Arcdella gibbosa?

[janvangastel]

I think I found Arcella gibbosa. Please correct me if I am wrong.

[Plasmid]

Awesome shot, are you using a DsLr cam?

[75RR]

Nice looking Arcella

As to the ID, have you looked at conica?

https://www.arcella.nl/arcella-conica/

[janvangastel]

Awesome shot, are you using a DsLr cam?

Thank you. I am not using a DSLR but a mirrorless camera, Panasonic Lumix G9.

As to the ID, have you looked at conica?

No, I mised that somehow. I think it looks more like conica. Thank you.

[Bruce Taylor]

Lovely video I wouldn't ID to species without seeing the shell in profile. A conica is easily confused with A. costata.

If you rush to identification, you might overlook something unusual, like the new (and still unnamed) species of Arcella I discovered a few years ago: https://www.arcella.nl/arcella-n-sp/

[janvangastel]

OK, thank you.

[75RR]

If you rush to identification, you might overlook something unusual, like the new (and still unnamed) species of Arcella I discovered a few years ago: https://www.arcella.nl/arcella-n-sp/

That was cool! Does n-sp mean it has not been named yet?

[Bruce Taylor]

That was cool! Does n-sp mean it has not been named yet?

Yes, the process of formally describing and naming the critter has been slow! There are only a few weeks in each year during which live organisms can be collected for sequencing and imaging, and these times need to coincide with periods in which both my collaborator and I are free. Unexpected events keep derailing the project...the sudden death of a mentor, a roof failure, the closure of my sampling area because of COVID, etc.

[janvangastel]

Bruce,
I see pictures of many orientations of the Arcella species you discovered. Did you manipulate the same species for all these observations or did you find many indiciduals? In the last case: how to know that it is the same species every time?

[Chris Dee]

Great work janvangastel, very nice to see a live sample, good illumination too.

[janvangastel]

Thank you Chris.

[Bruce Taylor]

Bruce,
I see pictures of many orientations of the Arcella species you discovered. Did you manipulate the same species for all these observations or did you find many indiciduals? In the last case: how to know that it is the same species every time?

Your question is a good one! I've examined thousands of them, and collected hundreds of living specimens (picking them out with a pulled-glass pipette). In this case, it is very easy to recognize this as a single population. The collecting is done at the same site and stratum every time (a very distinctive habitat among certain floating plants in a dystrophic lake). When blooms occur, this very angular Arcella becomes quite abundant, the little shells strewn about in the sample like dice. While the shell shape is somewhat variable (which is normal for many Arcella species) all specimens have an unusual crenulated flower-like aperture, so there is really no doubt that they are conspecific. Other species of Arcella do appear in that water, but they are very different, and never bloom together. The foremost authority on arcellinids has said these are "certainly a new species," so there is no doubt about that.

The images on Ferry's site were taken by him, from a vial I sent him. My collaborator in Canada has taken some gorgeous SEMs, which I can't share. Here are a couple I made with a cheap USB cam and cranky old Olympus BHB:

Arcella-profile-view.jpg (164.17 KiB) Viewed 4096 times

Arcella-ventral-view-1.jpg (168.41 KiB) Viewed 4096 times

And some video: https://www.youtube.com/watch?v=dLcb4x6 ... e=emb_logo

[janvangastel]

Thanks for your comprehensive answer and the very nice pictures and video Bruce.

[cesarius]

Very nice Shot!