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Three new species of Gomphonema Ehrenberg (Bacillariophyta), from Eastern Himalayas, with a note on the unique girdle band structure

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Abstract

Three new diatom taxa belonging to the genus Gomphonema were recorded during a survey of streams of the Eastern Himalayas from the state of Arunachal Pradesh, India. Detailed light (LM) and scanning electron microscope (SEM) observations are used to characterize the morphology and ultrastructure of the three new Gomphonema taxa. Comparisons are made with similar taxa and characters delimiting these new species. All three new taxa have three different kinds of external areolar patterns, confirming the presence of three different groups of Gomphonema in one habitat. Further, one of the species showed a unique fimbriate structure in head pole region of the girdle band. This is the first time such a structure is observed in the freshwater gomphonemoid diatoms.

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... Studies on the diatom flora of the Himalayan region have been confined to Nepal (Jüttner et al. 2000(Jüttner et al. , 2004(Jüttner et al. , 2010a(Jüttner et al. , 2010b(Jüttner et al. , 2017Van de Vijver et al. 2011;Krstić et al. 2013), Tibet and China (Mereschkowsky 1906;Kociolek 1992;Huizhong & Jiayou 2000;Li et al. 2010aLi et al. , 2010bGong & Li 2011;Hu et al. 2013;Gong et al. 2015;Jiang et al. 2018;Liao & Li 2018). Studies on the freshwater diatoms from the Indian Territory of the region are limited to a few recent records (Das et al. 2018;Wadmare et al. 2019). Beyond floristic and biodiversity discovery studies, several efforts have also been made for ecological assessment of streams, rivers and lakes through diatom studies in the adjoining Nepalese Himalayas (Ormerod et al. 1994;Jüttner et al. 1996Jüttner et al. , 2003Sharma et al. 2012;Gurung et al. 2018). ...
... We have begun an initial survey of biodiversity discovery and floristics in Northeastern India. Das et al. (2018) described three new Gomphonema species from a river in Western Arunachal Pradesh including Gomphonema mayamae Sudipta K. Das, C. Radhakrishnan, Kociolek et B. Karthick (Das et al. 2018), which had a fimbriate structure in the girdle band near the head pole. This morphological feature is unique among the freshwater Gomphonema species. ...
... We have begun an initial survey of biodiversity discovery and floristics in Northeastern India. Das et al. (2018) described three new Gomphonema species from a river in Western Arunachal Pradesh including Gomphonema mayamae Sudipta K. Das, C. Radhakrishnan, Kociolek et B. Karthick (Das et al. 2018), which had a fimbriate structure in the girdle band near the head pole. This morphological feature is unique among the freshwater Gomphonema species. ...
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A new freshwater diatom species, Gomphonema adhikarii sp. nov., is described from a small road-side pool from the alpine region of Arunachal Pradesh, Eastern Himalayas, India. Detailed valve morphological features, based on both light and scanning electron microscopy, is presented and this taxon is compared with similar species. Gomphonema adhikarii has a distinct asymmetry about the apical axis and slightly bent foot pole area. The outline of the valve is slightly undulate, the valve centre is swollen and both apices are broadly rounded. This new species described from the Eastern Himalayas supports the idea of the area being rich in biodiversity, even with respect to the freshwater diatom flora.
... WG is home to more than 150 taxa of Gomphonema (Alakananda et al. unpublished list). Gandhi described 30 Gomphonema taxa from the Western part of India, particularly from the WG (Gandhi 1956(Gandhi , 1958(Gandhi , 1959(Gandhi , 1960(Gandhi , 1964(Gandhi , 1966(Gandhi , 1970(Gandhi , 1998Gandhi et al. 1983 Karthick et al. 2015, Karthick et al. 2016, Das et al. 2018, Pardhi et al. 2020, Radhakrishnan et al. 2020a. Nearly 30 % of these species are endemic to India, especially restricted to the biodiversity-rich hotspots such as the WG . ...
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A new freshwater diatom species, Gomphonema rajaguruii sp. nov., is described from a wet wall at Mahabaleshwar, Western Ghats, Maharashtra, India. The new species is described based on light and scanning electron microscopy. Features that distinguish this new species from morphologically-similar species such as G. kallarense and G. lujanense include valve shape, which is broad at the centre and narrower near the poles, a distinctly lateral, undulate raphe system and costa-like striae, which are comprised of two rows of slit-like areolae. Although G. rajaguruii also resembles some taxa from the genus Gomphoneis, such as G. eriense and its close allies, it differs from them by lacking an axial plate. The description of G. rajaguruii sp. nov. increases the knowledge on the diatom diversity in the region.
... It comprises two important biodiversity hot spots: the Eastern Himalaya and Indo-Burma. Compared to other plant groups, phycological explorations in this region are meagre (Das & Adhikary 2014), specifically diatoms, which were documented very recently (Das et al. 2018Wadmare et al. 2019;Bhatt & Karthick 2020;Radhakrishnan et al. 2020). However, there are many diatom records from the adjacent Nepalese territory (Jüttner et al. 2010a(Jüttner et al. , 2010b(Jüttner et al. , 2018Van de Vijver et al. 2011;Krstić et al. 2013;Wetzel et al. 2019;Chudaev et al. 2020). ...
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We describe Adlafia kociolekii sp. nov. from aerial habitats in Sikkim, India, a part of the Eastern Himalayas. The species is described based on light and scanning electron microscopic observations. The main diagnostic features include valves are clear elliptical, a narrow axial area at the centre, radiate to convergent striation, and distinctive Voigt discontinuity at both apices. In terms of ultrastructure, the features that identify this species as new are the internally presence of raphe on the elevated sternum, with distal raphe ends distinctly deflected to opposite sides of proximal ends, and distal ends terminating in long and thickened helictoglossae. The species was also recorded from wet walls and freshwater habitats of northeast India, in the present study. The morphological features of the species are compared with other closely similar taxa of Adalfia and other naviculoid genera.
... Most of the earlier works on moss-inhabiting diatoms were confined to mountainous habitats of Polar Regions (Hickman and Vitt 1973;Beyens 1997, 1999;Alfinito et al. 1998;Gremmen et al. 2007;Kopalova et al. 2014), temperate regions (Cantonati 2001;Bertrand et al. 2004;Nováková and Pouličková 2004;Pouličková et al. 2004;Buczko and Wojtal 2005;Buczko 2006;Kulikovskiy 2008;Szulc et al. 2014) and few from other parts of the world (Round 1957;Ando 1978;Mayama 1993;Chen et al. 2012;Ress and Lowe 2014). But, the Indian Himalayan region, specifically Eastern Himalayas are devoid of any such studies so far except the taxonomic explorations started very recently (Das et al. 2018;Wadmare et al. 2019). ...
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... Diatom studies in Indian Eastern Himalayan region are rare, with only a few recent reports (Das et al. 2018;Wadmare et al. 2019). In comparison, records of diatoms from the Nepalese Himalayas (Jüttner et al. 2004(Jüttner et al. , 2010a(Jüttner et al. , 2010b(Jüttner et al. , 2017(Jüttner et al. , 2018Van de Vijver et al. 2011;Krstić et al. 2013;Wetzel et al. 2019) are numerous. ...
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A new species of Pinnularia is described from a stream from Sikkim, India, falls under Eastern Himalayas biodiversity hotspot. Features that help make this species distinctive include having triundulate margin, a broad, central fascia, a central depression, and oppositely-deflected external distal raphe fissures. Pinnularia sikkimensis sp. nov. is compared with its morphologically similar species, such as Pinnularia nodosa, P. biceps, P. grunowii, P. septentrionalis, P. graciloides var. jogensis and P. ferrophila. The taxon is also recorded from two stream sites in Vietnam suggesting a wide distribution across Southeast Asia. In addition to the description of the new species, a checklist of endemic Pinnularia taxa from India is also presented.
... The region is still unexplored in terms of diatom research is concerned. However, recent studies from the Eastern Himalayas and Meghalaya (Das et al. 2018;Wadmare et al. 2019;Roy et al. 2020) highlighted the need for exploring the diatom flora in the various habitats of Northeast India. ...
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... Though this place has immense floristic wealth, the history of its phycological exploration is only few decades old (Reddy et al., 1986;Singh et al., 1997;Singh and Gupta, 2000;Gupta et al., 2002;Adhikary, 2012, 2014;Das, 2015Das, , 2016, which were only restricted to some novel distributional records. Recently, Das et al. (2018) described three new freshwater diatoms species from the state. In the present study, a new chrysophycean species from this region, was described. ...
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A new species of the rare chrysophycean genus Dermatochrysis Entwisle & R.A. Andersen is described from eastern Himalayas (Arunachal Pradesh, India). The comparative morphology of this taxon with allied species showed its uniqueness in thallus structure and cellular arrangements, thus is proposed as a new species, i.e. Dermatochrysis himalayensis
... But among the photosynthetic organisms, the algal flora (including diatoms) are perhaps the least studied from Sikkim (Prasad and Khanna 1987;Bhakta, Das, and Adhikary 2010;Das and Keshri 2016). Our knowledge of the diatoms from the Himalayas is very limited (Jüttner, Cox, and Ormerod 2000;Jüttner, Reichardt, and Cox 2004;Jüttner, Chimonides, and Cox 2011;Van de Vijver et al. 2011;Krstić et al. 2013;Das et al. 2018). ...
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... Scale bars : Figs 179, 180, 184 = 3 μm, Figs 181, 183, 185, 186 = 1 μm, Fig. 182 = 600 nm. 1 − 8) has wider striae (10 − 12 in 10 μm) and differs in ultrastructure, with C-, E-or S-shaped areola openings. Gomphonema saparense S.K. Das, C. Radhakrishnan, Kociolek & B. Karthick is wider (5.2-6.5 μm); the areola openings are mostly slit-shaped, C-shaped only along the axial area and striae become biseriate at the head pole (Das et al. 2018). (Figs 187-210) Description LM (Figs 187-200). ...
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This paper describes seven new Gomphonema species from the Himalaya and provides information about their ecology with respect to water chemistry and habitat character. Diatoms were collected during surveys of over 200 Himalayan streams between 1993 and 2000. The geographical distribution, which covers a 1000 km east-west range in the Himalaya of north-west India and Nepal, is discussed along with the occurrences of these taxa in relation to environmental conditions.
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A diatom species published by Ehrenberg (1854) under the name “Gallionella campylosira” was observed and investigated in the light microscope (LM) from mica-strips found in the Ehrenberg collection at the Natural History Museum, Humboldt University of Berlin (Germany). The raw material from which the mica-strips were made has also been observed and investigated in the scanning electron microscope (SEM). According to valve morphology it was found that this taxon belongs to the genus Aulacoseira Thwaites and so its formal transfer into this genus is proposed. The observed valve morphology and ultrastructure of this species are discussed and compared with those of related species to show valve pattern variability.
Article
Cyclotella atomus Hust., C. meneghiniana Kütz., C. comta (Ehr.) Kütz., C. antiqua W. Sm., C. michiganiana Skv., C. ocellata Pant., C. glomerata Bachmann, C. pseudostelligera Hust., and C. stelligera (Cleve et Grun.) V. H., were selected for ultrastructure investigations on the basis of their ready availability. Specimens were examined employing both transmission and scanning electron microscopy. Strutted processes, labiate processes, spines and other special features were surveyed in all species. On the basis of these observations the species of Cyclotella observed seem to be in one of 3 morphological groups, the meneghiniana group, the comta group, and the stelligera group.
Article
Conservationists are far from able to assist all species under threat, if only for lack of funding. This places a premium on priorities: how can we support the most species at the least cost? One way is to identify 'biodiversity hotspots' where exceptional concentrations of endemic species are undergoing exceptional loss of habitat. As many as 44% of all species of vascular plants and 35% of all species in four vertebrate groups are confined to 25 hotspots comprising only 1.4% of the land surface of the Earth. This opens the way for a 'silver bullet' strategy on the part of conservation planners, focusing on these hotspots in proportion to their share of the world's species at risk.
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