Download - Phylum Bryozoa - Florida State University
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Phylum Bryozoa“moss animals”
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Bryozoa Characteristics•Approximately 4000 pecies of Bryozoans
•All are aquatic (marine or freshwater)
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Body Plan
anus
lophophore
mouth
esophagus
stomach
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Bryozoa CharacteristicsGas Exchange
•lophophore
Circulatory System• no organs, coelomic fluid
Excretion• no organs, simple diffusion
Nervous system
• nerve ring surrounding pharynx and nerves in tentacles (no sensory organs)
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Bryozoa CharacteristicsSkeletal system
• most have a cuticle composed of chitin or calcium carbonate (zoecium)
zoecium
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Bryozoa CharacteristicsDigestive System
• lophophore: a contractile ring of ciliated tentacles surrounding the mouth• complete digestive system• U-shaped with anus outside lophophore (ectoproct)
lophophore
mouthanus
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Bryozoa Characteristics
Reproduction• most are monoecious• most species brood their eggs externally or within special cavities in their bodies• freshwater species are capable of asexual reproduction using statoblasts (similar to gemmules)
statoblasts
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Bryozoa CharacteristicsColonial
• bryozoans are sessile and live in colonies (zoarium)• colonies can be encrusting (thin sheets) or stoloniferous (plant-like)
encrusting bryozoan stoloniferous bryozoan
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Bryozoa Characteristics
stoloniferous Bryozoan Hydrozoan
Superficially, stoloniferous Bryozoans resemble colonial Hydrozoans
Major differences include: the structure of the digestive system, the zoecium, the number of tissue layers…
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Bryozoa CharacteristicsColonial
• all zooids within a colony (zoarium) are connected by pores in each individuals zoecium
lophophore
operculum muscle
retractor musclepore
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Bryozoa CharacteristicsColonial
some Bryozoans are polymorphic and contain defensive zooids called avicularia
Used in defense and anti-fouling
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Annelida
Mollusc
a
Arthro
podaEch
inodermata
ChordataPlat
yhelm
inthe
sNem
atoda
acoe
lom
ate
pseu
doco
elom
ates
eucoelomates
Rotifer
a
deuterostomes
Bryozo
a
Traditionally Bryozoans were considered to be primitive deuterostomesbased on aspects of their development
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Annelida
Mollusc
a
Arthro
podaEch
inodermata
Platyh
elmint
hes
Nemato
da
acoe
lom
ate
pseu
doco
elom
ates
eucoelomates
Chordata
Rotifer
a
deuterostomes
Bryozo
a
More recently they have been placed with theprotostomes based on molecular sequence data
protostomes
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Phylum Echinodermata“spiny skinned”
animals
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EchinodermataCharacteristics
•Approximately 6000 species of Echinoderms
•All are marine and are benthic as adults
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Annelida
Mollusc
aArth
ropoda
Echinoderm
ataChord
ata
Platyh
elmint
hes
Nemato
da
acoe
lom
ate
pseu
doco
elom
ates
eucoelomates
Rotifer
a
deuterostomes
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Deuterostome Mouth Formation
blastopore archenteron(primitive gut)
Future mouth
anus
Blastopore becomes the anus and the mouth forms secondarily
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Deuterostome: Radial Cleavage
2 cells 4 cells 8 cells
Blastomeres divide in a symmetrical fashion, producing layers of cells directly on top of one another
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Deuterostome: Regulative Development
One blastomere is removed
Development continues
Development continues
4-cell stageeach blastomere is capable of
regulating its development even when separated from the others
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Deuterostome: Enterocoelyblastocoel
early mesodermal
pouchseparation of
pouches from gut developing coelom
ectoderm endoderm mesoderm
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Echinodermata Characteristics1. Water Vascular System
A system of coelomic canals that functions in: circulation, gas exchange, excretion, and locomotion.
ring canal
radial canal
madreporitestone canal
tube feet
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Echinodermata CharacteristicsWater Vascular System
podium
ampulla
The structure of the tube foot
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Tube feet
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Echinodermata Characteristics2. Dermal Endoskeleton
• All echinoderms have a dermal endoskeleton that is composed of calcareous ossicles and is covered by epidermis.• The endoskeleton allows continuous growth and provides protection.
Fused to form a test(e.g. sea urchins)
Articulating plates(e.g. starfish)
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Echinodermata CharacteristicsDermal Endoskeleton
• In many echinoderms the skeleton bears spines or bumps that are used for defense.
Sea urchin Spines on crown of thorns starfish
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Echinodermata CharacteristicsDermal Endoskeleton
•The epidermis covering the endoskeleton contains many specialized structures:
Dermal branchiae(respiration): an extension of the coelomic cavity
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Pedicellaria(anti-fouling)
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3. Mutable connective tissue: echinoderms can rapidly and reversibly change the stiffness of their connective tissue
Echinodermata Characteristics
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4. Secondary radial or biradial symmetry
Echinodermata Characteristics
• this bilaterally symmetrical larval form undergoes metamorphosis into an adult with radial pentameroussymmetry (with 5 or more radiating areas)
bilateral larval stage radial pentamerous adult
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Feeding and digestion
Grazers
Predators
Most species have a complete digestive system.
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Nervous system
•circumoral nerve ring
•radial nerves
•no sense organs in most species (except eyespots)
•no cephalizaion (no head)Radial nerves
circumoral nerve ring
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mouth
Nervous system anus
circumoral nerve ring
radial nerves
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Echinodermata Characteristics
Reproduction• usually dioecious • usually external fertilization (eggs and sperm are shed into the water where fertilization occurs; broadcast spawning)• indirect development with the presence of a free-swimming, bilateral larval stage (some have direct development)
bilateral larval stagespawning sea urchins
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Phylum Echinodermata
Class AsteroideaClass EchinoideaClass OphiuroideaClass HolothuroideaClass Crinoidea
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Echinoderm Radiation
Crinoidea• on a stalk• feathery arms
Holothuroidea• secondarily bilateral
Ophiuroidea• no ambulacral region• no anus
Asteroidea• arms
Echinodea• fused ossicles
ambulacral region
aboral region
oral region
anus
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Class Asteroideathe “sea stars”
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anus
madreporitemouth
ambulacral groove: lined by tube feet
OralAboral
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Digestive gland
gonads
cardiac stomach
pyloric stomach
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Class Echinoideathe“sea urchins”, “sand dollars”, “heart urchins”, “sea biscuits”…
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Class Echinoidea• globular or disc- shaped with no arms• ossicle plates are fused to form a compact skeleton called a “test”• ambulacral grooves closed • movable spines with interspersed tube feet• tube feet usually have suckers • anus and madreporite aboral• pedicellaria present• Aristotle’s lantern
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Class Echinoidea
aboralaboral
where the spines attach
ambulacral region
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Class Echinoidea
- complex chewing mechanism- 5 teeth are attached
aboraloral
Inside the animaloral
oral
Aristotle’s lantern
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Sea Urchins are important grazers on reefs, in sea grass beds, and in Kelp forests
Without urchins (or with to many of them) these habitats become altered
Prior to the early 1980s, the long spined urchin (Diademaantillarum) was very abundant
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In 1983, a pathogen killed 99% of the Diadema in the Carribean
This led to an increase in algal abundance and a decrease in coral cover
0
10
20
30
40
50
60
70
80
% a
laga
lcov
er
0
10
20
30
40
50
60
% c
oral
cov
er2 weeks 4 weeks 4 months 1970 1990
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Sea otter abundance Urchin abundance Kelp abundance
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Class Ophiuroidea“brittle stars” and “basket stars”
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Class Ophiuroidea• star shaped with arms around an obvious central disc• ambulacral grooves closed and covered by ossicles(no tube feet within them)• tube feet without suckers and are not used for locomotion• incomplete digestive system no anus• pedicellaria absent
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Class Ophiuroideaoral aboral
Central disc
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Class Ophiuroidea
• Although they don’t have any eyes, some brittle stars have photosensitive “lenses” all over their body.
• They can detect light/dark such as shadows and change color.
night
day
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Class Holothuroidea• cucumber-shaped with no arms• secondarily bilateral• ambulacral grooves closed • microscopic ossicles are embedded in muscular body
soft body• tube feet with suckers and some are modified around the mouth as feeding tentacles • pedicellaria absent• respiratory tree for gas exchange
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Class Holothuroidea
ambulacral region with tube feet
mouth
oral aboral
anus
feeding tentacles (modified tube feet)
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Class Holothuroidea
• Many cucumbers have a “pearlfish”living inside them.
• It is unknown whether the pearlfishis a parasite that feeds on the internal organs of the sea cucumber or whether it leaves the sea cucumber unharmed.
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Class Crinoideathe “sea lilies” and
“feather stars”
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Class Crinoidea• flower-shaped • arms bearing pinnules• stalked• ciliated ambulacral grooves on oral surface with tentacle-like tube feet for food gathering• body disc and stalk contain ossicles• madreporite, spines, and pedicellaria absent
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Class Crinoidea
arm
stalk
pinnules
aboral
oral
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Regeneration• Most Echinoderms are capable of regenerating parts of their bodies when they are lost.
Regenerating arm
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Regeneration• Some sea stars and brittle stars use regeneration as a way to reproduce asexually.
“comet” sea star brittle star
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Regeneration• Most sea cucumbers are able to expel their intestine out of their anus, and regenerate the lost structures. •This is done in defense and during times of the year when food supply is low.
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Faculty research: Don Levitan
The evolution of gamete characteristics in broadcast spawning invertebrates
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Bateman’s Principle: since sperm are more numerous than eggs, male reproduction is limited by access to mates.
This principle has been very successful in explaining patterns of sexual selection and the evolution of sexual dimorphism.
Male widowbird
Female widowbird
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Does Bateman’s principle apply to broadcast spawning species?
In relevance of Bateman’s principle to broadcast spawners is probably related to population density.
Strongylocentrotus franciscanus
sperm limitation sperm competitionpopulation density
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Dr. Levitan’s research has examined the role of sperm limitation and sperm competition in the evolution of gamete traits three species of sea urchins.
1. Strongylocentrotuspupuratus
2. S. franciscanus3. S. droebachiensis
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1. Strongylocentrotus pupuratusSmall eggs, fast/ short lived sperm
2. S. franciscanusIntermediate eggs, intermediate sperm
3. S. droebachiensisLarge eggs, slow/ long lived sperm
Fert
iliza
tion
succ
ess
These differences are due to differences in egg size-larger eggs are better targets
Sperm dispersal time
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Fert
iliza
tion
succ
ess
1. Strongylocentrotus pupuratusSmall eggs, fast/ short lived sperm
2. S. franciscanusIntermediate eggs, intermediate sperm
3. S. droebachiensisLarge eggs, slow/ long lived sperm Sperm dispersal time
sperm limitation sperm competitionpopulation density
S. dro
ebac
hiens
isS. fr
ancis
canu
sS. p
urpu
ratu
s
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Bateman’s Principle: since sperm are more numerous than eggs, male reproduction is limited by access to mates.
Dr. Levitan’s research suggests that under conditions of sperm limitation, female traits (i.e. egg size) evolve to increase fertilization success.
Male widowbird
Female widowbird