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Pop Quiz 2
• Give the dominant body form for each
– Scyphozoa
– anthozoa
• List 2 causes of coral reef damage.
• What is the function of a colloblast?
Phylum Platyhelminthes
Flatworms - the Simplest
Bilateral Animals
Bilateral Body Design
• cephalized
– sensory organs concentrated in head
• body directions:
Triploblastic Body Design
based on Hickman Fig. 14-3
Three Basic Tissues
ectoderm
mesoderm
endoderm
muscle layers
mesoderm
epidermis
ectoderm
ciliated
epidermis
ectoderm
parenchyma
mesoderm
pharynx
nerve cord
ectoderm
gut
endoderm
General Features of Flatworms
• Cephalized
– Sensory organs and ganglia concentrated in
head
– Suitable for directional locomotion
• Acoelomate
– no fluid-filled body cavity between gut and
body wall, instead, “parenchyma” tissue
• Epidermis of living, often ciliated cells
Typical Organs and Organ Systems
compare Hickman Fig. 14-6
cephalic ganglion ovary
nerve cord
yolk glands
auricle
seminal receptacle
penis
eye
protonephridia
gut
testes
pharynx
seminal vesicle
Platyhelminthes Classification
• Class Turbellaria
– Planarians and other free-living flatworms
– Benthic, planktonic
– Marine, freshwater, terrestrial
• Classes Trematoda and Cestoda
– next lecture
• Class Monogenea (fish parasites)
Some Turbellarians
triclad planarian
in moist or aquatic habitats
protrusible pharynx
terrestrial flatworm
polyclad flatworm
on coral reef
Fig 14.6C
Feeding and Digestion
• predators or saprophages
• branched, incomplete gut
– Serves as circulatory system in largest ones
– Lacking in tapeworms and smaller turbellarians
– Muscular, sometimes protrusible pharynx
Reproduction
• Sexual reproduction:
– mostly hermaphroditic (= monecious)
– good, since any two individuals can mate
• Reproduce asexually by transverse fission
microturbellarians, forming asexual chains
Review of Organ Systems
compare Hickman Fig. 14-6
cephalic ganglion ovary
nerve cord
yolk glands
auricle
seminal receptacle
penis
eye
protonephridia
gut
testes
pharynx
seminal vesicle
Nervous and Excretory Systems
• nervous system
– ganglia in head
– ventral nerve cords
– sense organs for light and chemicals
• excretory + osmoregulatory system
– protonephridia: flame cells and tube cells
• flagella and collar resemble collar cells
Review of Organ Systems
compare Hickman Fig. 14-6
cephalic ganglion ovary
nerve cord
yolk glands
auricle
seminal receptacle
penis
eye
protonephridia
gut
testes
pharynx
seminal vesicle
Parasitic Platyhelminthes
Flukes (Trematoda)
And
Tapeworms (Cestoda)
Parasitic Relationships
• Parasites steal food from host
– usually not lethal, but weaken or reduce growth
or reproduction of host
• Parasites have great reproductive capacity
– Chances of transmission to another host are
small under normal circumstances
• Life cycles are complex
– Larval stages in other hosts
– Asexual reproduction in larval stage
Class Trematoda
• internal parasites of vertebrates
– Intestine, liver, blood vessels, bladder, etc.
• epidermis is not ciliated, but absorptive
– Consists of syncytial cells
• complex life cycles
– Larval stages in other hosts
– Asexual reproduction in sporocyst and redia
stages
Trematoda
Anatomy
compare Hickman Fig. 14-7
Contrasts With Turbellaria
- anterior mouth with sucker
-
another, ventral sucker
larger uterus (greater fecundity)
food-absorbing epidermis
reduced sensory organs
Syncytial
Epidermis
of Flukes
Hickman
Fig. 14-17
adults
(unusual because diecious)
eggs
Schistosome
Fluke Life
Cycle
Fig. 14.13
cercaria
Redia
(not shown)
miracidium
sporocyst
reproduces asexually
Tapeworms - Class Cestoda
• live in vertebrate intestines
– up to 7 m long, full length of human small
intestine
• absorb digested food through epidermis
– mucus and acidic compounds defend against
host enzymes
• live without oxygen
– necessary , but very inefficient- use much food
Tapeworm Adult Anatomy
compare Hickman Fig. 14-19
Scolex -anchors worm,
buds asexually
Gravid Proglottids break off and
release eggs
testes
uterus
gonopore
ovaries
Proglottid reproduces sexually
in person’s stomach, larva
emerges from cyst
person eats
undercooked
beef
encysted larva
occurs in
”measly” beef
Life Cycle
of the Beef
Tapeworm
final host
gravid proglottids
drop off and exit
with feces
egg hatches
and migrates
into cow’s
muscles
cow ingests egg
alternate host
resistant egg is
released on grass
Like Hickman 14-9
Tapeworms and Health
• human tapeworm infections are common
– compete for food in intestine
– abundant before effects are noticeable
• dog tapeworm can harm people when we
become intermediate hosts
– requires oral exposure to dog feces
– larvae move from intestine to liver or muscles
and form large cysts
Cerebratulus
An example of spiral clevage from the Phylum Nemertea
Phylum Nemertea
•
•
•
•
•
Ribbon worms
Mostly marine, known for their
proboscis
Excellent example of spiral clevage
Similar to platyhelmithes but mostly
dioecious
Pilidium larvae
Acoelomate,bilateral
Cerebratulus
Proboscius everted from Rhyncocoel
Feeding and Defense
Rhynchocoel an
extendable
proboscis that lies
in a sheath.
muscular pressure
on fluid filled
cavity everts
muscles retract it
Cerebratulus
Locomotion
use a combination
of musculature and
cilia
Can use stylet
(from proboscius)
to attach and draw
body forward
Circulation
closed system,
pumping achieved
by muscular
contraction
Cerebratulus
Basidiodiscus
Nervous system
brain connected to
a series of
longitudinal nerves
that extend
posteriorly
ocelli, tactile
papillae, sensory
pits and grooves
Cerebratulus
Reproduction and Development
Dioecious, discharging both sperm and
eggs into the water.
Determinate, spiral clevage
Pilidium larvae
dorsal spike of fused cilia
Chapter 14
Integrated Principles
of Zoology
Eleventh Edition
Hickman/Roberts/Larson
(c) The McGraw-Hill Companies, Inc.
The End.