Cnidarians

Can’t

Touch This

Examples● Jellyfish● Corals● Sea Anemone● Hydra

Characteristics● Radial Symmetry● Stinging Cells (Cnidocyte)● Two different Body Plans During Life Cycle

(exceptions)● Polyp● Medusa

Structure and Function● Cnida – Stinging Organelle

● Nematocysts● Spearing Cnida

● Generally on Tentacles

The Sting

• So what would you do if you were stung by a jellyfish?• Jelly Fish Invasion

Ouch!

Yummy Nematocysts● Leatherback Sea Turtle

Why not use the toxin?● Nudibranchs

True Jellyfish (Class Scyphozoa)● Predominant life stage

● Medusa● Generally not strong swimmers● Photoreceptors

● Box Jellies Closely Related

Hydrozoans● Mostly Colonial

● Specialized Polyps● Feeding Polyp● Reproductive Polyp

Anthozoans (Flower Animal)● Sea Anemones

● Polyps● Larger, heavier and more complex than hydra● Most 1.5 to 10cm in Diameter● Deep and Shallow Water● Retracts Tentacles If Disturbed● Essentially Sessile

Anthopleura elegantissima

Anthozoan Cont. and Gorgonian● Corals

● Hard Corals● Secrete a skeleton of calcium carbonate (Reef Building Coral)● Large Colonies of Small Polyps

● Gorgonians (Most Common Soft corals)● Soft Corals

● Colonies that look like plants

Nutrition and Digestion● Gastrovascular Cavity

● Digestion and movement of materials within animal● Waste if forced back out of the mouth after digestion

(Yum!)

Reproduction● Asexually

● Generally during polyp state resulting in more polyps● Sexually

● Generally in the medusa stage

Life Cycle

Ecological Relationships● Predator-Prey

● Predator to many species (stinging cells)● Prey to sea turtles, some fish and mulluscs

● Crown-of thorns sea star feeds on coral

● Habitat Formation● Coral reefs provide a solid surface

Ecological Relationships● Symbiotic Relationships

● Portuguese man-of-war and man-of-war fish● Coral and zooxanthellae● Hermit crab and anemone (Eupagurus prideauxi and

Aamsia palliata)