The Characteristics of Phylum Cnidaria

Phylum CnidariaPhylum Cnidaria

Class Anthozoa

Class Hydrozoa

Class Scyphozoa

Class Cubozoa

CoralsAnemones

HydraPortuguese Man-Of-War

Stinging LimuFire Coral

True jellyfish Box jelliesSea wasps

Characteristics of Phylum Cnidaria

• radial symmetry• blind sac gut (= coelenteron or gastrovascular cavity)• diploblastic with mesoglea• polyp and medusa body forms• nematocysts (= specialized stinging capsules)• nerve net• lack excretory, circulatory & respiratory systems• complex life cycle• many colonial forms exhibiting polymorphism

Radial Radial SymmetrySymmetry

aboral

oral

Polyp

Radial SymmetryRadial SymmetryJellyfishJellyfish

Phylum CnidariaPhylum Cnidaria

Medusa

Blind Sac GutBlind Sac Gut

Diploblastic- two germ layersDiploblastic- two germ layersPhylum CnidariaPhylum Cnidaria

NematocystsNematocysts

Nematocyst PictureNematocyst Picture

Nematocyst

More NematocystsMore Nematocysts

http://www.youtube.com/watch?NR=1&v=-Tp38DUjUnM&feature=endscreen

Nerve NetNerve Net

Diffusion Across the Body WallDiffusion Across the Body Wall

Sea AnemonesSea Anemones

Circulation in a Circulation in a Moon JellyfishMoon Jellyfish

The Cnidarian Life CycleThe Cnidarian Life Cycle

The Cnidarian Life Cycle

ColonialityColonialityCoral

Phylum Cnidaria

• polyps and medusa stage, although polyp stage is dominant.

• gut cavity of polyp is simple, lacking a pharynx and not divided by mesenteries.

• tetramerous (four-part) radial symmetry.

• gonads are ectodermal (found in the epidermis).

• medusa stage may possess specialized balance organs called statocysts and photosensitive organs called ocelli.

• solitary or colonials; some colonial forms highly polymorphic.

• includes hydroids (“stinging limu”), fire coral, pink coral, and siphonophores.

Class Hydrozoa(Gr. hydra, water serpent)

The Cnidarian Life CycleThe Cnidarian Life Cycle

The Hydrozoan Life Cycle

Hydrozoan Colony

Hydrozoan Colonies“Stinging Limu”

Hydrozoan Medusa

Hydrozoan Medusa

Hydrocorals

Fire CoralFire Coral

By-the-Wind-SailorA Floating Colony of Polyps

Coloniality and Polymorphism

Poly,orphism in the Poly,orphism in the Portuguese Man- of-WarPortuguese Man- of-War

• medusae stage dominate.

• polyp stage (scyphistoma) goes through strobilization to produce young medusa.

• bell margin lacks a velum.

• tetramerous (= four-part) radial symmetry.

• gut divided into a complex system of radial canals.

• some with a simple single mouth, but many with thousands of microscopic “mouths” at the ends of oral arms.

• gonads endodermal (found in the gastrodermis).

• specialized sense organs called rhopalia with ocelli & statocysts .

• includes some 200 marine species.

• "true" sea jellies.

Class Scyphozoa(Gr. skyphos, cup)

Moon Jelly Moon Jelly AnatomyAnatomy

Scyphozoan Life Cycle

strobilascyphistoma

Sea Jellies

• medusae dominate stage.

• polyp stage develops directly into medusa.

• bell margin with a velarium.

• tetramerous (= four-part) radial symmetry; bell cube-shaped with tentacles arising from each corner.

• gonads endodermal (found in the gastrodermis).

• specialized sense organs called rhopalia with ocelli & statocysts .

• includes some 15 marine species.

• includes box jellies and sea wasps.

Class Cubozoa(Gr. kybos, a cube)

Box Jellies

Seawasp

Box Jelly Anatomy

• Polyp stage only

• Blind sac gut

• mesenteries radiate inwards from the body wall

• gonads endodermal, borne on the mesenteries

• hexamerous (6-part) or octamerous (8-part) radial symmetry or biradial

• sea anemones, “true” stony corals, sea fans, sea pens, organ pipe coral, precious black coral, & zoanthids

(Gr. anthos, flower)Class Anthozoa

Subclass ZoanthariaOrder ActinariaSea Anemones

Sea Anemone Anatomy

Subclass HexacoralliaOrder Zoanthidae

• No hard skeleton• May be tough and leathery• Shallow water forms• Encrusting forms• Some with zooxanthellae• Polyp stage only

Subclass HexacoralliaOrder Antipatheria

Black Coral & Wire Coral

Wire coral

Black coral

Subclass HexacoralliaOrder Scleractinia

“True” Stony CoralsHermatypic- reef building, zooxanthellaeCommon species:

• Acroporidae- table• Acroporidea- rice • Agariciidae- flat lobe, corrugated• Faviidae- crust, ocellated• Fungiidae- humpback, mushroom• Pocilloporidae- lace, antler, cauliflower• Poritidae- finger, lobe, plate

“True” Stony Coralslobe

finger

mushroom

Porites rus

Octocorals

Sea pen

Organ pipe coral