A small flagellate; sorry, no photo (picture added)

[Pat Thielen]

I'm not sure if anyone can help with this as I wasn't able to get a photo. I saw a small flagellate, oval in shape, obviously moving rather quickly with his flagella. The off thing is he had a strand that came off his end -- Like a long flagella but it wasn't moving (a tail, I guess). I would guess that he was maybe 100 - 125 microns long (including the extra flagella). So, a bit bigger than a Euglena and smaller than a paramecium.

Any ideas? I've not seen this particular animal before.

[75RR]

It is not uncommon for protists to have two flagella, one longer than the other (with no apparent function) that trails behind it as it moves.

[Pat Thielen]

It is not uncommon for protists to have two flagella, one longer than the other (with no apparent function) that trails behind it as it moves.

Thanks -- I didn't know this was a thing. So, protists have tails! You learn something new every day!

[Pat Thielen]

Aha! I did in fact take a picture of the little green beastie and so I'll post it here. You can see both flagella; the longer one was the one that was propelling him along (towards the left).

Anyway, I hope this helps. Thanks!

It was taken using phase contrast lighting but I can't recall whether this was taken at 200x or 400x.

[Bruce Taylor]

. So, protists have tails!

Well, more of a moustache, really. What you're describing is almost certainly a euglenoid, such as Anisonema or Entosiphon. In such critters, both flagella emerge from a ciliary pocket at the front end of the cell, but one of the whiskers (the "recurrent" or "trailing" flagellum) curls around so that it trails behind the cell. The trailing flagellum often makes a visible "question mark" shape on the surface of the cell, as at 0:23 in this old video:



(ETA: I just noticed that you've added a photo, after all! Looks like Anisonema, to me).

[actinophrys]

I will second Anisonema. You can see a hint of a large flagellar pocket, in place of any developed ingestion apparatus like some other gliding euglenoids. The oval shape and much longer trailing flagellum are typical.

These are actually posterior gliders – it may look like it is just dragging behind, but I understand the trailing flagellum is what propels them along surfaces, and is also useful for quick reverses of direction.

[75RR]

... and is also useful for quick reverses of direction.

As shown on the video ... very effective!

[Bruce Taylor]

These are actually posterior gliders – it may look like it is just dragging behind, but I understand the trailing flagellum is what propels them along surfaces

Yes! Have you read Saito et al. on gliding movement in Peranema trichophorum? They used nickel chloride to stop the anterior flagellum from beating, but the cells kept on gliding anyway! Evidently, anisonemids do something similar, but in reverse, gliding on that long, thick posterior cilium.