|
Phylum Nematoda
Canadian Campbell Page 745 - 746)
These are the so-called round worms and are unsegmented. Representatives of this group may be free-living, animal parasites or plant parasites. Nematodes cause such important human diseases as ascariasis, elephantiasis, hookworm and pinworm, to mention a few. Nematodes are also important in causing diseases in various wild and domestic animals and plants.
Examine the cross-sections of Ascaris (Male
and Female)
Examine
the preserved Ascaris from your lab
Note the general body form as well as the sexual dimorphism between males and females. Most nematodes have this same basic body plan despite the variety of habitats they occupy. Note the arrangement of the three body layers, ectoderm, endoderm and mesoderm. A special body cavity known as the pseudocoelom exists between the endoderm and mesoderm.
Examine a fresh mount of the vinegar eel Turbatrix
An example of an interesting as well as important nematode is Parelaphostrongylus tenuis. The adult of this worm is found on the covering of the brain for that reason it is commonly referred to as the meningeal worm. In Manitoba, this parasite is normally found in deer and moose. It is a relatively innocuous parasite in deer, but in moose, the worm is found within the nervous tissue of the brain rather than on the covering of the brain. Here it causes serious damage often leading to the death of the infected animal. P. tenuis is a relatively common parasite in the southeastern region of Manitoba, and according to some reports, the parasite is extending its range in a westerly direction.
