looks like a testate amoeba (cf. Difflugia)

1, thank you Willem! quite hard loricа may be ... as for testacea i do think... but i don"t know

2, Dear Willem, you know i got message from protistologist Prof. Sabine Agatha-she conformed your suggestion! Thanks you all very much!!!

Larysa:

Could you please provide a scale and information about the mineralogical composition of the test?

Best

Syed

Dear Saed, unfortunately no. sorry

but i do have two original photos from that sample, the second one is an algae Micrasterias conferta. So, knowing that size of algae is around 80-100 micrones, seems this protist is bigger in 2-2.5 times

have also to add that the sample was for crustaceans, so it was usual plankton net

would like to share also that the sample was collected from mountain lake "Hirske Oko" 1000 asl in Carpathian mountains (Ukraine) in april 2015 at the Cheremosky National Park. Beautiful lake!!! But the park is suffer from illegal deforestation, we are trying to help them to make an inventory and reveal unique elements needed to protect.

Thank you in advance for any information.

Larysa:

Thank you so much for providing wonderful details. I tend to support identification of Willem. It is Difflugia sp.. Scanning Electronmicroscopy would help in species identification (see link):

http://www1.nencki.gov.pl/pdf/ap/ap879.pdf

Best

Syed

раковинная амёба

Difflugia...oblonga? The apertural is is needed to see the species...

It is close to Thecamoeba. They are usually benthic but in a certain period they enter the water column, too.  

Hi there, definitely Difflugia oblonga. Taxonomy of testate amoebae is still unresolved but some lake researchers use the strain-based approach given there is much morphological variability even among the same species. See link below for lake taxa key, it's a little outdated now but best available currently:

http://www.nhm.ac.uk/hosted_sites/pe/1998_1/dalby/issue1.htm 

This specimen would fall under Difflugia oblonga "oblonga". Hope this helps.

Have you found any other specimens?

Larisa,

 look like some simple Difflugia. But needs to be measured and from different points of wiev ! Look, please, some articles about Vorochevo lakes and Svidovets lakes from my site, altitude about 660 m, and 1400 m. I studied it enough well, but hardly to identify from this photo. Testate amoebae needs to see their oral form and collar< important is if flattend body, some "neck" like Pontigulasia. Can ask Volodia Pliashechnik from Uzhgorod (he has site) or if need perfect qualification call Prof. Vassil Golemansky. Anyway perfet key of mazei & tsiganov in Russian. i made the very good PDF, just put for smbd like reply for question.

important if this lake has some water flows in & out. if no, will be like swampy area with special faunal list...

Andrey