ID Help

[JimT]

These guys swim exceedingly fast. Finally it slowed down enough for a quick photo. About 60 um's. No cilia apparent but I think a small flagella on the flat side which is the rear although not visible in this image. Reminds me of a slice of bread.

Canon 60D with 20x obj. Any guesses appreciated.

[gekko]

My guess (and it is only a guess) is that it has another flagellum, and that this is a dinoflagellate (maybe Peridinium sp.?)

[actinophrys]

I'll second that these seem like dinoflagellates, particularly if they were flattened. Those have two flagella from the middle, but the anterior one is tied around the girdle so not very apparent. Most are brownish, yellow, or green. This would probably not be Peridinium, which are armoured so more angular, but they tend to be hard to identify.

If they were colourless and more cylindrical, the other type with this shape is Urocentrum. Those are ciliates, but with cilia in only two bands plus an off-centre tail spike, which might seem flagellum-like if they did not stay still. They have a posterior contractile vacuole and a neat habit of spinning in place.

[JimT]

Colourless and flat. They move really fast and no spinning. First time I saw these was last year and I called them the sliced bread protist. They have a flagella in the rear because sometimes it will attach to some debris and they drag it along like a tail. The fact that they sometimes drag a "tail" leads me to think that it must have other means of propulsion but nothing I could see. Even when this one finally slowed down I could not see any other cilia or flagella. Also doesn't look like any of the dinoflagellate images I have seen on the WEB.

Thanks for the input. If I get another chance I will try to take better pictures and get some DNA

JimT