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
nM
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
-hGg
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
E3u8
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