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In this section, we will explore the general body parts of a nematode by looking at the systems and the
funtions of the different structures within them. We will refer to the diagram on the right for the various sections of this page.
For your convenience we have broken down the structures into the following sections:
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The nematode’s anatomy consists of structures that provide survival and existence
for the organism. Without these crucial anatomical characteristics the organism
may be limited or all together non-existent. Before one looks at these
characteristics it is wise to first gain some knowledge about the origins of
the various structures of the nematodes.
Ectoderm: excretory system, nervous system, epithelial of the rectum, epithelial cells of the pharynx, epithelium of the mouth, body of the epithelium
Mesoderm: glia cells, somatic gonad cells, post embryonic mesoblast, intestinal muscle cells, anal depressor muscle, anal sphinctor muscle, body-wall muscle cell
Endoderm: intestines
Germ cells
Note: It is not necessary that all structures will be described in detail in the following section.
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Nematodes have a linear digestive system.
Digestion is mostly extracellular and nutrients are absorbed by the thin wall of the intestines.
Pathway of food: mouth(stoma) --> pharynx --> intestines --> rectum --> anus
Waste is given off once every 1-2 minutes.
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Nematodes rely on their skin for respiration. There are no specialized organs for gas exchange which
occurs across the extracellular levels. Wastes leave through the gut or diffuse back across the body wall.
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RENETTE is their glandular system whose function is believed to be something like an excretory system.
RENETTE varies among the species.
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Nematodes have both male and female organs.
However, most nematodes have separate sexes,
where they are either male or female at a given time, but never both at the same time.
This characteristic is called GONOCHORISTIC.
This feature allows cross-fertilization (variety) to occur.
HERMAPHRODITISM occurs in some species, particularly in C.elegans.
In this case, the nematode gonads produce and store spermatozoa until the eggs are produced.
PARTHOGENISIS can also occur.
This is when an unfertilized egg can become completely functional without sperm fertilization.
This unfertilized egg is able to become a completely functional adult.
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- Seminal Vesicle: Sperm storage area
- Vas Deferens: Tube that carries the sperm away from the testis. It is usually subdivided into a tubular and grandular reigon.
- Ejaculatory duct: Conducts the release of the sperm out of the male's system.
- Testis: Sperm is produced here. One testis is most common in nematodes, however 2 testes are also possible.
- Copulatory Spicules: Help to
dialate the vulva and can serve as a canal for the sperm.
- Bursa: Bodywall around the cloaca, helps to orient the male and holds the two nematodes together for mating purposes.
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- One or Two Ovaries: Produces the oocytes.
- Seminal Receptacles: Stores the sperm until they are ready to fertilize the oocyte. This is where the eggs are fertilized.
- Uteri: Where the oocyte develops into an egg.
- Orijector: Muscular structure that assists in expelling the egg through the vagina.
- Gonopore: Contains muscles that dialate the vulva in order for insertion of the male reproductive structure for successive sperm deliverance.
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FACT or fiction?
Question: Male nematodes are usually (with slight exceptions) twice the ‘size’ of the female nematode.
Question: Different types of spermatozoa can be used to characterize different taxonomic groups of nematodes.
Question: Depending on taxonomic groups some nematodes lay eggs while others give birth to live nematodes.
Question: A female's oviduct can not be used to characterize different orders.
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Basics