Download Nematoda

Nematoda
By: John Lee, Jon Fuller,
and Vicky Hung
Phylum & Sample Animals
 Phylum: Nematoda
 Classes: Adenophorea,
Secernentea
 Sample Animals:

Caernorhabditis Elegans

Trichinella Spiralis
 Involves in aging in human
 It’s a model organism for
research
 Acquired by ingesting
infected pork
 Develop along the
intestinal muscles
 Invades muscle cells and
control it.
Body Cavity
 Pseudocoelom:
It has a body
cavity only
partially lined
by tissue
derived from
mesoderm.
Body Symmetry
 Radial Symmetry.
 Any imaginary slice
through the central
axis divides the
animal into mirror
images.
 They have no head
or read end, no left
and right side.
Nervous System
 Nematodes have a simple nervous
system, with a main ventral nerve
cord and a smaller dorsal nerve cord.
http://www.absoluteastronomy.com/topics/Nematode
Circulatory System
 There is no circulatory system
Digestive System
 Nematodes have a digestive system which
includes separate sites for food intake.
 The system is divided into three parts:
stomodeum, intestine, and proctodeum.
 The stomodeum consists of the esophagus,
the “mouth” and “lips”, and buccal cavity.
http://nematode.unl.edu/digestive_system.html
Excretory System
 Simple and tubular with no
cilia/flagella.
 Consists of one or two single celled
glands called renette cells
 Functions: (1) excretion of metabolic
waste, (2) Osmoregulation, (3)
secretion and export of hormones to
target tissues,
http://www.infoplease.com/ce6/sci/A0835177.html
Locomotion/musculature
 Movement due to longitudinal
muscles that when contracted
produced a thrashing motion.
Skeletal Type
 Nematodes have a hydrostatic
skeleton.
 The pressure from the pseudocoelom
and the muscles change an
organism’s shape and produce
movement.
http://www.ucmp.berkeley.edu/phyla/ecdysozoa/nematoda.html
Sensory Structure
 Nematodes have
amphids, and
phasmids.
 Amphids are on
the anterior.
 Phasmids are on
the posterior
end.
http://www.ucmp.berkeley.edu/phyla/ecdysozoa/nematoda.html
Reproductive system
 Reproduction is usually sexual.
 Involves internal fertilization.
 Female may deposit 100,000 or more
fertilized eggs per day.
 Zygotes are resistant cells and can
survive harsh conditions.
 Females are larger than males
Gas Exchange
 Gas exchange occurs through
diffusion.
 Some parasitic nematodes have a
form of hemoglobin in the body
fluids.
 Anaerobic and Aerobic metabolism is
also common.
http://entomology.ifas.ufl.edu/creatures/nematode/marine_nematodes.htm
Unique Features



Trichinella (a type of
nematode) has been dubbed
“animals that act as viruses”
because they invade muscle
cells and control genes which
code for proteins which make
cellselastic enough to house
nematodes.
The Cuticle which is a hard
exterior that the worm sheds
and excretes as it grows.
Blastula


Resulting from the folding of
the mesoderm.
Protosome
Questions
1. How do the nematoda use there
musculature for motion differently from the
others?
2. What is the skeletal system called? What
does this mean?
3. Why are some nematodes called “animals
that act like viruses”?
4. Which type of symmetry do nematodes
exhibit? How can you tell?
Answers
1.
2.
3.
4.
Nematoda have longitudinal muscles that they
contract rapidly and create a thrashing motion.
They have hydrostatic skeletal systems that react to
the environment and the pressure that is exerted
upon them
Some have learned to control the muscles of humans
in order to receive the nutrients they need to survive.
The nematodes have radial symmetry that can be
proven by the fact that they can be cut anyway
through the central axis to create mirror images.