Nematoda

1
Nematoda

• By John Lee, Jon Fuller, and Vicky Hung

2
Phylum Sample Animals

• Phylum Nematoda
• Classes Adenophorea, Secernentea
• Sample Animals
• Caernorhabditis Elegans
• Involves in aging in human
• Its a model organism for research
• Trichinella Spiralis
• Acquired by ingesting infected pork
• Develop along the intestinal muscles
• Invades muscle cells and control it.

3
Body Cavity

• Pseudocoelom It has a body cavity only partially
  lined by tissue derived from mesoderm.

4
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.

5
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

6
Circulatory System

• There is no circulatory system

7
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

8
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.h
  tml

9
Locomotion/musculature

• Movement due to longitudinal muscles that when
  contracted produced a thrashing motion.

10
Skeletal Type

• Nematodes have a hydrostatic skeleton.
• The pressure from the pseudocoelom and the
  muscles change an organisms shape and produce
  movement.

http//www.ucmp.berkeley.edu/phyla/ecdysozoa/nemat
oda.html
11
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/nemat
oda.html
12
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

13
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
14
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

15
Questions

• How do the nematoda use there musculature for
  motion differently from the others?
• What is the skeletal system called? What does
  this mean?
• Why are some nematodes called animals that act
  like viruses?
• Which type of symmetry do nematodes exhibit? How
  can you tell?

16
Answers

• 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.