By: Cristina Ortiz & Angie Sevilla

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Cnidarians are part of the
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Phylum Cnidaria
They are carnivorous animals
 that contain stinging tentacles
Stinging cells are called
 cnidocytes
Within each cnidocytes is a nematocyst

Two stages: Polyp and Medusa
Polyp:
Cylindrical body with arm-like tentacles
Mouth points upward
Medusa:
Motile, bell-shaped body
Mouth on the bottom
Each has:
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Body wall that surrounds an internal space called a gastrovascular cavity
The gastroderm is the inner lining of the gastrovascular cavity, where digestion takes place
The epidermis is the outer layer of cells
The mesoglea is a layer that lies between these two tissues

Polyp on the left & Medusa on the right

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Polyps:
Asexually by budding
(two types)
1) Swelling on the side of an existing polyp & grows into a new polyp
2) Polyps produce tiny medusas that separate and become new individuals
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Sexual reprodction:
External fertilization
Takes place outside the female’s body
Female releases eggs into the water and male releases sperm
Zygote grows into a freeswimming larva
Larva attaches to a hard surface and develops into a polyp
Polyp buds and releases a medusa

Jelly Fish:
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Class Scyphozoa
Scyphozoans means “cup animals”
Live their lives primarily as medusas
Can be quite large
Reproduce sexually
Hydras:
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Hydras lack a medusa stage
Reproduce asexually by budding or sexually by producing eggs & sperm
Get nutrition from capturing, stinging, and digesting small prey
Sea Anemones and Corals:
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Sea Anemones live at the depth of the ocean & use nematocysts to catch a variety of marine organisms
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Coral Polyps are colonial and grow together in large numbers, while limestone is created.
Reproduce sexually and asexually

Human Uses:
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Medicine
Food
Effects:
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Can be toxic to humans
Stinging structures