What is Cnidarian?

• Marine Invertebrates

• 9,000 species

• Jellyfish, Coral, Sea Anemones, Hydras

• Found Worldwide

Cnidarian Characteristics

• Radial Symmetry– Arranged in

circular pattern

• One body opening– Mouth & anus

• Simple nervous system

• Stinging cells

Cnidarian Body Forms• Polyp

– Tube-shaped body with a mouth surrounded by tentacles

• Medusa– Umbrella shaped with

tentacles hanging down

Polyp-Forms

• Hard Corals • Hydra

Sea anemones

Bulb Tentacle Sea anemone

Leathery Sea anemone

Haddon’s Sea anemone

Skunk Anemonefish

False Clown Anemonefish

Medusa form:

Feeding

• Each cnidocyte contains bulb-like nematocysts

• Each nematocyst contains a barbed, coiled structure that pierces prey when triggered by touch or chemicals

• Tentacles then bring the paralyzed prey into the cnidarian’s mouth

Digestion

• Nematocysts– Tiny, harpoon-like

structures found at the tips of tentacles that are used to poison and immobilize prey.

• Gastrovascular Cavity– Inner body layer where

digestion takes place via enzyme release

Cnidrian Oxygen Demands

• O2 diffuses directly into the body cells from water

• CO2 and other wastes diffuse out of the cells

Cnidarian Nervous System

• Nerve Net– Conducts nerve impulses

from all parts of the body

– No brain (control center)

– Causes contractions of muscle-like cells in the tentacles and bodies

Reproduction in Cnidarians

• Alteration of Generations– Male releases sperm and

female releases eggs into water (sexual)

– Zygote becomes a free-swimming larva and swims to a suitable area for attachment and settles

– Polyp then grows and begins to form buds that become tiny medusa (asexual)

– One by one, the medusa move away from the parent polyp and the cycle begins again

Jellyfish are categorized into 4 classes as follows:

• Hydrozoa (Portuguese man-of-war• Scyphozoa (true jellyfish; most

common)• Cubozoa (box jellyfish; most toxic.

NOT found in Caribbean)• Anthozoa (sea anemones and

corals)

Class Scyphozoa

• Range in size from the thimble sized jellyfish to the Arctic Lion’s Mane whose tentacles stretch over 100 feet in length

Scyphozoa Characteristics

• Found Worldwide

• 95% water

• No heart, brain, blood or gills

• Feed on zooplankton

Scyphozoa Structure• Bell

– Body of jellyfish

• Oral Arms– Help bring food toward mouth

• Mesoglea – – “jelly-like” substance– Separates and connects the

two other tissue layers • Tentacles

– Contain Nematocysts

Scyphozoa Tissue Layers• Epidermis –

– outermost tissue layer

– Acts like a “skin”– Provides

protection

•Gastrodermis – •Inner tissue layer•Lines the body cavity•Carries out digestion•Produces reproductive cells

Scyphozoa Senses• Chemoreceptors

– Sense chemical signals for smell and taste

• Balance– Sacs located on rim of

bell– Help keep the jellyfish

in the right direction

How Do Jellyfish Swim?

• Jet Propulsoion– Contract

coronal muscles that push water out of the hollow bell

– Drift in the currents

Stinging Cells- Nematocysts

• Consist of a capsule with a sensory hair, a lid, and a interior stinger

• Fires in milliseconds– One of the fastest

processes in nature

Scyphozoa Reproduction:Alternation of Generations

Miscellaneous Facts• Nematocysts may still

fire even when the jellyfish is dead

• Loggerhead Sea turtles and Ocean Sunfish are known to eat jellyfish

• The name of the “jelly-like” material is called Mesoglea

Class Hydroza- Portuguese man-of-

war • Not only is it not a jellyfish, it's not even

an "it," but a "they." • The Portuguese man-of-war is a

siphonophore, an animal made up of a colony of four separate polyps called zooids, that serve different functions and act like different body parts of a single organism.

• Commonly in the Pacific and Indian oceans, and the northern Atlantic Gulf Stream, although found in warm seas throughout the world

• a translucent structure tinted pink, blue, or violet - which may be 3 to 12 inches long and may extend as much as 6 inches

• Will eat anything it can get• Sting is excruciatingly painful

Purple Jelly

– Up to 5 inches– Cape Cod to

Florida– Purple bell is

dotted red– Sting: painful

Moon Jelly

– Size: 3-20 inches– Atlantic Coast– Color: translucent

white pink or beige– Sting: Mild

Cannonball Jelly

– Size: Up to 1 foot– North Carolina to

Florida– Sting: Mild

Lion’s Mane Jelly

• Up to 8 ft• Maine to Florida• Color: Deep red,

purple or yellow• Sting: Painful

Sea Nettle Jelly

• Size: 1-12 inches• Cape Cod to Florida• Color: Semi-

transparent, reddish stripes

• Sting: Painful

Upside Down Jellyfish

• Appearance provides protection from predators (looks more like a water flower)

• Crabs tend to carry these on their backs for protection

• Depend on zooxanthellae for partial nutrition– Reason why it lives upside down

(the algae live inside the bell and needs sunlight, so the jellyfish floats upside down in the water, and lives in shallow water so it can rest on the bottom upside down)

Class Cubozoa - Box Jellyfish

• Characteristic cube-like shape

• Nineteen species in this group

• Sea wasps are best known and most deadliest creature on land or water– Determined by how many

people an ounce of the venom can kill, and how long it takes you to die from the venom after being bitten, stung, or stuck

Box Jelly Stings• An ounce of sea wasp venom

can kill 60 adult humans and can cause death in less than 3 minutes

• Only one survivor has been recorded (Ian McCormick from New Zealand). He survived 5 stings on his arm

• A single tentacle can have 5000 nematocysts

• Have 4 eyes, but no brain so we don’t know what they see

• Normally found around Australia, New Zealand, Hawaii and Philippines

• Mostly found in shallow water and like the intersection of the ocean and rivers if there are any

• There has been an explosion around Australia, attributed to climate change and reduction of jellyfish predators due to over fishing.

• Number of deaths has risen • Protection: special wetsuits, nylon pantyhose

Class Anthozoa –sea anemones and corals• Characteristics:

– are stinging polyps that spend most of their time attached to rocks on the sea bottom or on coral reefs waiting for fish to pass close enough to get ensnared in their venom-filled tentacles

• Anatomy: – Sea Anemones come in many shapes, sizes, and colors. – Radially symmetric, they have a columnar body with a single body

opening, the mouth, which is surrounded by tentacles. – The tentacles protect the anemone and catch its food; they are

studded with microscopic stinging capsules.

Class Anthozoa –sea anemones• Diet:

– Sea Anemones are carnivores that eat fish, mussels, zooplankton (like copepods, other small crustaceans, and tiny marine larvae), and worms.

– They catch food using the tentacles, which have poisonous stingers (called nematocysts).

Class Anthozoa –sea anemones• Mutualism:

– Clown fish always live near anemones; they are immune from (and protected by) the stinging tentacles. The clown fish help the anemone by cleaning the tentacles (as the fish eat detritus) and perhaps by scaring away predators.

– Some anemones, establish symbiotic relationships with green algae. In exchange for providing the algae safe harbor and exposure to sunlight, the anemone receives oxygen and sugar.

– Sometimes sea anemones hitch a ride on hermit crabs or decorator crabs. The sea anemone can protect the crab and if the crab is a messy eater, the sea anemone can pick up bits of food from the crab and eat it