I have been seeing lots of these but what are they

[D0c]

As the title says what are these I keep seeing them and i cannot make up my mind.

My gut says some sort of Litonotus sp.

https://www.flickr.com/photos/154534235 ... ateposted/
https://www.flickr.com/photos/154534235 ... ateposted/

[Bruce Taylor]

We see a very flat, lanceolate cell, with a ridged upper surface...obviously a pleurostomatid. I agree that these look, overall, like some kind of Litonotus (as loosely defined). However, they don't fall neatly into any of the common species I know about, and it's difficult to see their features clearly in these videos. I can't see any oral extrusomes, if they are present (an important feature for identifying pleurostomatid ciliates). I find it very difficult to see the exact distribution of contractile vacuoles (there are hints, now and then). We don't see somatic ciliation at all, and the macronuclear nodules are none too clear. Finally, how big are these guys? Size matters.

So, we don't have a lot to go on, apart from the overall cell shape, which is somewhat reminiscent of Litonotus armillatus, but evidently longer (and without the distinctive CV placement of that species). Recent work on pleurostomatids has revealed new Litonotus-like genera, such as Apolitonotus and Protolinotus, reminding us that there is more diversity within the group than earlier workers suspected. So, while I could be overlooking something common and obvious, I'd be reluctant to shoehorn these guys into a genus, or even a family, without seeing things like the distribution of extrusomes (which in this group are toxin-containing darts, used to immobilize prey). I would put them in order Pleurostomatida, and try to observe more specimens as closely as possible to record traits that would help narrow things down.

[D0c]

Thanks Bruce.

Below is couple more videos of them. The first video is interesting in certain parts you can see two macronucleus in the centre of the body and a small CV in the tail.

As far size I estimate them to be about 200µm. They are also very quick and very supple so very hard to keep in focus.

https://www.flickr.com/photos/154534235 ... ateposted/
https://www.flickr.com/photos/154534235 ... ateposted/

[charlie g]

Thanks DOc for these wee protists from your collecting. Indeed thank you Bruce T. for the quick and polished assesment of field markings of this live and furtive wee protozoan, and your suggestions for what would enable a more specific taxonomic sorting out of this wonderful creature in our world.

Have you ever considered using methylcellulose 1.5 % on a slide of these organisms ( 50/50, water sample/methylcellulose) use with your wetmount slides, DOc? This viscosity tool slows your observed organisms down..much less traumatically than simply squashing the organisms under a drying out wet-mount slide cover slip.

Videos capture behaviors of our neighbor protists and meiofauna...but with viscosity tool of methylcellulose ...you can go as far as 100X objective ( hmmm...I have no higher mag objective than 100X)...to drink up, to savor rich aspects of organisms structure and functions...all quite a treat for your video observation projects. thanks for this shared observation of a protozoan ( I love this word: protozoan, even with authors clarifications on it's limitations...said authors keep use of : protozoa alive in current communications.) thanks for this shared microscopy, DOc charlie guevara, fingerlakes/US

[D0c]

I have heard about methylcellulose and have considered using it but unfortunately have not got round to buying some yet but I think I will now. I usually just put the slide to one side and wait for the water to evaporate a bit and then take another peek. I can see the benefits of using methylcellulose as some of these protists are pretty quick.

Thanks for words of advice charlie they are much appreciated.

[Bruce Taylor]

The second set of videos clarifies a few things. We see multiple contractile vacuoles, apparently in a row along the dorsal surface. I think I caught a quick glimpse of oral extrusomes, at one point...really hard to be sure, though.

For immobilizing ciliates, especially large ones, a recommended technique is to place a dab of vaseline on each corner of the coverslip, then gently compress the mount with something like a dissecting needle (being careful not to press so hard that you explode the poor ciliate). You can achieve similar results by using an absorbent tissue to suck out water from the edge of the coverslip. This will distort the cell shape, but in many cases will pin the ciliate in place so that you can study it closely. Some cellular features (such as somatic ciliation) will be more easily visible if you open the iris diaphragm and enhance contrast in your camera software; others (e.g. extrusomes and CVs) are easier to see with the diaphragm closed and illumination increased.