Phylum Cnidaria & Ctenophora
Kingdom: Animalia
Phylum Cnidaria
Class Hydrozoa
Class Scyphozoa
Class Anthozoa
Phylum Ctenophora
Major Characteristics
Presence of specialized tissues Also called Coelenterates Comprised of sea anemones, jellyfish, corals Have radial symmetry Two forms polyps and medusa
Body Structure
All have radial symmetry, where similar parts of the body are arranged and repeated around a central axis
Radial vs. Bilateral Symmetry
Diagram A
Radial Symmetry
Two Main Body Forms - Polyp
A polyp is a sac like stage.
Sessile or non-motile
Two Main Body Forms - Medusa
A medusa is bell-like, which is similar to an upside down swimming polyp
Free floating or swimming
Polyp vs. Medusa
Some spend their life as both at some point or as one or the other the entire time
Diagram B
Polyp vs. Medusa
Diagram D
Three Basic Layers:
Three Basic Layers
Ectoderm/Epidermis – outer layer that contains the stinging cells
Endoderm/Gastrodermis – lines the gut Mesoglea – Jelly like substance in
between the Ectoderm and Endoderm which contains scattered cells and collagen fibers
Exoskeleton
Coral will create a calcium carbonate shell in which it will live
Body Structure
The mouth is located on the top of the polyp or underside of the medusa
It is the only opening on the organism so is also shares the function of being an anus
Diagram E
Body Structure
Diagram F
Tentacles
Slender finger like structure used to capture and handle food
Location of nematocysts
Nematocysts
The main characteristic of Cnidaria is the presence of nematocysts
Stinging structures found on the tentacles
Nematocysts
Coiled – like stinger Spring into the prey and
releases toxin Most not harmful to humans
because they cannot penetrate skin
Some fatal
Nervous System
Main characteristic is the presence of a nerve net
Nerves cross over each other, at every connection, communication occurs
In humans millions cross over millions and no communication occurs
Nerve Net
Diagram C
Digestive System
All cnidarians are carnivorous Paralyzed by the nematocysts Enzymes in gastric cavity break down
the food and nutrients are absorbed by cells in the endoderm
Wastes are sent out the mouth/anus
Digestive System
Reproductive
Cnidarians have the ability to reproduce sexually and asexually
One method that is commonly seen is budding
Class Anthozoa
Largest group of Cnidarians
Stay in the polyp stage throughout life cycle
Solitary or colonial Includes sea
anemones
Class Hydrozoa
Can consist of just a polyp stage, just a medusa stage, or both
Can join together to form complex colonies such as the Portuguese Man-O-War, which develop floats
FLOAT
Class Scyphozoans
Medusa is the dominant life stage Swim with rhythmic contractions of the bell,
though limited Contain the most dangerous/fatal stings
BELL
Phylum Ctenophora
Comb Jellies Not a member of the
Cnidarian Phylum even though they share similarities
Cnidaria vs. Ctenophora
Ctenophora Have cilia at the
base of the medusa to move
Engulf food Do not have
nematocysts Have an additional
layer between endo and ecto layers
Anal pore