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Ecdysozoa-Molting Animals
Ecdysis- “an escape”
-molting of exoskeleton or cuticle
Phyla- Nematoda and
Arthropoda
Phylum Nematoda
1. Nematodes:
roundworms
2. Nemata- “ thread”
3. Bilateral symmetry
4. Tube within a tube
structure-mouth and
anus
5. 3 germ layers w/
pseudocoelom
6. Smaller than
flatworms, taper at
both ends
Pseudocoelomate
Ectoderm
Mesoderm
Endoderm
Fluid filled cavity between the endoderm and ectodermpseudocoelom
Differs from a true coelom because….
• It is not entirely lined with mesoderm tissue
• Organs are not suspended or attached to membranes3
(mesenteries)
Lifestyle
1. Thick outer covering (cuticle) to
protect them from harsh environment
ex. Stomach acid
2. Move bodies with thrashing motion
3. Free living-Decomposers and
predators (tremendously abundant)
4. Parasitic- ex. Ascaris, hookworm,
heartworm-host is dog
5. Sexually reproduce:
• most are separate sexes
• some species are hermaphrodites
Nematodes
 Found everywhere




Soil
Oceans
Polar ice
Hot springs
 Parasites of nearly all
plant and animal
species!
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Body Systems
 No Respiratory or Circulatory Systems- limits
size of worm due to distribution of nutrients via
osmosis and diffusion
 Complete Digestive
 Nervous
 Muscular
 Excretory
 Reproductive
Digestive System
Complete Digestive Tract Mouth
 Pharynx
 Intestine
 anus
Muscular System
 Longitudinal muscles
only
 creates thrashing
movement
Nervous System
Nerve ring – “brain”
Dorsal and
ventral nerve cords
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Excretory System
 Excretory cells
 Ducts
 pores
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Nematode Reproductive Systems
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Dioecious- separate
sexes
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Life cycles of parasitic
roundworms
ASCARIS
•
lives in intestines and
feeds off blood
•
ingest eggs from dirty
hands or unwashed
veggies contaminated
with fecal matter
•
eggs hatch in intestines
and enter bloodstream
•
larval worms bore into
lungs, must be coughed
up and swallowed
•
move to intestines
where they mature
TRICHINELLA
•bore into muscles causing
painful cysts or live in
intestines
• ingest cysts in
undercooked/raw meat
(usually pork)
•cysts open up in intestines
and reproduce there
• larvae move into muscle
tissue and form cysts
HOOKWORMS
• lives in intestines
• feeds on blood, causes
major damage to intestines
• eggs deposited on soil from
contaminated wastes
• larvae live in soil
• burrow into feet or exposed
skin of host
• larvae travel through
bloodstream, to lungs,
coughed up, swallowed
• attach to intestinal wall
where they mature
PINWORMS
• most commonly infects
children
• lives in intestines
• ingest eggs from
contaminated soil or
sand
• hatch in intestines
• female lays eggs near
anus at night causing
severe itching
Wuchereria bancrofti
 Lives in lymphatic
system
 Obstruct lymph to
cause swelling
 Elephantiasis
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Elephantiasis
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Life Cycle of Wucheria spp.
Fig. 11.15
11-13
Source: Redrawn From Centers for Disease Control, Atlanta, GA.
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Loa loa
 Eye worm
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Dracunculus medinesis
 Fiery serpent
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Dirofilaria immitis
 Dog heart worm
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The End
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