What are Roundworms? - Types, Examples & Characteristics

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  • 0:01 An Intestinal Infection
  • 0:48 What Is a Roundworm?
  • 1:14 Characteristics
  • 1:57 Types
  • 3:31 Treatment & Prevention
  • 4:21 Lesson Summary
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Lesson Transcript
Instructor: Ebony Potts

Ebony has taught middle and high school physical science, life science & biology. She's also been an assistant principal and has a doctorate in educational administration.

Have you ever heard of roundworm? Do you know anything about this kind of parasite? In this lesson, you will learn about the different types of roundworms and some of the characteristics they share.

An Intestinal Infection

''Come here, boy'', you yell, calling your dog Charlie in from the yard. Charlie is your beloved pet and your daily responsibility - you feed and walk him every day. But within the past few days, you've noticed that Charlie has been acting strangely. He seems a little tired, and you've noticed that his stomach is swollen. As time goes on, you notice that Charlie is getting worse rather than better, so you take him to his veterinarian. Dr. Ruiz gives Charlie a series of tests and, within a couple of days, calls you back with the results. You learn that your dog has heartworms, a type of roundworm.

What are roundworms and how did Charlie get them? Will he be alright? Dr. Ruiz assures you, that since the infection was caught early enough, Charlie will be just fine. Let's take a few moments to learn more about roundworms.

Hookworm, a type of roundworm

What is a Roundworm?

Roundworms, also known as nematodes, are parasitic worms that comprise the phylum nematoda. This phylum is made up of at least 25,000 known species, and some scientists believe the actual number could be much higher. They can be found everywhere, including in topsoil and in the water. Many roundworms infect an organism's intestine to survive, just like the ones that were living in Charlie. Roundworms can infect humans, cats, birds and many other types of animals.


Some nematodes live in so many different environments, they're different in many ways. For example, roundworms in environments with low food supply tend to be hermaphroditic - they have both male and female parts and so can self fertilize their eggs and carry them until they hatch. Other nematodes reproduce sexually, meaning there are males and females, and both participate in the production of offspring. But roundworms also have many shared characteristics. All Nematodes:

  • are invertebrates, and many are microscopic
  • have an elongated, slender, snakelike shape
  • have a rigid but flexible cuticle outer layer
  • move with a whip-like motion
  • have a sense of touch and can detect light and certain chemicals
  • breathe across their whole body
  • obtain nutrients via diffusion


While we couldn't possibly discuss each of the thousands of identified roundworms, we can talk about the most common types. The most famous nematodes are the ones that cause infection, like the roundworms that infected Charlie.

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