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
Cnidarian circulation
Simple Nervous net
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
Class Scyphozoa
• Example– Aurelia (Moon Jelly)
Planula of Aurelia
Aurelia Scyphistoma - & strobilus
Aurelia sp. ephrya
Class Anthozoano medusa stage
• Examples– Sea Anemones:
Metridium sp.– Corals (hard and
soft)
Metridium External Anatomy
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)