Systematic Adaptations of Phylum CnideriaThe Jellies, Anemone and Corals

Objectives (Chapter 13)1. Identify characteristics distinguishing

phylum Cnideria2. Discuss adaptations characteristic of the

phylum Cnideria with regard to ◦ Body form, morphology & embryonic development◦ Feeding and digestion◦ Excretion◦ Movement/locomotion◦ Reproduction◦ Sensory/Motor response

3. Define “dimorphism”. Distinguish between the polyp and medusa form of Cniderians

Objectives (Chapter 13)4. Describe structure and function

of cnidocytes 5. Distinguish between the

taxonomic Classes in the Phylum Cnideria. Give examples

6. Discuss the ecological significance and development of coral reefs

7. Compare & Contrast Ctenophores with Cniderians

1. Identify characteristics distinguishing phylum Cnideria

Radial symmetryTissue level of organizationIncomplete gastrulation (one

opening to the digestive cavity)Diploblastic

◦Endoderm and Ectoderm only – No mesoderm

Tentacles with stinging “cnidocytes”

2. Discuss adaptations characteristic of the phylum Cnideria

Body form, morphology & embryonic development

Feeding and digestionExcretionMovement/locomotionReproductionSensory/Motor response

Body Form & Development

Body Form and Development

Epidermis◦ Derived from

embryonic ectoderm

Gastrodermis◦ Derived from

embryonic endoderm

Mesoglea◦ Middle jelly

Tentacle◦ With cnidocytes

DimorphismMedusaeBell ShapedMotileUsually sexually

reproducingJellyfish

PolypsTube shapedSessileUsually asexually

reproducingAnemone and

Corals

https://www.youtube.com/watch?v=Szt42nG-hGg

Integumentary & MuscularEpidermis is a single cell layerMuscle fibers associated with the

base of the epitheliumTrue muscle is mesodermal in

origin. Cnideria are diploblastic (no mesodermal tissue)

Movements are simple and non-specific

Nervous & SensoryNo central nervous systemNerve cells in a diffuse “nerve

net” ennervate the epitheliomuscular cells

https://www.youtube.com/watch?v=7fScolnOCtI

DigestiveOne opening to the digestive

cavityDigestive enzymes secreted by

the gastrodermis (“extracellular” digestion)

https://www.youtube.com/watch?v=bcmLxsJ5SAg

ReproductionCnideria have a variety of life cycles, from

simple to complex.Generally, the polyp form is used for

asexual reproduction. ◦ https://www.youtube.com/watch?v=hXaswpUjK-M◦ https://www.youtube.com/watch?v=bcQs3dkrH0A

Sexual reproduction occurs in the medusae◦ https://www.youtube.com/watch?v=8zSZtZDwabo◦ https://www.youtube.com/watch?v=Id53jmsdxfQ

Both monoecious and dioecious forms exist,

Characteristic Cniderian Life Cycle

Cnidocytes

• https://www.youtube.com/watch?v=6zJiBc_N1Zk

• https://www.youtube.com/watch?v=-Tp38DUjUnM

Cniderian ClassesHydrozoa Scyphozo

aCubozoa Anthozoa

Asexual polyps, sexual

medusae

Polyp stage reduced or

absent

Polyp stage reduced

All polyps, medusae absent

“velum” at the rim of the bell

in the medusae to

aid propulsion

Medusae lack a velum. Bell margin with

sense organs

Cube shaped medusae. No

velum, but “vellarium” with similar

function

Cnidocytes in the

gastrovascular cavity

See the life cycle diagram on page 261 in the textbook

Enlarged mesoglea (the “jelly” in the

jellyfish”)

Blade shaped “pedalium” at the base of the

tentacles

Septa (mesenteries)

separating gastrovascular

cavity

Freshwater and marine

All marine All marine All marine

Hydra, Portugese Man

of War

What we think of when we

think of jellyfish

Very poisonous.

Stings may be fatal to humans

Corals and Anemone

Hydrozoa

• https://www.youtube.com/watch?v=yqXkaZwiu6s

• https://www.youtube.com/watch?v=9MEt0Ot7Pkc

• https://www.youtube.com/watch?v=zPdkxdu9rfs

• https://www.youtube.com/watch?v=RBdCpcapB0s

Scyphozoahttps://www.youtube.com/watch?v=1oIBwWY04ZI&list=PLdHUIRuQuOel4SQpONiusXIA4taUC0Wgk&index=4

Anthozoa • https://www.youtube.com/watch?v=a2m59UoTEgs

• https://www.youtube.com/watch?v=z0Q7LgAgW1k

Cubozoa

https://www.youtube.com/watch?v=CCuNMIT67y8

Coral Reefs

• https://www.youtube.com/watch?v=eIul2ObvKV8• https://www.youtube.com/watch?v=wbNeIn3vVKM

Ctenophores (Comb Jellies)

Superficially similar to Cniderian medusae, but:◦ “Comb plates” for

locomotion◦ No nematocysts◦ True muscle

(derived from mesoderm?)

◦ Complete digestive tract

• https://www.youtube.com/watch?v=Wc11fhK4o90

• https://www.youtube.com/watch?v=icKB9EfURhQ

• https://www.youtube.com/watch?v=Qy90d0XvJlE

Video LinksGreat Barrier Reef Documentary

(long!)◦ https://

www.youtube.com/watch?v=EueBzS3kPe8

Cniderian Diversity◦ https://

www.youtube.com/watch?v=6VAp7DHut_E

Cniderian Movement◦ https://www.youtube.com/watch?v=sJn8vB

5hBOQ