Using a Microscope to hunt Rotifers!

Using a Microscope to hunt Rotifers!

A rotifer is a microscopic aquatic organism belonging to the phylum Rotifera. Rotifers are incredibly diverse and are found in various freshwater and marine environments, including ponds, lakes, rivers, and even damp soil. They are also known as "wheel animals" due to the presence of cilia on their heads that create a rotating, wheel-like motion, allowing them to move and feed.

Here are some key characteristics of rotifers:

  1. Size: Most rotifers are quite small, ranging from around 50 micrometers to a few millimeters in length. Despite their small size, they are complex multicellular organisms.

  2. Body Structure: Rotifers have a well-defined body structure with a head, trunk, and foot. The head often bears a crown of cilia, called the corona, which creates the characteristic rotary motion used for locomotion and feeding.

  3. Feeding Mechanism: Rotifers are primarily filter feeders, using their corona to create water currents that bring in microscopic particles, such as algae, bacteria, and other organic matter. They have a specialized structure called the mastax, which contains jaws known as trophi. These trophi grind and break down the ingested particles before they enter the digestive system.

  4. Reproduction: Rotifers can reproduce both sexually and asexually. Asexual reproduction is common and often involves the production of eggs that develop into offspring without fertilization. Sexual reproduction typically occurs when conditions are less favorable and involves the formation of specialized reproductive structures.

  5. Diverse Species: There are thousands of known species of rotifers, each adapted to specific environmental conditions. Some species are free-swimming, while others are sessile or attached to substrates.

  6. Role in Ecosystems: Rotifers play an important role in aquatic ecosystems. As filter feeders, they help control the population of microscopic algae and bacteria, contributing to nutrient cycling and maintaining water quality. They are also an essential food source for many small aquatic organisms.

  7. Resilience: Rotifers are known for their ability to survive in a wide range of environmental conditions. They can endure extreme temperatures, high salinity, and even desiccation. Some rotifer species form protective structures called cysts during unfavorable conditions, allowing them to survive until conditions improve.

Because of their small size and importance in aquatic ecosystems, rotifers are commonly studied in ecology, biology, and environmental science. Their rapid reproduction, diverse adaptations, and unique features make them fascinating subjects for scientific research and exploration.

Typically you would use a DIC Microscope to explore your sample and enjoy viewing these fascinating creatures.  Our top choice for a DIC scope would be the Olympus BX51 DIC 

A differential interference contrast (DIC) microscope, also known as Nomarski interference contrast microscope, is a specialized type of light microscope that enhances the contrast and provides detailed visualization of transparent and unstained specimens, such as living cells and small organisms like rotifers. DIC microscopy is particularly useful for observing structures with subtle variations in refractive index, which might not be easily visible under conventional brightfield microscopy.

When using a DIC microscope to observe rotifers, here's how the process might work:

  1. Sample Preparation: Collect a water sample from the aquatic environment where rotifers are expected to be present. The sample should be carefully collected to avoid damaging the delicate organisms.

  2. Slide Preparation: Place a drop of the water sample onto a glass microscope slide. You can use a cover slip to gently press down and spread the sample evenly, making sure not to crush the organisms.

  3. Microscope Setup: Set up the DIC microscope with the appropriate objectives for the level of magnification you need. DIC microscopy requires specialized optics, including polarizers and prisms, to generate contrast by detecting differences in refractive index.

  4. Polarization: DIC microscopy involves splitting a light beam into two polarized beams that pass through the specimen and then recombine. As the polarized beams pass through different areas of the specimen with varying refractive indices, interference patterns are created, resulting in enhanced contrast.

  5. Observation: Look through the microscope eyepieces and adjust the focus and the DIC optics to optimize the contrast and visibility of the rotifers. The organisms will appear in three-dimensional relief, with light and dark areas that highlight their structures and movements.

  6. Image Capture: If needed, you can capture images or videos of the rotifers using a digital camera attached to the microscope or through an integrated camera system.

Remember that observing live rotifers can be a bit challenging due to their small size and their potential movements. It's important to handle the sample gently to avoid disturbing or damaging the organisms. Additionally, DIC microscopy requires some expertise in microscope operation to achieve the best results.

If you're specifically interested in observing rotifers, it's also worth considering other microscopy techniques, such as phase contrast microscopy or darkfield microscopy, which can provide valuable insights into their behavior and structure without the need for staining or intricate sample preparation.

We feature several videos by our friend Desirée, that include Rotifers and other microorganisms on our Instagram page  

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