Nematode Nervous System

Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

Nematodes, or roundworms, are a diverse and interesting group of animals. In this lesson, you'll learn about their simple nervous system, which helps the worm move and react to its environment.

Phylum Nematoda

Nematodes are the roundworms that belong in phylum Nematoda. There are lots of different kinds of 'worms' in the world, but we're not talking about the earthworms in your backyard. No, nematodes are things like hookworms, heartworms, whipworms, and pinworms. There are tens of thousands of named species in this phylum that include some free-living worms, as well as both animal and plant parasites.

Many nematodes are agricultural pests.
nematode soybean pest

Nematodes are interesting animals because they have bilateral symmetry, meaning that their two sides are mirror images of each other (like you and me!), and they also have a complete digestive tract that runs from one end of the body to the other. Nematodes also have a simple nervous system, which is the focus of this lesson.

Nematode Nervous System

Despite being a very diverse phylum of worms that range from the very short (a few millimeters) to the very long (several meters!), nematodes have strikingly similar body forms. They have that bilateral symmetry we talked about, but they are also long and thin, much like you would expect a worm to be. Throughout this long, thin body runs a nervous system that consists of four longitudinal nerve cords. These run dorsally (along the back), ventrally (along the bottom), and laterally (on both sides).

All four nerve cords fuse at both the head and the tail end of the worm. If we look to the head we find the 'brain,' though these worms don't really have a brain per se. It's more like a ring that forms around the worm's pharynx at the back of the mouth area. This nerve fusion is called the head ganglia. Where the nerves fuse at the tail end is called the tail ganglia.

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