What a wonder! A new unknown critter!

[NachoBen]

I have come across this freshwater organism in the last month in two different ponds. It has both flagellate and ameboid features. While moving, the cell looks like Euglena or Peranema, but it has two long flagella. When disturbed, it quickly contracts and protrudes several short and (apparently) rigid appendages. After a variable time, the cell reabsorb the appendages and recover its former shape to keep moving on. The body is sometimes ameboid in the sense of a changing shape. If it were an euglenoid we'd call this “metaboly”.

Please see this video:



When contracted, some specimens resemble a heliozoan with short axopodia. Others, like the one in the video, bring to my memory an old depiction of a comet.

Thank you all for any help.

[macnmotion]

That's so cool. Hoping someone can explain it.

[ddy5]

That is bizarre. I've seen a few amoeba with what looked like flagella, but nothing like this.

Although it doesn't really seem to apply here, I did find this quote from a research paper:

"The amoeba, Naegleria gruberi, changes from the amoeboid form to a free-swimming flagellate form in about two hours after it is transferred to distilled water. The change involves the development of a strong polarity and an alteration in the character of the membrane." https://doi.org/10.1016/0014-4827(61)90338-X

[NachoBen]

Thank you very much for your help, ddy5.

I really did think of Naegleria but I did not find any papers explaining the bizarre protrusion of the appendages.

Now I hesitate about my critter being an amoeba at all.

That is bizarre. I've seen a few amoeba with what looked like flagella, but nothing like this.

Although it doesn't really seem to apply here, I did find this quote from a research paper:

"The amoeba, Naegleria gruberi, changes from the amoeboid form to a free-swimming flagellate form in about two hours after it is transferred to distilled water. The change involves the development of a strong polarity and an alteration in the character of the membrane." https://doi.org/10.1016/0014-4827(61)90338-X

[Bruce Taylor]

Naegleria is a heterolobosean amoeboid, a group in which pseudopods are formed eruptively (kind of like bubbles erupting from the leading edge of the cell). We don't see that, here: it is moving like an amoebozoan. With those short, digitate pseudopods, I think this is probably a species of Mastigamoeba. See: https://arcella.nl/mastigamoeba/

[NachoBen]

Thank you, Bruce.

I already checked Mastigamoeba but all my specimens have two flagella, not just one. Nevertheless, Mastigamoeba sports spines that resemble the appendages in my critters.

Maybe this a good clue to follow.

[Bruce Taylor]

Oh, I'm sorry...I overlooked the second flagellum! I think flagellated amoebozoans (in the Archamoeba clade) mostly have a single cilium, though the type species of Mastigella, M. polymastix, has more. Perhaps a cercozoan amoeboid, then? Cercomonads are biflagellate. But amoeboids are outside my comfort zone, and I've already exhausted the little I know!

[ddy5]

I found an extensive paper on cercomonads that might help. A few of the species shown have at least a passing resemblance to the mystery creature.

The paper is much too large to attach, so I trimmed it to just a few of the figures that seem promising. If anyone wants a pdf of the full paper, PM me with your email address, and I'll be happy to send it.

Cheers, David

Cercomonad figures 3.pdf

(454.56 KiB) Downloaded 82 times

[NachoBen]

Thank you Bruce and David.

After finding this post on a German forum https://www.mikroskopie-forum.de/index. ... ic=31340.0 I think now that Heliomorpha (Dimorpha) mutans or, better, Tetradimorpha tetramastix could be good candidates.