The genera Lobocharacium Kugrens, Clay etAguiar, 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 strains. Phylogenetic analyses based on 18S rDNA and rbcL sequences confirmed the position of the three genera within the Characiosiphonia clade. The molecular analyses indicate that the genus Characiochloris is not monophyletic. Based on its unique features and the irregular contractile vacuoles in cells, we describe the strain-FACHB-3671 as a new species and named it Characiochloris papillata sp. nov. Given the current limitations in the molecular data of Characiochloris Pascher (particularly the lack of its type species), further research is necessary to resolve its polyphyly and clarify the taxonomic boundaries of the Characiosiphonia clade.
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 in thallus form, branching pattern, trichome structure, heterocyte positioning, and habitat preference. Phylogenetic analyses based on 16S rRNA gene sequences placed this strain in a clade distinct from closely related genera within the family Scytonemataceae. The 16S rRNA sequence of this strain shared less than 95% genetic identity with currently described Scytonemataceae genera. Based on apolyphasic approach including data on morphology, ultrastructure, ecology, 16S rRNA phylogeny and secondary structure, we propose Parabrasilonema hainanensis gen. et sp. nov. as a new cyanobacterial taxon. Additionally, phylogenetic analyses showed that strain FACHB-3638, along with uncultured cyanobacteria clone Z32 from wall biomats in a deep sinkhole in northeastern Mexico, forms a well-supported monophyletic clade, exhibiting 97.51-99.28% nucleotide similarity. These findings suggest that these uncultured cyanobacteria likely belong to the genus Parabrasilonema, broadening our understanding of its diversity across distinct habitats.
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 pattern is likely due to it being overlooked on specimens where papillae are densely spaced, and if there is a papilla in the geometric center of each hexagon. Mallomonas korshikovii is the closest modern congener to M. lottii, with both species sharing multiple scale traits. The primary difference is that scales of M. lottii lack a papilla at the geometric center of each hexagon.
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 helices) of the 16S-23 rRNA Internal Transcribed Spacer (ITS) regions of both novel strains exhibited unique sequential differences from phylogenetically related taxa. Based on the combination of morphological characters and well-supported phylogenetic data, we describe a new genus and species: Pushkarnema curajae gen. et sp. nov. in accordance with the International Code of Nomenclature for Algae, Fungi, and Plants (ICN).
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 from the corresponding sampling locations. We here designate a sequenced specimen as epitype as the holotype of Prasiola yunnanica C.-C. Jao is a formaldehyde-fixed specimen that cannot be sequenced. By combining molecular phylogenetics and morphological observations, we provide a comprehensive assessment of three Prasiola-like collections, identified through integrative taxonomy, as Eaprasiola yunnanica (C.-C.-Jao) comb. nov., a species distinct from Eaprasiola highlights the effectiveness of the reverse taxonomy approach in detecting rare algae, and emphasizes the importance of integrative methods for achieving a thorough and accurate assessment of algal taxonomy and diversity.
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 be kept as separate species. Staurosira binodis, first observed in a fossil diatomite sample from Santafiora (Italy), shows some morphological variability in its central constriction. Finally, Staurosira venter is typified using a fossil diatomite sample from Berlin (Germany), settling a decade-long uncertainty about its exact morphology. In addition to these four Ehrenberg taxa, two unknown Staurosira taxa, also present in the original material, are described as new: Staurosira venteriformis sp. nov. and S. venterilonga sp. nov.
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, Stauroforma subcassubica is described splitting it from S. cassubica, the latter having larger valves. The results of this revision will enable a more exact identification of the different Stauroforma species observed in freshwater and brackish water bodies in Europe.
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 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; it is less clear in valve view and becomes weaker in the largest frustules, which are nearly symmetrical along the apical, transapical, and pervalvar axes. Valve ends are acutely rounded and blunt, but in shorter and more sigmoid valves, they become pointed to nearly triangular. Morphology and comparison with related taxa suggests the Aras Dam species is new and here described as Nitzschia arasensis Atazadeh, Ghavam et Edlund sp. nov. Water chemistry in the Aras Dam suggests that N. arasensis inhabits fresh to slightly brackish water.
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 a silica flap with a wavy margin, giving the appearance of undulating raphe ends. A comparison of S. undulata with the morphologically similar taxa S. delicatula and S. obtusiuscula suggests that the latter two may in fact be conspecific. Both new species were found growing epiphytically on the chlorophyte Cladophora prolifera (Roth) Ktttzing collected from a sheltered tide pool. Detailed ultrastructural descriptions are provided, along with comparisons to morphologically similar species. The present work is the first report of new benthic diatom species described from the Canary Islands.
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 sequences. Analysis of ribosomal ITS sequences, plastid tufA sequences, and morphology revealed four distinct taxa among these strains, including two new species, C. salsodica and C. subsphaerica, and two new varieties of C. yingshanensis, C. yingshanensis var. apiculata and C. yingshanensis var. ovata. C. salsodica, C. subsphaerica, and C. yingshanensis var. apiculata were only found in the sodic-saline slicks, whereas C. yingshanensis var. ovata was only found in the barrens grassland soil. To date, no other Coelastrella species have been found in these sites.
In the framework of a study of the genus Luticola Mann we collected and processed samples from different ecoregions ofArgentina, analyzed them with light microscopy (LM) and scanning electron microscopy (SEM). In aerophilous samples collected in Misiones Province, Argentina, we found colonial specimens. The aim of this work is to elucidate the identity of the colonial forms found in aerophilous samples in NE Argentina. In the present study, we describe the genus Neoluticola Simonato, Sala et Kociolek and four species: Neoluticola spinosa Simonato, Sala et Kociolek sp. nov., Neoluticola arrechensis Simonato, Sala et Kociolek sp. nov., Neoluticola alegrensis Simonato, Sala et Kociolek sp. nov., and Neoluticola salvadoriana Simonato, Sala et Kociolek. Neoluticola comprises a group of aerophilous colonial species that share with Luticola a conspicuous isolated pore in the central area, distinctly punctate striae, and marginal channels. The new genus differs from Luticola in the location of the isolated pore on the valve face/mantle junction, colonial life habit, special structures (spines or silica projections) that join cells together, very thin slit-like areolae on the valve mantle, an elevated fascia expanded side to side, internal proximal raphe ends strongly curved, and fimbriate girdle bands. We compare the species of the new genus with morphologically similar ones from Luticola and discuss the geographic distribution of Neoluticola gen. nov.
A total of 81 strains morphologically corresponding to the circumscription of Mallomonas intermedia were isolated from 27 freshwater localities across Europe and North America. Molecular genetic analyses revealed two distinct lineages with a strict geographical pattern, which diverged approximately 8 million years ago. According to comparative morphological analyses, we concluded that European populations corresponded to M. intermedia, whereas North American populations were described as a new species, M. retimedia sp. nov. The most notable morphological difference between the species is in the number of pores enclosed in the mesh formed on the siliceous scales. While in M. intermedia the mesh typically surrounds only one pore, meshes of M. retimedia usually encircle 3-4 pores. By incorporating fossil evidence into our time-calibrated phylogeny, we propose that the ancestor of M. intermedia and six related species likely lacked a thick secondary layer but had a distinct transverse rib, present in extant M. galeiformis, M. intermedia and M. retimedia species. The evolutionary history of this group further reveals that parallel ribs on the siliceous scales have evolved independently at least three times during the Miocene epoch, suggesting an adaptive significance, although their exact function remains unclear.
During studies on the diversity of Frustulia in the state of Parana, Brazil, two different morphological populations did not correspond exactly to any known described species. This paper describes these species as Frustulia lineata sp. nov. and Frustulia magnifica sp. nov. The samples were collected in lotic environments inserted in the south Brazil Atlantic Forest region. Frustulia lineata sp. nov. is mainly characterized by linearlanceolate valves with small dimensions, sharing morphological similarities with Frustulia marginata Amoss & eacute; and Frustulia saxonica f. indica Sarode et Kamat. Frustulia magnifica sp. nov. is significantly larger than other species of the genus, having morphological similarities with Frustulia aotearoa Lange-Bertalot et Beier, Frustulia bahlsii Edlund et Brant, Frustulia rhomboides f. occidentalis Sovereign, and Frustulia sanctarosae Lange-Bertalot et Sterrenburg. Studies using light and scanning electron microscopes have revealed that the morphology and dimensions of the central nodule and the porte-crayon were primary distinguishing features that substantiate the proposal of the new species.
The charophyte algae of the genus Streptosarcina (Hormidiellales) are quite rare terrestrial protists, according to current knowledge. The genus consists of two species, S. arenaria and S. costaricana, which are isolated in Eastern Europe and Central America, respectively. Only five strains of the genus have been studied using microscopy and/or molecular methods, based on published data. Here, we examined two strains, IRK-A 417 and 448, isolated from the chestnut soils of the Primorsky Range at the southwestern shore of Lake Baikal. The combination of molecular (18S rDNA, ITS, rbcL) and microscopy data (LM and TEM) was used to determine the taxonomic and phylogenetic position of the studied plants. It is established that they are most similar to the filamentous Streptosarcina species from Central America. IRK-A strains represent a new genetic lineage of the genus. The description of the new variety, S. costaricana var. goloustica, is proposed.
Significant changes have been proposed for the order Rhopalodiales, including subsuming Rhopalodia O.Mull. into Epithemia Kutz. to maintain monophyly and recognition of the genus Tetralunata Hamsher et al. However, hesitancies about adopting these higher-level classifications remain. We report widespread and homologous internal valve and life history traits as evidence to guide higher-level classification within the Rhopalodiales. We provide the first reports of internal valve formations in five species and show examples from six species representing multiple branches in the Rhopalodiales: Epithemia (Rhopalodia) gibba (Ehrenb.) Epithemia catenata Schvarcz, Stancheva et Steward, and Epithemia reicheltii Fricke. This observation, along with shared, unique cell development and life history traits including endosymbiosis and sexual reproduction, should be considered in phylogenetic revisions.
An algal strain with the morphological characteristics of the Eustigmatophyceae was isolated from a small pond in Itasca State Park, Minnesota, USA. Phylogenetic analyses of the DNA sequences from the nuclear 18S rDNA and the plastid rbcL loci both placed the strain in the order Eustigmatales and family Chlorobotryaceae. The new strain was not clearly allied with any lineage within the Chlorobotryaceae. Morphological features as determined by both light microscopy and transmission electron microscopy were typical for the Eustigmatales, except for the presence of an irregular surface of the cell wall (including the presence of stipitate or digitate projections on some cells) and the production of yellow-orange inclusions in the cytoplasm of cells in stationary-phase cultures. Upon transfer to fresh media, these inclusions are subsequently expunged from the cells during autosporulation. Based on these features and the results of phylogenetic analysis, we describe Flavoaurantia irregularis gen. et sp. nov.
Loricate golden algae (Chrysophyceae) are photosynthetic microorganisms characterized by a lorica, a rigid or semi-rigid protective casing made of organic material, sometimes reinforced with silica or iron. The lorica's diverse shapes and intricate ornamentation serve as both adaptive strategies and taxonomic markers. Here, we identified, for the first time, the molecular phylogenetic position of a loricate genus Chrysococcus, based on genetic investigations of two freshwater populations in Poland. The genus was resolved to form a wellsupported clade with Chrysosaccus within the order Chrysosaccales. Accordingly, this order represents one of the morphologically most diverse lineages of Chrysophyceae, including naked flagellates, coccoid organisms, amoebae and flagellates dwelling in loricae, and mucilage-secreting cells. The phylogenetic resolution of Chrysococcus provides key evidence for understanding the evolutionary transitions within Chrysophyceae, highlighting the complex relationships between loricate and non-loricate taxa.
Disconnected pools are temporary habitats of great ecological importance that can maintain high aquatic biodiversity. However, little is known about the composition and distribution of algal communities in the Mediterranean basin. During a diatom flora study conducted on the Iberian Peninsula, several populations of unknown taxa were found. Detailed observations with optical and scanning electron microscopes allowed for the description of three new taxa to science: Sellaphora temporalis sp. nov., Sellaphora catalonica sp. nov., and Nitzschia curvirecta sp. nov. Differential diagnostic criteria with respect to similar taxa are briefly described, and ecological information is provided. All of this highlights the importance of disconnected Mediterranean pools, often overlooked in terms of conservation.
Aulacoseira Thwaites is one of the oldest known diatom genera to inhabit freshwater ecosystems, having been recorded from multiple localities from the late Cretaceous. The genus continued to evolve throughout the Cenozoic and today continues to thrive in aquatic environments globally, often forming an important contributor to phytoplankton communities. Morphological characters that define Aulacoseira had largely evolved by the Eocene, and many additional species have been uncovered since that time, especially in the Miocene. The Virgin Valley Formation, located in the northwestern portion of Nevada, USA, represents an extensive deposit that dates to middle Miocene (similar to 14.4 Ma) and spans a period of time that covers the end of the Middle Miocene Climatic Optimum (MMCO) and onset of the Middle Miocene Climatic Transition (MMCT). The formation contains strata consisting of organic lignite, mudstones and diatomite, ranging in thickness from a few cm to tens of meters. During an investigation of the biological remains, Aulacoseira was found to dominate many of the strata, indicating the importance of this diatom in these ancient aquatic ecosystems. The objective of this communication is to provide a detailed accounting of the most common Aulacoseira species found at the Virgin Valley locality, including the descriptions of six new species. Collectively, the new taxa represent a wide range of morphological characters, and their remains are used to infer aspects of the paleoecology of the ancient habitats.
