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a–aa. Achnanthes coarctata, LM, Osogovo Mountain, Macedonia: (1a–m) size diminution series of the R–valve, (1n) frustule in girdle view, (1o–aa) size diminution series of the P–valve. Scale bar 10 μm.
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Four species of Achnanthes sensu stricto have been observed in several subaerial habitats/localities
in Macedonia. The morphological features of all recorded species have been described based on light and
scanning electron microscope observations. Two species posses similar morphological features as already
described species and were identified as...
Citations
... In Round's classification system, Achnanthes sensu stricto encompasses around 150 species and infraspecific taxa, predominantly found in marine and brackish water environments (Toyoda et al. 2005a;Rybak et al. 2020). Only a limited number of species are known to inhabit freshwater and terrestrial environments (McIntire & Overton 1971;Round et al. 1990;Toyoda et al. 2003Toyoda et al. , 2005aToyoda et al. , 2005bPoulíčkova & Hašler 2007;Lowe et al. 2009;Lee et al. 2013;Tofilovska et al. 2014;Lobo et al. 2018;You et al. 2019;Rybak et al. 2020). So far, 155 taxa of Achnanthes have been identified in China (Liu et al. 2021); however, Yu et al. (2022) argue that some species listed in Achnanthes could belong to Achnanthidium. ...
A new freshwater diatom species, Achnanthes licunese sp. nov., was found on pebble samples collected from Licun River in Shandong Province, China. The various taxonomic characteristics of Achnanthes licunese sp. nov. is observed under light and scanning electron microscope. The living cells of A. licunese sp. nov. possesses two chloroplasts. Its valves exhibit a linear to linear-lanceolate outline, slightly constricted in the middle part, with uniseriate striae. The central area of the raphid valves is expanded into a linear and thickened stauros, and the raphe is filiform. On the araphid valves, there is no central area, and the axial area (sternum) is located in the valve margin. The valve of the A. licunese sp. nov. possesses the marginal spines, but no marginal ridge and terminal orbiculi. By comparing the new species with similar Achnanthes species, A. licunese sp. nov. was confirmed to be sufficiently different regarding valve size, striae density, and the presence of marginal spines. The discovery of this species increases the diversity of freshwater diatoms.
... Indeed, putativ el y desiccation toler ant diatom taxa suc h as P. australomicrostauron and H. amphioxys were listed as indicators of old lakes, while other desiccation-resistant diatoms (e.g. Achnanthes coarctata , Pinnularia borealis ; Souffreau et al. 2010, Tofilovska et al. 2014 wer e completel y absent in young lakes . T hese r esults br oadl y conform to our expectations, given that more desiccation tolerant taxa should be found in habitats where desiccation is more likely (i.e. ...
Glacier recession is creating new waterbodies in proglacial forelands worldwide, including Antarctica. Yet, it is unknown how microbial communities of recently formed 'young' waterbodies (originating decades to a few centuries ago) compare with established 'old' counterparts (millennia ago). Here, we compared benthic microbial communities of different lake types on James Ross Island, Antarctic Peninsula, using 16S rDNA metabarcoding and light microscopy to explore bacterial and diatom communities, respectively. We found that the older lakes host significantly more diverse bacterial and diatom communities compared to the young ones. To identify potential mechanisms for these differences, linear models and dbRDA analyses suggested combinations of water temperature, pH, and conductivity to be the most important factors for diversity and community structuring, while differences in geomorphological and hydrological stability, though more difficult to quantify, are likely also influential. These results, along with an indicator species analysis, suggest that physical and chemical constraints associated with individual lakes histories are likely more influential to the assembly of the benthic microbial communities than lake age alone. Collectively, these results improve our understanding of microbial community drivers in Antarctic freshwaters, and help predict how the microbial landscape may shift with future habitat creation within a changing environment.
... Diatoms are almost omnipresent, they exist wherever water is present, in water bodies and terrestrial ecosystems as well as in aerosols (Jahn et al., 2007). They occur in terrestrial environments such as mosses, wet rocks and soils (Falasco et al., 2014;Tofilovska et al., 2014). Most of diatoms are common in the plankton and benthos in all aquatic habitats including freshwater and marine (Smol and Stoermer, 2010), except the warmest and most hypersaline environments (Round et al., 1990). ...
The marine environment is the largest ecosystem, richest in biodiversity and biological activity. Diatoms are almost omnipresent and common in the plankton and benthos in both freshwater and marine environments. They have a major influence on their environment whereas representing a significant part in primary production and carbon fixation in marine ecosystems. Microscopic examination and cell culture technique have been applied to detect, isolate and study the diatom species. On the other hand, molecular methods have contributed to overcome the drawbacks of the classical methods and also to accomplish the research objectives more efficiently. Metagenomics is an advanced molecular method utilizing direct collected microbial samples and has been used in various fields of microbial studies. It provides obvious details on the taxonomy, biodiversity, ecology and further information around the potential functions. Consequently, it can explore the biochemical components that have significant importance in various biotechnology, ecology, biomedicine and industry applications. This review focused on the effectiveness of the metagenomics method for exploring microbial communities and recruiting this to discover the diatom community.
... In the Republic of Serbia, the pioneering study was performed by Popović et al. (2015a, b;2016a, b, c;2017a, b). Similar research endeavors in the region were conducted in the Republic of Slovenia (Klemenčić and Vrhovšek, 2005;Mulec andKosi, 2008, 2009;Mulec et al., , 2012 the Republic of Croatia (Ercegović 1925(Ercegović , 1932Golubić, 1967) and the Republic of Macedonia (Tofilovska et al., 2014). ...
Phototrophic microorganisms from two caves in Serbia (Podpeć and Stopić) were examined. Samples were taken from the entrances where natural light was present, as well as from the inside caves near artificial light (lampenflora community). Cyanobacteria, Chlorophyta, Bacillariophyta and Xanthophyta were documented, with 51 taxa in total. The highest number of taxa recorded in the Cyanobacteria were coccoid cyanobacteria; Gleocapsa and Chroococcus were dominant. According to the redundancy analysis (RDA), Cyanobacteria were dominant at cave entrances while other groups (Chlorophyta, Bacillariophyta and Xanthophyta) were documented in lampenflora samples. Temperature, relative humidity, and light intensity were measured, as well as chlorophyll a concentrations and biofilm parameters (water, organic and inorganic matter content). Ecological parameters did not show significant variation, while light intensity de-pended on the position of sampling sites. RDA showed that the water content was higher in biofilm samples from cave entrances, while levels of inorganic matter were increased in lampenflora samples. The concentration of chlorophyll a did not show significant correlations with any of the measured ecological or biofilm parameters. Although the ecological parameters inside the cave did not show significant variation, they should be monitored because of the potential influence on the development of the lampenflora community that has a negative aesthetic impact on cave formations.
... and Luticola D.G.Mann (Levkov 2009. More recently, subaerial habitats have become the focus of detailed biogeographic observations (Tofilovska et al. 2014, Levkov et al. 2017, resulting in the description of a number of new species. Several populations of unknown Muelleria taxa were also observed during these studies, many of them recorded in subaerial habitats and intermittent alpine ponds. ...
Background and aims – An increased interest in the diatom flora from subaerial habitats in the Republic of North Macedonia has revealed the presence of a large number of interesting and often unknown, species. During a recent biodiversity survey, seven Muelleria species were recorded, several of which could not be identified based on the available literature. Methods – Using both Light Microscopy and Scanning Electron Microscopy techniques, the morphology of several Muelleria species has been analysed. The morphology of all taxa is described, illustrated and compared with other possible similar Muelleria taxa, known worldwide. Key results – Four already documented Muelleria species, M. gibbula, M. islandica, M. terrestris and M. undulata (= Navicula gibbula f. undulata) were identified, while two distinct species are described as new. These new species belong to the M. gibbula complex, and can be differentiated by valve size, stria density, shape of the proximal raphe ends and the shape of external areola foramina. The identity of one taxon remains uncertain due to a low number of observed specimens in the samples. As their ultrastructure is almost entirely unknown, they are briefly discussed. Conclusions – The diversity of Muelleria in Europe and the North Hemisphere is most likely underestimated and some of the previous records of M. gibbula belong to other species. Observations of diatoms from “extreme” habitats such as intermittent ponds, wet mosses and soils can reveal the existence of interesting and new species.
... Although Achnanthes C. Agardh 1824 was previously a large genus more than 1000 species and subspecific epithets associated with it per DiatomBase (Kociolek et al. 2019), the genus is now considered more narrowly circumscribed, with most species being robust and being found in marine and brackish water environments (Mclntire & Overton 1971;Round et al. 1990;Toyoda et al. 2003Toyoda et al. , 2005aToyoda et al. , 2005b. In subaerial freshwater environments, Achnanthes species have been reported and described from the continental United States (Johansen et al. 2007), Antarctica (Kellogg & Kellogg 2002), Hawaii (Lowe et al. 2009) and Macedonia (Tofilovska et al. 2014). ...
... The distinctly punctate striae have cribra in the areolae (Toyoda et al. 2003(Toyoda et al. , 2005aToyoda & Williams 2004) and many species have a rapheless sternum on the rapheless valve that is offset to one side relative to the raphe sternum (e.g. Round et al. 1990;Tofilovska et al. 2014). Cox (2006) and Cox and Williams (2006) pointed out that Achnanthes could be transferred to Mastogloiales by evidence from protoplast and frustule data, based on cladistic analyses of valve morphology. ...
... All of the species are monoraphid, robust in structure, having complex, external volate occlusions, and most are heterovalvate, with the position of the raphe being located in the center of the valve, while the central sternum of the rapheless valve is offset to one side. Nearly all of the species assigned to the genus are marine, though Tofilovska et al. (2014) list species recently described from freshwater. Many species possess a large opening at both ends of the rapheless valve called 'terminal orbiculus' whose function is unknown. ...
... Ultrastructural studies of cell frustules during the 90's and posteriorly by means of scanning electron microscopy have allowed the split of Achnanthes into several new genera, such as Gliwiczia Kulikovskiy Bukhtiyarova et Round. Hence, many taxa originally described as Achnanthes have been transferred to more suitable genera, so that Achnanthes sensu stricto remains mostly to designate robust, halophilous (marine to freshwater), and aerophytic forms similar to the generitype Achnanthes adnata Bory (= A. brevipes C.Agardh) and its allies (Cox 2006;Tofilovska et al. 2014;Majewska et al. 2017). ...
... rostrata Hustedt "as a transitional form or synonym of [...] A. rostrata Østrup". Moss & Carter (1982) presented an emended description of A. lanceolata and A. rostrata based on the examination of original materials, re-establishing Østrup species on the basis of the presence of a true cavum (and not a sinus) in the rapheless valve as a main differential character, although this discrimination was later criticized by Krammer & Lange-Bertalot (1991) who had observed transitional forms between both structures in this clade, hence rejecting also the infraspecific classification proposed by Straub (1985Straub ( , 1990 of morphotypes belonging to A. rostrata following Moss & Carter's work. ...
... Remarks: Straub (1985Straub ( , 1990 investigated several populations of Achnanthes from the Jura Mountains (Switzerland) and found six morphological "Sippen" or groups, which were distinguished according to their cell size and valve outline. These populations were also illustrated by Lange-Bertalot & Krammer (1989), Krammer & Lange-Bertalot (1991) and Lange-Bertalot (1993) who presented the first micrographs of Straub's populations from Swiss lakes. ...
Thirteen Planothidium species are illustrated and discussed in a detailed morphological account based on light and scanning electron microscopy analysis of modern and historic materials related to the names Planothidium rostratum (Østrup) Lange–Bertalot and Planothidium frequentissimum (Lange–Bertalot) Lange–Bertalot. Eight species from freshwater environments in Europe, Asia and South America are proposed as new. All taxa here discussed and illustrated belong to the group of species characterized by the presence of a cavum in the rapheless valve. Additional information concerning their distribution and ecology is briefly commented based on a thorough literature revision.
... Diatom species were identified using Krammer and Lange-Bertalot (1986, 1991a, 1991b, Krammer (2000), Lange-Bertalot et al. (2003), Werum and Lange-Bertalot (2004), Taylor, Harding, and Archibald (2007), Levkov (2009), Żelazna-Wieczorek (2011, and related literature (e.g., Cejudo-Figueiras et al. 2011;Delgado et al. 2015;Gibson, Anderson, and Haworth 2003;Taylor et al. 2014;Tofilovska et al. 2014;Tuji and Houki 2004;Tuji and Williams 2006;Wetzel et al. 2015). ...
The thermo-mineral springs of Sardinia have historically been the object of several geochemical studies, whereas the biota and ecology have been totally neglected. The aim of this work is to contribute to the knowledge of the diatom microflora and ecology of the Casteldoria spring (northern Sardinia), in the hottest geothermal district of the Island. A total of 132 diatom taxa (56 genera) were found from three investigated substrates: rock (near the water emergence point), cobbles and sediments (in the spring-fed rivulet). Overall, 62 taxa (47% of the total) were common to other thermal springs of the Mediterranean area. Significant differences in the species composition among all substrates were highlighted by the ANOSIM test (global R = 0.554; p = 0.1%). The assemblages from rock formed a separated cluster from assemblages from cobbles and sediments in the nMDS plot. Rock-dwelling assemblages also had a lower species richness, probably due to the higher water temperature. Total suspended solids, discharge, water temperature and bromine were the most correlated environmental variables with diatom species and seem to influence both species composition and structure of assemblages. Some abundant taxa, such as Pinnularia joculata and Rhopalodia operculata, which fit well on high temperature and mineral content, can be considered representative taxa of the studied spring. This study underlines the importance of investigating different substrates to document diatom biodiversity in a more exhaustive way. It contributes to the knowledge of diatoms and ecology in thermo-mineral springs of Sardinia, providing first information on species composition at small-spatial and seasonal scale.
... Diatoms are unicellular, photosynthetic, eukaryotic organisms that inhabit almost all bodies of water. They are found in springs, rivers, ponds, lakes, ditches and in freshwater, brackish and marine waters (Smol & Stoermer 2010) and occur in terrestrial habitats such as wet rocks, mosses and soils, even caves (Falasco et al. 2014;Tofilovska et al. 2014). They are either planktonic (living in the open water) or benthic (growing associated with or attached to a particular substrate); they can, on occasion, be found in tap water (Schneider 1980), bathwater (Ago et al. 2011), well water Nikolova et al. 2002) and even airborne (Geissler & Gerloff 1966;Dayan et al. 1978;Romero et al. 1999). ...
Diatoms are unicellular, photosynthetic, eukaryotic organisms often classified as
among the algae. There are around 15 000 known species, but many more have yet to be described.
Their uniqueness lies in the siliceous covering of the cell, each being encased in a pair of silica
valves. Silica is virtually inert and indestructible, so after the organism’s death the silica parts
remain. The silica parts provide information for the classification of these diverse organisms. Diatoms
have been used in forensic science in a variety of ways, the most frequent being the diagnosis
of death by drowning. When a person drowns, water will enter the lungs and then enter the bloodstream
through ruptures in the peripheral alveoli before being carried to the other organs such as the
liver and heart. Naturally, the microscopic contents of the water, which will include diatoms, will
pass into the blood as well. The detection of diatoms in the organs can contribute to a diagnosis of
death by drowning, a process referred to as the ‘diatom test’. We will discuss this test in more detail,
illustrating our discussion with real examples.
... The monoraphid genus Achnanthes, originally described by Bory in 1822 from material collected by Lyngbye (1819), has long been considered one of the largest genera in the world, mainly based on a very broad generic concept. Over the past decades, a large number of taxa formerly placed in Achnanthes sensu lato were split off and transferred to other, often newly erected genera such as Achnanthidium Kützing, Psammothidium Bukhtiyarova et Round, Pauliella Round et Basson and Planothidium Bukhtiyarova et Round, leaving less than 150 recognized taxa in Achnanthes sensu stricto (Toyoda et al. 2005, Tofilovska et al. 2014. The genus is characterized as being clearly heterovalvar, with a raphe valve (RV) and a rapheless valve (RLV), and bent about the median transapical plane in girdle view (Round et al. 1990). ...
It has been known for a long time that marine mammals, such as whales and dolphins, host a very specific epizoic community on their skin. Whether or not a similar community exists on the carapaces of sea turtles is less studied. The present paper describes two new epizoic diatoms from the genus Achnanthes sensu stricto, Achnanthes elongata and Achnanthes squaliformis, found on the carapaces of nesting olive ridley sea turtles (Lepidochelys olivacea) in Ostional Beach on the Pacific coast of Costa Rica, based upon detailed scanning electron microscopy and comparison with the type material of Achnanthes groenlandica var. phinneyi and Achnanthes pseudogroenlandica. The two taxa appear to be closely related on the basis of their morphological features including long, slender valves, absence of terminal orbiculi, large cribrate areolae and absence of typical costae on the internal virgae of both valves. They can, however, be differentiated from each other by the number of areolae per stria, the position of the rapheless sternum and differences in their length/width ratio.
