Download Pseudocoelom

Phylum Nematoda
The Roundworms
What are Nematodes?
• 80,000 species of roundworms are
known
• There may be about 800,000 species
that have yet to be identified!
• They are among the most numerous of
all animals
» > 1 million roundworms present in one shovel load
of soil . . .
Lifestyles of Nematodes
• Many nematodes are
free-living
• Freshwater and
marine environment
• Moist soil
• Parasitic forms
• Affecting BOTH
plants and animals
• Troublesome in
agricultural practice
“What do they look like?!?”
~ General Characteristics ~
• Bilateral Symmetry
• Anterior / posterior
• Dorsal / ventral
• Cylindrical bodies
• Tapered at both ends
• Covered by tough
cuticle
Nematoda
• Range in size
• < 1 mm extending up to
> 1 meter
But what about the inside?
Internal Structure of Nematodes
• Pseudocoelom … at last!!!!
. . .but its fake!!!
» NOT completely lined with mesoderm
• They have a “tube-within-a-tube” structure
What about
digestion?
• Simplest animals
having a complete
digestive system:
– Two separate
openings
– One-way flow
– Digestive gland to
aid in digestion
Definitely motile . . .
• Roundworms have a
simple nervous
system and welldeveloped muscles
– Muscle fibers located
in body wall
– Move in whip-like
fashion
The Success of
Roundworms
• Specialized
Reproductive
System
– Separate sexes
– Internal fertilization
within female
– Fertilized eggs have
thick outer shell
(free-living forms)
– some release juvenile
larva(parasitic forms)
Internal Fertilization
Parasitic Roundworms
• Many harmful effects
– Agricultural
»Deformatio
n of roots
– Health related
»Infection
of other
animals
Agricultural Parasites
• Roundworm damages plant cells
– Nematode can pierce through tissues
• Results in damage to roots
– Inhibits efficient root function
– Limits growth
Carrot root
nematodes
Health Concerns
• 250 million people in
the tropics are
infected by
roundworms of the
group Filaria
– Results in conditions
such as elephantiasis
Sanitation: an end to roundworms
• Many of the diseases caused by
roundworms can be prevented through
adequate sanitation practices
– Good personal hygiene
– Water treatment facilities
– Washing and proper cooking practices
Phylum Nematoda : looking back
• Major advancements include:
– The presence of a coelom
– But, remember . . .
» Pseudocoelom!!
– Complete digestive tract
– Separate mouth and anus
– Accessory digestive gland
– Reliance on sexual reproduction
– With internal fertilization
– Production of capsule around egg
– Release of larval stage