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Invertebrates I:
Porifera, Cnidaria,
Ctenophora,
Platyhelminthes, Annelida
Tree
of
Life
Figure CO 7
I.
Invertebrates - Background
•
Kingdom Animalia
•
97% of all animal species are
invertebrates
II. Phylum Porifera (Sponges)
•
Simplest multicellular animals
•
Most are marine (~9000 species)
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sessile (attached to substrate)
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Diversity of shapes, sizes, colors,
habitats
•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
Fig. 7.2
Shapes:
Tiny cups, broad branches, tall vases, encrusting round masses
II.
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
Beat flagella to pump water through sponge
traps food particles
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 (wandering cells)– Secrete spongin and spicules, transport and store food
particles, transform into other types of cells, repair
Water-OUT
through osculum
II. Phylum Porifera (Sponges)
B. Feeding
•
Suspension feeders
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Filter feeders (active suspension feeders)
C. Reproduction
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Asexual
Sexual
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Water/food IN
through ostia
Broadcast spawning
Fig. 7.3
II. Phylum Porifera

3 classes – defined by internal
skeleton

Class Calcarea
• CaCO3 spicules
• Shallow tropical waters

Class Demospongiae
• Bath sponge

Class Hexactinellida
• Glass sponges, silica spicules
• Deep waters
II. Phylum Porifera


3 classes – defined by internal skeleton
Class Calcarea
• CaCO3 spicules
• Shallow tropical waters (Leucosolenia,
Scypha, Leucandra, Leucilla)
• (drawing of Scypha slide)
II. Phylum: Porifera

Class Hexactinellida
• Glass sponges, silica spicules
• Deep waters
• (Euplectella specimen-Venus’s flower
basket sponge, spicules slide)
 Gr. Plecta = lace, this genus is known
for lace-like skeleton fused glass
spicules
II. Phylum: Porifera

Class Demospongiae
• Silica, spongin, or both, or lack skeleton
• Bath sponge, rounded, spongin fibers
• Encrusting forms, bright colors on rocks
and corals
• Boring types, through CaCO3
• (Spongia specimen, note siliceous
spiculation, internal budding)
III. Phylum Cnidaria
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9000+ species
•
•
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Sea anemones
Corals
Jellies
A. Body Plan
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Body forms
•
•
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Polyp - sessile
Medusa – free floating
Radial symmetry
•
•
Oral surface
Aboral surface
Fig. 7.5
III. Phylum Cnidaria
A. Body Plan
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Cnidocytes (stinging cells)
•
•
•
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Defense
Prey capture
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Contain nematocysts (stinging capsule)
Simple nervous system
No true organs
Single opening
Mucus traps food
Trigger hair
fluid
coiled thread
Undischarged
< 0.1 mm
Discharged
www.calacademy.org/research/izg/nematocyst.htm
III. Phylum Cnidaria
B. Class Hydrozoa
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Polyp forms
•
•
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Millepora species
colonial
Specialized polyps (zooids)
• Gastrozooid - Feeding
• Gonozooid – Reproduction
• Dactylozooid – Defense (tentacles)
Medusa forms
•
Siphonophores – Colonial (e.g.- Portugese man
of war)
III. Phylum Cnidaria, Class Hydrozoa
gastrozooid
gonozooid
Fig. 7.7
III. Phylum Cnidaria
C. Class Scyphozoa
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Desmonema glaciale
Medusae large
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E.g. – Cyanea capillata (Lion’s Mane)
• Bell > 2 m
• Tentacles 60+ m
Swim by contracting bell rhythmically, pulsating
contraction
Stings *
Cyanea capillata
III. Phylum Cnidaria
D.
Class Anthozoa
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•
Polyp
Passive suspension feeders
1.
Solitary forms
•
2.
Anthopleura xanthogrammica
Sea anemones
Colonial forms
a.
b.
c.
d.
Corals
•
Stony corals – branching and massive
- Some build reefs
•
Soft corals
Gorgonians
Sea pens
Sea pansies
Branching Corals
Doming Corals
Sea Pen
Soft Corals
Sea Pansy
Gorgonians (Sea Whips)
Gorgonians (Sea Fans)
III. Phylum Cnidaria
E.
Class Cubozoa
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Sea wasps, Box jellyfish
square bell
4 tentacles or bunches
Highly toxic
IV. Phylum Ctenophora (comb jellies)
•
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Biradial symmetry
8 rows of ciliary combs (ctenes)
• swimming
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Carnivorous
• Lack nematocysts
• Capture prey with sticky colloblasts
•
May occur in swarms
• Heavy predators
Pleurobrachia
Beroe
V. Phylum Platyhelminthes
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Flatworms Dorsoventrally flattened
•
Bilateral symmetry
•
Simplest organism with
organs and organ
systems
•
Digestive tract has 1
opening
•
No circulatory,
respiratory, skeletal
systems
•
Hermaphroditic
V. Phylum Platyhelminthes
A. Class Trematoda (Flukes)
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Parasitic – Feed on tissues, blood, gut contents
Complex life cycles
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B.
Adults in vertebrate
Larvae in invertebrates
Vertebrate eats intermediate host
Body covered with cuticle resistant to digestion
Cestoda (Tapeworms)
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Parasitic
Live in vertebrate intestines – (uncooked meat)
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Head attaches w/4 suckers or hooks
Gutless – absorb nutrients through body wall
50 feet!! (sperm whales)
V. Phylum Platyhelminthes
C. Class Turbellaria
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Mostly free-living carnivorous species
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commensal animals inside invertebrates
(oysters, crabs, etc.)
Most commonly seen (Why?)
Label ocelli=eyespots
VI. Phylum Annelida
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Segmented worms (1mm-3m) – flex/move
more easily
•
Internally and externally, internal
structures in tandem
•
Protective elastic cuticle
•
Body composed of repeated segments
• Gut runs through all segments in body
cavity (coelom-space around gut)
• Coelom filled with fluid – hydrostatic
skeleton
• Coelom divided with septa-correspond to
segments
Leech
Sabella pavonina
Nereis sp.
Lumbicus terrestris
VI. Phylum Annelida
A.
•
Class Polychaeta – tube worms, feather
dusters
Body segments have pairs of parapodia
• Parapodia for locomotion, feeding, gas
exchange, protection
• tipped with setae (bristles), often 4 pairs
• Respiration: some with gills, exchange
through body
VI. Phylum Annelida
A. Class Polychaeta
• Larva = Trochophore
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Band of cilia around body
Diverse lifestyles
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Free-living predators
Burrowing
Tube building
Fig. 7.14
VI. Phylum Annelida
B.
Class Oligochaeta - earthworms
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C.
© 2004 Amanda Demopoulos
Few marine species
Benthic – mud and sand (deposit feeders)
No parapodia
Locomotion – expansion and contraction
Class Hirudinea (Leeches)
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Freshwater mostly
No parapodia
One anterior/one posterior sucker to attach
Hirudin – anticoagulating chemical so blood does
not clot