Transcript Phylum Cnidaria

The Flowers of the Sea
A. Entirely aquatic; mostly marine.
B. Radial symmetry with no definite head
C. Two stages in life cycle; Polyps and Medusae
D.
Body containing two layers: Epidermis and Gastrodermisthus we say they are diploblastic.
E. Central Gastrovascular Cavity with a single opening that serves
as a mouth and an anus.
F. Presence of nematocysts within tentacles to capture prey.
G. Nerve net which carries information both ways
H. Asexual Reproduction by budding; Sexual by sperm and egg,
can be monoecious or dioecious.
I. No true coelomic cavity, excretory, or respiratory system.
A. Cnidarians have two distinct body forms – a free swimming
medusa stage, which usually has hanging tentacles
B. Cnidarians also have a sessile polyp stage, which usually has
tentacles reaching upward; there are exceptions to both.
Figure A. (Medusa)
Figure B. (Polyp)
Stinging cells on
tentacles called
Cnidocytes have
special stingers called
nematocysts with
barbed filaments used
to capture and
paralyze prey.
The Nerve Net is
made of sensory
cells.
The
Epitheliomuscular
tissue is made up
of myofibrils and
epitheliomuscular
cells.
Budding most
common form
of asexual
reproduction.
Bud
forming
Cnidarians also
have sperm
and egg – as
hermaphrodites
They have both
ovaries and
testes.
Testes
develop
here
when not
budding,.
Ovary
(Examples: Hydra; Obelia; Portuguese Man-O-War)
1. Hydra – Only
freshwater hydrazoan
– also only one with
NO medusa stage and
is a singular organism
rather than colonial.
b. Hydra has a mouth located above the
hypostome, a raised portion inside the
ring of tentacles.
c. Hydra’s mouth opens into the
gastrovascular cavity.
d. Water filled gastrovascular cavity
forms a Hydrostatic skeleton for structure
and support.
2.Obelia
a. Obelia is a colonial, marine Hydrazoan
b. Specialized feeding zooids (or polyps) are
known as Hydranths, found in the asexual
colony.
c. Specialized asexual polypoid structures
called Gonangia produce Gonopores,
which develop into Medusae.
d. The sexual free-swimming stage in
the life cycle is called the medusa.
a.Pneumatophore
The gas filled sail or
float of a Man-o-War
b. Gastrozooids
The feeding, or
digestive polyps
of a Man-o-War
c. Dactylozooids
The capturing,
or stinging
polyps of a
Man-o-War
These are the creatures most of us think of
as the REAL jellyfish.
Jellyfish (Scyphozoans) have the most
distinctive and obvious medusa in all
of the Phylum Cnidaria.
Jellyfish have two very important
sensory structures:
Rhopalia – which act like sensory
receptors for touch
Ocelli – which are light sensitive
organs that help them determine light
intensity.
Life
Cycle
of
Aurelia
There is no doubt that
the Anthozoans are the
true beauties of the
Phylum Cnidaria!
Sea Anemones exist only in polyp form. They
DO NOT have a medusa stage. The same is true
with corals.
Sea
Anemone
Polyp
Sea anemones
have an
oral disc that
contains the
mouth – which
leads into the
pharynx.
Cross section of the oral disc of a sea anemone
On either side of
the mouth and
pharynx is a
grooved structure
called the
siphonoglyph. Its
function is to pull
water into the
gastrovascular
cavity.
Many sea anemones live in a mutually
symbiotic relationship with clown fish, or
anemone shrimp.
Corals are very similar to miniature sea anemones,
except that they secrete their own “skeletal”
structures and have no siphonoglyphs.
Corals take on many shapes, “skeletal” structures, and
classifications. There are hard ones, soft ones, and
even corals that look like fans.
Certain Corals
called Hermatypic
Corals have a
mutually symbiotic
relationship with a
special algae called
Zooxanthellae, that
live inside them.
Fringing Reef
Shallow reefs
that are close to
shore
Barrier Reef
Atoll
How reefs
are
formed
Separated from the
mainland by a lagoon
Generally large and
conspicuous
Volcanic mountain
That has completely sunk,
Leaving a lagoon inside
A circular reef
That’s all Folks!
Test next class day!