2. Classes of Cnidaria
Class Hydrozoa (e.g., Hydra, Obelia)
Class Scyphozoa (e.g., Aurelia)
Class Cubozoa (e.g., cube jellies)
Class Anthozoa (anemones and corals)
Subclass Hexacorallia (sea anemones, hard
corals)
Subclass Octocarallia (sof corals)
3. General Characteristics
Entirely aquatic; mostly marine, but with a
few freshwater species;
may be solitary or colonial
Metazoan, with true tissues.
Diploblastic – two germ layers
outer cell layer known as ectoderm
(epidermis),
inner cell layer known as endoderm
(=gastrodermis),
with a non-cellular mesoglea between.
4. General Characteristics
The internal body space (gastrovascular
cavity) lined with gastrodermis
has a mouth, but no anus (incomplete
digestive tract)
Possess cnidocytes with special cell
organelles - nematocysts, used for
defense, offense and anchorage.
5. General Characteristics cont.
Phylum exhibits polymorphism
Metagenesis- alternation of generation
Polyp (often sessile) and the medusa (free
swimming).
The polyp stage reproduce asexually,
while the medusa stage usually
reproduces sexually
Reproduction is asexual by budding and/or
sexual, producing a ciliated planula larva
21. Class Scyphozoa
True Jellyfishes
polyp stage reduced or absent
bell-shaped medusae
margin of bell with eight notches which
are provided with sense organs
all marine
28. Class – Anthozoa
Sea Anemones and Corals
all species occur as polyps only, no
medusae;
gastrovascular cavity partitioned by at
least eight septa with nematocysts
Solitary or colonial
all marine.
61. General Characteristics
Biradial symmetry
Eight rows of comb plates
Tentacles possess colloblasts
Triploblastic (three cell or germ layers)
Mesoglea (loose mesenchyme) is jelly-like material
strews with fibers and amebocytes and contains true
muscle cells
Aboral sense organ (statocyst)
Digestive system: mouth, pharynx, stomach, branched
canals and anal pore
Monoecious, with both eggs and sperm produced from
endodermal lining of digestive canals beneath comb
plates
