Desmids of Brahmaputra valley, a major southern Asian river basin

: Inadequate information on the diversity and dispersion of desmids has led to incomplete floristic data in the northeastern region of India. The present study focuses on contributing to the information on the diversity and geographical distribution of desmid in water bodies of the Brahmaputra River basin of the Indian subcontinent. During the period 2019–2022, desmid flora of 91 waterbodies were studied. Two-hundred-and-thirty-one taxa belonging to five families and 25 genera were recorded, out of which 94 were new records for the northeastern India. Desmidiaceae was the dominant family with 195 species and with 69 species Cosmarium was the dominant genus.


INTRODUCTION
The Indo-Malaya/northern Australia desmid floral region (Coesel 1996) which covers the entire southeastern Asian river basins is one of the 10 desmid floral regions (Krieger 1933(Krieger , 1937) ) of the world.The Brahmaputra which originates in Tibet Himalaya and flows through India and Bangladesh up to the Bay of Bengal has the longest and largest river basins in the region covering an area of 2,900 km which includes altogether 180 watersheds, 24 major tributaries, and around 16,037 numbers of large to medium lentic water bodies up to the maximum size of 2,500 ha (Dadhwal et al. 2014).The prevailing eco-climatic conditions is concomitant with the humble and less destructive life styles of the aboriginal people help to maintain the pristine environments in the majority of the water bodies excluding those in urbanised centres/ towns that lead to support a rich desmid flora therein.
The members of this group not only prefer to grow and flourish in pure and less populated water but also quickly respond to the slightest change in pH or nutrient content in the substratum (Borics et al. 1998;Fehér 2003), which makes them ecologically sensitive and are therefore, considered as one of the indicators of good water quality.Recently, the information on desmids is seen to be documented as baseline data for any ecological and biomonitoring investigation in aquatic systems and the conservation of the same as well (Aquino et al. 2017;Paul et al. 2017) in the line of work of Coesel (1998) who proposed to determine the nature conservation value (NCV) based on parameters like species richness, presence of rare taxa, and the occurrence of taxa signifying ecosystem maturity.
Though a good number of workers (Baruah et al. 2009(Baruah et al. , 2013(Baruah et al. , 2020;;Deka & Sarma 2011;Adhikary & Jena 2012;Bordoloi & Baruah 2015;Nath & Baruah 2020) have documented algal flora in different regions of Brahmaputra river basin in recent days, exclusive information on diversity and distribution of desmids is very much limited from this floristically wealthier sandwich region between Indo-Burma and Himalaya biodiversity hotspots (Bordoloi 1983;Deka et al. 2011;Yasmin et al. 2011;Phukan & Bora 2012;Baruah & Baruah 2013;Das 2020).The present endeavour was therefore undertaken to explore and document the hidden wealth of desmid flora in different lentic and lotic aquatic ecosystems of the Brahmaputra River basin of the Indian subcontinent.

Sample collection and Identification
A total of 91 waterbodies (Table 1) were randomly explored in the entire reach of the mighty Brahmaputra River (Figure 1) for the collection of desmid samples.The collection of desmids was done by filtering technique using plankton net of mesh size 25 µm from January 2019 to December 2022.The samples were examined freshly under different magnifications (20X, 40X, and 60X) of the compound microscope (Euromex Delphi X Observer series) and photomicrographs were taken with the help of a digital camera (Euromex 20MP).Image view software was used for micrometric measurements of desmids.The remaining samples were preserved in Lugol's iodine solution for further investigations.Identification of desmids were done by following monographs of Croasdale et al. (1983), Prasad & Misra (1992), Lenzenweger (1996Lenzenweger ( , 1997Lenzenweger ( , 1999Lenzenweger ( , 2003)), John et al. (2005), Ahmed et al. (2007), and Das & Keshri (2016).Updated nomenclature of the species was given by following Guiry & Guiry (2022) and was systematically arranged following Ruggiero et al. (2015).

RESULTS
In the present study, 231 taxa of desmids belonging to 25 genera, under five families, and two orders were recorded from the selected water bodies of the entire Brahmaputra River basin located under the Indian subcontinent.Desmidiaceae was reported to be the dominant family with 195 species, of which Cosmarium was recorded as the dominant genus with 69 species.Site of collection: Dhamar Beel, Goalpara; Sorbhog Pond, Barpeta.
New to northeastern India (Image 21).

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Basionym: Cosmarium suborthogonum Raciborski Cells small sized, about 1.4-1.5 times longer than broad; median constriction deep, sinus narrowly linear and closed but slightly dilated at the apex, semicells subsemicircular, the basal angles broadly rounded, the lateral sides in the basal portion of the semicell parallel, the upper lateral sides with two undulations, retuse at the middle, cell wall smooth, cells 17-24 µm long, 12-16 µm broad and isthmus 5-6 µm broad.
Cells very small sized, almost as long as broad, deeply constricted at middle, sinus narrowly linear and slightly opened at extremities, semicell subrectangular, lateral margins without undulations, apex with rounded angles and almost straight border, cell wall smooth, axial chloroplast with one pyrenoid in each cell, cells 7-10 µm long, 7-9 µm broad and isthmus 3-4 µm broad.
New to northeastern India (Image 27).
Cosmarium quadrum var.minus Nordstedt 1873: 11 Cells small sized, slightly broader than long, deeply constricted at the middle, narrowly linear sinus with a slightly opened extremity, semicells sub rectangular, rounded basal angles, broadly rounded apical angles, lateral walls slightly convex, apex slightly retuse, cell wall densely granulated with solid granules arranged in decussating sequence, at the margins of the semicells 23 granules are shown, in the middle of the apex the size of granules is slightly reduced, axile chloroplasts with two pyrenoids per semicell, cells 27-31 µm long, 30-34 µm broad and isthmus 9-11 µm broad.
Previous records and distribution in northeastern India: Deepor Beel, Baruah et al. (2020) Cells very small sized, almost as long as broad, median constriction deep, sinus widely open, semi-cells rectangular with broadly truncate, rounded apical angles and wide sunken vertex, wall of the semicell with 6 small granules, 2 apical and 2 lateral, another two granules on the face of the semicells, chloroplasts with single pyrenoid in each semicell, cells 12-15 µm long, 10-12 µm broad and isthmus 4-5 µm broad.
New to northeastern India (Image 36).
New to northeastern India (Image 39).Cells small sized, about 1.2 times longer than broad, median constriction deep, sinus linear and closed, semicells sub-semicircular with convex lateral walls, apex flat with rounded angles, entire margins including apex with faint undulations, 9 undulations in each semicells, cell wall smooth, single axial chloroplast with a central pyrenoid in each semicell, cells 18-25 µm long, 15-20 µm broad and isthmus 5-7 µm broad.

Genus: Desmidium
Desmidium aptogonum Brébisson ex Kützing 1849: 190 Cells medium-sized, triangular, attached one another to form a long filament, about 1.8 times broader than long, median constriction shallow, sinus widely open, semicells transversely oblong with a small basal swelling around the isthmus, then gradually narrowed towards the apex, apex is broad and concave in the midregion, apex produced at the angles to form connecting processes, cells 13-16 µm long, 24-29 µm broad and isthmus 18-20 µm broad.
Previous records and distribution in northeastern India: Chandubi Beel, Nath & Baruah (2020).Cells small sized, about 1.4 times longer than broad, pyramidal semicells with broad basal lobe and truncate apical lobe, apex inflated, furnished with acute granules at the lateral walls and apical lobes, three large warts and three scrobicles at the central protrusion, median constriction deep, sinus linear, narrow, almost closed inside but open towards extremities, terminal lobes contain projected long stout spines, cell wall punctate, chloroplast with single pyrenoid in each semicell, cells 26-32 µm long, 18-22 µm broad and isthmus 6-7 µm broad.
New to northeastern India (Image 42).
Previous records and distribution in northeastern India: Dachi Lake, Hajong & Ramanujam (2018) Cells medium-sized, about 1.5 times longer than broad, deep median constriction, sinus linear and open, semicells truncatedpyramidal, basal angles broadly rounded and furnished with 3-5 stout spines, apical angles with a shout spine and the apical margin of polar lobe with a U-shaped deep incision at the middle, slightly lower to the lateral side of spiral angles with small spines, apex of polar lobe mancate, cell wall smooth, cells 36-45 µm long, 24-29 µm broad and isthmus 6.5-8 µm broad.

Euastrum coralloides var. trigibberum Lagerheim 1888: 3, pl. I [1]
Cells medium-sized, about 1.5 times longer than broad, nearly sub-rectangular in outline, median constriction deep, sinus narrowly linear and almost closed, semicells sub-pyramidate, 5-facial swellings, broader basal lobe with bilobed lateral walls, polar lobe bi-lobed, lower one short and upper one with single angular spine on each side, apical margin with undulations, somewhat lobed with a 'U' shaped long median open notch, on each sides of notch two prominent swellings, 3 swellings arranged in one row within basal lobe, cells 33-39 µm long, 21-25 pm broad and isthmus 6-7 μm broad.
Euastrum denticulatum F. Gay 1884: 335 Cells small sized, about 1.3 times longer than broad, median constriction deep with narrowly linear and closed sinus, semicells 3-lobed and subtrapeziform in shape, each angle furnished with tiny spine, apical lobes appear wide with a deep V-shaped incision at the middle, cells 25-27 μm long, 18-20 μm broad and isthmus 5-6 μm broad.
Previous records and distribution in northeastern India: North Eastern India, Yasmin et al. (2011).
Cells medium-sized, about 1.5-1.6 times longer than broad, deep median incision, sinus narrow, linear and closed outside, semicells truncate pyramidal, basal lobes broadly rounded, lateral margins retuse to polar lobe, apex slightly inflated, apical angles broadly rounded, apical margin flat and with a short median notch, a mucilage pore present at middle of each semicell, cells 62-74 um long, 38-47 um broad and isthmus 9-11 um broad.
Euastrum exile var.kaliganjense A. K. Islam & Begum, 1991: 75 Cells small sized, almost rectangular in outline, about 2.2-2.4 times longer than broad, median constriction deep, sinus narrow, linear and slightly dilated inside and outside, lateral walls with 3 undulations, basal lobe slightly broader than the apical lobe, apical angles furnished with an stout and erect spine, apical margin undulate with a shallow median incision, semicells with a median swelling, cell wall ornamented with 4 large marginal and 4 small J TT internal crescentic processes, cells 27-31 µm long, 11-14 µm broad and isthmus 4-5 µm broad.
New to northeastern India (Image 49).
Euastrum lapponicum Schmidle 1898: 47, pl.I [1]: fig.29 (as 'Lapponicum') Cells small sized, about 1.6-1.7 times longer than broad, median constriction deep, sinus narrow, linear and closed, broad basal lobes with undulate lateral walls, polar lobes short, broad with parallel margins, apical margin flat, angles furnished with a short spine, apex with a short median notch, face of semicell with a prominent protuberance bearing a pair of large granules, cell wall granulate, oval in vertical view, poles knob like with a subapical swelling on either side, oval or broadly elliptical in side view, cells 27-31 µm long, 16-18 µm broad and isthmus 6-7 µm broad.
Euastrum serratum Joshua 1886: 639, pl.23: figs 1, 2 Cells medium-sized, ellipsoid in out line, about 1.7 times longer than broad, median constriction deep, sinus linear and closed, semicell semipyramidate, lateral margins serrated, basal lobes divided into 2 short lobules, each lobule with a shallow notch at the tip, incision between apical lobe and upper basal lobe fairly deep, above this incision a single subapical lobule of polar lobe with depressed tip present, upper lobule of polar lobe broadly truncated, apex undulate with a deep and open median notch, apical angles furnished with a small horizontal spine, at base of each basal, lateral, and polar lobes in all 6 small processes present, cells 42-49 µm long, 24-28 µm broad and isthmus 7.5-9 µm broad.
New to northeastern India (Image 55).
Euastrum subhypochondrum F. E. Fritsch & M. F. Rich 1937: 176, fig. 10 A-E Cells medium-sized, almost as long as broad, median constriction deep, sinus 'V' shaped and open outwardly, semicells with very broad basal and narrow apical lobes, apex with undulation, apical angles furnished with two stout spines, angles of basal lobes also furnished with small spines but more in numbers, cell wall granulated, cells 49-58 µm long, 45-50 µm broad and isthmus 12-14 µm broad.
Previous records and distribution in northeastern India: Chandubi Beel, Nath & Baruah (2020) Cells medium-sized, quadrate in outline, about 1.1-1.2times longer than broad, median constriction deep, sinus linear and closed, basal angles narrowly rounded and produced, lateral walls retuse forming 'V'-shaped incision and forming narrowly rounded lateral lobes, apical lobes more produced than the typical, apex slightly retuse near the midregion, lobes furnished with short blunt spines, face of the lobes with scattered spines, face of the semicells with granules arranged in circle at the middle, cell wall otherwise smooth, cells 44-55 µm long, 37-43 µm broad and isthmus 10-12 µm broad.

Genus: Hyalotheca
Hyalotheca dissiliens Brébisson ex Ralfs 1848: 51, pl.I [1]: fig. 1 a-i Cells small sized, about 1.2 times broader than long, united one another to form long filaments, sinus a very slight median depression in the lateral walls, semicells cylindrical-discoidal, the lateral walls slightly convex, the apices broadly truncate, cylindrical in vertical view, one axial chloroplast in each semicell with a centrally placed pyrenoid, and several radiating ridges flattened at extremities, cells 12-15 µm long 15-19 µm broad and isthmus 14-16 µm broad.
Hyalotheca mucosa Ralfs 1848: 53, pl.I [1]: fig. 2 Basionym: Conferva mucosa Mertens Cells small sized, almost as long as broad, attached end to end to form a short filament, no median depression, very slightly constricted at the joints; semicells transversely sub-rectangular, lateral walls almost parallel, convex with broadly rounded apical angles, apex broad and truncate, cell wall smooth except two series of tiny granules just beneath the apices, cells 12-16 µm long and 13-15 µm broad.

Genus: Micrasterias
Micrasterias alata Wallich 1860: 279, pl.XIII [12]: fig.11 Cells large sized, almost as long as broad, median constriction deep, sinus widely open towards extremities, the upper margin of the upper member extends vertically, parallel to the polar lobe, and is divided from it by a deep and narrow incision, lateral lobes were once divided, the lower member was simple, and all divisions were deep, lobules were swollen at the base before abruptly and narrowly tapering to tridentate extremities, polar lobe slender with parallel sides, abruptly branching at apex into 2 slender diverging processes, cell wall smooth, cells 125-157 µm long, 121-134 µm broad and isthmus 18-21 µm broad.

Micrasterias americana Ehrenberg ex Ralfs 1848: xix [Errata and Addenda]
Cells large sized, about 1.1-1.2times longer than broad, median constriction deep, sinus open, acute towards apex, semicells semielliptical 5-lobed with conspicuously protruding polar lobe, retuse apex and angles produced into stout, diverging narrow incision processes with ends truncate and denticulate, from the base of each process arise 2 similar accessory processes, one on each side, lateral lobes divided into 2 lobules single spine or with comparatively shallow incisions dissecting them, cell wall granulate, granules scattered, cells 110-132 µm long, 92-108 μm broad and isthmus 23-26 μm broad.

Micrasterias ceratofera
Micrasterias foliacea Bailey ex Ralfs 1848: 210, pl.XXXV [35]: fig. 3 Cells medium-sized, sometimes occur singly or united with one another to form filaments, cells rectangular, about 1.4 times broader than long, median constriction deep, sinus linear, lateral lobes divided to the second and third order, different, the lower lobules horizontal, the upper lobules diverging, its upper part reduced to a conical projection, polar lobe very distinctive, basal part narrow with erect parallel margins, the middle of the apex features a very broad, deep subrectangular excavation, with the upper three-quarters of the lobe significantly extended, angles stout, ending in 2 widely divergent teeth, a depressed portion of the apex bearing two unequal stout spines on each side, cells 50-56 µm long, 71-80 µm broad and isthmus 13-15 µm broad.

Micrasterias mahabuleshwarensis J. Hobson 1863: 169, first fig. (as 'Mahabuleshwarensis')
Cells large sized, about 1.2 times longer than broad, median constriction very deep, sinus widely open, polar lobe in lower half quadrate, above widely expanding into narrow diverging processes at the angles, with more nearly erect accessory processes at their base, arising asymmetrically, one at the front and one at the back of the apex, apex nearly straight, lateral lobes once divided into narrow and tapering processes, processes with serrated walls, ends tri-denticulate, semicells with a row of acute intra-marginal granules along the inner part of the major incisions, with a small granulate central protuberance above the isthmus, cells 140-165 µm long, 118-133 µm broad and isthmus 26-28 µm broad.
Site of collection: Dighali Beel, Nagaon.Previous records and distribution in northeastern India: North Eastern India, Yasmin et al. (2011).
Micrasterias tropica Nordstedt 1870: 219, pl.2: fig 15 Cells large sized, about 1.3 times longer than broad, median constriction very deep, sinus widely open, polar lobe with erect, parallel-sided lower part and a diverging upper part, the apex flat between the long and spreading processes, lateral lobe undivided, horizontally extended, strongly tapered; with small stout marginal spines toward the ends of the lateral lobes and polar processes, and similar spines within the margins of all but the extremities, spines paired at the depressed apex, in top view semicells fusiform, marginal and inter-marginal spines present, cells 101-122 µm long, 85-93 µm broad and isthmus 17-19 µm broad.
New to northeastern India (Image 60).
Micrasterias zeylanica F. E. Fritsch 1907: 246, fig. 4 C Cells medium-sized, almost as long as broad, median constriction deep, sinus open at extremities, semicells 3-lobed, lobes separated by incisions, ends of terminal lobe bluntly pointed, lateral lobes with two blunt processes, separated by a narrow and shallow depression, the processes next to the sinus being horizontal, the other bent down toward the sinus, polar lobe widely spreading, slightly drawn out at each extremity into a horizontal or deflected process, apex flatly convex, cell wall smooth, cells 49-55 µm long, 50-57 µm broad and isthmus 8-9.5 µm broad.

7-11
Cells small sized, rectangular in outline, about 1.5 times broader than long, deeply constricted, sinus linear inside, and open towards extremities, cells attached by a cellular extension called cornua and form a long filament, a row of minute teeth present between cornua, cells 12-16 µm long, 18-24 µm broad and isthmus 4-5 µm broad.
Pleurotaenium kayei (W.Archer) Rabenhorst 1868: 439 Basionym: Docidium kayei W. Archer Cells cylindrical, about 4.6 times longer than broad, median constriction prominent, sinus widely open, each semicell broader at the base and gradually tapering towards the apex, lateral walls undulate up to the base of the apex and furnished with 5-ring-like whorls of spiny outgrowths from the base of semicell up to below the apex, apex flatly truncate with a ring of 10-12 short spines, cells 277-318 µm long, 59-68 µm broad, isthmus 30-32 µm broad and apex 40-44 µm broad with spines.
New to northeastern India (Image 63)., sinus open at extremities, the lateral angles furnished with a long stout converging spine, apical processes about as long as the spines, the apex slightly raised and undulate, cells joined end to end forming long pseudofilament, cells 14-17 µm long, 22-28 µm broad and isthmus 5-6 µm broad.
Site of collection: Jor Beel, Jorhat.New to northeastern India (Image 65).Cells small sized, compressed, about 1.5 times broader than long, median constriction deep, sinus narrowly linear and open outwardly, the apical process of the semicells very short, often tuberculate and does not overlap the adjoining cells, chloroplast with single pyrenoid in each semicells, cells 10-12 µm long, 13-18 µm broad and isthmus 5-6 µm broad.

Sphaerozosma vertebratum
Site of collection: Shamaguri Beel, Nagaon.Previous records and distribution in northeastern India: Loktak Lake, Jena & Adhikary (2011).Cells medium-sized, compressed, about 2 times broader than long, median constriction deep, sinus widely open, semicells wedged with converging processes, with a serrate-toothed margin at the apex of the trifid, base and the apex of the semicells with 3 series of transversely arranged verrucae, basal part of each side emarginate with 4 or 8 short projections placed vertically (2, 2) decorated, fusiform in top view, cells 32-36 μm long, 64-75 μm broad and isthmus 9-10 μm broad.
Staurastrum bifidum Brébisson ex Ralfs 1848: 215 Cells medium-sized, about 1.5-1.6 times broader than long, median constriction moderately deep, the sinus widely open, semicells semielliptical, the basal margins symmetrically convex to acutely rounded apical angles which bear two long sharp and superimposed spines, the apical margin broadly convex, cell wall smooth, cells triangular in top view, the margins concave, the poles bifurcate and furnished with 2 long and stout spines, cells 30-35 µm long, 48-55 µm broad and isthmus 10-12 µm broad.
New to northeastern India (Image 70).
New to northeastern India (Image 71).
Staurastrum duplex Wolle 1883: 29, pl.XXVII: fig. 10, 10a Cells small sized, about 1.2 times longer than broad, median constriction moderately deep, sinus open, semicells transversely rectangular, the vertical margin convex and then concave into lower, bi-spinate basal processes, lateral walls parallel to the upper angles which are similarly extended into short, truncate, bi-spinate processes, the apical margin broadly convex, cell wall smooth, cells triangular in top view, the margins broadly concave, the angles protracted into bifurcate and bi-spinate processes, cells 24-28 µm long, 20-23 µm broad and isthmus 9-10 µm broad.
New to northeastern India (Image 75).

Staurastrum freemanii
West & G. S. West Cells medium-sized, subfusiform, about 1.6-1.7 times broader than long, median constriction deep, sinus acute and widely open, lateral angles produced to form moderately long, stout and tapering divergent processes furnished with 2 stout spines at the end, apex slightly convex, rarely flat, cell wall granulated, a pair of additional spines alternately located on each semicell, cells 38-45 µm long, 65-76 µm broad and isthmus 12-13 µm broad.
Staurastrum furcatum Brébisson 1856: 136 Cells medium-sized, almost as broad as long, median constriction deep, sinus widely open, semicells transversally oval to subglobose, apical margin broadly convex and angles furnished with a pair of stout, bi-spinate processes, dorsal as well as ventral walls almost equally convex, basal margins convex towards lateral angles and each with a stout bi-spinate process , cell wall smooth, cells 25-29 µm long, 27-33 µm broad and isthmus 6-7 µm broad.

Staurastrum longibrachiatum (Borge) Gutwinski 1902
Basionym: Staurastrum bicorne var.longebrachiatum O. Borge Cells medium-sized, about 1.7 times broader than long, median constriction shallow, sinus a notch and open widely, semicells bowl shaped, margins gradually diverging into apical processes, processes with two bi-spinate protrusions at the base, also furnished with a series of denticulations on ventral margin and series of incisions and verrucae at the margins of semicell, apical angles protracted into horizontally directed long and slender processes with 2 small spines at the tip, apical margins truncate and furnished with a series of verrucae, cells 35-40 µm long and 61-69 µm broad and isthmus 7-9 µm broad.
Previous records and distribution in northeastern India: North Eastern India, Yasmin et al. (2011).circular with angles produced into long processes, the entire margin of processes with continuous small undulations and tips with 2 stout, unequal, divergent spines, apex flat and with another 2 pairs of oppositely directed spines in each semicell, cells 25-31 µm long, 46-54 µm broad and isthmus 7-8 µm broad.
New to northeastern India (Image 79).
Staurastrum simonyi Heimerl 1891: 67, pl.V [5]: fig.23 Cells small sized, almost as long as broad, median constriction deep, sinus acute and widely open, semicells sub-fusiform or sub semi-circular, dorsal and ventral margins equally convex, lateral angles truncate and provided with 2-4 small spines, apical margin with a series of 4 spines between each pair of consecutive angles, the two median ones being the largest and projecting conspicuously from the apex, further with an occasional series of 4 smaller spines beneath the first series, triangular in top view, lateral walls straight or slightly concave or convex, angles obtusely rounded and furnished with 2-4 small spines, angles occasionally with traces of about 2 or 3 concentric series of minute distant denticulations, cells 24-28 µm long, 23-26 µm broad and isthmus 8-9 µm broad.
Results also revealed that the Desmidiaceae was the dominant family with the highest representation of 19 genera and 195 species followed by Closteriaceae (1 genus and 27 species), Gonatozygaceae (1 genus and 4 species), Mesotaeniaceae (2 genera and 3 species), and Zygnemataceae (2 genera and 2 species).Amongst the genera, Cosmarium was the dominant one with 69 spe-  2).It was noted that the Cosmarium showed overall dominance in the majority of waterbodies in Bangladesh also (Islam & Haroon 1980;Islam & Irfanullah 2006).
The results further showed that the number of desmids (231) recorded during the present exploration suppresses the earlier records of desmids from northeastern India (Bordoloi 1983;Deka et al. 2011;Yasmin et al. 2011;Phukan & Bora 2012;Baruah & Baruah 2013;Das 2020) and it was found that out of the 231 reported species, a total of 94 species were reported for the first time from the northeastern region of India.
As the Brahmaputra River basin harbours a higher number of desmids ( 231), the region could be considered a suitable habitat for the desmids diversity and could be explored for bio-prospection in a phased manner.Another interesting fact that emerged in the present study is that Cosmarium forceps, Micrasterias foliacea, and Micrasterias pinnatifida were universally present in a majority of the water bodies located in the entire stretch of Brahmaputra River which invites an in-depth ecological study.

Figure 1 .
Figure 1.Location map showing desmid collection sites in Brahmaputra valley.