Cnidarians

• Hydrozoa – Hydras

• Scyphozoa – Sea Jellies , “ Jelly fish”

• Anthozoa- Sea Anemones

Cnidarians• Cnida- “nettle”

• Diploboastic – – Gastrodermis & Epidermis

• Radial Symmetry

• Cnidocytes- Nematocysts

• Polyp – Medusa

• Incomplete digestive tract

• Simple Nervous net, contractile cells

Polyp Medusa

Aboral

AboralOral

Oral

Cnidarian Body Forms

Cnidarian Cnidocytes

Cnidocyte trigger

Symmetry

Hydra nutrition

Cnidarian circulation

Simple Nervous net

Hydra sp.

Epidermis

Cross section

Nematocysts

Female Male

Obelia

Gonangium

Hydranth

Gonotheca

Ceonosarc

Medusa Buds

Perisarc

Ceonosarc

Hydrotheca

Hypostome

Perisarc

Obelia sp. life cycle

Obelia sp. medusae

Protective pantyhose worn by north Queensland life savers

Near fatal sting by C. fleckeri on a 13 year old boy at Cairns, Australia

Cnidarian Body Forms

Cnidarian Cnidocyts

Hydra w.m.

Hydra

Class Scyphozoa

• Example– Aurelia (Moon Jelly)

Planula of Aurelia

Aurelia Scyphistoma - & strobilus

Aurelia sp. ephrya

Ephyra anatomy

Aurelia sp.

6

15

4

3

2

1

2

3

4

5

6

78

Medusa anatomy

Aurelia Anatomy

Class Anthozoano medusa stage

• Examples– Sea Anemones:

Metridium sp.– Corals (hard and

soft)

Sea Anemones

Metridium External Anatomy

Metridium c.s.

Metridium c.s.

Enlargement of Pharynx

• 1. Siphonoglyph• 2. Retractor muscle• 3. Primary septum• 4. Pharynx• 5. Gastrovascular

Cavity

1

2

9

4

3

6

5

10

7

11

8

Close-Up of Septa

• 1. Primary septum• 2. Secondary septum• 3. Tertiary septum• 4. Retractor muscle• 5. Septal filament• 6. Gastrovascular

cavity

Close-Up of Body Wall

• 1. Epidermis• 2. Mesoglea• 3. Gastrodermis• 4. Septal filament• 5. Primary septum• 6. Secondary septum

Phylum Ctenophora

• Comb jellies possess rows of ciliary plates and adhesive colloblasts

• Comb jellies use retractable tentacles to capture food.

PHYLUM CTENOPHORA

• Characteristics– Comb plates– Colloblasts (glue cells)

Pleurobrachia

Ctenophorans