Download Phylum Playthelminthes

Body cavity
• As you develop, cells from a ball
(blastula) that folds in on itself
(gastrula).
• It makes 3 layers (germ layers):
– Ectoderm (outside) becomes skin, etc.
– Endoderm (inside) becomes organs
and other tissues
– Mesoderm (in between) becomes
muscle
Body cavity
• What germ layers are where
indicates type of body cavity
– acoelemate has no body cavity. It is
completely filled in (sponges, jellies,
flatworms)
– Pseudocoelemate appears to have a
body cavity, but is not surrounded
by muscles/tissues (round worms)
– Coelemates have a true body cavity
surrounded by muscle/other
tissues (segmented worms,
arthropods, mollusks, chordates,
echinoderms)
Platyhelminthes
• Flat worms
• Bilateral symmetry
• Exchange O2/CO2 through skin
(diffusion)
• No circulatory system
• Incomplete digestive system (1
opening … gut)
• Cephalized (sensory organs at
“head”)
• Pseudocoelemate…2 layers with fluid
in between
• Many are parasites
• e.g. Planaria (Class
Turbellaria)
• Scavenge for food, taken
in through pharynx
• Water excreted
through flame cells
• Cerebral ganglia
collection of nerves
(“brain”)
• Fission/sexual repro.
(herm, exchange
sperm)
• Eye spots sense light
Flat
worms
Flat worms
•
•
•
•
•
e.g. Flukes (Class Trematoda)
Live blood, intestines, lungs, liver…
Suckers to attach, draw in body fluids
Hermaphroditic
Life cycle with
more than 1
host
• E.g. schistosomiasis
Schistosome
• Big one is female,
little one is male
• Spread by snails!
• Causes
enlargement of
liver/spleen
Schistosomiasis
Flat worms
• e.g. tapeworms
(class Cestaoda)
• live in intestines,
absorb nutrients
• Scolex (head) has
hooks and
suckers to
attach
• Produces eggs in
proglottids
(segments)
Tapeworm
Marine Flatworm
Marine Flatworm
Nematoda
• Round worms
• Bilateral symmetry
• Pseudocoelemate…2 layers with
fluid in between
• Complete digestive system (2
openings)…specialized organs
with specific functions
• Separate sexes
• Many are parasites
Roundworms
• Ascaris
– Live in intestines block them
• Hookworms
– Live in intestinal wall, feed on blood anemia
• Trichinella
– Live in muscle pain, stiffness, death
• Pinworms
– Live in mesentaries of intestine, crawl out at night to lay
eggs
• Filarial worms
– Live in lymph system
– Elephantiasis
– Heartworms
Ascaris Worms
Hookworms
Heartworm
Trichinella
Pinworm
G
Pinworm
Filarial worms
Filarial Worms
Elephantiasis
• Even once the
worms are
removed, it will
stay like this the
rest of their life
• Often infects
genitalia/anal
• Often gets other
infections that
kill the person
Annelida
• “little rings”… segmented worms
• bilaterally symmetrical
• complete digestive tract
• true coelem … 2 layers, space
between, allows body to
expand/contract in parts
• segments allow worm to survive
when some parts are damaged
Segmented worms
• Earthworms
– Moves via setae, and 2 sets of muscles
(circular and longitudinal)
• Squeeze circular muscle, and worm anterior
moves forward, plants setae, squeeze
longitudinal muscles to bring posterior
up
– Complete digestive system (mouth,
pharynx, crop, gizzard, intestine,
anus)
– Closed circulatory system (blood moves
posterior on dorsal side, anterior in
ventral side)
Segmented worms
– breathe through skin (why you see them
on sidewalk when it rains)
– ventral nerve cord and cerebral ganglia
(“brain”)
– nephridia (primitive kidney) in each
segment
– hermaphroditic, but exchange sperm to
reproduce, then lay eggs
– clitellum secretes mucus to hold them
together
Earthworm
Leeches
• No setae…sucker at each end
• Secrete an anesthetic, so you
don’t feel them, and a
anticoagulent to keep blood
from clotting
• Will fall off when “full,” otherwise
pull them off (don’t cut or
burn!)
• Used for reattachment surgery!
Class Hirudinea
OK…to end on a
peaceful note, these,
too, are segmented
worms….
They’re marine worms
called feather dusters…