Section 5: Cnidarians

Radial or biradial symmetry

The type of symmetry cnidarians have.

Cnidae

Specialized stinging organelles in cnidarians, most commonly nematocysts.

Cnidocytes

The location of cnidae.

Two (diploblastic: epidermis + gastrodermis with mesoglea in between)

The number of germ layers cnidarians have.

Both — can be solitary or colonial

The existence of cnidarians as single organisms or colonies.

Dimorphic

The term meaning cnidarians alternate between polyp and medusa body forms.

Polyp form

A tubular body with tentacles upward and a pedal disc that attaches to substrate.

Yes, for specific functions (feeding, reproduction, defense)

Whether colonial polyps can be specialized.

Sessile, but can glide using pedal disc

The motility of polyps.

Asexually

The method by which polyps reproduce.

Medusa form

A free-swimming, bell-shaped body with tentacles/mouth directed downward.

Planula larva

What the zygote of a cnidarian develops into.

Polyp

What the planula larva develops into.

Asexually (produce more polyps or medusae)

How polyps reproduce.

Sexually, releasing gametes

How medusae reproduce.

Dioecious (separate sexes)

Whether cnidarians are usually monoecious or dioecious.

Nerve net

The type of nervous system cnidarians have.

Bidirectional

The direction of cnidarian nerve transmission.

Hydrozoa

Examples include Hydra, Portuguese man-o-war, fire coral.

Scyphozoa

The group that includes the 'true jellies'.

Staurozoa

The cnidarian class that has no medusa stage and 8 arms.

Cubozoa

The cnidarian class that includes 'box jellies'.

Strong swimmers, advanced sense organs, effective predators

What makes Cubozoa unique compared to other cnidarians.

Myxozoa

The cnidarian class that is parasitic in fish and has lost most of its genome.

Anthozoa

The cnidarian class that includes corals and sea anemones.

They form coral reefs and support marine ecosystems

Why Anthozoa are ecologically important.