Notes on Cnidaria

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  • Topic: Cnidaria, Jellyfish, Polyp
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  • Published : December 19, 2012
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Cnidaria
Hydra, Jellyfish, Coral, & Sea Anemones
Phylum Cnidaria-
Examples
Sea Anemones and Corals - Anthozoa
Hydra- Hydrozoa
Jellyfish - Scyphozoa
Ctenophores - non stinging Cnidarians;
Comb Jelly
Anatomy
A. Polymorphism- Cnidarians have more than one body form:
1.Polyp
2. Medusa

Polyp Form
Tube with tentacles around the mouth
Sessile

Medusa Form
Umbrella Shape
Tentacles around mouth
Motile, Free-swimming

Tentacles
Have nematocysts (stinging cells) coiled thread discharges like a harpoon Contains neurotoxin
Paralyzes prey

Level of Organization
A. Cnidarians have tissues
B. No Organs
C. Most Cnidarians have Radial Symmetry

Radial Symmetry
Radial

Habitat:
Aquatic:
1.Most Marine
2.Few Freshwater

Feeding
A.Carnivores (predators)
B. Process of feeding
1. Tentacles sting prey with
Nematocysts
2. Tentacles grab prey
3. Prey pulled into mouth

Process of feeding
4. Prey stuffed into gastro-vascular catvity (GVC)
5. GVC makes enzymes, extra cellular digestion
6. Undigested food back out mouth

Respiration
Via diffusion
Body is two cell layers thick

Internal Transport
Via diffusion

Response
A. No nervous system
B. Nerve net around mouth

Locomotion
A. Medusa- motile, free-swimming
B. Polyps- sessile, attached to hard substrate
Exceptions:
1. Hydra humbles on tentacles
2. Sea anemones glide on pedal disc

Reproduction
1. Asexual
Budding
2. Sexual
a. Medusae release sperm and eggs
b. Larvae are free-swimming

Ecological Role
A. Predators and prey
B. Neurotoxins in medical research
C. Coral - Jewelry , building, reefs (surfing)
D. Cora Reefs - habitat for many
Great Biodiversity
Protect coastline
E. Symbiosis with other organisms
Portuguese Man O' War ( a Hydrozoan) NOT a true jelly fish
Man O' War Can measure up to 30cms across
Crescent wind thing that glides it

Polyps can be either food gathers and some are reproductive. As low as 10m long



Jellyfish...
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