Kingdom AnimaliaKingdom Animalia

Phylum Cnidaria (Coelenterata) Phylum Cnidaria (Coelenterata)

http://videos.howstuffworks.com/hsw/11758-the-world-of-animals-phylum-cnidaria-video.htm

Two Body Forms Two Body Forms

Cnidarians include: Jellyfish, Sea Cnidarians include: Jellyfish, Sea Anemones, Hydras, and CoralsAnemones, Hydras, and Corals

All have radial symmetry (“little rings”)All have radial symmetry (“little rings”) Two body forms:Two body forms:

– Medusa- Free-floating, jelly-like and often Medusa- Free-floating, jelly-like and often umbrella shapedumbrella shaped

– Polyp- Tubelike and usually attached to a rock Polyp- Tubelike and usually attached to a rock or other surfaceor other surface

Two Body FormsTwo Body Forms

Tentacles surround mouth, located at free end Tentacles surround mouth, located at free end of body of body

Three layers of cells:Three layers of cells:– Outer layer from ectodermOuter layer from ectoderm– Inner layer from endodermInner layer from endoderm– Middle layer of mesoglea (jelly-like)Middle layer of mesoglea (jelly-like)– Cells arranged into tissuesCells arranged into tissues

Coelenteron-Coelenteron- digestive cavity where digestive cavity where enzymes digest foodenzymes digest food

Two Body FormsTwo Body Forms

Body FormsBody Forms

CnidocytesCnidocytes– Stinging cells located on Stinging cells located on

the tentaclesthe tentacles

– Distinguishing Distinguishing characteristic of Cnidarianscharacteristic of Cnidarians

– Small, barbed harpoon Small, barbed harpoon (nematocyst) within each (nematocyst) within each CnidocyteCnidocyte

– Used for defense or to spear Used for defense or to spear preyprey

– Toxins can be deadly or Toxins can be deadly or only stunonly stun

Extracellular digestionExtracellular digestion– Digestion begins Digestion begins

outside the cell in the outside the cell in the gastrovascular cavitygastrovascular cavity

– Enzymes break food Enzymes break food into smaller fragmentsinto smaller fragments

– Cells lining cavity Cells lining cavity engulf fragments and engulf fragments and finish digestion finish digestion intracellularlyintracellularly

http://video.google.com/videoplay?docid=-7505220246577159769&ei=QPWqSLrmO4OcrwLvmayYAQ&q=cnidarians&vt=lf&hl=enLrmO4OcrwLvmayYAQ&q=cnidarians&vt=lf&hl=en

Class HydrozoaClass Hydrozoa

Freshwater hydrozoaFreshwater hydrozoa– Genus Genus Hydra Hydra exist only exist only

as Polyps less than .4” as Polyps less than .4” longlong

– Attach to objects with Attach to objects with sticky secretion from the sticky secretion from the basal diskbasal disk

– Can glide on objects or Can glide on objects or tumbletumble

– Have a nerve net- Have a nerve net- branching system of branching system of nerves with no brainnerves with no brain

Class Hydrozoa Class Hydrozoa

Marine HydrozoaMarine Hydrozoa– Often live in coloniesOften live in colonies– Can be medusas or Can be medusas or

polypspolyps– Ex: Portuguese man-Ex: Portuguese man-

of-warof-war– PhysaliaPhysalia- floats on - floats on

water and dangles water and dangles tentacles with powerful tentacles with powerful neurotoxins (nerve neurotoxins (nerve poisons)poisons)

Reproduction in HydrozoaReproduction in Hydrozoa

Most hydrozoans are colonial and reproduce Most hydrozoans are colonial and reproduce asexually by buddingasexually by budding

Some species are sexualSome species are sexual– Most single sexes, but some hermaphroditesMost single sexes, but some hermaphrodites

Genus ObeliaGenus Obelia– Colonize a single polyp with budsColonize a single polyp with buds

– Reproductive polyps produce medusasReproductive polyps produce medusas

– Medusas reproduce sexually and produce ciliated Medusas reproduce sexually and produce ciliated larvae called planulae, which develop into new polyps larvae called planulae, which develop into new polyps

Obelia ReproductionObelia Reproduction

Class ScyphozoaClass Scyphozoa

True jellyfish and True jellyfish and active predatorsactive predators

Range from thimble Range from thimble size to queen-size size to queen-size mattressesmattresses

Mostly medusas which Mostly medusas which reproduce sexuallyreproduce sexually

Polyp stages early in Polyp stages early in lifelife

Jellyfish relatives:Jellyfish relatives:– Cubozoans- Small box-shaped medusas Cubozoans- Small box-shaped medusas

with tentacles on corner of “box”with tentacles on corner of “box”– Inconspicuous polyp stage Inconspicuous polyp stage – Ex: Box jellysish or Sea wasp can be Ex: Box jellysish or Sea wasp can be

deadlydeadly– Phylum Ctenophora- Comb jellies have Phylum Ctenophora- Comb jellies have

only a medusa stage and no only a medusa stage and no nematocystsnematocysts

» Class Tenaculata- with tentaclesClass Tenaculata- with tentacles» Class Nuda- without tentaclesClass Nuda- without tentacles

– Irukandji Jellyfish (Carukua Irukandji Jellyfish (Carukua barnesi)barnesi)

» 2.5 cm in diameter2.5 cm in diameter» Kills in daysKills in days

Jellyfish RelativesJellyfish Relatives

Class AnthozoaClass Anthozoa

Largest class existing only Largest class existing only as polypsas polyps

Includes anemones, coral, Includes anemones, coral, sea pansies, sea fans, and sea pansies, sea fans, and sea whipssea whips

Nearly all contain Nearly all contain symbiotic algae, symbiotic algae, dinoflagellates, in dinoflagellates, in exchange for foodexchange for food

Many of the brilliant Many of the brilliant colors come from the colors come from the algaealgae

Some reproduce Some reproduce asexually by buddingasexually by budding

Others sexual with Others sexual with sperm and egg being sperm and egg being released into the ocean released into the ocean where fertilization where fertilization occursoccurs

Zygotes develop into Zygotes develop into planulae that settle and planulae that settle and develop into polypsdevelop into polyps

Class AnthozoaClass Anthozoa

Class AnthozoaClass Anthozoa Sea anemones- Small and Sea anemones- Small and

colorful in coastal areascolorful in coastal areas– Highly muscular- can retract Highly muscular- can retract

when touchedwhen touched

– Reproduce asexually by Reproduce asexually by splitting themselves into twosplitting themselves into two

CoralsCorals– Colonies called reefsColonies called reefs

– Secrete calcium carbonate Secrete calcium carbonate skeleton that cements to skeleton that cements to skeletons of neighborsskeletons of neighbors

– Top layer is living polypsTop layer is living polyps

– Bottom layers are old skeletonsBottom layers are old skeletons

http://video.google.com/videoplay?docid=2146135098468558056&ei=QPWqSLrmO4OcrwLvmayYAQ&q=cnidarians&vt=lf&hl=en

Great Barrier ReefGreat Barrier Reef

http://ngm.nationalgeographic.com/ngm/0101/feature2/media.html

http://www.aims.gov.au/docs/online-data/reef-from-space.html