Phylum Cnidaria: More than Just Jellyfish

Don’t Forget Sponges!

• Phylum:– Porifera

• Anatomy & Physiology:– Osculum, Spongocoel (asymetrical)– Archaeocytes, choanocytes, spicules

• Ecology:– Filter feeders

Cnidarians have Cnidocytes• Cnidocytes are

stinging cells that produce toxins and inject it into prey.

• They are used to stun and capture prey.

Cnidocyte

Two Major Groups of CnidariansAnthozoa Medusozoa

Sea anemones

Corals

Sea Pens

hydrozoa

True jellies

Box jellies

Cnidarian Life Cycle

• Two main phases:– Polyp (stationary)– Medusa (mobile)

• Some Cnidarian species have only a single phase. This is a general description.

Cnidarian Anatomy

Cnidarian Anatomy

Sea Anemones

• Anemones spend most of their time attached to rock or coral, though they can move.

• They are predators

Clownfish & Anemone

• One of the best examples of symbiosis in all of biology

• What does each organism get from the other?

Corals • Brain coral shown at left

• Corals are colonies of many tiny polyps.

• They are carnivores.• They have no medusa stage in their life cycle – all polyp

FlowerCoral

Coral Reefs • Corals CaCO3 holdfasts are what coral reefs are made of.

Sea Pens & Sea Fans: “Soft” Corals – No CaCO3 “bones”

Box Jellyfish: Deadliest Venom?

• Cnidocytes on the tentacles of box jellies may have killed more people than any other venom!

True Jellies: Scyphozoa

Hydrozoa: Weird Misfit Cnidarians

• Many sizes and shapes

• Many variations on life cycle

• Poorly defined group

Deadly Portugese-Man-O-War

Hydra

In Summary

• Cnidarians have stinging cells called cnidocytes.

• The Cnidarian life cycle includes polyp and medusa stages.

• Cnidaria includes a wide variety of species, including jellifish, anemones, and hard and soft corals.

• They are all predators.