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