Phylum CnidariaPhylum CnidariaCnidarians Include Cnidarians Include Hydras, jellyfish, sea anemones & coralsHydras, jellyfish, sea anemones & coralsRadially symmetricalRadially symmetricalAcoelomateAcoelomateTwo basic forms:Two basic forms:

–PolypPolyp: Cylindrical form which attach bases to substratum: Cylindrical form which attach bases to substratum–MedusaMedusa: Flattened, mouth down version of the polyp. Moves freely: Flattened, mouth down version of the polyp. Moves freely

Forms of CnidariansForms of Cnidarians

Body PlanBody Plan

Basic Body Plan:Basic Body Plan:

Has an outer epidermisHas an outer epidermis

Has an inner Has an inner gastrodermisgastrodermis which which forms a forms a gastrovasculargastrovascular cavitycavity

Has a middle "jelly filled" Has a middle "jelly filled" layer called layer called mesogleamesoglea

CnidocytesCnidocytesCnidarians are predators which have tentacles possessing batteries of special cells Cnidarians are predators which have tentacles possessing batteries of special cells called called CnidocytesCnidocytes

Cnidocytes contain special stining capsules called Cnidocytes contain special stining capsules called nematocystsnematocysts..

When triggered, these cells shoot out a discharge thread which can entangle When triggered, these cells shoot out a discharge thread which can entangle and/or poison it's intended preyand/or poison it's intended prey

ReproductionReproduction– Reproduction can occur sexually by Reproduction can occur sexually by

fertilization of egg and sperm forming fertilization of egg and sperm forming larvae.larvae.

– Reproduction can also occur asexually Reproduction can also occur asexually through through buddingbudding

3 Major classes3 Major classes– Class Class HydrozoaHydrozoa: Hydras: Hydras– Class Class ScyphozoaScyphozoa: Jellyfish: Jellyfish– Class Class AnthozoaAnthozoa: Anemones and corals: Anemones and corals

Class Hydrozoa: The HydrasClass Hydrozoa: The Hydras

Polyp phase is Polyp phase is dominantdominant

Generally microscopicGenerally microscopic

Generally freshwaterGenerally freshwater

Class Scyphozoa: The JelliesClass Scyphozoa: The Jellies

Generally refered tro Generally refered tro as jelliesas jelliesMedusa stage is Medusa stage is dominantdominantCome in a variety of Come in a variety of formsformsAggressive Aggressive predators, and can predators, and can be dangerous to be dangerous to humanshumans

JellyJelly

PortugesePortugeseMan-o-warMan-o-war

Class Anthozoa: Anemones & CoralsClass Anthozoa: Anemones & Corals

Appear like plants but are Appear like plants but are animals.animals.

Polyp form is dominant.Polyp form is dominant.

Corals build calcium Corals build calcium shells to protect shells to protect themselvesthemselves– Have symbiotic relationship Have symbiotic relationship

with algae.with algae.

Can build extensive Can build extensive masses which can form masses which can form land masses.land masses.

AnemoneAnemone

Coral PolypsCoral Polyps

Coral ReefsCoral Reefs

Clownfish living inClownfish living inAn anemoneAn anemone