PHYLUM: CNIDARIAPHYLUM: CNIDARIA

Classes of CnidariaClasses of Cnidaria

Class Hydrozoa (e.g., Class Hydrozoa (e.g., Hydra, ObeliaHydra, Obelia)) Class Scyphozoa (e.g., Class Scyphozoa (e.g., AureliaAurelia)) Class Cubozoa (e.g., cube jellies)Class Cubozoa (e.g., cube jellies) Class Anthozoa (anemones and Class Anthozoa (anemones and

corals)corals) Subclass Hexacorallia (sea anemones, Subclass Hexacorallia (sea anemones,

hard corals)hard corals) Subclass Octocarallia (sof corals)Subclass Octocarallia (sof corals)

General CharacteristicsGeneral Characteristics

Entirely aquatic; mostly marine, but with a Entirely aquatic; mostly marine, but with a few freshwater species; few freshwater species;

may be solitary or colonialmay be solitary or colonial Metazoan, with true tissues.Metazoan, with true tissues. Diploblastic – two germ layers Diploblastic – two germ layers

outer cell layer known as outer cell layer known as ectodermectoderm ( (epidermisepidermis), ), inner cell layer known as inner cell layer known as endodermendoderm

(=(=gastrodermisgastrodermis), ), with a non-cellular with a non-cellular mesogleamesoglea between. between.

General CharacteristicsGeneral Characteristics

The internal body space The internal body space (gastrovascular cavity) lined with (gastrovascular cavity) lined with gastrodermisgastrodermis

has a mouth, but no anus has a mouth, but no anus (incomplete digestive tract)(incomplete digestive tract)

Possess Possess cnidocytescnidocytes with special cell with special cell organelles - organelles - nematocystsnematocysts, used for , used for defense and offensedefense and offense

General Characteristics General Characteristics cont.cont.

Phylum exhibits polymorphismPhylum exhibits polymorphism MetagenesisMetagenesis- alternation of generation- alternation of generation

Polyp (often sessile) and the medusa (free Polyp (often sessile) and the medusa (free swimming). swimming).

The polyp stage reproduce asexually, The polyp stage reproduce asexually, while the medusa stage usually while the medusa stage usually reproduces sexuallyreproduces sexually

Reproduction is asexual by budding and/or Reproduction is asexual by budding and/or sexual, producing a ciliated planula larvasexual, producing a ciliated planula larva

Figure 13.02Figure 13.02Two generalbody forms

Class HydrozoaClass Hydrozoa

solitary or colonialsolitary or colonial alternation of asexual polyps and alternation of asexual polyps and

sexual medusaesexual medusae

Figure 13.09Figure 13.09

Life Cycle of Hydra

SEXUALREPRODUCTION

ASEXUALREPRODUCTION

HydraHydra with Bud with Bud

Ovary Bud

HydraHydra with Gonads with Gonads

Testes

HydraHydra c.s. c.s.

Epidermis

Mesoglea

Gastrodermis

Gastrovascularcavity

Figure 13.09Figure 13.09

Obelia Life Cycle

ObeliaObelia - Medusa - MedusaGonad

Gastrovascular cavity

Tentacle

Obelia – Hydroid colonyObelia – Hydroid colony

Gastrozoids = Hydranth

Gonozoids = Gonangium

ObeliaObelia – Hydroid Colony – Hydroid Colony

Gonozooid

Hydrozooid

GonionemusGonionemus

Gonad

Physalia Physalia –– Portuguese Man-O-War - a colony, not an Portuguese Man-O-War - a colony, not an

individualindividual

It is not a jellyfish!!

Class ScyphozoaClass ScyphozoaTrue JellyfishesTrue Jellyfishes

polyp stage reduced or absentpolyp stage reduced or absent bell-shaped medusae bell-shaped medusae margin of bell with eight notches margin of bell with eight notches

which are provided with sense which are provided with sense organsorgans

all marineall marine

AureliaAurelia - Medusa - Medusa

Aurelia - Aurelia - Planula larvaPlanula larva

Aurelia - Aurelia - ScyphistomaScyphistoma

AureliaAurelia - Strobila - Strobila

Aurelia - Aurelia - EphyraEphyra

Class – AnthozoaClass – AnthozoaSea Anemones and CoralsSea Anemones and Corals

all species occur as polyps only, no all species occur as polyps only, no medusae; medusae;

gastrovascular cavity partitioned by gastrovascular cavity partitioned by at least eight septa with nematocysts at least eight septa with nematocysts

Solitary or colonialSolitary or colonial all marine.all marine.

Some HydrozoansSome Hydrozoans

Figure 13.07Figure 13.07

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Figure 13.15aFigure 13.15a

Figure 13.15bFigure 13.15b

Some ScyphozoansSome Scyphozoans

Jellyfishes

Figure 13.16Figure 13.16

Figure 13.17Figure 13.17

Some AnthozoansSome Anthozoans

Sea Anemones

Figure 13.25Figure 13.25

Figure 13.29Figure 13.29

Corals

Figure 13.32Figure 13.32

Figure 13.33aFigure 13.33a

Figure 13.33bFigure 13.33b

Figure 13.28Figure 13.28

0039.jpg0039.jpg

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0047.jpg0047.jpg

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Figure 13.26bFigure 13.26b

Figure 13.26cFigure 13.26c

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Phylum CtenophoraPhylum Ctenophora

The CombjelliesThe Combjellies

General CharacteristicsGeneral Characteristics

Biradial symmetry Eight rows of comb plates Tentacles possess colloblasts Triploblastic (three cell or germ layers) Mesoglea (loose mesenchyme) is jelly-like material

strews with fibers and amebocytes and contains true muscle cells

Aboral sense organ (statocyst) Digestive system: mouth, pharynx, stomach,

branched canals and anal pore Monoecious, with both eggs and sperm produced

from endodermal lining of digestive canals beneath comb plates

Figure 13.36Figure 13.36

Figure 13.36aFigure 13.36a

Figure 13.38Figure 13.38

Figure 13.38aFigure 13.38a

Figure 13.38bFigure 13.38b

Figure 13.35Figure 13.35

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