Download File - Taran D. Thompson

CNIDARIANS
What makes Cnidarians Unique?
• Cnidarians are group of animals that are
very diverse from stony coral to jellyfish.
What common thread keeps this phyla of
animals together?
Common Thread
• Cniadarians are DIPLOBLASTIC (2 Layers –
epidermis and gastrodermis)
• TRUE TISSUES(muscular, nervous, gastric)
• CNIDAE (stinging tentacles)
Diploblastic Body
• The two tissue layers are the epidermis
and the gastrodermis
• Mesoglea- Jelly like portion between that
separates the two layers.
True Tissues
• True tissues: muscular, nervous, gastric
Cnidae
Cnidocytes used in defense, feeding, and
attachment
Some Cnidocytes can produce Nematocysts
or stinging cells
Nematocysts
Food gathering and defense.
Long tube with spines that penetrates prey
delivering toxin
Nematocysts
Two Body Forms
• Polyp: tentacle up (anenomes, coral,
hydra)
• Medusa: tentacle down (jellyfish)
Polyp Stage
• Sessile, Asexual Reproduction, usually
attached to substrate, some “walk”
Polyp Stage
• Budding
• Fission
Polyp Stage
Polymorphism in
polyps
Medusa Stage
• Dioecious, free swimming, sexual
reproduction
• Develop reproductive organs (testis and
ovaries)
Reproduction
• Sexual and Asexual reproduction
• Alternation of generations
Reproduction (sexual)
• Egg and Sperm released from GVC
• Once combined egg + sperm will form a
planula (free swimming larva)
• Once GVC devolops forms a Polyp
Reproduction (asexual)
• Budding
• Fission
Alteration of Generations
• 2 Stages: Polyp & Medusa (dimorphic)
• Polyp Stage – some species asexual
reproduction by budding, usually sessile
Nutrition
• Gastrovascular Cavity: Functions in
digestion, the exchange of respiratory
gases, metabolic waste, and release of
gametes
Nutrition
• Feeding: Prey mostly small crustaceans
(copepods)
• Nematocysts paralyze prey, contractile
cells move prey to mouth, GVC releases
enzymes
Skeletal System
• Hydrostatic – fluid filled body (mesoglea)
• Epitheliomuscular cells (longitudinal and
circular)
Nervous System
• Nerve Net –
Nervous system is
spread throughout
entire body
• Most primitive
nervous system
• Some sensory
structures – ocelli
sense light
Circulation, excretion, respiration
• No special
structures or
tissues, these life
functions are carried
out directly with the
environment
Hydrozoa
• Alteration of generation
• Mostly Marine (although a few freshwater)
Hydra
Obelia
Physalia
Scyphozoa
•
•
•
•
True Jellyfish
Mostly found in Medusa stage
Some harmful some not to humans
Ocelli (rhodopalia) allow for Phototaxis
(move toward light)
Cubozoa
• Box Jelly Fish
• Some possess
dangerous
nematocysts
• Active swimmers
and feeders
• Tentacles on
corners of
medussa
Anthozoa
• Corals & Anemones
• Lack medusa stage
Anemones
• Can move slowly over some surfaces
• Live as individuals but in colonies
• Feed on fish and crustaceans or organic
debris
Corals
• Secrete a calcium
skeleton
• Stony coral, large
polyped stony corals, and
soft corals
• May use symbiotic algae
called zooxanthelle for
autotrophism.
• Can live individually or in
groups.
Zooxanthelle
• Symbiotic Algae
that provides
food for the
coral
• Found in reefbuilding coral
Soft Coral
• No hard calcium skeleton (although may
contain fragments inside them)
Large Polyped Stony Coral
(Octocoral)
• Have both soft tissue as well as produces
a hard calcium skeleton
Stony Corals
• Little soft tissue mainly hard calcium
skeleton
Reef building
• Corals can grow on one another to create
entire reef systems
Issues Affecting Reefs
• Many Reef Ecosystems are in peril from
being destroyed.
• There are many culprits aiding in
destruction of the reefs.