Seltsames Verhalten bei Arcella

[tlansing]

Hallo Forum

Ich möchte das Fachwissen in diesem Forum nutzen, um nach einer merkwürdigen Beobachtung zu fragen, die ich bei der Testat-Amöbe Arcella gemacht habe.  Ich habe eine Reihe von Arcella-Individuen beobachtet, die eine große Gruppe bildeten.  Alle Individuen in der Gruppe schienen lebendig und von unterschiedlichem Alter zu sein, was sich an der Farbe der Tests der verschiedenen Individuen ablesen lässt.  Ich denke, dass es sich bei diesem Phänomen um Plasmogamie handelt, aber ich bin mir nicht sicher und würde mich über jeden Einblick/Kommentar dazu freuen.

Viele Grüße
Tim

[Gerd Schmahl]

Hallo Tim.
habe ich so noch nie gesehen. Da bin ich auch gespannt, ob da jemand was gehaltvolles dazu beitragen kann. Ich jedenfalls nicht.
LG Gerd

[Michael Plewka]

Hi Tim,

This is an eye-catching image of an aggregation of Arcellas!
I am pretty sure that you already looked in the www. for "plasmogamie + arcella" (or equivalent). Did you  find something that would support your hypothesis?  Up to now I did not find a conformation that sexual processes ooccur at all  in Arcella or how they look like...


I think it is also worth mentioning that neither I have seen such an aggregation of Arcellas (and I have seen many!) nor  could I find any photographs of  an aggregation like this one shown here, so maybe it is a very rare event.

BUT: there are (some important imho) questions!!

You don´t describe your preparation, you don´t describe your sample. Did you observe the aggregation of specimens or did you observe how the Arcellas  aggregated? From this single image there is no evidence that the specimens are alive.  There are no pseudopodia visible.  So how do the specimens keep together? Can you exclude (see question >>sample?) that there are other organisms (like mosquito larvae etc.) in the sample that may have eaten these arcellas and digested them only in parts? There would also be the question  what causes the aggregation of the Arcellas. There must be a chemical attractant then...


Best regards
Michael Plewka

[tlansing]

Hello Michael

Thank you for your comments and questions.  I should have been more cautious in my idea about what the nature of this aggregation of Arcellas could be but I suggested the idea to get feedback from others who might have seen this and had some additional insight.  I did some literature searches to see if anyone had reported on something like this.  I did not find anything, another reason to seek help from this forum.

Now to address some of your more specific comments.  This was a completely serendipitous observation from a sample collected from a stable pond.  There was no special preparation.  When I looked through the cluster, each test appeared to have an amoeba inside.  Each amoeba was attached to the sides of the test as seen, for example, in the clear test in the upper right hand corner of the photo.  I could not take a photo that showed all of the Arcellas in the same focal plane.  So how did this aggregate form?  I do not know but from the same sample on the same slide there may be a clue.  In the picture below, the Arcellas seem to be "connected" together in a line.  Perhaps this is a precursor to the formation of a larger aggregate but this is just a wild guess.  Perhaps, as you suggest, there is some kind of chemical attractant that brings the Arcella together.

Best wishes,
Tim

[Michael Plewka]

Hi Tim,

thanks for your response;

and your new image here is -again- very enigmatic. Never before I have seen such a constellation of Arcellas...Thanks for showing!

Best
Michael