Kingdom: Animalia, Phylum: Cnidaria

Tentacle

Phraynx

Gonads

Column

Septum

Cinclide (pore)

Acontium

(defensive stinging tentacle)

Pedal disk

Oral disk

Mouth

Collar

Stomata

Septum

Retractor muscle

Cnidaria is a phylum containing over 9000 species found only in aquatic and mostly

marine environments. “Cnidaria” comes from the Greek word "cnidos," which means

nettle.

There are two major body forms among the Cnidaria - the polyp (sea anemones and

corals) and the medusa (jellyfish).

There are four major groups of cnidarians:

• Anthozoa: corals, anemones, and sea pens

• Cubozoa: box jellies

• Hydrozoa: siphonophores, hydroids, fire corals

• Scyphozoa: jellyfish

Sea anemone polyp anatomy

Cnidaria have stinging

cells called nematocysts

that are used for defence

or capturing prey.

When the trigger is touched

the nematocyst tube springs

out and injects venom into

the prey.

Red, or southern, or bubble, or

mulberry anemone

Phlyctenanthus australis

Waratah anemone

Actinia tenebrosa

(pronounced “Nye-dare-ree-ah”)

Sea anemones sometimes found in the touch tank

Image by Byron Inouye manoa.hawaii.edu