Transcript Class Hydrozoa - Somerset Academy

Invertebrates I:
Porifera, Cnidaria,
Ctenophora,
Platyhelminthes, Annelida,
Sipuncula, Echiura
Tree
of
Life
Figure CO 7
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)
Phylum Porifera (Sponges)
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Simplest multicellular animals
Most are marine (~9000 species)
Sessile (attached to substrate)
Diversity of shapes, sizes, colors, habitats
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Found from low tide line to 3.5 miles deep
•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)
Feeding (Digestion is intracellular)
Suspension feeders
Filter feeders (active suspension
feeders)
Reproduction
Asexual
budding, break off tips of
branches
“branches” regenerate,
identical to parent
Sexual
Water/food IN
through ostia
•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
Fig. 7.3
II. Phylum Porifera
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3 classes – defined by internal skeleton
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Class Calcarea
 CaCO3 spicules
 Shallow tropical waters (Leucosolenia,
Scypha, Leucandra, Leucilla)
 (drawing of Scypha slide)
II. Phylum: Porifera
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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
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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
Big steps from
simple sponges to
evolution of tissues
> 10,000 species
All are aquatic,
mostly marine
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Sea anemones
Corals
Jellies
III. Phylum Cnidaria
Radial symmetry- similar parts
of body are arranged and
repeated around central
axis. Look the same from
all sides and have neither
head or tail, front or back
Oral surface (mouth)
Aboral surface (opposite)
Fig. 7.5
III. Phylum Cnidaria
2 basic forms
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Polyp: anemone, tube with a mouth surrounded
by tentacles, specialized in sedentary (sessile) life
attached to substrate
Medusa: jellyfish, bell-shaped free-floating, swim
by pulsating contractions
III. Phylum Cnidaria-feeding
No true organs
Tube/sac with single opening (mouth)
Mouth opens to gut
Tentacles capture food
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CNIDOCYSTS (stinging cells, NOTE
NAME)
Defense
Prey capture
Contain NEMATOCYSTS =thread
bag (stinging capsule)
Simple nervous system
Trap food using mucus secreted at mouth
and tentacles
Some with symbiotic zooxanthellae,
provides host with nutrients, O2, use
up CO2
Cnidocyte
with
nematocyst
Trigger hair
fluid
coiled thread
Undischarged
< 0.1 mm
Discharged
www.calacademy.org/research/izg/nematocyst.htm
III. Phylum Cnidaria
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Reproduction-asexual and sexual, details to
follow
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Asexual
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Budding, binary fission (split down lateral axis), regenerate
Sexual
III. Phylum Cnidaria
4 Classes of cnidarians
Class Hydrozoa (includes hydras, hydroids,
hydromedusae, chondrophorans, siphonophores,
hydrocorallines)
Feathery, bushy colonies of tiny polyps attach to
pilings, shells, surfaces
Alternate between polyp and medusa form
III. Phylum Cnidaria
Class Hydrozoa
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Polyp forms
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colonial
Specialized polyps (zooids)
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Gastrozooid - Feeding
Gonozooid – Reproduction
Dactylozooid – Defense (tentacles), studded with nematocysts
(examples: Hydra with budding (Hydra littoralis), Hydra nematocyst slides
Medusa forms
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Siphonophores – Colonial (e.g.- Portugese man of war) – polyps and
medusa forms simultaneously
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Medusae serve as floats-propel colony through water
Polyp morph represented by gastrazoids, gonozooids, and dactylozooid
(Obelia colony slide (label gastrozoids and gonozooids), Obelia medusa
slide)
III. Phylum Cnidaria, Class Hydrozoa
gastrozooid
gonozooid
Fig. 7.7
III. Phylum Cnidaria
Class Scyphozoa-jellyfishes
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All marine species, few hundred
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Medusae large (dominant stage)
E.g. – Cyanea capillata (Lion’s Mane)
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Desmonema glaciale
Bell > 2 m
Tentacles 60+ m
Swim by contracting bell
rhythmically, pulsing contraction,
at mercy of currents
Stings *, sometimes fatal
Aurelia
Cyanea capillata
III. Phylum Cnidaria
Class Anthozoa (most are)
Polyp (more complex than hydrozoan, scyphozoan
Sexes usually separate
Oviparous (egg-bearer) and viviparous (young bearing)
Passive suspension feeders
Solitary forms
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Colonial forms
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Anthopleura xanthogrammica
Sea anemones
Corals
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Stony corals – branching and massive
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- Some build reefs
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Soft corals
Gorgonians
Sea pens
Sea pansies
(Drawings: Brain coral and Gorgonian specimen)
Branching Corals
Doming Corals
Sea Pen
Soft Corals
Sea Pansy
Gorgonians (Sea Whips)
Gorgonians (Sea Fans)
III. Phylum Cnidaria
Class Cubozoa, “scyphozoa cubed”
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Sea wasps, Box jellyfish
square bell-cuboidal swimming bell
4 tentacles or bunches
Highly toxic
IV. Phylum Ctenophora (comb-bearing)
Exclusively Marine (100 species)
Aka comb jellies
Resemble Cnidarians
Most primitive
Biradial symmetry (radial + bilateral symmetry)
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8 rows of ciliary combs (ctenes)
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Equally spaced on body surface
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Each row is a ridge, paddle of fused cilia
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Beat aboral to oral, propels mouth forward
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Organ system: Digestive system-mouth to pharynx to stomach
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Predatory and Carnivorous
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Lack nematocysts
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Capture prey with sticky colloblasts
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May occur in swarms
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Heavy predators
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(consume lots of fish larvae)
Pleurobrachia
Beroe
V. Phylum Platyhelminthes
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Flatworms Dorsoventrally flattened
Flatness enables O2/CO2
exchange, hiding
Bilateral symmetry
Simplest organisms with
organs and organ systems
Central nervous system,
organs
Digestive tract has 1
opening (like Cnidarians
and ctenophores)
No circulatory,
respiratory, skeletal
systems
Hermaphroditic
V. Phylum Platyhelminthes
Class Trematoda (Flukes)
Largest group of flatworms (6000 species)
Parasitic – Feed on tissues, blood, gut contents
Complex life cycles
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Adults in vertebrate
Larvae in invertebrates
Vertebrate eats intermediate host (fluke larvae)
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Body covered with cuticle resistant to digestion
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Clonorchis slide (label suckers), common liver
parasite
V. Phylum Platyhelminthes
Class 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
Body covered with cuticle resistant to
digestion
50 feet!! (sperm whales)
Dipylidium slide (label solex-head w/4
suckers, and proglottid-sections on
neck)-common dog tapeworm
Proglottids stem from neck at rate of
several per day (fast growth)
V. Phylum Platyhelminthes
C. Class Turbellaria
Mostly free-living carnivorous species
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commensal animals-live in close relation to other animals, or
on their surface, (oysters, crabs, etc.)
Most commonly seen marine flatworm (Why?)
Planaria – have eye spots
Planarians are the freshwater species
VI. Phylum Annelida
Segmented worms (1mm-3m) – flex/move more easily
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Internally and externally, internal structures in tandem
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Protective elastic cuticle
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Bilateral symmetry
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Digestive system of many has 2 openings,
mouth and anus (some have no gut)
Body composed of repeated segments
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Gut runs through all segments in body cavity (coelomspace around gut)
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Coelom filled with fluid – hydrostatic skeleton
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Coelom divided with septa-correspond to segments
Leech
Sabella pavonina
Nereis sp.
Lumbicus terrestris
VI. Phylum Annelida
Class Polychaeta – tube worms, feather dusters
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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
Class Polychaeta
Larva = Trochophore
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Diverse lifestyles (mostly benthic, some
pelagic)
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Band of cilia around body
Free-living predators
Burrowing
Tube building
(parapodia slide, feather duster)
Fig. 7.14
VI. Phylum Annelida
Class Oligochaeta - earthworms
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Few marine species
Benthic – mud and sand (deposit
feeders)
No parapodia
Locomotion – expansion and
contraction
(oligochaete slide)
© 2004 Amanda Demopoulos
©2004 Amanda Demopoulos
VI. Phylum Annelida
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
(leech specimen)
VII: Phylum Echiura
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Sand/mud burrows, rock crevices
140 species so far, shallow mostly
Mm to 8 cm
Proboscis-used for feeding, contains
brain, can’t be retracted
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May extend > 25 times size of animal (200 cm
for 8 cm animal)
Cilia move food to gut
Most are deposit feeders (few suspension
feeders)
Trochophore larvae
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Bonellia viridis (males contained w/in femalesup to 20)
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Sex of embryos not determined at fertilization
Only at contact with female’s proboscis (turns
male)
VIII: Phylum Sipuncula
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All marine, 350 species
Vermiform – worm shaped, no
segments
Found in burrows, sand, mud,
shells, tubes
Introvert-unlike proboscis, can
be retracted into body
Lack circulatory system w/heart
and blood vessels
Pelagospera larva-trochophore
larva develop into this, can
disperse over long distances
http://www.flickr.com/photos/80125969@N00/256020109/