Worms and worm-like micro-organisms are some of the oldest living creatures on the planet. So it’s no wonder scientists often observe worms under a microscope. It has always been fascinating to look into the intricate details of organisms that lived millions of years in this world. Over time, worms have evolved into distinct organisms.
Studies about ancient worms in fossils revealed that they have features still present in their modern-day descendants. For instance, the fossilized bristle worm found in British Columbia in 2018 is believed to have lived 500 million years ago. It has tiny hairs made for swimming and tube-like palps that work as sensory organs. They are considered the ancestors of leeches and earthworms.
Early Studies About Worms
One of the first studies about worms was done by Antoni van Leeuwenhoek in 1674. He used a microscope and discovered tiny creatures living in the water. He believed that these creatures were essential to explaining why there is mud and slime on earth. Later, scientists associated his observations with roundworms and parasitic worms.
MIT Professor Phillip Sharp and his colleagues determined that worms reproduce by growing their sperm. It allowed them to penetrate the outer cells of a female worm, which attaches itself to the uterus.
Also, Charles Darwin, who studied worms during his travels, was one of the first scientists to conclude that earthworms are beneficial for human beings. They left behind nutrient-rich soil, which benefits plants and flowers. In addition, they help aerate the ground through their tunneling activities.
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Introduction to Worms
Worms are soft-bodied invertebrates that live on the earth’s surface, in water or soil. They range from microscopic bacteria to several feet in length. These oganisms come in many different colors and shapes. Some can even change their body color to lure prey, while others camouflage themselves to protect themselves against predators.
Worms are essentially legless and move by creeping using specific muscles, but organisms with the hair-like structure that helps their movement.
Worms can be found in a variety of locations throughout the world. While earthworms may be found in many wet terrestrial settings (in the dirt or decaying organic debris), Polychaetes are common in marine environments.
While some types of tubeworms (Riftia Pachyptila) dwell on the seafloor and form a beneficial symbiosis with sulfur bacteria, other worms may be parasites that live in plants, animals, and even in the human body.
The following physical characteristics know worms:
- Most species have a digestive system
- All have a nervous system
- Worm bodies are formed from a primary germ layer
- These creatures have a coelom as a body cavity
Common Types of Worms
Many types of worms exist in the world today. For instance, leeches, tapeworms, and roundworms are three common worm families. However, there are other types of worms that live in unique environments.
- Leeches – have been known to humans since ancient times. There are more than 650 species of leeches in the world. Also, these worms are known to feed by attaching their teeth-covered or sucker-shaped ends to animals or humans.
- Tapeworms – are segmented worms that usually live in the intestines of vertebrates like pigs, cows, and humans. Tapeworm can also be found in insects, snails, and fish. Their segments reproduce independently inside their host’s digestive system by growing eggs or releasing larvae into the water with their feces.
- Roundworms – have a cylindrical body surrounded by a layer of adherent cells. They do not have mouths or digestive tracts, so they absorb nutrients through their skin. Roundworms live in the inner layers of moist soil and feed on organic matter. In humans, these often cause illness when ingested from undercooked food.
- Polychaete worms – is segmented worm that lives in marine environments. They have long hair-like arms called parapodia, which they use to move along the seabed and feed on bacteria. In general, these worms may look like serpents when seen from a distance.
- Hookworms – are parasitic creatures that live in the small intestine of humans and animals. These worms can cause severe blood loss, malnutrition, anemia, and even death.
- Pseudobiceros fulgor – is a type of marine flatworm that inhabits coral reefs, seagrass beds, and the ocean’s depths. These worms have two lips on their heads and can move forward or backward using a wave-like motion.
- Yellow Papillae Flatworms – are free-living organisms that feed on plankton and small creatures. These organisms have a fleshy, gelatinous body with numerous brownish-yellow protrusions coming from their surface.
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Objectives of the Experiment
It is always an exciting experiment to discover the unique structures of this creepy crawlies under an electron microscope. It is also an exciting task to observe how worms move when placed under a microscope.
A worm under a microscope may be used to compare one type of flatworm, roundworm, and segmented worm to another. It will also allow researchers to identify specific similarities and distinctions between these worms.
With such experiments, students will learn the following skills:
- Using an electron microscope to observe a specimen
- Understand specimen preparation for observation
- Compare and contrast the worm shapes of the three categories.
Using a magnifying glass to examine the worm before viewing it under a microscope is always advised. It will give the student a broad view of what the specimen looks like.
Because a magnifying glass has lower magnification power than a microscope, it may be used to magnify the image many times to get an overall sense of the morphology.
Preparing for the Experiment
You may use prepared slides of worms or place your specimens directly in your slides. The latter will give you better results because you can adjust the electron microscope set to get more detailed images of your subject. You can also choose to light your worm specimen using a dark field or bright field.
The following are materials you will need to prepare for this experiment:
- Cotton swabs and ethanol (95%) to clean the slides
- Slide, coverslip, and tape
- Microscope mounted with 100-200x objective lens
- Tweezers and forceps for manipulating specimens
- Darkfield and bright-field settings
- Petri dish
- Mini Shovel
- Specimen (earthworm, eelworm, and planarian flatworm or tapeworm)
Procedure for Collecting Specimen
- When collecting specimens, put on gloves and use a sieve to collect dirt and soil samples.
- Take out the worms using the tweezers from the ground and transfer them into a petri dish. You may need to cover it partially to prevent them from escaping.
- Take a look at the container’s water to determine whether you can get any flatworms or tapeworm. Use a container to take water from a shallow pond or river.
- Here, you’ll have to examine more carefully and use the magnifying glass on the water to see if you were successful.
- These worms are tiny, typically ranging from 3 to 15mm in length. They may be black, gray, or brown, depending on the type.
Since eelworms are so tiny (0.4-1.2 mm) that they can be challenging to spot with the naked eye, collecting them might be tricky. However, the worms may be found by recognizing an infected crop, such as tomatoes or rhubarb, potatoes, etc.
The following technique may be used to collect eelworms:
- Break the infected portion of the crop (e.g., leaves) into tiny pieces
- Place the leaves in a glass container with water for 30 minutes.
- After 30 minutes, you’ll notice eelworms (in a group) crawling around the bottom of the container.
- Take off the water carefully, avoiding the eelworm mass.
- You can keep the eelworms in the jar or gently pour them into a Petri dish with a bit of water.
- After you’ve captured the entire sample in each Petri dish, use the magnifying glass to examine carefully. It may be done while the worms are still in the dish.
Observing Worms Under a Magnifying Glass
Segments on the skin along the worm’s whole length will be visible under a magnifying glass, revealing its complex structure. These dividers enable the creature to flex and twist at will. If you have access to proper lighting, you may discern the worm’s internal organs (e.g., vessels) under it. On the other hand, some species might have a darker epidermis, making it difficult to identify anything.
The head at the front of the body is tiny and pointed (smaller than other segments). In the middle of the body, you will notice a distinct area that appears swollen and lighter in color than different sections. The clitellum is a segment near the midsection of the body that plays a role in reproduction.
You may also observe the setae, hair-like structures on the segments and skin, and the earthworm’s cylindrical body using a magnifying glass.
Flatworms have an elongated body but are significantly smaller (3 to 15mm) than earthworms with a flattened body (leaf-like). They are usually colorless but may have some pigmentation, so it is difficult to observe the belly. However, you will be able to notice its triangular or leaf-like anterior sections under a magnifying glass.
The posterior end (tail) is more pointed than the anterior part (wide). Eyespots may also be seen near the head region and a pharynx positioned in the middle of the body (central portion of the body).
Compared to Earthworms and Flatworms, eelworms are notably smaller in form. They are also cylindrical-shaped, but the abdomen is distinguishable. In addition, eelworms aren’t segmented, unlike worm species that may be observed under a magnifying glass.
It would be impossible to tell one part of the body from another under a magnifying lens. They may, however, be observed moving in a group.
The Earthworm Under The Microscope
With an electron microscope, you’ll be able to see both the outside skin and internal (through dissection) anatomy of the earthworm.
You will need the following for this experiment:
- Earthworm specimen
- Glass slide
- A pair of tweezer
- Alcohol solution
- Place a drop of alcohol solution on a glass slide and place the earthworm specimen on it. Be sure that the specimen is within the field of view under the lens.
- Switch on your microscope and observe what you can see from different magnifications.
- Using tweezers, carefully remove the earthworm’s skin (outer covering) and observe the internal parts. The clitellum will be in the middle part of this organ, an essential reproductive organ in earthworm species.
- Make a cross-section through the worm’s structure (e.g., using a scalpel). Observe what you can see from different magnifications form.
- Continue making cross-sections from different parts of the worm. Observe what you can see from different magnifications, as well as dissection (if possible).
Apart from an electron microscope, a stereo microscope can be used to observe the external anatomy and the earthworm. For this experiment, the procedure is as follows:
- Place the worm in a Petri dish and then turn the revolving turret to fix the lowest magnification objective.
- Place the Petri dish on the stage and carefully inspect it. Focus by gently rotating the focus knob while looking through the eyepiece.
- The condenser may be adjusted to change the light’s intensity.
- After focusing on the images, look for the worm’s anterior end and then move the setup to examine the anatomy of the rest of the creature.
- To expose the worm further, place the object at lower power (high magnification) and repeat the process. Make notes while doing so.
To observe the behavior of a live earthworm, repeat these procedures and watch how the body and mouthparts move.
Observations on the Earthworm
A fleshy bump can be seen at the front of the worm under higher magnifying power. It is known as the prostomium, and it surrounds the worm’s mouth area. The anus is located at the rear end of the worm. A septum may be visible between individual small body segments under a microscope.
The worm’s ventral aspect (which is rounded and darker) is flatter than the dorsal side (which is pointed and paler). The setae (minute hair-like bristles) and pores (pores on each body segment) may also be seen. Aside from the pores on the body regions, you should also acquire a good view of larger pores (genital pores) near the worm’s front end.
Dissecting the Earthworm
To further study the worm’s internal anatomy, you need to dissect it for another observation under the microscope.
The requirements for dissection include:
- dissecting tray
- dissecting pins
- earthworm specimen
- dissecting blade, knife, or scissors
The procedure will be as follows:
- Place the specimen on the dissecting tray with its belly facing up.
- Secure the specimen’s end with the dissecting pins. It will entail pinning both ends of the sample so that it does not move during dissection.
- Using the blade, make a small incision below the clitellum.
- Using the forceps, lift the skin and insert the dissecting scissors before cutting along a straight line towards the head and towards the rear end.
- Remove the epidermis using forceps and carefully place it into the tray. It will take many pins to ensure that the worm’s internal anatomy can be seen clearly.
Things to Observe
The internal anatomy of the earthworm may be seen in detail as you examine it. It will showcase clear images of the head and skin surfaces.
You will be able to see the following:
- The heart of the worm is formed by five dark loops surrounding the esophagus.
- The pharynx is located at the front of the worm, in the mouth. It’s made up of a few muscles and will look like a barely pigmented organ.
- The reproductive organs are near the heart, and they’ll appear as white or translucent tissues.
- The gizzard is located behind the crop and is used to store food.
- The intestine is a long tube that extends from the gizzard to the rear of the body.
- The dorsal nerve cord – which is found on the rear of the body – may be seen by shifting the intestines to one side (The nerve cord will resemble a long white string where the blood passes).
The Flatworm Under the Microscope
For observing the flatworm, you need to prepare the following materials.
- Compound Microscope
- Glass slides
The procedure for observing live flatworms will be as follows:
- Add a tiny amount of hot agar (4 to 5 percent agar) on a clean glass slide – The agar used for this technique is Oxoid Agar Technical and cupric sulfate.
- Use a new slide to smooth the agar.
- After the agar has solidified, carefully remove the slide (used to flatten the agar)
- Add a droplet of water to the agar with a dropper.
- Place the flatworm on the drop of water and top with a coverslip carefully to avoid escape of the specimen.
Before carefully pressing the coverslip against the flatworm, a little bit of vaseline should be applied to the edge of it. Be careful not to crush the specimen.
Observing the Flatworm Under the Microscope
After preparing the slide, the next step is to observe the flatworm. The procedure will be as follows:
- Turn the turret to set the lowest power objective in position before mounting the slide.
- Place the slide on the stage and secure it with the clips.
- Look through the eyepiece and turn the focus knob to bring the image into sharper focus.
- Using the stage adjustment knob, move the stage gently to view different parts of the sample.
- Switch to a higher power to inspect the sample.
- Before removing the slide, lower the stage.
Things to Observe
If you look at a flatworm, you’ll notice that it is flattened (resembling a flat-leaf plant). The eyespots are near the head area (anterior portion of the worm) may also be seen. These colored cuts are sensitive to sunlight and serve as eyes.
The head may have a pointed profile on the sides, depending on the species. Auricles are these points, which serve as sensitive sensory organs for smell and touch. It’s also feasible to detect the pharynx that feeds in the midsection.
The Eelworms Under the Microscope
Compared to earthworms and flatworms, eelworms are significantly tinier in form. Therefore, you may need a culture media to grow them first before inspecting.
To culture eelworms, you will need the following materials:
- Glass culture dish
- vinegar eels
- cider vinegar
The procedure will be as follows:
- Using a dropper, add 200ml of vinegar into a clean glass culture dish.
- Cut the apples and add them to the glass dish in slices.
- Cover the container and introduce the eelworms (to minimize evaporation, cover the container loosely)
- Using a clean pipette, agitate the culture (to force air into the culture medium)
It’s also possible to view the image using a stereoscope after examining the Petri dish (with a dark paper beneath it)
Observing the Roundworm (Eelworm) Under the Microscope
To start observing the eelworm, you have to prepare the following materials.
- Compound microscope
- Glass slide
The procedure will be as follows:
- Try putting a few specimens on the bottom of the Petri dish (in the liquid culture) using a dropper.
- About two droplets of the liquid should be placed on several glass slides.
- Mount the slide on the stage (following the steps outlined above) and check it out at low magnifications first before going to higher magnifications.
Things to Observe
If a worm is found, it will be translucent like the epidermis of an earthworm. The eelworm will be cylindric (tube-like) with a pointed posterior compared to the flatworm’s body.
The body posterior may be observed through higher magnification. The mouth and esophageal bulb is seen at its anterior, with an intestine running from there to the animal’s rear.
The reproductive organs are also visible, usually at the end of the worm.
Many different types of worms may be found throughout the world. Some exist in a free-living state while others are considered parasites and creepy crawlies.
It’s also beneficial to collect a wide range of bacteria and organisms from your area (or even order them online) and compare their anatomical features in an attempt to discover how they survive in their unique settings.
But what’s more important is that you can quickly learn about these creatures by using a microscope. Observing the worms (and other living things) may prove to be challenging, but it will be worthwhile once you discover exciting features of their anatomy and habits under the microscope.
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