High Tide Aquatics

Pests under microscope... what are these things?!

Recently I've had a lot of brownish stuff covering the sand, and to an extent the rocks too. At first I thought it was diatoms, but after reading more, dinoflagellates sound more likely. I have a cheap USB microscope that I use for electronics so I decided to put a sample of the sand under it to see what they look like.

The video is sped up by 6x to make the movements more obvious. The width of the full image is about 2mm.


It looks like there are maybe three things here:

1) Large roundish things moving around quite a bit. Unsure if they are moving on their own, or water movement is blowing them around.
2) Small elongated things crawling around. Are these dinoflagellates?
3) Small round things stuck to the sand that don't appear to be moving much if at all.

Can anyone with more biology knowledge help me identify these?
 
That is awesome, I looked into getting a microscope for my tank but life distracted me from the idea, would you mind sharing what telescope you used? My only hesitation last time was lack of knowledge and not being able to pick a specific one.

Thanks in advance.
 
Nice recording. It would help me take a more educated guess about what these might be if I knew the magnification level. How much water flow is passing over the areas you're filming? It is possible that a lot of the movement is just from water movement. However, all dinoflagellates have 2 "tails" called flagella (singular: flagellum) that allow them to move around. One of these flagella is "furry" and is used to steer the cell while the other is a "whip" flagellum used for propulsion similar to the flagellum of a human sperm cell.

Without the magnification level, I can't be certain that these guys are within the size range of dinoflagellates, but we must remember that there are over 2000 species of dinoflagellates (including the "zooxanthellae" that live in our corals). The largest ones are just visible as little specks to the naked human eye and the smallest ones require a microscope to notice them at all.

If these little guys are moving on their own, they are almost certainly not diatoms as diatoms cannot move on their own (except for their version of sperm, which do have flagella, but are almost certainly too small to be seen at this magnification level).

Another interesting possibility is that the larger things you're seeing there are coral or other invertebrate larvae. Have any of the corals or clams or anything in this tank spawned recently?

The truth is that the microscopic world is so diverse that, in many cases, it is difficult or impossible to confidently identify individual organisms without DNA evidence. Give me more info about these images (or a higher magnification) and maybe I could take a better guess as to their identity.

I'll leave you all with an interesting fact about our family history. You probably all already know that we are cousins with all other animals, including fish, corals, and even sponges. But dinoflagellates and diatoms are so distantly related to us that they make us and bread mold (and all other fungi) look as if we are siblings by comparison. Yet even dinoflagellates and diatoms look like our close relatives compared with most life on earth: bacteria. Through this lens, it's pretty easy to feel a kinship with the pets in our aquaria :)
 
Great reply, @gaberosenfield! Thanks a lot.

The full width of the frame is 2mm across. (measured by pointing it at a ruler using the same magnification). That makes the larger objects around 40-50um in diameter, and the little rod-shaped guys about 20um long and 5um wide. Unfortunately I can't get any more magnification with my crappy little microscope. As far as I know, nothing has spawned though I suppose I could be unaware of it.

This was taken with the sand/water sample on a small saucer, so there's no active water movement. I'm unsure how much water movement to expect at this scale just from other organisms moving around, or from residual energy when the saucer was moved?

The larger things seem as though they are attached to threads and blowing in the wind, but perhaps I'm imagining that.

Very interesting about our relative distance to various organisms. If mold really is like a sibling, it would explain why it's always getting into my fridge without asking. :D

Anyway, this is making me want to get a decent microscope. :) If I were to get a regular, compound microscope, can it be used for top-illuminated objects like this or do slides have to be prepared?

Thanks again for the info!
 
That is awesome, I looked into getting a microscope for my tank but life distracted me from the idea, would you mind sharing what telescope you used? My only hesitation last time was lack of knowledge and not being able to pick a specific one.

Thanks in advance.

I have this one: https://www.adafruit.com/products/636

Works well for electronics (usually on the lowest magnification). I definitely wouldn't recommend it for looking at aquarium stuff though. It's a pain to adjust (you have to physically adjust the height of the microscope to focus) and as you can see, the magnification isn't quite enough.
 
The full width of the frame is 2mm across. (measured by pointing it at a ruler using the same magnification). That makes the larger objects around 40-50um in diameter, and the little rod-shaped guys about 20um long and 5um wide.

These sizes put both the larger and smaller guys within the size range of dinoflagellates. It also puts the larger guys in the size range of coral or other invert larvae.

If this is in a saucer, they are probably moving on their own power, although some of the smaller movements could just be due to brownian motion. I don't see any threads in the video, but I understand why you say that as it does look like most of the larger guys are kind of twisting around the same spot. It is certainly possible that they are connecting themselves to the substrate somehow, but I really can't tell from the video.

If I were to get a regular, compound microscope, can it be used for top-illuminated objects like this or do slides have to be prepared?

One can illuminate sample from the top while using a compound microscope. However, you will need to use slides anyway if you want to get higher magnification images because the higher the magnification, the closer the lens must be to your sample. By the time you get up to 200x magnification (20X objective + 10X eyepieces), your objective would be in the water in your saucer and I'm sure the saltwater would ruin your objective! But slides and cover slips are dirt cheap and can even be reused for your purposes. I could just give you a few if getting those is a problem.
Some advice for those shopping for a compound microscope to explore the tiny world around us:
1) newer != better
2) off brand chinese microscopes are often lower quality
3) you get what you pay for (to an extent)
4) the best microscopes will have 4 different contrast settings: Bright Field (BF), Dark Field (DF), Phase Contrast (PC, often referred to as just "phase"), and Differential Interference Contrast (DIC). All microscopes offer BF, because this is simply shining light through the sample towards your objectives. DF is just like looking at a negative version of BF. PC allows you to see differences in the refractive index of different parts of your sample. This means that you can often see little organelles and flagella and things using PC that you could not see with BF. Both BF and PC only give you a 2D image, but DIC gives you a sort of 3D image based upon the difference in refractive indicies of different parts of your sample. It isn't a true 3D rendering of the sample, but it does give you a different view.

Here is an example of the same human cheek cells in BF (a), PC (b), and a technique similar to DIC (c):
upload_2016-1-22_12-25-42.png
(Source: https://micro.magnet.fsu.edu/primer/techniques/contrast.html)

My parents purchased a compound light microscope for my 16th birthday. In retrospect, although it looks cool, it isn't a great instrument. It was a relatively cheap ($300) chinese knock-off that only does BF. I would not purchase a compound microscope that doesn't at least have PC. DIC is a nice touch, but comes at a higher price. Without PC, you will have trouble visualizing the details of samples without killing and staining them, which is probably more trouble than beginner microscopists want to get into. Plus then you can't watch them swim around :) If I were in the market now, I would purchase a used on brand micrsocope, just like this one on ebay. A decent used microscope like this will probably put you out at least $500, but I don't really think it's worth it to buy a crappy one. Feel free to ask me about any specific microscope you're thinking about purchasing. Just a final disclaimer: I am not a microscope expert. I know the basics of how to use them, and that's about it!
 
This one might also be cool because it is inverted, allowing you to use a little clear saucer or petri dish to view and manipulate samples while you're watching them. However it comes with lower power objectives, so you can only get 200X maximum magnification (which is probably plenty unless you want to see subcellular structures clearly or bacteria).
 
It may be possible, but if the USB camera isn't designed to fit that particular microscope, you may have to do some finagling. Additionally, remember that the eyepieces on that scope add 10X magnification to the image, so removing one will decrease the maximum magnification to 20X. My experience has been that you would be better off getting a piece of PVC pipe that fits tightly over the eyepiece and fitting that to the camera, so you can just take pictures through the eyepiece. However, it never works as well as a camera that is designed to fit on the camera mount of a trinocular scope. Unfortunately, a trinocular scope will cost you more, and unless your camera is designed for that particular scope, you may still have to do some finagling.
 
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