Fottea, 2026 (vol. 26), issue 1
Original article
Revision of the genus Stauroforma (Staurosiraceae, Bacillariophyceae) based on varieties of Fragilaria virescens described by Albert Grunow
Bart Van de Vijver, Tanja M. Schuster, David M. Williams, Wolf-Henning Kusber
Fottea 2026, 26(1):1-16 | DOI: 10.5507/fot.2025.011 
A revision of the genus Stauroforma is proposed based on the analysis of several historic slides prepared by Grunow to describe Fragilaria virescens var. exigua. The original materials are analysed using both light and scanning electron microscopy together with a critical examination of the original drawings and notes Grunow made on his new taxa. Based on this, the genus description of Stauroforma is emended and the morphological descriptions of S. exiguiformis and S. inermis are updated. Grunow's variety subsalina is raised to species level as Stauroforma subsalina. A new species,...
Pushkarnema curajae gen. et sp. nov. (Nodosilineales), a novel filamentous cyanobacterium isolated from a freshwater reservoir of northwest India
Sonam Sonam, Anuj K. Tomer, Dale A. Casamatta, Pawan K. Dadheech
Fottea 2026, 26(1):17-28 | DOI: 10.5507/fot.2025.010
During the exploration of cyanobacterial diversity of the semi-arid region of northwest India, a non-heterocytous cyanobacterium was isolated from an aquatic habitat and characterized using a polyphasic approach based on morphology, ecology and sequencing of the 16S rRNA gene. Two strains (AT2016/6; SN2021/02) were isolated and characterized by cells longer than wide, the presence of a thick sheath, and the formation of nodules. 16S rRNA gene sequences revealed that the strains formed a highly supported, distinct clade within the Nodosilineales, ranging from 89.52% to 92.76% similarity to other strains. Secondary structures (the D1-D1´, BoxB, and V3...
Parabrasilonema hainanensis gen. et sp. nov. (Scytonemataceae, Nostocales), a novel filamentous cyanobacterium isolated from a tropical reservoir in China
Qi Zhang, Lin Li, Tianli Li, Lingling Zheng, Lirong Song
Fottea 2026, 26(1):29-39 | DOI: 10.5507/fot.2025.012
A filamentous, heterocytous cyanobacterial strain FACHB-3638 was isolated from Yongzhuang Reservoir, a tropical drinking water reservoir on Hainan Island, southern China. This cyanobacterium formed macroscopic, felt-like mats on submerged concrete substrates, covering extensive areas of the shallow riverbed. The filaments were isopolar, cylindrical, and nearly straight or flexuous, exhibiting infrequent scytonematoid false-branching and producing firm, often layered and colored sheaths. Morphologically, the strain resembles members of the Scytonemataceae family, particularly Brasilonema, but phenotypically differed from other scytonematoid genera...
Morphology, taxonomy and epitypification of Eaprasiola yunnanica (C.-C.-Jao) comb. nov. (Prasiolaceae, Trebouxiophyceae) from China using reverse and integrative approaches
Feilong Su, Yukang Liu, Qingyu Dai, Benwen Liu, Guoxiang Liu, Huan Zhu
Fottea 2026, 26(1):40-48 | DOI: 10.5507/fot.2025.013
The Prasiola-like Prasiolaceae includes some 35 species of monostromatic green algae found in a wide range of habitats, including marine, freshwater, and terrestrial environments, across polar, cold, temperate, and subtropical regions. They exhibit considerable phenotypic plasticity, complicating identification based on morphology alone. Here, we used a approach based on full-length 18S rDNA amplicon sequencing to identify Prasiola-like specimens from China. Amplicon sequence variants (ASV) belonging to Prasiolaceae were detected in material collected at W'umonshan, Yunnan Province, China, and living specimens were subsequently collected...
Two new species of diatoms (Bacillariophyceae) from the coast of Tenerife, the Canary Islands, Spain
Adil Y. Al-Handal, Michael J. Sullivan, Ana Tronholm, Angela Wulff
Fottea 2026, 26(1):49-56 | DOI: 10.5507/fot.2025.014
In a study of epiphytic diatoms from the coasts of Tenerife, Canary Islands, two new species, Caloneis virgaestriata and Seminavis undulata, were discovered and analyzed using light and electron microscopy. Caloneis virgaestriata is characterized by its small size, areolae rows that expand to cover the virgae between striae, and distal raphe ends curved in opposite directions. This last feature is present in only one other species currently placed in the genus, C. hustedtii. Seminavis undulata exhibits a novel morphological trait not previously recorded in the genus: its external proximal raphe ends are located beneath...
Analysis of the original Ehrenberg materials of the Staurosira construens complex (Staurosiraceae, Bacillariophyceae)
Bart Van de Vijver, Paul B. Hamilton, Wolf-Henning Kusber
Fottea 2026, 26(1):57-76 | DOI: 10.5507/fot.2025.015
The genus Staurosira comprises a limited number of small-celled araphid diatom species that are often quite common in waterbodies worldwide. Despite a global occurrence, their taxonomic identity is poorly known, due to the lack of good knowledge of their type material. In the present contribution, the taxonomic history and morphology of four often-cited Staurosira taxa are unravelled based on light and scanning electron microscopy analysis of the original samples collected by Christian G. Ehrenberg. Staurosira construens and S. pinnata, both described from New Haven (Connecticut, USA), showed sufficient differences to...
Nitzschia arasensis sp. nov. (Bacillariophyta), a new diatom species from the Aras River and Dam, northwestern Iran
Ehsan Atazadeh, Amin Ghavam, Mark B. Edlund, Gholamreza Dehghan, Zahra Shojaei, Mahtab Kohansal, Leila Sadeghi
Fottea 2026, 26(1):77-84 | DOI: 10.5507/fot.2025.016
During recent investigations on the diatom and algal flora from the Aras Dam, northwestern Iran, an interesting epilithic diatom species belonging to the genus Nitzschia was collected and examined using both light and scanning electron microscopy. This diatom species shares morphological and taxonomic features with Nitzschia clausii, N. kurzeana, N. filiformis, N. obtusa, N. lowei, and N. potapovae; however, the taxon possesses narrow, elongate frustules that are weakly sigmoid in both valve and girdle views. The sigmoid character shows itself mostly at the apex of the valve and sometimes results in a rhomboid-like appearance;...
Mallomonas lottii sp. nov., a new fossil species in section Papillosae from the Eocene that forms hexagonal patterns on its scales
Peter A. Siver
Fottea 2026, 26(1):85-93 | DOI: 10.5507/fot.2025.017
A new fossil species in section Papillosae of the genus Mallomonas is described from the Giraffe Pipe maar lake located near the Arctic Circle in northern Canada. The new species, Mallomonas lottii, has scales with papillae arranged in regular hexagonal patterns on the base plate, a prominent V-rib, a shallow and recessed dome, an unornamented posterior flange, and lacks base plate pores and anterior submarginal ribs. A survey revealed that formation of hexagon patterns is a common feature of Mallomonas species in sections Papillosae, Quadratae and series Mangofera of section Torquatae. The underreporting of the honeycomb...
Morphology and molecular phylogeny of phylogroup Characiosiphonia (Chlamydomonadales, Chlorophyceae), with the description of a new species Characiochloris papillata sp. nov.
Qingyu Dai, Yangliang Chen, Huan Zhu, Benwen Liu, Guoxiang Liu
Fottea 2026, 26(1):94-106 | DOI: 10.5507/fot.2025.018
The genera Lobocharacium Kugrens, Clay et Aguiar, Characiosiphon Iyengar, and Characiochloris Pascher form a distinct phylogenetic clade within the order Chlamydomonadales, here referred to as the Characiosiphonia clade. These taxa share a similar overall cell morphology, characterized by a narrowed apex and a basal attachment structure. However, these genera also exhibit different characters, and previous studies have not provided a comparative morphological analysis to distinguish among the three genera within this clade. In this study, we conducted detailed morphological and molecular investigations of four algal...
New taxa of the genus Coelastrella (Scenedesmaceae, Sphaeropleales) from Warren Prairie Natural Area, Arkansas, USA
Sara Ambrocio Paque, Marvin W. Fawley, Karen P. Fawley
Fottea 2026, 26(1):107-118 | DOI: 10.5507/fot.2025.019
Coelastrella Chodat is a green alga frequently found in subaerial habitats that is typically characterized by ribbed cell walls. During our research on the soil algal community of sodic-saline slicks in Warren Prairie Natural Area, Arkansas, USA, we found several algal strains with the features of Coelastrella. We also expanded our study to include soil samples from sites in the barrens grassland soil around the sodic-saline slicks, which also yielded Coelastrella strains. There were also other strains that lacked ribbed cell walls but could be placed in the genus Coelastrella using nuclear ribosomal 18S and ITS1-5.8S-ITS2 DNA...