Cnidarian characteristics

1. Phylum: CnidariaPhylum: Cnidaria
(Coelenterata)(Coelenterata)
Stinging cell animalsStinging cell animals

2. CnidariansCnidarians
• Over 9,000 species
– Mostly marine
• Ex. Jellyfish, sea anemones, and theEx. Jellyfish, sea anemones, and the
Portuguese man-of-war.Portuguese man-of-war.
• Important to coral reef systems

3. Classes of CnidariaClasses of Cnidaria
• Class: AnthozoaClass: Anthozoa
• Anemones and Coral PolypsAnemones and Coral Polyps
• Class HydrozoaClass Hydrozoa
• Portuguese man-of-war & HydraPortuguese man-of-war & Hydra
• Class ScyphozoaClass Scyphozoa
• JellyfishJellyfish
• Class CubozoaClass Cubozoa
• Box JelliesBox Jellies

4. CharacteristicsCharacteristics
• Radial symmetry

5. CharacteristicsCharacteristics• Diploblastic
– Epidermis
– Gastrodermal
• Mesoglea layer (middle glue)
– Gelatinous
– Bwt epidermal and gastrodermal

6. CharacteristicsCharacteristics
• No Circulatory System
• Gastrovascular cavity (Incomplete- 1 open)

7. CharacteristicsCharacteristics
• Nervous system
– In the form of a nerve net
– No brain

9. CharacteristicsCharacteristics
• Cnidocytes (stinging cells)
– Defense
– Feeding
– attachment
Nematocyst wall

10. CnidocyteCnidocyte
• This is a diagram of aThis is a diagram of a
cnidocyte, the stinging cellcnidocyte, the stinging cell
of a Cnidarian.of a Cnidarian.
• The hollow thread thatThe hollow thread that
delivers the venom is coileddelivers the venom is coiled
inside the nematocystinside the nematocyst
(capsule that holds it)(capsule that holds it)
• The nematocyst is filled withThe nematocyst is filled with
so much water that the lid isso much water that the lid is
just waiting to pop open andjust waiting to pop open and
release the pressure.release the pressure.

11. After a cnidocyte has been dischargedAfter a cnidocyte has been discharged
into its victim and the venom has beeninto its victim and the venom has been
injected, it looks like this.injected, it looks like this.
At the base of the stinging thread thereAt the base of the stinging thread there
are three barbs that anchor the tentacle/sare three barbs that anchor the tentacle/s
to the animal so it can’t escape.to the animal so it can’t escape.
The nematocyst will be shed and a newThe nematocyst will be shed and a new
one will regenerate in its place.one will regenerate in its place.