Phylum: CnidariaPhylum: Cnidaria(Coelenterata)(Coelenterata)

Stinging cell animalsStinging cell animals

CnidariansCnidarians

• Over 9,000 species– Mostly marine

• Ex. Jellyfish, sea anemones, and the Ex. Jellyfish, sea anemones, and the Portuguese man-of-war.Portuguese man-of-war.

• Important to coral reef systems

Classes of CnidariaClasses of Cnidaria• Class: Anthozoa Class: 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

CharacteristicsCharacteristics

• Radial symmetry

CharacteristicsCharacteristics• Diploblastic– Epidermis– Gastrodermal

• Mesoglea layer (middle glue)– Gelatinous– Bwt epidermal and gastrodermal

CharacteristicsCharacteristics• No Circulatory System

• Gastrovascular cavity (Incomplete- 1 open)

CharacteristicsCharacteristics• Nervous system

– In the form of a nerve net– No brain

CharacteristicsCharacteristics• Cnidocytes (stinging cells)

– Defense– Feeding– attachment

Nematocyst wall

CnidocyteCnidocyte• This is a diagram of a This is a diagram of a

cnidocyte, the stinging cell cnidocyte, the stinging cell of a Cnidarian.of a Cnidarian.

• The hollow thread that The hollow thread that delivers the venom is coiled delivers the venom is coiled inside the nematocyst inside the nematocyst (capsule that holds it)(capsule that holds it)

• The nematocyst is filled with The nematocyst is filled with so much water that the lid is so much water that the lid is just waiting to pop open and just waiting to pop open and release the pressure.release the pressure.

After a cnidocyte has been discharged After a cnidocyte has been discharged into its victim and the venom has been into its victim and the venom has been injected, it looks like this. injected, it looks like this.

At the base of the stinging thread there At the base of the stinging thread there are three barbs that anchor the tentacle/s are 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 new The nematocyst will be shed and a new one will regenerate in its place.one will regenerate in its place.