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Invertebrates:
Sponges and Cnidarians
Sponges:
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Phylum Porifera
means- pore bearer
Simplest of all animals
Assymetrical animals that live in
shallow waters
Sessile filter-feeders whose bodies
have many pores
Acoelomates-no body cavity
Obtain oxygen by filtering water
Uses: cleaning, bathing, cosmetics
No nervous system or organ systems
Sponge Reproduction
• Reproduce Asexually by
budding:
• Buds form from sides of parent
sponge, bud break off and grow
into new individual identical to
the parent
• can grow back missing parts
(regeneration)
• Reproduce sexually:
• Hermaphrodites: produce both
eggs and sperm
• Gametes are released into
water
Sponge Reproduction
• Many are asexual: branches or buds break off and
grow into separate sponges identical to the
original one.
* No Sound *
Sponge Reproduction
• Sexually: When both sexes release gametes
during the spawning season.
Spawning
Sponge Reproduction
• Most sponges can produce both male and
female gametes in the same individual and
is called monoecious
• Some are dioecious meaning that they
have separate sexes in each individual
(either male OR female…not both)
Are we monoecious or dioecious?
Sponge Reproduction
• Once the egg is fertilized, a larva is formed
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Larva: Is an immature stage that may undergo a
dramatic change in structure before changing to the
adult body form
• After no more than 2 days of free-swimming
existence, the larva settles to the substrate and
begins to develop into the adult form
What is “Substrate”?
Sponge Body Structures:
• Osculum: large
opening at the top of
the sponge
• Pore cells (Ostia):
openings to bring in
water
• Collar cells
(choanocytes): line
interior, have flagella
to help filter water
• Spicules: hard,
supportive structures
found in body of
sponge
Porifera: Anatomy
• Water leaves through the osculum, a large
opening on the top
Choanocytes (Collar Cells)
• Food is trapped here.
Porifera: Eating
• After choanocytes trap food on their collar, and is
moved along to the base of the collar
• Food is then engulfed by the cell to form a food
vacuole, and is digested by enzymes and pH
changes
• Digested food is passed to amoeboid cells, &
distributes it to other cells
The Anatomy of a Sponge
Section 26-2
Osculum
Central cavity
Pores
Water flow
Choanocyte
Spicule
Pore cell
Pore
Epidermal cell
Archaeocyte
Commercial Importance
• Bath Sponges: Harvested & used to
bathe with
• Medical: Some act as antibiotics & others
have painkilling properties (still
researching)
Cnidarians:
• Phylum Cnidaria: means
“stinging cell”
• Marine
• Radial symmetry
• Have tentacles
• Predators: capture and poison
prey with stinging cells on
tentacles (NEMATOCYST)
• Acoelomates
• Oxygen diffuses into body from
water
Cnidarian Body Forms
• Polyp: body with
tentacles hanging
upward
• Ex: hydra, sea
anemone
• Medusa: body with
tentacles hanging
downward
• Ex: jellyfish
Cnidarian Reproduction:
• Asexually reproduce by
budding
• Sexually reproduce in
medusa form only, sperm
and eggs are released into
water
• Thousands of gametes are
released at a time
Time to Think!
Why do sponges and cnidarians release
so many gametes into the water?
The body plan of an animal relates to its
complexity. What does that tell you
about sponges and Cnidarians since they
are both acoelomates?
Cnidarian Structures:
• Basal disc: sticky end of polyp
form which allows them to stay in
one spot
• One body opening (mouth) for
food to enter and wastes to exit
• Gastrovascular cavity: interior
cavity where food is digested &
nutrients are circulated around
the body
• Nerve net: net of nerves that
allow impulses to travel around
the body, senses the environment
• Muscles: some muscles are
present; allows for some
movement
Three groups of cnidarians
• Hydrozoans: colonies which
appear to be one organism
• Ex: portugese-man-of-war
• Scyphorozoans: independent
medusas
• Ex: jellyfish, box jellies
• Anthozoans: colonies of polyps
• Ex: corals, sea anemones
Quiz
1. Sponges __ animals.
a. are
b. are not
2. Sponges can reproduce asexually by ___.
a. budding b. regeneration c. both
3. Hydras have their tentacles pointing upwards. They
are __.
a. medusas b. nematocysts c. polyps
4. All cnidarians have ___ symmetry.
a. bilateral b. radial c. no symmetry
5. Cnidarians poison their prey with stinging cells called
___.
a. choanocytes b.nematocysts c. osculum