Maybe Achnanthidium, Achnanthes or Gomphonema. It really a little strange. More pictures is needed. Is it a culture?

Dear Wang. It’s not a Gomphonema because it is a mono raphid diatom, It is more or less certainly Achanthidium; the best optic microscope photos are these I put here. Thank you for help.

Stefano

Hy Guert

Yes it is similar at A. pyrenaica ...but is much larger ...

It is the first time that I found this diatom. I found it in a Po Plane spring. It have 36-46 striae, more or less 20 for half valve

measures are microns, not  millimeters ... excuse me!!!

Attached are several examples of a very confusing complex of Achnanthidium from the Great Lakes. We believe they fall in the range of A. microcephalum/minutissimum v. jackii. Although some of these look similar to yours, your scale bar suggests yours is much larger. In any case, that's the closest guess I have. Because your specimen has capitate ends I do not believe it is pyrenaicum: http://westerndiatoms.colorado.edu/taxa/species/Achnanthidium_pyrenaicum

Dear Stefano, I agree with my colleagues that it is an Achnanthidium, and it reminds me of a species rather recently described from French rivers: A. druartii. It is an invasive species, quickly spreading over Europe. However, to be sure I need to know dimensions and the number of striae per 10 mu.

Dear Euan, thanks for the answer, but A. minutissimum var jackii is definitely much smaller ....

Stefano

Dear Frans, thanks for your valuable suggestion !!!!

I have also speculated that this diatom could be an alien species .... but I have not publication about them

Ok ... it has from 9 to 13 striae in10 mm.

Are you able to send me one publication about A. druartii?

Stefano

Yes Guert .... This diatom is long more or less 40 mm, the bar is 10 mm

Excuse me ... but I can not write "micron" ....

Dear Geurt, for overall size it may be similar to A. gracillimum, but the diatom I have found is centrally wider and has a smaller number of striae ...

Wow !!! ... Indeed, the diatom resembles to A gracillimum of "Westerdiatom" but the size of the diatom I found is more larger... but when I look 'im Diatomen subvasser ..... " diatoms are narrower. The diatom length could also be correct (but not the width) ....

I have seen A. duartii on "westerndiatom".... Although this species appears to be much smaller (14-25 microns against 40 microns of mine...), then the capitates end seem more marked and closer ...

Based on the number of striae It doesn't belonge to A. microcephalum/minutissimum group Euan.

Thank Ines for your suggestions!

I mounted other slides and I carefully watched and measured other diatoms (more or less 70 diatoms )....Well,  40 microns is the maximum length, and is characteristic of only few samples ... the average is 30- 32 microns.

At this point I think these diatoms are A. gracillimum .... very developed. The reason? Nutrients in the water? The area is an agricultural area ....

Thank you for your invaluable help.

Stefano

I agree Ines. Stefano's diatom is much larger and coarser, and is something I'm not familiar with.

It certainly looks like Stefano, but the number of striae is too low for A. gracillimum.

Sorry. :(

OK!

Thank to Geurt and Ines!!!

Dear Stefano,

also agree with you and it seems that the species in the picture should be Achnanthes Microcephala Synonyms: Achnanthidium microcephalum kutzing.

Thank you Habib

It's more close to A. druartii than to A. microcephalum or A. gracillimum, IMHO

I think it achnanthes definetly you can check at western diatoms

 Yes it's closed to Saul but still not A. druartii because of less striae number in the center and the ends of the valves, and it is a littler bit slender. I suggest to name it as a new species or as a variety (as a consequence of different environment).