Journal of Threatened Taxa | www.threatenedtaxa.org | 26 April 2025 | 17(4): 26928–26931

ISSN 0974-7907 (Online) | ISSN 0974-7893 (Print)

https://doi.org/10.11609/jott.9106.17.4.26928-26931

#9106 | Received 18 April 2024 | Final received 25 February 2025 | Finally accepted 05 March 2025

Occurrence of a rare desmid Tetmemorus laevis Ralfs ex Ralfs from Yumthang Valley, northern Sikkim with a note on the genus in India

Debjyoti Das ^{1 ,} Jay Mal ² & Jai Prakash Keshri ³

¹ Department of Botany, Khalisani Mahavidyalaya, Chandannagar, West Bengal 712138, India.

^2,3 Phycology Laboratory, CAS in Botany, The University of Burdwan, Burdwan, West Bengal 713104, India.

¹ debjyotidas72@yahoo.in, ² jaymal8942@gmail.com, ³ keshrijp@gmail.com (corresponding author)

Editor: Asheesh Shivam, Nehru Gram Bharati (Deemed to be University), Uttar Pradesh, India. Date of publication: 26 April 2025 (online & print)

Citation: Das, D., J. Mal & J.P. Keshri (2025). Occurrence of a rare desmid Tetmemorus laevis Ralfs ex Ralfs from Yumthang Valley, northern Sikkim with a note on the genus in India. Journal of Threatened Taxa 17(4): 26928–26931. https://doi.org/10.11609/jott.9106.17.4.26928-26931

Copyright: © Das et al. 2025. Creative Commons Attribution 4.0 International License. JoTT allows unrestricted use, reproduction, and distribution of this article in any medium by providing adequate credit to the author(s) and the source of publication.

Funding: UGC, New Delhi & Ministry of Environment Forest & Climate Change for funding under AICOPTAX programme

(No. F. No. 2018/15/2015-CS (Tax) dated 18th January 2018).

Competing interests: The authors declare no competing interests.

Acknowledgements: Authors acknowledge to UGC, New Delhi for financial support to carry out this investigation & head of the Department of Botany, The University of Burdwan for laboratory facilities. Special thanks are due to the Home Department, Govt. of Sikkim for various help and Forest Department, Govt. of Sikkim. Support of fund from MoEFCC in AICOPTAX programme is also highly acknowledged.

Abstract: The rare desmid genus Tetmemorus Ralfs ex Ralfs with a single species T. laevis Ralfs ex Ralfs is reported for the first time from the Yumthang Valley of northern Sikkim. This genus is characterized by apical incision apart from the lateral median constriction. Only five species have been reported from different parts of India. This is the first record of the specimen from eastern Himalaya as well as northern part of India. Occurrence of the other species of the genus in India has also been discussed.

Keywords: Algae, eastern Himalaya, new record, Phytoplankton, Sikkim.

Tetmemorus Ralfs ex Ralfs, an interesting desmid genus, was first described by Ralfs (1848) with its three species, viz., T. brebissonii Meneghini ex Ralfs, T. laevis Ralfs ex Ralfs, and T. granulatus Brébisson ex Ralfs. Although having an apical incision like Euastrum it differs from the latter in cylindrical body lacking any lobes or sinuation (Ralfs 1848).

Several species of Tetmemorus have been reported from different parts of the world but in India it was recorded by only a handful of investigators. First report of this genus was from upper Batong Valley, Sikkim by Dickie (1882). He reported T. granulatus Brébisson ex Ralfs from this region. Turner (1892) reported T. brebisonii Meneghini ex Ralfs from eastern India. Agarkar & Agarkar (1977) reported two taxa of Tetmemorus, viz., T. brebissonii var. minor De Bary and T. laevis Ralfs ex Ralfs from Pachmarhi, Madhya Pradesh. Later, Agarkar et al. (1983) reported T. laevis Ralfs ex Ralfs & T. laevis var. minutus (De Bary) Willi Krieger from Madhya Pradesh. T. brebissonii var. minor de Bary has been reported from Tamil Nadu (Suxena 1983). From Kerala T. euastroides A.M. Scott & Prescott was reported by Shaji et al. (1988) & T. laevis Ralfs ex Ralfs was recorded from Chathannoor (Sindhu & Panikkar 1995). T. laevis Ralfs ex Ralfs has been reported from West Bengal (Santra & Pal 2006). Distribution map of the recorded taxa in India is depicted in Figure 1.

During systematic investigations on desmids of eastern Himalaya the authors recorded T. laevis Ralfs ex Ralfs from the Yumthang Valley of northern Sikkim.

Materials and Methods

Algal samples were collected as algal mass by hand or by forceps and scalpels from different spots of this region at about 0930–1030 h (Das & Keshri 2016). Totally, 12 collections were made. Samples were mainly collected from small streams & wet rocks and immediately fixed on the spot in 5% formaldehyde aqueous solution. Water samples were preserved in 500 ml bottle with 1% Lugols’ Iodine to study the microscopic phytoplanktons as well. The water temperature (using non-mercuric alcohol thermometer by Labworld), pH (using standard pH paper by Merck), and habitats were recorded during the study. Initial observations were made in the laboratory under Olympus GB compound microscope using GWF as mount medium (Bando 1988). Photomicrographs were also taken in Zeiss Axioscope plus research microscope with Axiocam-503 attachment.

Study area

Eastern Himalaya including Sikkim is considered as one of the four biodiversity hot spots in India (Hajra & Verma 1996). Sikkim is the home of several indigenous plant species. Several regions of eastern Himalaya are still unexplored. Most of the parts of northern Sikkim are even inaccessible and hence very little explored. Very few works in phycological investigations have been carried out from northern Sikkim till date. Santra (1984) recorded a few Cyanophyceae from northeastern Sikkim. Das & Keshri (2013) reported several algal taxa from Gurudongmar Lake.

In this work authors investigated an uncommon desmid taxon Tetmemorus laevis Ralfs ex Ralfs from Yumthung Valley, northern Sikkim (Figure 1). The extremely scenic Yumthang Valley is situated at an elevation of 3,545 m in the north of Sikkim and is popularly known as ‘Valley of flowers’ due to the intense blossom of Rhododendron flowers of various colours. This work has been carried out during the phycological exploration of eastern Himalaya by the authors during 2009–2015. This region is about 150 km away from Gangtok, the capital of Sikkim. The nearby inhabited area is Lachung.

Results

Tetmemorus laevis Ralfs ex Ralfs [Pl. 1, fig. A-C]

Ralfs 1848, p.146, pl. 24, f. 3a–g; Prescott et al. 1975, p. 149, pl. 56, f. 1–3, 6–8; John et al. 2011, p. 727, pl. 180K

Cells cylindrical, 3.87 times longer than broad, with a conspicuous, median constriction, and a deep & narrow apical incision in the broadly rounded apex; semicells in face view slightly tapered, lateral walls slightly concave; cell wall finely punctate; chloroplast axial, with 7–8 radiating longitudinal plates, pyrenoid large, single in each chloroplast.

Length: 85–86 μm, Breadth: 22–23 μm, Isthmus: 19–20 μm, Apex: 11–14 μm.

Distribution: India, Sikkim, northern Sikkim, Yumthang Valley, 27.80493⁰ N, 88.70476⁰ E, 5 May 2010, D. Das & J.P. Keshri.

Habitat: The alga is rare in the study area. It has been recorded as phytoplankton from running water of a small stream. water pH: 6, water temperature 7⁰C at the time of collection.

Discussion

Desmids are oligotrophic in occurrence, indicators of low pollution level & conductance (Brook 1981; Brook & Johnson 2011). Studies on its biodiversity are not extensive except a few (Turner 1892; Santra & Pal 2006; Das & Keshri 2016). The genus Tetmemorus is known to occur abundantly in shallow waters of wetlands and slow flowing streams but infrequent as metaphyton and plankton (Hall & McCourt 2015). This the third report of the species from India and first report from northeastern India. Earlier it was reported from Kerala (Sindhu & Panikkar 1995) and Madhya Pradesh (Agarkar 1977). Dickie (1882) reported Tetmemorus granulatus Brébisson ex Ralfs from northeastern India more than 125 years ago. This investigation added one more rare taxon which reveals that extensive investigations are needed in Sikkim. Since desmids are also indicator of low pollution further investigations may help in the typification of habitats (Bellinger & Sigee 2015).

Table 1. Ecological notes of the samples collected from the field (Yumthang Valley).

Sample number	Co-ordinates	pH	Water temperature (°C)	Habitat
DD-656	27.79265⁰ N 88.70560⁰ E	6.5	6.5	Brown powdery mass with thin filamentous mass on the rock from a small water body.
DD-657	27.79723⁰ N 88.70461⁰ E	6.5	6.5	Brownish filament on the surface of a wet rock.
DD-658	27. 79873⁰ N 88.70558⁰ E	6.5	6.5	Powdery mass and filaments along with semi aquatic weeds from a shallow water body.
DD-659	27.79993⁰ N 88.70543⁰ E	6.0	6.5	Green filaments on the surface of the wet soil.
DD-660	27.80493⁰ N 88.70476⁰ E	6.0	7	Phytoplankton sample from running water of a small stream.
DD-661	27.80497⁰ N 88.70476⁰ E	6.5	7	Light green filaments on the water surface along with yellowish green filament and dark powdery mass of a small stream.
DD-662	27.80499⁰ N 88.70476⁰ E	6.5	7	Brownish mass on rock surface under water of a small stream.
DD-663	27.82468⁰ N 88.69596⁰ E	6.9	7.5	Bright green powdery mass on soil under water from a small water body.
DD-664	27.82468⁰ N 88.69596⁰ E	6.9	7	Dark green scum on the surface of a wet rock.
DD-665	27.82609⁰ N 88.69581⁰ E	6.9	7	Brownish powdery mass with wet moss on a tree trunk.
DD-666	27.82626⁰ N 88.69585⁰ E	6.5	7	Bluish scum on the surface of wet rock beside a small waterfall.
DD-667	27.82612⁰ N 88.69564⁰ E	6.5	7	Brownish powdery mass from a small water body beside a small waterfall.

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