Tardigrades that seem cute to some and creepy to others are interesting living creatures contributing to the ecosystem. They are widely observed by students and researchers when studying microscopes and microscopic examinations. Tardigrades usually live in ponds, lakes, and meadows but also found in deserts and sand dunes.
But How to Observe Tardigrades Under the Microscope?
This article covers the appearance of tardigrades under a microscope, their impact on human health, and how they contribute to the ecosystem.
Table of Contents
Can You See a Tardigrade under a Microscope?
The answer to whether you can see Tardigrades under a microscope relies on another question, “How big are tardigrades?”
Tardigrades are 0.5 to 1 mm long and can be easily observed under a light microscope. Typically, choosing the best compound microscope is preferable, but you can also use a stereo microscope with 40x magnification.
When observing tardigrades under a light microscope, ensure your microscope offers at least 40x to 100x magnification to see the sample thoroughly. Furthermore, a digital microscope will help you take images and videos while observing the tardigrade.
Prepare slides or use permanent mounts to study tardigrades under a stereo or compound microscope.
Besides bright field, dark field microscopy offers better imaging because of a dark background, while phase contrast allows you to study the structure more clearly. At the same time, polarizing microscopy gives them a colorful appearance.
How to Find a Tardigrade for Observation under Microscope?
Tardigrades live on mosses on low and high altitudes, so you can probably find one on a moss around you. While you set out on your hunt for a moss, make sure you have the following at hand:
- A container with water
- Microscope
- Slides and coverslips
- Dropper or pipette
Here’s how to find and observe a tardigrade under a microscope:
- Look around in a park or garden to find moss.
- Bring it home and soak it in a small container with water for an hour.
- Use a dropper or pipette to take out the water sample from the bottom without mixing it.
- Transfer the water sample to a slide and cover it with a cover slip and prepare a wet mount.
- Observe this slide under your light microscope to find the tardigrade.
Repeat the same process without disturbing the water if you do not spot a tardigrade on the first attempt.
Tardigrades are not as small as bacteria, allowing you to observe the structure explained later in the article. Sometimes, you may not see them moving, but in their dormant state.
How to Activate Tardigrades for Observation under Microscope?
Apart from the method explained above, you can follow a different process to give time to dormant tardigrades to activate for better examination.
- Divide your moss samples into small pieces.
- Transfer the pieces to multiple strainers lined with tissues.
- Place each strainer (with tissues and sample) in a separate bowl.
- Pour distilled water over the moss until it touches the bottom of the moss in the strainer.
- Let them sit overnight.
- Remove the strainer with the samples in the morning.
- Then, use a dropper or pipette to take water from the bottom of each bowl and drop it into a slide or petri dish.
- Observe the samples under the microscope one by one, and you might get to see one or more moving tardigrades.
Leaving the samples overnight allows the tardigrades to rehydrate and return to their normal state so you can observe the structure easily.
What is a Tardigrade?
Tardigrades, also known as water bears or bears of the moss, are tiny eight-legged animals primarily visible under the microscope; the names come from their preference to live on mosses and lichens.
Tardigrades got their name, tardigrade, in Italian from the Latin word translating to slow walker. These invertebrates walk slowly on their short legs, propelling from one area to another.
Despite being so small, they are put into the kingdom Animalia because of their structure and features. They belong to extremophiles and are believed to be the first organisms to leave the ocean and settle on dry land. However, tardigrade animals need a thin layer of moisture (water) on their bodies to prevent dehydration.
These tiny animals exhibit excellent resilience because of a damage suppressor (Dsup) in their DNA that protects them from ionizing radiation and extremely high or low temperatures.
Tardigrades reproduce sexually and asexually by either parthenogenesis or the male depositing the sperm in the cuticle of an egg-carrying female; the eggs may take 40 to 90 days to hatch.
Tardigrade Anatomy & Physiology
Scientists have identified over 1,300 species of tardigrades globally with a similar basic structure comprising a tough cuticle. They all belong to the phylum Tardigrada and shed their cuticles to grow over the years. These 0.5 mm long organisms also have muscles, eyes, a brain, a complete alimentary canal, and a digestive system.
Furthermore, tardigrades obtain nutrients from plants and microbes through their bucco-pharyngeal apparatus by sticking to them using four to six claws on each foot.
Their body is divided into five body sections, four of which have pairs of legs with claws, and one is the head. The legs on the last segment are backward, allowing them to grasp surfaces for movement and ingestion.
Tardigrades Living States
The tardigrade life cycle comprises three basic living states: active, anoxybiosis, and cryptobiosis.
- Active: It refers to the tardigrades’ reproduction and growth period. They eat, fight, grow, and reproduce in the active state.
- Anoxybiosis: Anoxy means a lack of oxygen; thus, this state of their life activates in areas lacking oxygen. Tardigrades swell up and float around until the oxygen levels settle down, and they can enjoy their active living state.
- Cryptobiosis: Cryptobiosis is the state of being ‘almost dead,’ but not dead; it occurs when their habitat is dry. Tardigrades squeeze the water out of their bodies and roll into a dry ball called a Tardigrade tun to survive. They retract their limbs and heads, impacting their normal bodily systems and entering a dormant state (no metabolic activity). They lose 97% of their body moisture and appear one-third of their original size.
Are Tardigrades Harmful to Humans?
While these tiny organisms live around us comfortably, they do not pose harm to humans. Instead, they colonize harsh environments that provide food to larger creatures. Tardigrades are not a part of drinking water or food naturally and are not added to edibles either.
You might think, “Still, what if I swallow tardigrades?”
Tardigrades can survive many harsh conditions, but (fortunately) the stomach acid disintegrates its structure. So, don’t worry; you won’t get an infection.
Tardigrade Fun Facts
Tardigrades are Older than Dinosaurs
Dinosaurs are known to be around 400 million years old, whereas the presence of tardigrades goes back almost 600 years, making them even older!
Germans Called them Kleiner Wasserbär
German pastor J.A.E. Goeze described these tiny organisms in 1773 for the first time; he called them kleiner Wasserbär in German, translating to little water bear.
Tardigrades are Born Adults
Opposed to humans, frogs, or even closely related arthropods, tardigrades are born in their fully developed form, only slightly smaller in size. They shed their cuticles throughout their life but do not undergo metamorphosis or any other similar developmental process.
2.5 Years Tardigrade Life Span
The normal lifespan of a tardigrade is approximately 2.5 years, yet cryptobiosis allows them to live for years and decades.
They’re Heads Only
Though the segments of tardigrades’ bodies are categorized into one head and five body segments, researchers mention that their segmented bodies closely resemble the heads of arthropods. So, they may just be called a couple of heads.
Tardigrades can Reproduce Even After Freezing
A researcher kept two tardigrades in a freezer for over 30 years, and they survived through cryptobiosis. Just after 22 days of their rehydration, researchers observed eggs inside one’s body, eventually resulting in 14 live hatchlings.
They Inspired Glass-Makers
Tardigrades are said to survive in their tun state by turning their cell fluid into a glasslike substance that protects their biological structures. In 2015, scientists developed a glass type that resembled crystals and was more efficient at directing light. So, it could improve the efficiency of LEDs, solar cells, optical fibers, etc.
Tardigrades may even Survive the Apocalypse!
Tardigrades may be tiny, but they are tough organisms who may outlive everyone. They can live for over 30 years without water or food. Moreover, they have been subjected to -272.95°C, 150°C, 40,000 kPa, high concentrations of carbon monoxide and sulfur dioxide, and managed to return to their active life. If you wonder, “Can tardigrades survive in space?” They have been in space and survived the high-temperature UV rays. So, yes, they can!
The Bottom Line
Tardigrades are tiny organisms, around 0.5 to 1 mm long, living in water and land. Researchers have found 1,300 species of tardigrades so far, and they all belong to Tardigrada. While their average life span is 2.5 years, tardigrades can live for decades, thanks to cryptobiosis. In extremely harsh conditions, they squeeze themselves, turning into dry balls called tuns that make it possible for them to survive. While tardigrades can survive extreme temperatures and high pressure, stomach acid kills them. So they do not infect humans.
FAQs
Can you see a tardigrade with your eye?
Tardigrades are not generally observable until you put effort into seeing them. Their size (1 mm) allows them to be seen by the human eye in the right light. However, you cannot see their structure in detail, and they require a microscope for that.
Can children observe tardigrades?
Examining tardigrades under a microscope with children can be a fun activity. They can help you with sample preparation and study the slide; if you do not want to risk an expensive microscope, get a microscope for children under 5 years or older according to your needs.
Can a tardigrade bite you?
Tardigrades have the potential to stick to and bite human skin, but no species have been seen to do so. Thus, you do not have to worry about being bitten by a tardigrade during examination.
Do tardigrades have a heart?
While tardigrades have a brain and a digestive system, they do not possess particular organs for respiration or blood circulation. They use their body cavity fluid to transport oxygen and blood.
What has to happen for a tardigrade to become a tun?
Tardigrades curl up into a ball-like structure and shrink their bodies to one-third by squeezing all the water out. They synthesize trehalose sugar that replaces the water they lose when becoming tardigrade tuns.
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