MARIN

E SCIE

NCE

PHYLU

M C

NID

ARIA

What are Cnidarians?

Soft-bodied animals with stinging tentacles

Ex: Jellyfish, anemones, corals, hydras

Over 9,000 species

MORPHOLOGY

Who thinks they know what type of symmetry most cnidarians exhibit?

THAT

’S R

IGHT

RADIAL

SYMMETR

Y!!!!

!!

Body forms:Medusa, What Shape is this structure?

Polyp, What Shape is this structure?

Single opening surrounded by tentacles Is both mouth and anus

Simple Nervous systemNo brain

INTERNAL STRUCTURE: Epidermis

Mesoglea (Jelly-like material in between layers)

Gastrodermis

Which layer is the inner layer?

Gastrovascular cavity: internal space where digestion takes place

HOW D

O YOU

THIN

K CNID

ARIANS

PROTE

CT

THEMSELV

ES?

F IST F

IGH

T, W

EAPON

S,

TOXINS ,

F IGH

T OR F

L IGH

T?

DEFENSENematocysts: Stinging

structures located on tentacles

Spring loaded poison-filled darts

Captures and paralyzes prey Defense

Jellyfish sting!

**Not all tentacles have nematocysts; some used for reproduction, feeding

WE KNOW THAT PORIFERA

REPRODUCED MULTIPLE

WAYS, HOW ABOUT

CNIDARIA, HOW DO YOU

THINK THEY REPRODUCE?

REPRODUCTION

Most Cnidarian life-cycles involve an alteration of generations:

two different body forms

dominant and conspicuous medusa form

smaller polyp form, often restricted to the larval stage.

Jellyfish reproduce sexually, and individuals are either male or female. The reproductive organs (gonads) develop in the lining of the gut.

QUICK GUESS HOW MANY

CLASSES OF CNIDARIANS

DO YOU THINK THERE

IS???

CLASSES OF CNIDARIANS:There are four classes of Phylum

Cnidaria:

1) Class Hydrozoa– “water animals”

2) Class Scyphozoa– “cup animals”

3) Class Anthozoa– “flower animals”

4) Class Cubozoa– “cube animals”

CLASS HYDROZOA“WATER-ANIMALS”

Can have polyp, medusa or both shapes; often have alternation of generations

Mostly colonial*

Some live in fresh water

Ex: Portuguese Man-O-War, Hydras

*live in colonies

CLASS SCYPHOZOA“CUP-ANIMALS”

True Jellyfish

Adult stages have medusa shaped bodies

Tentacles can be over 30 m long in some species!!

Some can cause painful stings

CLASS ANTHOZOA“FLOWER-ANIMALS”

Sea anemones and corals (hard and soft)

Only polyp-shaped bodies

Usually sessile

Coral polyps secrete a calcium carbonate skeleton for protection

Symbionts with photosynthetic algae

CLASS CUBOZOA

Cubozoans are the box jellies. They have a cubical shape when viewed from above

Their tentacles are evenly spaced

This is the smallest class in terms of species

Some box jellies contain deadly toxins in their nematocysts

TREATMENT OF STINGS

First: Carefully remove the tentacles. As long as tentacles remain on the skin, they will continue to discharge venom.

Second: Apply meat tenderizer, vinegar, tobacco or sodium bicarbonate

If stung by a box jelly, seek medical attention immediately! An antivenom is available to prevent mortality.

Don’t rub the sting site!

Don’t use: Alcohol or human urine. These actually stimulate stinging cells and may increase pain and cause severe skin reactions.

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