I found a published photo where author writes that this is diatom species Hyalosira delicatula. But I have some doubts about such conclusion.
Unfortunatedly I do not have any photographs and the description of Hyalosira delicaula. So, can anyone familiar with the genus Hyalosira confirm or refute this conclusion?
Based on the areola shape and occlusion type, as well as sturdy girdle bands with only a single row of areolae, this species would belong to the recently erected genus Placosira.
Hi Anton,
As far as I know, there are currently only two species of Placosira described: P. araneosa and P. plana. The taxon from these images seems to be very similar to P. araneosa, but there are no internal views available and the rimoportula is not visible. Since I also do not know how large the scale bars are, I am not sure whether the size and stria density agrees with the description of P. araneosa. Maybe you can check it if the source file also contains the legend that explains what length(s) the scale bars represent.
Dear Anton,
The genus Hyalosira was amended and lectotyped by Lobban et al. (2021); Diatom Genus Hyalosira (Rhabdonematales emend.) and resolution of its polyphyly in Grammatophoraceae and Rhabdonemataceae with a new Genus, Placosira, and five new Hyalosira species, Protist 172, 25816.
H. obtusangula, which is one of the species together with H. delicatula described by Kützing (1844), was chosen as the lectotype of Hyalosira.
The specimens that you are showing in the pictures clearly do not match Hyalosira emend Lobban, Ashworth and Majewska in terms of girdle band morphology: copulae bearing two rows of areolae separated by a midrib.
Even when certain characters are not in view, the bands bring the displayed material closer to Placosira as mentioned by Roksana in her answer.
All the best.
Eugenia
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