Arcella intermedia? Help for id and process

[carlos.uruguay]

Link:
http://www.youtube.com/watch?v=e-rNaHx8pFA&feature=plcp

I ask your help to confirm whether it is Arcella intermedia.
Approximate diameter 65um
And to know what it means the brown circular object in one of them at end of the video.
He understood that in the young arcellas the theca is transparent. But in this sample, all have this feature.
At the same time at the end of the video one of them has inside it a brown object unknown to me.
Another ercella?
Thanks in advance
carlos

[Ferry]

Hi Carlos,

It is Arcella intermedia.
The brown object is probably a shell of Pyxidicula operculata. See here: http://www.arcella.nl/pyxidicula-operculata.
All Arcella-shells are transparant. Only young ones are colorless. Older shells are getting more and more brown.

Ferry

[carlos.uruguay]

Thank you so much Ferry!
You wrote: "All Arcella-shells are transparant"
You mean like young organisms?
Ferry, it is possible that all copies of the same sample are young?
As I have observed all these days have their theca colorless
carlos

[Ferry]

Transparent is not the same as colorless. It means: you can look through the shell wall as through glass, even if the shell is brown.
Only older shells get darker, because of iron/mangan in the water. If all your shells are light colored, it could indicate that they multiply fast.

[carlos.uruguay]

Thank you very much Ferry
Sorry for the language difficulties and my very bad english
Curiously I have this sample for two weeks and I have never seen a brown arcella
Which may be? Lack of a mineral?
carlos

[Ferry]

Yes, that might be possible, a lack of minerals.
Your English isn't so bad. English is for both of us just a means to communicate. And we can understand each other very well! So it's OK!

Ferry

[carlos.uruguay]

Thank you Ferry.
Sometimes words like "transparent" and "colorless" in spanish are used as synonyms