unknown flagellate

[Bix]

Hi all

Found this one in a fresh water pond. Any guesses? Definitely has a flagellum and what appears to be a spiral lorica. Viewed at 200x

https://youtu.be/KT0xeMJLv-0

Thanks, Tina

[Bruce Taylor]

Heteronema spirale.

[Bix]

Thanks so much, Bruce!

Tina

[Bix]

Bruce - could you tell me more about the flagellate? I looked it up online and now assume that it doesn't have a lorica, just a spiral body. Is that right?

Are there any sources online or in print that would help with ID and info about organisms , like flagellates? I like to know more about them, curious creatures that they are!

Thanks, Tina

[Bruce Taylor]

I looked it up online and now assume that it doesn't have a lorica, just a spiral body. Is that right?

Yes, that's right. It's an understandable error. The pellicle is thick and rather stiff, and does look a bit like a lorica!

Heteronema spirale is a heterotrophic (non-photosynthetic) euglenoid, first described in 1893, by G.A. Klebs. Here's his original illustration:

Heteronema spirale 2.jpg (3.93 KiB) Viewed 1246 times

It's a freshwater critter that glides on a long forward-projecting flagellum (i.e. it is what Thomas Cavalier-Smith called a "front-glider," like Peranema, and unlike, say, Anisonema which glides on its rear flagellum). The second flagellum is short and floppy, and trails alongside.

The species is widespread, but hasn't had a lot of recent attention from researchers. There was a brief redescription in a Polish paper from 2005, along with some photos: https://bibliotekanauki.pl/articles/58667.pdf

The genus Heteronema itself is a bit of a "wastebasket taxon" for any heterotrophic euglenoid with two flagella of unequal lengths. The genus has a lot of nominal species, but most probably belong in some other place. H. spirale has not been sequenced.

[Bruce Taylor]

Re. sources...I can't think of many comprehensive guides to heterotrophic flagellates, and the ones I know of are old and difficult to get.

Part of the problem is the word "flagellate" itself, an obsolete classification that ropes together all kinds of unrelated organisms. The ancestor of all eukaryotes (including us!) would have been a flagellate, so cells with that body plan occur in every branch of the eukaryotic tree of life. The diversity is staggering.

A handy "starter" guide to the diversity of flagellated critters (very sketchy, but it might narrow things down a bit, to groups like choanoflagellates, bicosoecids, euglenoids, etc.): https://www.sciencedirect.com/science/a ... 1013000795

Once you have a rough idea of what kind of "flagellate" you're looking at, you can search within a narrower group. In this case, that would be Euglenozoa. The nearest thing to a complete "field guide" to euglenoids (both heterotrophic and photosynthetic) is old but still useful if you can find it:

Huber-Pestalozzi, Gottfried. "Das Phytoplankton des SuBwassers. 4. Teil. Euglenophyceen." Die Binnengewasser (1955).

A couple of others that cover a lot of euglenoid diversity (also difficult to find, I'm afraid):

Vetrova, Z. I. "Colorless Euglenoidina algae of the Ukraine." (1980).

Zhukov, B. F. "Atlas of freshwater heterotrophic flagellates." Russian Academy of Sciences, Institute of the Biology of Inland Waters, Rubinsk (in Russian) (1993).

When trying to identify a particular critter, I will also look at papers containing descriptions of organisms found at particular sites. There are too many to list, but a search on "heterotrophic flagellates" in Google Scholar would turn up some good resources. You'll find that certain authors come up a lot, e.g. Won Je Lee, D. J. Patterson, Alastair Simpson.

One more source, indispensable for older texts: https://www.biodiversitylibrary.org/

[Bix]

Thanks so much, Bruce! I really appreciate that you shared this - gives me some ideas of the thinking process for identifying and understanding these amazing creatures. It is hard to know where to start sometimes. The basics are getting easier - cilia, no cilia, flagellum, no flagellum but I know that isn't even definite identifier.

Thanks also for the suggested resources! It is very enjoyable to learn more about the microorganism beyond just giving them a name.

Best, Tina