Anemones Coral

• Sea anemones live as individuals and coral lives
  in colonies.
• Coral secretes calcium carbonate to protect
  itself.
• This creates a hard shell around their soft
  bodies.
• As you may know coral reefs are endangered.
• Their health depends on proper water
  temperature, adequate light, and appropriate
  water depth.
• Rises in water temperature pollution pose a
  threat to this pretty cnidarian.

12
Summary

• The notes from the past two days have described
  the body structure, digestive nervous systems,
  reproduction, and diversity of cnidarians.
• You need to read study these notes in addition
  to completing the labs and color plates!!!!
• REMINDER DO NOT WRITE IN THE COLOR PLATE
  BOOKS!!!