BISC 306 Chapter Notes -Strobilation, Rhopalium, Mesoglea

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Published on 19 Nov 2012
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BISC306
PORIFERA
General:
Rigid, perforated bag lined with flagellated collar cells or choanocytes (inside).
o Generate currents to maintain circulation
o Capture small food particles
o Capture sperm
Empty space in the middle is called the spongocoel
Between inner choanocyte layer and outer pinacocyte (epidermis) layer is the mesohyl.
o Gelatinous, acellular
o Contains free floating archaeocytes (amoeboid)
Digest food, give rise to sperm/eggs, defense, eliminating wastes and specialization for
secretion of spicules
Spicules are siliceous or calcareous
o Discourage predation
Spongin is also a supporting material
Gemmules are dormant structures from which a sponge emerges
o Resistant to dessication, etc
o Alternative to tissue regression
Pinacocytes form the pinacoderm (outer layer)
o Do not secrete a basal lamina
o Contractile
Ostia (ostium) in, oscula (osculum) out
Water comes in through porocytes
Asconoids are the simplest body type. A bag.
Syconoids are more complex, with pockets of choanocytes
Leuconoids lack a large spongocoel. Pockets and pockets of choanocytes increase surface area, and
instead of one osculum, they have many oscula.
Hermaphroditic, or reproduction by fragmentation
Internal fertilization and development
Secrete poisons that range from large organic molecules or small ones
o Have anticancer, etc, properties
Calcarea
Demospongiae
Hexactinellida
Bear CaCO3 spicules
Spongin or silica spicules (but
never CaCO3). Also contain
chitin.
Supported entirely by
interconnected six-rayed
spicules of silica and chitin
Include asconoid, syconoid and
leuconoid
Nearly all leuconoids
Syconoid or leuconoid
80% of all sponge species
Symmetrical, bilaterally
Only asconoids are in this class
Outer layer is multi-neuclei-ed
No pinacoderm layer
CNIDARIA
General:
Two adult stages
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o Polyp
Mostly stationary
Asexually reproduces
Tubular body
o Medusa
Swims
Reproduces sexually
Not hermaphroditic
Basic radial symmetry
Two layers of living tissue, separated between them by a mesoglea (gelatinous)
o Mesoglea is nonliving but may contain living cells (amoebocytes)
o Epidermis and gastrodermis
All cnidarians secrete nematocysts
o Defensive structures
o Secreted within cells called cnidoblasts (or nematoblasts)
o Cnidae are the most widespread
o Rounded proteinacious capsule with an opening at one end
o Hollow tube shoots out explosively, turning inside out
o Triggered by chemical and tactile stimulation
o Specialization for wrapping small objects, sticking to surfaces, penetrating, secreting toxins
o Function in food collection, defense and locomotion (sort of)
Food passes through only one hole, the mouth
Mostly carnivorous, though some eat phytoplankton
Reef building (hermatypic) corals generally have symbiotic algae or something to colour them
No central nervous system, but “nerves” and “muscles”
o Nerve nets
o Slow conducting branched nerve system that goes both ways
o Less branched fast conducting neurons have more directed transmission
Greater diameter, fusion of smaller fibres during development
Diploblastic Musculature cannot originate in the mesoderm
o Muscle layers are composed of elongated, contractile bases in the mesoglea in the ecto and
endodermal cell layers
Epitheliomuscular cells
Form either longitudinal or circular musculature
Mesoglea acts as support system, oxygen store
Nematocysts secrete digestive enzymes and then phagocytose and digest intracellularly
Planula larvae result from sexual union
Polymorphs of polyp colonies
o Gastrozooids eat
o Gonozooids fuck
o Dactylozooids defend
Myxozoa (Non-medusozoans)
o Extracellular, spore-forming parasites
o Possess organelles called polar filaments coiled in polar capsules
o No well defined nervous system
o Sometimes worm shaped
Hydrozoa
Anthozoa
Cubozoa
Scyphozoa
Greater polyp
representation
No medusa stage at all
No operculum or
Small, highly toxic,
most derived
Asexual replication by
strobilation
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Gastrodermal layer
lacks nematocysts
cnidocil
Coelenteron partitioned
by mesenteries (septa)
cnidarians
Medusa stage
dominates
(Polyp strobilates in layers
to release ramets [ephyra,
juvenile medusa])
Order Hydroida
Marine and
freshwater
Thick mesoglea
Rhopalia, manubrium,
gonochronistic
medusa
Shelf of tissue (velum)
increase propulsion
Stolon (connects GVC
of different polyp
polymorph), hydranth
(oral end of a polyp)
Commonly encased in
perisarc [surrounding
the hydranth =
thecate]
All marine
Gametes produced by
polyp planula (feeds
on phytoplankton and
stuff like that)
Four tentacles or
clusters of tentacles
near four rhopalia
Marine
Complex, possibly
image forming eyes
Jellyfish Mesoglea is firm
gelatin
Reproduce asexually by
pedal laceration (cutting
off pieces of foot) as it
moves along slowly
Polyp stage does not
strobilate, polyp stage
buds more polyps that
become ramets
Medusoid with
nematocyst studded
tentacles
Mouth opens into
tubular pharynx and
siphonographs (one or
two discrete ciliated
grooves from pharynx
to mouth)
Increase surface area
for secreting digestive
enzymes and absorbing
nutrients
Mouth at the end of a
muscular cylinder, the
manubrium.
Anthozoa Subclass
Hexacorallia
Possess tentacles and
mesenteries in
multiples of six
Most are solitary
Lack specialized
covering
Never polymorphic
best known ones are
stony (true) corals that
secret calcareous
skeletons
Also called
scleractinian corals (are
both reef-building and
not)
Symbiosis with
zooxanthellae drive the
reaction to make
CaCO3
Order Siphonophora
Free floating
polymorphic colonies
Some have
nectophores for
propulsion lack
mouth and tentacles
Pneumatophores filled
with gas so they float
mesoglea absent
Modules within the
colony occur in
clusters cormidia-
arranged on a stem
Phyllozooids bracts
of nematocysts
Well developed system of
fluid filled gastrovascular
canals, distributed among
four gastric pouches
Mesenteries are either
complete or incomplete
Free edge is trilobed,
ciliated and studded
with nematocysts, cells
that secrete digestive
enzymes, and others
that phagocytose
bacteria
Contain longitudinal
muscles and bear
gonads
Also obtain nutrients from
zooxanthellae that live
symbiotically in tissues
Sensory organs: rhopalia
[statocysts, ocelli],sensory
lappets distributed
along margins of
swimming bell
Gonochoristic (single
sexed) medusae
Usually gonochronistic,
but sometimes
hermaphroditic
Planula is nonfeeding, and
develops to a scyphistoma
(sessile, no sensory
stuff) polyp
Order Hydrocorallina
Colonial, secret CaCO3
skeleton
Restricted to warm
waters
Dactylozooids
especially abundant
Acontia are at the
bottom of the
mesenteries and can be
extended near the base
for defense or offense
Subclass Octocorallia
Tentacles and
mesenteries in eights
Tentacles are pinnate
bear numerous
outfoldings called
pinnules
Polyp has thinner
mesoglea
Acrorhagi are little
round bulges in rings
Polyp reproduces by
budding, then creates
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