Phylum Cnidaria

Phylum CnidariaExamples:Sea anemonesCoralsSea PenSea FanSea PlumeHydraJelly fishPortuguese Man o’ WarBox Jelly Fish

General CharacteristicsCnidaria: nettle likeSimple animalsMost are sessile but some can move

around (jellyfish)More than 9000 species

HabitatFound in warm tropical regions in

shallow saltwater habitatsSome are found deeper or in open waterSome live in colonies Attach to rocks, shells or other animals

Ecological RelationshipNeurotoxins in medical researchRarely a food source for other animalsBuild coral reefs

Habitat for many other speciesUsed for jewelry

Ecological RelationshipSymbiotic relationships:

Algae frequently live in a mutualistic relationship in the tissues of cnidarians

Mutalism: when both species benefit from a relationship with each otherFish living within tentacles of a Sea anemone & clown fish

Man of War

Form and FunctionPolyp– a hydroid form which is adapted to a

sessile lifeCoral, hydra, anemone

Medusa – a jellyfish form which is adapted for a floatingJellyfish, man of war

Polyps Hydra, Anemones Most have tubular

bodies (radial symmetry)

A mouth surrounded by tentacles leads into a gastrovascular cavity

Basal Disk: Bottom end of the polyp that is attached to a rock/coral

MedusaeMedusae – (jellyfish)Free swimming Bell-shaped bodiesTetramerous

symmetry: can be divided into 4 identical parts

Mouth on the underside

Tentacles

Body Wall Three layers of the body wall:Outer epidermis: contains sensory cells,

nerve cells and sometimes gonadsInner gastrodermis: contains cilia and

muscle cells for movement and food circulation

Mesoglea: in the middle, jelly-like with few or no cells

CnidocytesCnidocytes: Found throughout the epidermis layerMost abundant in tentaclesContains cnida: tiny capsule that contains a

coiled “thread” Used for prey capture and defense from

predatorsMay contain nematocyst: tiny barbs that

deliver the toxinhttp://www.youtube.com/watch?v=-Tp38DUjU

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CnidocytesMost are not harmful to humans, however

Portuguese man-of-war and certain jellyfish are quite painful and sometimes dangerous

LocomotionPolyps can move about by gliding on their

basal disc, aided by mucus secretionsThey can also use the “inch worm” methodMedusae can move freely and swim by

contracting the bell, expelling water from ithttp://www.youtube.com/watch?v=Szt42nG

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ReproductionPolyps1. Budding: a knob of tissue

forms on the side of the polyp and develops a functional mouth and tentacles then detaches

Detached buds are CLONES of the original polyp

Undetached buds form a colony where food is shared

Reproduction2. Fission

one-half of a polyp pulls away from the other half

Creates 2 identical animals

3. Pedal Lacerationtissue is torn from

the basal disc and develops into new, tiny polyps

ReproductionMedusaeSome monoecious (both sexes) and some

dioecious (separate sexes)Sexual reproduction: release sperm & eggsA zygote develops into a free-swimming

larvaFertilization occurs in open water

http://www.youtube.com/watch?v=8zSZtZDwabo

Feeding and DigestionThe mouth opens into the gastrovascular

cavityEnzymes are released to digest foodIntercellular digestion: cells engulf food

and digest ithttp://youtu.be/4ykESFPhBVo

Phylum CnidariaFour classes of Cnidaria:

Hydrozoa – hydroids, fire corals, Portuguese man-of-

war, and othersScyphozoa

“true” jellyfishesCubozoa

cube jellyfishesAnthozoa

sea anemones, stony corals, and others

Class HydrozoaMost live in salt water

and are found in colonies

Asexual and sexual reproduction

Examples: Portugese man of warFreshwater HydraMoon JellyfishFreshwater jellyfish

Portuguese man-of-warhttps://www.youtube.com/watch?v=bPbQs4Zc85k

Portuguese man-of-war attack

Class Scyphozoa: true jellyfishIncludes most of the larger jellyfishBell sizes range from 2 cm to 2 meters in

diameterTentacles can reach 70 meters longRange in color from colorless to bright

orange and pinkSexual reproductionhttps://www.youtube.com/watch?v=aJUuotj

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Giant Jellyfish

Northern Sea Nettle

Class Cubozoa: Box JellyfishBells are almost squareA tentacle or group of tentacles if found at

each corner of the squareStrong swimmers and fierce predators,

feeding mostly on fishSexual reproduction

Irukandji jellyfish

Sea Wasp

Box Jellyfish

Box Jelly Videohttps://www.youtube.com/watch?v=uIf0kRpkQ_0

Sting of a Sea Wasp

The venom has cardiotoxic, neurotoxic and highly dermatonecrotic components

Class Anthozoa: Flower AnimalsNo medusa stageSolitary or colonialSexual and asexual reproductionThere are three subclasses

Sea anemones, hard corals, and othersTube anemones, thorny coralsSea fans, sea pens, sea pansies

Sea anemone

Coral reef

A Closer Look at Coralhttps://www.youtube.com/watch?v=1aX61LzmeYA

Tube anemone

Sea fans

Sea pens

Sea Pansies