A Primer on Marine Flatworms for K-12 Students

Department of Natural Resources and the Environment

College of Life Sciences and Agriculture

University of New Hampshire



Day-Glo Worms

When you think of worms, images of earthworms, roundworms, tapeworms, inchworms, or silk worms may pop into your mind, and in many cases, you may think of them as "yucky" or "slimy." But did you know that some of these animals are not even worms? Silk worms and inchworms, for example, are the larvae of moths.

So then, what are worms? To a zoologist, "worms" is a group of mostly long, creeping or wriggling invertebrate animals. Animals are divided, based on their body plan, into about 40 groups called phyla. Of these phyla, about half are worm-shaped.

Some of the worm phyla include the Annelida or segmented worms, the Nematoda or round worms, the Nemertea (ribbon worms), the Platyhelminthes (flatworms), the Echiura (spoon worms), the Sipunculida (peanut worms), and the Gastrotricha and Kinorhyncha, two phyla of tiny marine worms that don't have common names (although Gastrotricha translates into "bellyhairs" because these worms glide around on tiny hair-like structures along their bottom sides; Kinorhyncha means "movable snout" because these animals can withdraw their heads into their necks).

In these web pages, we concentrate on a group of flatworms called Polycladida. We want to show you how beautiful, interesting, and exciting these flatworms can be. We will take you on a tour of their biology, show you how they eat, live, and mate. We will also tell you about their past history, and how we can use flatworms today to teach us about the health of the environment. Although we will be concentrating on this particular group of flatworms, we have provided links for you to web sites covering other flatworms and other worms.

To navigate the primer, use the buttons in the right panel.


These pages are for educational purposes only. If you use any of the information or the images in your classes, please credit these web pages. © MK Litvaitis, 2005

Photo credits to Leslie Newman, Andrew Flowers, or Anne DuPont, unnless otherwise indicated.


Use the Links Below to Learn More About Marine Flatworms

striped flatworm

orange and blue striped flatworm

To report problems or broken links, please contact m.litvaitis@unh.edu