Nematoda
By: John Lee, Jon Fuller, and Vicky Hung
Phylum & Sample Animals
Phylum: Nematoda Classes: Adenophorea,
Secernentea Sample Animals:
Caernorhabditis Elegans Involves in aging in human It’s a model organism for
research Trichinella Spiralis
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?
Answers1. Nematoda have longitudinal muscles that they
contract rapidly and create a thrashing motion.2. They have hydrostatic skeletal systems that react to
the environment and the pressure that is exerted upon them
3. Some have learned to control the muscles of humans in order to receive the nutrients they need to survive.
4. 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.
