Week 7
Phylum Porifera: (porifera = pore-bearing)
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sponges
primarily marine
sessile
either single or colonial
simplest metazoans (multicellular organisms)
cellular level of organization
cells perform different functions but are not organized into tissues (no germ
layers)
asymmetrical
epidermis lined with pinacocytes
system of pores (ostea) and canals for water to travel through = incurrent
system
water and food travels into the sponge via the ostea
interior of the sponge is lined by flagellated cells called choanocytes/collar
cells
flagella creates currents to drive the water through the spongeoceol (interior of
the sponge)
spongeoceol opens to the outside via the osculum = excurrent system
no mouth or digestive system
filter feeders – eat plankton that they filter from the water
collar cells – function as the digestive system in that the phagocytize the food
and then pass it to ameobocytes in the mesohyl (gelatinous layer between
epidermis and collar cells)
ameobocytes function in the secretion of spicules and production of gametes
ameobocytes are motile cells
defining characteristics = collar cells and spicules
http://www.emc.maricopa.edu/faculty/farabee/BIOBK/bodysymm.gif
http://www.ucmp.berkeley.edu/porifera/images/morph1.gif
http://fig.cox.miami.edu/Faculty/Dana/spongeanatomy.jpg
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skeleton of spicules (calcium carbonate or glass) and the spongin protein
http://www-biol.paisley.ac.uk/biomedia/graphics/jpegs/SPICULES.gif
http://virtual.yosemite.cc.ca.us/randerson/Marine%20Invertebrates/Spicules_Sponge.jpg
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three classes of sponges:
(1) Hexactinellida - glass sponges (eg Euplectella)
6 rayed silica spicules
http://upload.wikimedia.org/wikipedia/commons/thumb/5/5d/Hexactinellida-on-kauri-uncertain-0123.JPG/450pxHexactinellida-on-kauri-uncertain-0123.JPG
(2) Demospongia– bath sponges (eg Spongia)
1, 2, or 4 rayed silica spicules
http://www.hewit.com/acatalog/Images/p-sponge.jpg
(3) Calcarea - calcareous sponges (eg Sycon)
1, 3 or 4 rayed Calcium carbonate spicules
http://images.google.com/imgres?imgurl=http://www.dpo.uab.edu/~acnnnghm/BY255L/BY255LImages/BY255LImagesPorifera/Mixed%2520spicules-01.jpg&imgrefurl=http://www.dpo.uab.edu/~acnnnghm/BY255L/BY255LPorifera.htm&h=480&w=640&sz=22&hl=en&start=16&tbnid=KjEM1DcUztLQM:&tbnh=103&tbnw=137&prev=/images%3Fq%3Dsilica%2Bspicules%26gbv%3D2%26ndsp%3D20%26hl%3D
en%26sa%3DN
http://www.esu.edu/~milewski/intro_biol_two/lab_9_porifera_cnidaria/images/scypha_canal_system.jpg
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radial symmetry or asymmetrical (majority)
three different types of canal systems
http://wwwuser.gwdg.de/~gwoerhe/calcarea_introduction.html
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asconoid sponges
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simplest architecture of the sponge
simple tube with pores
canals run straight through the sponge body
all choanocytes line the spongocoel
tend to grow in groups and are attached
http://www-biol.paisley.ac.uk/biomedia/graphics/jpegs/asc.jpg
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syconoid sponges
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intermediate architectural complexity
similar to asconoid sponges except that their body wall
is thicker
canals are branched
water flows a twisted route through a number of canals
spongocoel is not lined with choanocytes only the radial
canals are
water enters the radial canals through prosopyles into
the spongeoceol and exits through a single osculum
go through a asconoid stage in their development
do not normally form groups
http://www-biol.paisley.ac.uk/courses/tatner/biomedia/jpegs/sync.jpg
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leuconoid sponges
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most complex architecture
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canals are longer and more branched
canals lead to numerous small chambers lined with
collar cells
no real spongocoel just a central exit canal leading to
the osculum
water enters incurrent canals (spaces between radial
canals) to the prosopyles and exits the chambers
through apopyles, then excurrent canals and the
osculum
live in large groups with each individual sponge having
its own osculum
borders between individual sponges are often hard to
define (looks like one organism)
http://www-biol.paisley.ac.uk/biomedia/graphics/jpegs/leuc.jpg
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asexual reproduction
 gemmules
 made up of amoebocytes surrounded by a layer of
spicules
 can survive hostile conditions that would kill adult
sponges
 when the environment becomes less hostile, the
gemmule resumes growing
http://z.about.com/d/biology/1/0/Q/2/sponggem2.gif
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sexual reproduction
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monoecious (male and female sex cells in the same
sponge)
takes place in the mesohyl
male gametes are released into the water and are taken
into the pore systems of neighboring sponges in the
same way as food
spermatozoa are captured by collar cells, which then
lose their collars and transform into specialized,
amoeba-like cells that carry the spermatozoa to the eggs
fertilized egg develops into a blastula (amphiblastula
larvae), which is released into the water (in some
species, release takes place right after fertilization; in
others, it is delayed and some development takes place
within the parent)
larvae may settle directly and transform into adult
sponges, or they may be planktonic for a time
adult sponges are always sessile
Phlyum Cnidaria: (cniderian = stinging creature)
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jellyfish, hydra, sea anemones, corals and comb jellies
eumetazoans (true multicellular organism)
radially or biradially symmetric
tissue level of organization but no true organs
two germ layers (ectoderm and endoderm) = diploblastic
gastrovascular cavity (ceolenteron) with a single opening that serves as mouth
and anus
hydrostatic skeleton formed from fluid in the gastrovascular cavity
nematocysts surround the mouth = defining characteristic
 used to capture food
 have projecting hairlike triggers called cnidocils
 contains a coiled, tubular thread bearing barbs
 barbs may be poisonous
 discharged when prey or predator comes into contact
with it, driving its threads with barb and poison into the
flesh of the victim by means of a rapid increase in
hydrostatic pressure
http://kentsimmons.uwinnipeg.ca/16cm05/16labman05/lb5pg2_files/cnidocyte.gif
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2 basic body forms: (1) polyp (attached/sessile) and (2) medusae (free
swimming)  polymorphic condition
http://www.geocities.com/bballerchicklet7777777777777/cnidarian3.jpg
Generalized Cnidarian Life Cycle:
Vodopich DS, and Moore R. (2005) Biology
- polypoid
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corals and anemones
cylindrical body with mouth and tentacles facing up
other side is anchored
- medusae
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jellyfish
free swimmers
umbrella shaped body
tentacles and mouths are generally pointed down
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sexual reproduction in medusae form – planula larvae formed
asexual reproduction in polyp form = budding
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Classes:
(1) Hydrozoa = water serpent (eg Hydra, Obelia)
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polyp and medusa stages
medusa with a velum
fresh and marine species
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Hydra
 solitary polyps
 atypical because no medusa stage
 4 kinds of nematocysts –largest and most
striking type releases hypnotoxin that posisons
and paralyzes the prey
 basal disk used for attachment
 epitheliomuscular cells cover the body and are
used for muscle contraction
 interstial cells embedded in the epithelium and
totipotent
 asexual or sexual reproduction
 asexual = budding
 sexual – monoecious or dioecious
 testes found near the oral end and ovary found
near the basal end
http://biology.uwsp.edu/faculty/RSchmitz/RJSinvert/invertimages/hydra1.gif
Obelia
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colonial
polyp and medusa forms
 Feeding polyp
 Reproductive polyp
http://www.biology.ualberta.ca/courses/biol108/uploads/fall06/images/F34%20Obelia.jpg
 sexual and asexual reproduction
 medusae form produces egg and sperm which fuse
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to form a zygote
zygote develops into a free swimming planula larva
(ciliated)
larva settles and forms a polyp which eventually
becomes colonial
colonial hydra produce medusa buds in gonagia
(reproductive polyp) which break away and become
free swimming medusae
hydranth = nutritive polyp
http://kentsimmons.uwinnipeg.ca/16cm05/16labman05/lb5pg4_files/image002.jpg
Physalia
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Portuguese man-of-war
has an air bladder (sail) that allows it to float
floats on the surface of tropical, marine waters
floating hydrozoan
pushed by wind (no propulsion mechanisms)
dangerous to humans
eaten by sea turtles
http://animals.nationalgeographic.com/staticfiles/NGS/Shared/StaticFiles/animals/images/primary/portugueseman-o-war.jpg
(2) Scyphozoa = true jellyfish (eg Aurelia)
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solitary
medusa stage emphasized - dioecous
polyp reduced or absent
thick mesoglia (appear jellylike)
composed primarily of water
after fertilization a plannula larvae is formed (polyp)
which remains attached until it buds of in the medusae
form
feeding by nematocysts or by drawing plankton into the
ceolenteron by water currents
lack a velum (velum aids movement through the water)
mouth  gullet  stomach
http://www.pacificislandbooks.com/aurelia.jpg
http://thescyphozoan.ucmerced.edu/Biol/Ecol/LifeHistory/AureliaLH.jpg
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planula larva swims through the water to find a suitable place to
planula changes into a sessile, usually benthic (i.e. bottom
dwelling) polyp called a 'scyphistoma'
the scyphistoma, produces a new free-swimming medusa by
strobilation
strobilation involves change of the end of a scyphistoma into an
'ephyra', an immature medusa
ephra detaches and swims away
(3) Cubozoa (eg Carybdea, Chironex)
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solitary
polyp stage reduced
bell shaped medusa
all are marine
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all polyps
no medusa
gastrovascular cavity is subdivided by mesenteries
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Subclasses
(4) Anthozoa
a. Hexacroillia eg Metridium (sea anemone)
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oral disc = free end with a mouth and
tentacles
basal/pedal disc = attached end
sessile
can glide slowly via the basal disc
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mouth opens into a pharynx
pharynx leads to gastrovascular cavity
http://www.tonya.me.uk/Marine/graphics/Ecology/metridium-senile.jpg
http://rydberg.biology.colostate.edu/Dissections/Metridium/MedtTopview.JPG
b. Ceriantiparthia eg Cerianthes
c. Octocorilla eg Gorgonia, Renilla (corals)
http://www.hero.ac.uk/resources/C_Coral_vs_cricket_300.jpg