Chap 3 Poriferans

Porifera
The simplest form of multicellular animals
(Metazoans)
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Tree
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Life
Figure CO 7
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I.
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Invertebrates - Background
Kingdom Animalia
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97% of all animal species are invertebrates
Animals without a backbone
All major groups have marine representatives
(some are exclusively marine)
(3-15 million species)
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Phylum Porifera (Sponges)
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Simplest multicellular animals
98% are marine (~9000 species), no terrestrial
sponges.
Sessile (attached to substrate)
Lack nervous system
No true musculature
Suspension feeders
Diversity of shapes, sizes, colors, habitats
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Found from low tide line to 3.5 miles deep
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Shapes:
Tiny cups, broad branches, tall vases, encrusting round masses
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•Cellular organization-complex
aggregation of specialized cells
•No true tissues/organs, cells largely
independent from each other
•No organs, movable parts,
appendages
•Thus, cells are plastic, can change
from one type to another
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Phylum Porifera (Sponges)-Gr. “pore-bearers”
Complex sponge
many chambers, oscula
Simple sponge
1 chamber, 1 osculum
Body Plan (Structure)- Asymmetrical
Ostia – water enters-pumped through these pores
Choanocytes – Collar cells; line chambers
Osculum – water exits (driven by collar cells acting in synch)
Spongin – Elastic protein (spongy texture)
Spicules – Calcareous or siliceous structures, structural support, discourage predators
Amebocytes (archaeocytes, wandering cells)– Secrete spongin and spicules, transport and
store food particles, transform into other types of cells, repair
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Function of collar cells:
1. Beat flagella to pump water
through sponge.
2. Traps food particles
3. Trap sperms in water
DIVERSITY
Mesophyll: gelatinous, non-living layer
adjacent to Choanocytes
Contains the Archaeocytes
Archaeocytes functions:
1. Digestion of food particles
2. Store digested food
3. Give rise to sperms (flaggelated) and eggs
4. Elimination of waste
5. Secretion of supporting spicules
Asconoid
Syconoid
Pinacocytes: flattened contractile cells covering the outer layer of the sponge
Functions:
1. contraction for shape change
2. Regulate water flow
Leuconoid
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Water-OUT
through osculum
Phylum Porifera (Sponges)
Feeding (Digestion is intracellular)
Suspension feeders
Filter feeders (active suspension
feeders)
Water/food IN
through ostia
Reproduction
Asexual
budding, break off tips of
branches
“branches” regenerate,
identical to parent
Sexual
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•Most are hermaphrodites
•both male and female structures
produce both types of gametes (eggs
and sperm)
•Broadcast spawning of sperm (clouds)
•swept into sponge
•fertilize eggs
•eggs develop into larvae
•swept out via water currents
Fig. 7.3
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Sponge colony showing
buds
Amphiblastula
Gemmule Forms
Parenchymula
Development of sponge from amphiblastula
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Phylum Porifera
• 3 classes – defined by internal skeleton
• Class Calcarea
–CaCO3 spicules
–Shallow tropical waters (Leucosolenia)
–All forms are present in this Class
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Phylum: Porifera
• Class Demospongiae
– Silica, spongin, or both, or lack skeleton
– Never of CaCO3
– Bath sponge, rounded, spongin fibers
– Encrusting forms, bright colors on rocks and
corals
– (Spongilla)
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Phylum: Porifera
Class Sclerospongiae
-Hard sponge
-the smallest class
-have skeletons that contain all three kinds of
material: calcium carbonate, silica, and
spongin
-all members are of leuconoid construction
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Phylum: Porifera
• Class Hexactinellida
–Glass sponges, silica spicules
–Deep waters
–Either sycon or leucon constructs
–(Euplectella)
• Gr. Plecta = lace, this genus is known for
lace-like skeleton fused glass spicules
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