Have you ever thought about worms? Most people think of earthworms, like the common “Lumbricus terrestris,” also known as night crawlers. But did you know there are about 6,000 different types of earthworms alone? And that’s just a small part of the worm world! There might be hundreds of thousands of worm species out there, and some are as different from each other as we are from starfish. To learn more about these fascinating creatures, let’s dive into a conversation with Dr. Anna Phillips at the Smithsonian’s National Museum of Natural History.
Worms are long, thin creatures without backbones. But not everything that looks like a worm is actually a worm. The term “worm” is a general way to describe a certain body shape. There are about twelve different groups, or phyla, of worms. In the animal kingdom, a phylum is a big group of animals that are very different from each other. For example, humans belong to the phylum Chordata, which means we’re more closely related to squirrels and fish than any worm is to another worm.
At the museum, Dr. Anna Phillips shows us some fascinating worm specimens. There are marine worms called polychaetes, and there are worms like nematodes and tapeworms that live inside other animals. Tapeworms have a complex life cycle, starting as larvae before becoming adults in a different host. They might look like spaghetti, but don’t be fooled—they’re not for eating!
One of the most interesting worms is the giant Amazonian leech. This leech, affectionately called “Grandma Moses,” is quite large and feeds on blood. Leeches are part of the phylum Annelida, making them close relatives to earthworms. Unlike earthworms, leeches have a unique way of feeding, and they are hermaphrodites, meaning they have both male and female reproductive organs.
Collecting leeches can be an adventure! Dr. Phillips explains that to find leeches, you might have to wade into lakes or ponds and do the “leech dance” to attract them. It’s a bit like a dance move where you make ripples in the water to get the leeches’ attention. Once they attach, you carefully check your legs and remove them.
Worms are incredibly diverse and can be found in almost every environment on Earth. They live in oceans, freshwater, soil, and even inside other animals. There are about 66,000 known species of worms, but scientists believe there could be over 250,000 species waiting to be discovered. That’s a lot of work for worm scientists!
Worms play important roles in ecosystems. They help decompose organic matter, enrich the soil, and serve as food for other animals. Understanding worms can teach us a lot about biodiversity and the history of life on Earth. So, if you’re curious about nature, consider exploring the world of worms. Who knows, you might become a worm scientist and help discover new species!
Gather materials to create a small worm habitat. Use a clear container, soil, and organic matter like leaves or vegetable scraps. Observe how worms interact with their environment over a week. Document your observations and share them with the class.
Research and create a poster that classifies different types of worms into their respective phyla. Include images and interesting facts about each type. Present your poster to the class and explain the differences between the phyla.
Simulate the “leech dance” in a safe environment. Use a shallow tray of water and small objects to mimic leeches. Experiment with different movements to see which attracts the objects most effectively. Discuss why these movements might attract real leeches.
Participate in a role-play game where you act as different types of worms. Each student will receive a card with a worm type and its role in the ecosystem. Interact with classmates to understand how each worm contributes to the environment.
Choose a specific worm species to research in-depth. Create a report or presentation that includes its habitat, life cycle, and ecological importance. Share your findings with the class to help everyone learn about the diversity of worms.
**Sanitized Transcript:**
**Emily:** This episode is brought to you through a collaboration with the Smithsonian’s National Museum of Natural History in Washington, DC, and the Field Museum in Chicago, Illinois.
**Emily:** What do you think of when I say “worm”? My first thought is earthworms. The one most people are familiar with is “Lumbricus terrestris,” sometimes referred to as night crawlers. But I recently learned that there are around six thousand named and described species of earthworm alone. This is just the tip of the worm iceberg. There’s so much more to know about them, mostly because “worm” is a deceivingly misleading concept with no easy definition or description. In fact, there are perhaps as many as a few hundred thousand species of worms, and some of them are as different from one another as you or I are from a starfish. To help me answer the question, “What is a worm?” I came to the Smithsonian’s National Museum of Natural History to talk with Dr. Anna Phillips, who’s one of three curators of worms.
**Emily:** We are here. What collection are we in?
**Anna:** We are in the invertebrate zoology collections at the National Museum of Natural History, the Smithsonian. This room houses everything from mollusks to arthropods and crustaceans to worms.
**Emily:** So how many worms do you have in the collection here? I mean, the Smithsonian Museum has some of the largest collections in the world, if not the largest worm collection.
**Anna:** We have at least four hundred and twenty-seven thousand specimens of worms; we probably have more.
**Emily:** So, can you define what a worm is?
**Anna:** There are things that tend to be long and thin, and they don’t have backbones. There are a lot of things that can be like that that may not actually be worms, so it’s a little bit of a difficult question. It’s a general term that describes a sort of body plan. It may be surprising to some people, but there are many different kinds of worms out there. Turns out there’s about twelve phyla of worms in the world.
**Emily:** And so, if you can imagine the taxonomic tree of life, what does it mean to be a separate phylum?
**Anna:** So it goes from kingdom, phylum, class, order, family, genus, species. Phylum means that they’re all within the animal kingdom, and they all are very, very different from each other.
**Emily:** So what phylum are people in?
**Anna:** We’re in Chordata.
**Emily:** So we are more closely related to squirrels, lizards, snakes, and fish than any of these worms are related to one another.
**Anna:** Right.
**Emily:** So can we talk about some of these different worms now that we sort of know that “worm” is like a catch-all phrase?
**Anna:** Here we have a selection of some worms. Some of these are the larger specimens. We have everything from some polychaetes—these are marine worms—and then we also have worms that live inside of vertebrates, like nematodes and tapeworms, some of the larval stages of parasitic worms.
**Emily:** Like this one, these weird balloon things.
**Anna:** So these are larvae of tapeworms.
**Emily:** Those are baby tapeworms.
**Anna:** Yeah.
**Emily:** Really cute.
**Anna:** It’s a little different because they have complex life cycles, so they’re going to pass through this larval stage on their way to being an adult and a different host. You wouldn’t necessarily recognize that this worm looks very similar to this.
**Emily:** Yeah, like I mean this looks like some spaghetti.
**Anna:** Yeah, a lot of people compare it to pasta.
**Emily:** We probably shouldn’t do that; it will ruin pasta for people.
**Anna:** Don’t eat tapeworms.
**Emily:** Yeah, no, bad idea.
**Anna:** Not an approved weight loss method.
**Emily:** What other worms are we talking about today? Well, look at this guy!
**Anna:** Yeah, this is one of my favorite specimens.
**Emily:** Who’s this?
**Anna:** This is a giant leech. So this is the giant Amazonian leech, so you can guess where they live. Generally in the wild, they’re a little smaller, so this guy lived in a lab and had as much food as he wanted.
**Emily:** And when you say food, I mean, are you putting kibble in its tank?
**Anna:** No, this one feeds on blood. We affectionately call this leech “Grandma Moses” because she is quite large.
**Emily:** How long did she live in the lab?
**Anna:** I don’t know, but there’s a very famous picture of a famous leech biologist with Grandma Moses laying on his arm.
**Emily:** I really feel like I’ve met a celebrity leech today. And what kind of worm are they?
**Anna:** They are in the phylum Annelida. So leeches are our closest relatives to earthworms. They look a little different to a scientist because we know certain characteristics to look for, namely because they have that blood-feeding nature, whereas earthworms do not. But one of the things that makes earthworms and leeches similar to each other is that they are hermaphrodites, so they have both sexes at one time. Whereas the next closest relatives, the polychaetes, like marine worms, many of those are separate sexes.
**Emily:** How does one collect leeches?
**Anna:** It depends on which kind of leech you’re going for. My research was with medicinal leeches that like to feed on humans. That involves going out into places where you expect to find leeches, like lakes, ponds, and streams, and rolling up your pants legs and wading in. You make a little bit of movement—you do the “leech dance,” I like to say.
**Emily:** Is there an actual movement?
**Anna:** Yeah, you want to make ripples in the water so the leeches can feel the movement.
**Emily:** So there’s choreography to this.
**Anna:** Yes.
**Emily:** So you do the leech dance.
**Anna:** So you’re both moving at the same time, and they both stop, and you wait for the leeches to attach.
**Emily:** Wait, it’s like waiting for the bass to drop.
**Anna:** So then you have to pull one leg up at a time and examine to see if there are leeches on each leg.
**Emily:** Really slow?
**Anna:** Yeah, and of course, you’re standing in mud and rocks, and you’re trying to keep your balance, so it’s a very active sport.
**Emily:** I’m so tempted to try this the next time I’m in a swampy freshwater environment.
**Anna:** You should come out sometime; I can show you some really fun leeches.
**Emily:** Yeah, it will be the leech dance or yoga moves.
**Anna:** This is awesome. So when you talk about the number of specimens that are in the collection, are they all preserved in alcohol like this, in jars?
**Anna:** Another way of preserving worms, especially the very small ones, is best shown on glass slides. Because of the twelve phyla of worms that we have in our collection here, many of them are very small.
**Emily:** So these are the charismatic megafauna of the worm world.
**Anna:** Yes, exactly.
**Emily:** And for that, we have the biggest worm I’ve ever seen in my life.
**Anna:** This is, I think, the largest worm in our collection. This is what we call a super worm. So this worm was collected in the Caribbean, and the scientist who collected it saw a worm coming out of a coral reef. It was really big, and he grabbed it. But a lot of these worms will do is when they feel endangered, they will release part of their body.
**Emily:** Oh my goodness, that must be like five or six feet long.
**Anna:** Yes.
**Emily:** And this isn’t even the whole worm.
**Anna:** No. We don’t know how long the part was that got away.
**Emily:** How does the worm have any business being that large?
**Anna:** Just imagine what it eats.
**Emily:** So you mentioned that there are twelve different phyla of worms. How are there so many different kinds? How are they able to diversify so much?
**Anna:** Worms, in general, these phyla are very old groups in terms of the history of life and the history of animal life. When you’re that old, there are many different environments that they’ve been able to get into and diversify by and specialize in. So we have worms that live in the ocean, worms that live in freshwater, obviously worms that live on land because they’re in the soil like earthworms, and even worms that live inside of vertebrates. So just about anywhere you can think about, there’s probably a worm living there.
**Emily:** They’ve been able to colonize virtually every environment on the planet.
**Anna:** So there’s lots of diversity out there that we haven’t been able to collect yet, or that we have collected but haven’t described.
**Emily:** So, do you know how many different described worm species there are?
**Anna:** So at this point, just doing some rough calculations, it seems like there are around sixty-six thousand species of worms that are described.
**Emily:** That are already described—sixty-six thousand.
**Anna:** Right. There could be more than two hundred fifty thousand species of worms that are waiting to be described. What we need is more worm scientists.
**Emily:** There are so many worm scientists. That’s a lot of work that has to be done.
**Anna:** Yeah.
**Emily:** And I think it’s so…
**Anna:** Pretty daunting.
**Emily:** And it’s amazing if you think about worm diversity in comparison to vertebrate diversity. Like how many mammal species are there? There’s maybe eight or nine thousand species of mammals—just eight or nine thousand—and you’re talking about a quarter of a million different species of worms. I think everybody should be a worm scientist. You’ll never get all the work done otherwise.
**Anna:** We need help.
**Emily:** Yeah, come help Anna.
**Anna:** And then you have to pull out one leg and look carefully to see if you can see leeches on it. And if you do, then you pull them off.
**Emily:** Leeches, leeches, leeches.
**Anna:** Yes, you grab all the leeches.
**Emily:** This is me at the club.
**Anna:** (laughs)
Worms – Worms are long, soft-bodied invertebrates that often live in soil and help decompose organic matter. – Earthworms play a crucial role in breaking down dead leaves and enriching the soil.
Biodiversity – Biodiversity refers to the variety of living organisms in a particular habitat or ecosystem. – The Amazon rainforest is known for its incredible biodiversity, housing thousands of different species.
Ecosystems – Ecosystems are communities of living organisms interacting with their physical environment. – Coral reefs are vibrant ecosystems that support a wide range of marine life.
Species – A species is a group of similar organisms capable of interbreeding and producing fertile offspring. – The giant panda is an endangered species found in the mountain ranges of central China.
Leeches – Leeches are segmented worms, some of which are known for feeding on the blood of other animals. – In some ecosystems, leeches play a role in controlling the population of other aquatic animals.
Soil – Soil is the upper layer of earth in which plants grow, composed of organic matter, minerals, and living organisms. – Healthy soil is essential for growing crops and supporting plant life.
Marine – Marine refers to anything related to the sea or ocean. – Marine biologists study the diverse life forms that inhabit the ocean.
Phylum – A phylum is a major taxonomic group of organisms, ranking above class and below kingdom. – The phylum Arthropoda includes insects, spiders, and crustaceans.
Larvae – Larvae are the immature forms of animals that undergo metamorphosis, such as insects and amphibians. – The caterpillar is the larval stage of a butterfly.
Decomposers – Decomposers are organisms that break down dead or decaying matter, returning nutrients to the ecosystem. – Fungi and bacteria are important decomposers in forest ecosystems.
