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Porifera, Cnidarians and
• Are multicellular
• Cells do not form permanent tissue
– Metazoan organization
• Sessile – non-motile
• Radial
• Suspension feeders, use choanocytes to drive
water through canals and chambers
• Precambrian
• Classified according to chemical composition of
spicules, (internal skeleton)
4 different Classes
Calcarea – made of calcite or silica (bony)
Hexactinellida – Glass sponge, found in
deep water
Demospongiae – 90%of all sponges
Sclerospongiae – Skeleton made of calcium
Anatomy of a typical sponge
Asconoid Sponges
Syconoid Sponges
Leuconoid Sponges
Class Calcarea
• Skeleton composed of calcium carbonate
• Simple shapes: vase, pear, or cylinder
• Marine sponges only
Class Hexactinellida
• Spicules have 6 rays
• Marine sponges only
• Found in deep, cold water
Class Demospongiae
• 90% of all sponges are this type
• Marine and freshwater
Key Features
• Spicules have 4 basic symmetries
– Monaxon, triaxon, tetraxon and polyaxon
• Multicellular, body is a loose aggregate
– Of cells
• Body has pores, canals and chambers that
serve for passage of water
• All aquatic, mostly marine
• Radial symmetry or none.
• Epidermis of flat pinocytes, inner surface
of choanocytes that create water current
• No organs or tissue, digestion intracellular,
• Excretion and respiration by diffusion
• No nervous system
• All adults are sessile
• Asexual reproduction by buds and
• Sexual reproduction by eggs and sperm
• Free-swimming larvae
Important Environmental
As filter feeders, if there are
toxins/pollutants in the water, sponges
are usually the first to suffer,
becoming sickly and disappearing…..
A great indicator that something is
wrong with the marine environment.
4 classes of Cnidarians
• Hydrozoa
• Scyphozoa
• Anthozoa
• Cubozoa
Phylum Cnidarian (Coelenterata)
knide- needle; arian- having
-get their name from cells called cnidocytes which
contain the stinging organelles called nematocysts
-consist of plant-like hydroids, sea anemones,
jellyfish, sea whips, sea fans, hard corals that make
up reefs
Cnidarians have:
•Radial symmetry
•Diploblastic (double-layer of tissue)
•Simple , sac-like body
•Gastrovascular cavity
Two-stage life cycle of Cnidarians
Tentacles around the
mouth capture prey
animals and push
them through the
•Digestion begins in
the gastrovascular
cavity with the
undigested remains
being expelled
through the mouth.
•Tentacles are armed
with stinging cells,
called cnidocytes
Class Hydrozoa
It is a colony of individual medusae and polyps.
One contributes a large floating gas sac above the
water line
Certain polyps have roles:
1. Some are concerned with feeding
2. Some move the colony through the water
3. Some have tentacles to catch fish
4. Some are responsible for reproduction
Polyp stage
Class Hydrozoa
Portuguese Man-of-War
Two-stage life cycle of Cnidarians
Adult Medusa
(sexual phase)
Exists as males or
(asexual phase)
Produces multiple
Class Scyphozoa
• Class Scyphozoa consists of solitary marine
medusae called jellyfish because of the jellylike material of their cell wall
• The surface of the tentacles are made up of
many epitheliomuscular cells.
• Between these cells are specialized stinging
cells called cnidocytes grouped together in
• Each battery has a nematocyst and when prey
brush against the long triggers, venomous
threads impales through the flesh
The common jellyfish or Aurelia
• True jellyfish
• These often reach a diameter of 30 centimeters
• The arctic jellyfish can grow to a diamter of 2
• The mouth is surrounded by oral arms that
function in transferring small organisms to the
• The mouth is surrounded by oral arms that
function in transferring small organisms to the
• The stomach has four gastric pouches opening
into many radial canals of the umbrella
• The radial canals lead into the ring canal
• The canals assure equal distribution of nutrients
Class Scyphozoa
Class Anthozoa
• Are marine polyps
• Some are individuals like sea anemones and
some are colonial like coral
• Corals support themselves by secreting calciumlike skeletons
• Each polyp generation
• builds on the previous
• remains of earlier corals
Fringing coral surrounding
a volcanic island
Fringing coral surrounding
a subsiding volcanic island
An AtollFringing coral surrounding a submerged
volcanic island
Corals- generally found between
30º North and 30º South
Need shallow clear water for photosynthesis
and warm water for calcium production.
Class Cubozoa
box jellies and sea whips
• Most lethal
• Survival rate for
humans is in minutes
Comb jellies or sea walnuts
• Tentaculata – two tentacles
• Nuda – no tentacles
• Ctenophora (tĬnŏf´ərə), a small phylum of exclusively
marine, invertebrate animals, commonly known as sea
walnuts or comb jellies
• Ctenophores are characterized by eight rows consisting
of ciliated plates called ctenes (combs).
• Most ctenophores resemble biradially symmetrical
jellyfish (phylum Cnidaria) but lack the cnidarian whorl of
tentacles around the mouth.
• They lack the specialized stinging cells (nematocysts)
found in coelenterates
• In order to capture prey, ctenophores possess sticky
cells called colloblasts. In a few species, special cilia in
the mouth are used for biting gelatinous prey.
• Have a complete digestive system.
Cnidarian vs. Ctenophora
Very diverse
Fresh & salt water
Radial symmetry
Have cnidocytes
No biolumination
Incomplete digest sys
No comb plate
few species
all marine
bi radial symmetry
have colloblasts
have biolumination
complete digest sys
have a comb plate