Nematoda

Phylum & Sample Animals Phylum: Nematoda Classes: Adenophorea, Secernentea Sample Animals: Caernorhabditis elegans a model organism for research – human aging. Trichinella Spiralis Ingesting infected pork Invades muscle cells and control it

Body Cavity Pseudocoelom: It has a body cavity only partially lined by tissue derived from mesoderm.

Nervous System Nematodes have a simple nervous system main ventral nerve cord and a smaller dorsal nerve cord.

Digestive System Nematodes have a digestive system separate sites for food intake. Those that are free-living (not parasitic) Digest dead matter, returning usable nutrients to soil or marine environment

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.

Body Structure

Reproductive system Usually sexual. Involves internal fertilization. Females…100,000 fertilized eggs per day! Zygotes are resistant cells and can survive harsh conditions.

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.

Hookworms, Pinworm & Filarial worm Elephantiasis

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?

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.