nematoda by: john lee, jon fuller, and vicky hung

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.