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Radiate Animals

Phylum Ctenophora

>9,000 species

specialized cells (cnidocytes)

specialized stinging organelle, the nematocyst

fossils >700 mya

<100 species

Phylum Cnidaria

comb jellies/sea walnuts

Unicellular (acellular)

protozoan protists

Multicellular (metazoa)

Poorly defined

tissue layersDiploblastic Triploblastic

PoriferaPlacozoa

CnidariaCtenophora

Priapulida

Chaetognatha

Gastrotricha

Entoprocta

Loricifera

PlatyhelminthesRhynchocoela (Nemertea)

Mesozoa

Gnathostomulida

Rotifera

NematodaKinorhyncha

Acanthocephala

Nematomorpha

Annelida

Mollusca

ArthropodaOnychophora

Pentastomida

Pogonophora

Sipuncula

Echiura

EchinodermataHemichordata

Chordata

Brachiopoda

Phoronida

Bryozoa

Uncertain Acoelomate Coelomate Pseudocoelomate

Protostomes Uncertain (misfits) Deuterostomes

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8) tentacles: extensible projections for food capture with abundant nematocysts

Cnidarian Characteristics1) diploblastic: two well-defined germ layers: ectoderm & endoderm

mesoderm may be derived from ectoderm (ectomesoderm)

2) internal body cavity: the gastrovascular cavity

3) extracellular digestion occurs in the gastrovascular cavity;

gastrodermal cells enzymes for cellular digestion

4) nerve cells; nerve net but no central nervous system

5) sense organs: statocysts & ocelli

6) locomotion by muscular contraction : outer longitudinal & inner circular

7) unique feature: nematocysts (epidermis/gastrodermis)

18) no coelomic cavity

9) all aquatic/mostly marine

shallow marine environments

some fresh water

none terrestrial10) some symbiotically e.g. with algae in reef-building corals

11) radial symmetry: oral & aboral ends

12) dimorphism: free-swimming medusae & sessile polyps: ecological niches

13) some: exoskeleton or endoskeleton: chitinous, calcareous or protein

14) gastrovascular cavity: a single opening serving as both mouth & anus

15) reproduction: either asexual or sexual

16) planula larva may be present

17) no excretory or respiratory system

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Five Classes

I. Hydrozoa

Hydra: freshwater species

no medusa stage

Ectopleura

Corymorpha

budding

Hydroids

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Polymorphism

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Craspedacusta

freshwater hydrozoan

Portuguese Man of War Physalia physalis

colony of polyps & medusae gas float

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II. Scyphozoa (true jellyfish)

scyphozoan medusano velum

thicker mesoglea aids in buoyancy

III. Staurozoa stalked jellyfish (only polyp) no medusa

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IV. Cubozoa

V. Anthozoa

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Hard Corals

cup coral Tubastrea sp.

Hard Stony Corals

closed during day

Montastrea cavernosa polyps

open during night

zoantharian

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soft octocorals

8 pinnate tentacles

endoskeleton

spicules with horny protein

spicule

provides flexibility

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Limiting factors

sunlight photosynthesis

water clarity

Corals restricted habitats

shallow depths

warm temperatures

Dying Coral Reefs

human impact

pollution

development

global warming

Horny (gorgonian) Corals

red gorgonian Melithaea sp. sea fan Subergorgia mollis red whip Ellisella sp.

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Soft coral Dendronephthya sp.