Transcript Phylum Cnidaria

Phylum Cnidaria
•
jellyfish, hydras, sea anemones, coral
Cnidaria
• have cnidocytes (stinging cells) which
contain a nematocyst (harpoon-like
structure) for stinging and paralyzing
prey – located on tentacles
discharged
nematocyst
barbs
coiled
nematocyst
Tentacle
Cuticle
of prey
Thread
Nematocyst
“Trigger”
Thread
discharges
Cnidocyte
Thread
(coiled)
Cnidaria
• Radial Symmetry
•
•
made up of two tissue layers – endoderm and
ectoderm separated by mesoglea
Have two body forms: polyp and medusa
Polyp
Mouth/anus
Tentacle
Medusa
Gastrovascular
cavity
Endoderm
Body
stalk
Mesoglea
Ectoderm
Tentacle
Mouth/anus
– Some cnidarians alternate between the 2
body forms:
• polyp – sessile, usually perform asexual
reproduction
• medusa – free floating, usually perform
sexual reproduction
Feeding
polyp
Reproductive
polyp
Medusa
bud
ASEXUAL
REPRODUCTION
(BUDDING)
Portion of
a colony
of polyps
Haploid (n)
Diploid (2n)
Gonad
Medusa
Egg
SEXUAL
REPRODUCTION
Sperm
FERTILIZATION
Zygote
1 mm
Key
MEIOSIS
Developing
polyp
Mature
polyp
Planula
(larva)
• Class Hydrozoa – hydras, Obelia,
and Portuguese Man-of-War
– usually alternate between polyp
and medusa stages
Portuguese Man-of-War
• Class Scyphozoa – true jellyfish –
have medusa as their primary body
form
Jellies
• Class Anthozoa – exists only as
polyps, sea anemones and coral
Sea anemone (class
Anthozoa)
• Class Cubozoa – “box jellies”, sea wasps,
marine, box-shaped medusae, potent
venom
Sea wasp (class
Cubozoa)
Reproduction
•
•
•
asexual reproduction by budding
sexual reproduction by producing sperm
in testes and eggs (ova) in ovaries
fertilized egg becomes a larva which
develops into an adult
Digestion
•
•
food is taken in and wastes are
expelled through the same opening –
mouth
digestion and circulation occur in the
gastrovascular cavity
Polyp
Mouth/anus
Tentacle
Medusa
Gastrovascular
cavity
Endoderm
Body
stalk
Mesoglea
Ectoderm
Tentacle
Mouth/anus
Cnidaria
•
•
have nerve tissue for coordinated
movement
tissue level of organization