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Oricymba tianmuensis sp. nov., a new cymbelloid species (Bacillariophyceae) from Tianmu Mountain in Zhejiang Province, China

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  • Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences

Abstract and Figures

During a survey of freshwater diatoms from streams in the west region of the Tianmu Mountains, Zhejiang Province, China, a new Oricymba species, Oricymba tianmuensis sp. nov. has been recorded. A detailed morphology description of O. tianmuensis is presented, based on light and scanning electron microscopy. Oricymba tianmuensis sp. nov. is characterized by a ridge along the valve face typical of the genus, as well as a linear-lanceolate, symmetrical or slightly dorsiventral outline with a gibbous central portion gradually tapering or nearly paralleling towards the bluntly cuneate poles, a distinct rhombiclanceolate asymmetric central area with a distinct stigma on the ventral side of the central nodule, a slightly lateral raphe with widened proximal endings and strongly deflected distal endings, and weakly radiate striae. Morphological features of the taxon are compared with similar species, and the biogeography of the genus is summarized.
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Phytotaxa 236 (3): 257–265
www.mapress.com/phytotaxa/
Copyright © 2015 Magnolia Press Article PHYTOTAXA
ISSN 1179-3155 (print edition)
ISSN 1179-3163 (online edition)
Accepted by Saúl Blanco Lanza: 14 Nov. 2015; published: 1 Dec. 2015
http://dx.doi.org/10.11646/phytotaxa.236.3.6
257
Oricymba tianmuensis sp. nov., a new cymbelloid species (Bacillariophyceae) from
Tianmu Mountain in Zhejiang Province, China
WEI ZHANG1,3, YAN-LING LI2, J. PATRICK KOCIOLEK3, RUI-LEI ZHANG1,4 & LI-QING WANG1,4*
1Laboratory of Aquatic Ecology and Environmental Restoration, College of Fisheries and Life Science, Shanghai Ocean University,
Shanghai 201306, P. R. China.
2State Key Laboratory of Lake Science and Environments, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences,
Nanjing 210008, P. R. China.
3Museum of Natural History and Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309 USA.
4Water Environment & Ecology Engineering Research Center of Shanghai Institution of Higher Education, Shanghai 201306, P. R.
China.
*Corresponding author (E-mail: lqwang@shou.edu.cn)
Abstract
During a survey of freshwater diatoms from streams in the west region of the Tianmu Mountains, Zhejiang Province, China,
a new Oricymba species, Oricymba tianmuensis sp. nov. has been recorded. A detailed morphology description of O. tian-
muensis is presented, based on light and scanning electron microscopy. Oricymba tianmuensis sp. nov. is characterized by
a ridge along the valve face typical of the genus, as well as a linear-lanceolate, symmetrical or slightly dorsiventral outline
with a gibbous central portion gradually tapering or nearly paralleling towards the bluntly cuneate poles, a distinct rhombic-
lanceolate asymmetric central area with a distinct stigma on the ventral side of the central nodule, a slightly lateral raphe
with widened proximal endings and strongly deflected distal endings, and weakly radiate striae. Morphological features of
the taxon are compared with similar species, and the biogeography of the genus is summarized.
Key words: taxonomy, morphology, diatoms, new species, Oricymba, Tianmu Mountain
Introduction
The genus Oricymba was erected by Jüttner, Krammer, Cox, Van de Vijver & Tuji (2010) based on the freshwater
species Oricymba japonica (Reichelt) Jüttner, Cox, Krammer & Tuji (2010: 408= Cymbella japonica Reichelt in
Kuntze 1898: 391). Oricymba is characterized by a slightly dorsiventral or almost symmetrical valve outline, a marginal
ridge along the valve face, grooves along the girdle, small and shallow circular impressions in the axial and central
areas, and overgrowths of silica hiding the central endings of the raphe on the internal valve surface (Jüttner et al.
2010). Four species were originally assigned to Oricymba (Jüttner et al. 2010), and recently Kulikovskiy et al. (2015)
described one new species and transferred another to the genus. In terms of distribution of the genus, one species
(O. japonica) has been reported from several east Asian countries (Foged 1971, Nather Khan 1990, Lee et al. 1993,
Watanabe 2005, Joh 2011, Shi 2013, Kulikovskiy et al. 2015), two others (O. perjaponica (Krammer & Lange-Bertalot
in Krammer 2002: 64) Kulikovskiy et al. (2015: 127) and O. voronkinae Glushenko et al. in Kulivoskiy et al. (2015:
127), are known from Laos and Cambodia, and the other three species from the original description of the genus are so
far known only from Nepalese Himalaya (Jüttner et al. 2010).
In this paper we describe one new species of Oricymba from a low elevation stream in the Tianmu Mountains
region, Zhejiang Province, China. We give a detailed morphological description of this new taxon and compare our
new species with others in the genus. The newly-discovered species is valuable in improving our understanding of this
interesting diatom genus, especially its biogeography and ecology.
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258 Phytotaxa 236 (3) © 2015 Magnolia Press
Materials and methods
The Tianmu Mountains, located in the northwest of Lin’an City, Zhejiang Province, China, have an area of 4284
hectares, a latitude range 30° 18’ 30”–30° 24’ 55” N, a longitude range 119° 24’ 11”–119° 28’ 21” E, an elevation
range from 300 to 1556 m a.s.l., and are located in a typical subtropical forest ecosystem landscape characterized by a
distinctive monsoonal climate with an annual mean temperature of about 14 ºC and an annual mean precipitation of ca.
1390–1870 mm (Li et al. 2006). This unique combination of topographic complexity and favorable moisture conditions
in the region explains the enormous richness of biological diversity, with a high degree of endemism (Xu et al. 2002,
Li et al. 2006). For example, 157 species of bryophytes and 4209 insect species were observed on Tianmu Mountain,
including 220 new insect species described to date (Xu et al. 2002, Li et al. 2006). However, there have been very few
studies on the diatoms from this region. Li (1984) reported 55 taxa of freshwater algae in the west Tianmu Mountain
region, including 20 diatom taxa, and analyzed their relationship with water quality. Wang (1991) reported 167 taxa of
diatoms from the west Tianmu Mountains, most of them are common species previously reported from China.
In November 2014, algae samples were collected from Tianmu Canyon of the Tianmu Mountains. The species
described herein was found at 2 sites at low elevations (600–800 m). In the field, samples were scraped from stones
or remnant leaves in stream water, and fixed in 4% formalin for future analysis in the laboratory. Sub-samples were
treated with sulfuric acid (H2SO4), potassium dichromate (K2Cr2O7), and 30% hydrogen peroxide (H2O2) to remove
organic matter. After several rinses in distilled water, a portion of the cleaned diatom material was air-dried onto cover
slips and mounted onto slides using Canada balsam.
Specimens were examined under light microscopy (LM) with differential interference contrast optics using
an OLYMPUS BX53 (DIC, ×1000, oil immersion) research microscope and a DP73 monochrome digital camera.
Valve measurements were made from digital images using OLYMPUS Cell Sens Entry software. Further portions
were air-dried and then mounted on copper stubs, which in turn were gold coated for scanning electron microscope
(SEM) examination using a Hitachi S-3400N (Shanghai Ocean University, China). Diatom micrograph images were
compiled with Adobe Photoshop CS6. Both the samples and the prepared slides of mounted material are stored in the
Laboratory of Aquatic Ecology and Environmental Restoration, Department of Hydrobiology, College of Fisheries
and Life Science, Shanghai Ocean University (SHOU). Descriptions of the taxon are given along with LM and SEM
micrographs using terminology following Krammer (2002) and Jüttner et al. (2010).
Taxonomy
Division Bacillariophyta
Class Bacillariophyceae
Subclass Bacillariophycidae
Order Cymbellales
Family Cymbellaceae
Genus Oricymba
Oricymba tianmuensis W. Zhang & Y.-L. Li, sp. nov. (Figs 1–25)
LM: valves linear-lanceolate, symmetrical or slightly dorsiventral, with an inflated, gibbous central portion gradually
tapering or nearly parallel to bluntly-cuneate poles (Figs 1–9). Length 28–74 μm, width 11–15 μm, length/width ratio
3.0–4.8, median 3.6 (n=35). Raphe slightly lateral, external raphe fissures slightly undulate, internal raphe fissures
straight. Proximal endings of raphe widened, deflected towards the ventral side. External distal raphe fissures hooked
towards dorsal margin. Axial area lanceolate. Central area rhombic-lanceolate, strongly asymmetrical, near to half
the valve width, with 1–2 slightly shortened central dorsal striae, 4–8 shortened central ventral striae. Isolated stigma
distinct between the central nodule and the two central striae on the ventral side. Striae slightly radiate becoming
moderately radiate near the poles, 7–9 in 10 μm. Areolae visible, 20–25 in 10 μm, median 22 in 10 μm (n=45).
NEW CYMBELLOID SPECIES FROM CHINA Phytotaxa 236 (3) © 2015 Magnolia Press 259
FIGURES 1–10. Oricymba tianmuensis, LM, DIC. 1–9. Valve views, showing the valve variability of the holotype population. 10. Girdle
view. Scale bar = 10 μm.
SEM: valve exterior (Figs 11–18): raphe undulate with proximal raphe fissures slightly dilated, weakly bent
ventrally (Figs 11, 15), distal fissures hooked, deflected towards the dorsal side (Figs 11, 13, 14). Striae uniseriate,
occasionally biseriate, extending onto the mantle (Figs 11–18). Areolar openings adjacent to the axial area curved,
triangular or elongate; other areolae variable in shape, most slit-like, elongate rectangular openings (Figs 11–18).
Small, shallow circular or slightly atypically circular depressions irregular across the axial and central areas (Fig. 15).
Longitudinal ridges are very thick along the valve margins except near the valve terminus, and at the apical pore fields,
with shallow grooves along both the valve face and mantle edges (Figs 13–17). A relative small apical pore field is
present and clearly separated from the areolae (Figs 13–14). The epicingulum is distinct in the girdle (Figs 12, 17).
The striae of the mantle area are composed of five rows of areolae, both uniseriate or biseriate (Fig. 18). Valve interior
ZHANG ET AL.
260 Phytotaxa 236 (3) © 2015 Magnolia Press
FIGURES 11–18. Oricymba tianmuensis, SEM. 11. External view of a whole valve. 12. Girdle view. 13–14. External view of pole with
apical pole field. 15. External view of valve center showing striae, stigma and shallow circular impressions. 16. Details of a fractured
ridge. 17. Girdle view of pole showing ridge and groove. 18. Details of striae and external areola openings in the girdle. Scale bars = 20
µm (Figs11–12), 2 µm (Fig. 13), 3 µm (Fig. 14), 5 µm (Figs 15–17) and 1 µm (Fig. 18).
NEW CYMBELLOID SPECIES FROM CHINA Phytotaxa 236 (3) © 2015 Magnolia Press 261
FIGURES 19–21. Oricymba tianmuensis (teratological form), SEM. Fig. 19. External view of a whole valve. 20. External view of valve
center showing uniseriate-biseriate striae and stigma. 21. External view of pole with raphe endings. Scale bars = 20 μm (Fig. 19), 5 μm
(Fig. 20) and 10 µm (Fig. 21).
(Figs 21–25): striae formed by slit-like, elongate areolae separated by robust silica ribs (Figs 21–25). Internal proximal
raphe endings hidden by an overgrowth of silica, distal raphe ends offset, bent slightly towards the dorsal margin and
terminating in small, knob-like helitcoglossae (Figs 21–25). Two indistinct, narrow, elongate internal stigmal openings
on the ventral side occluded by fine ingrowths from the perimeter (Fig. 24).
Type:—CHINA. Zhejiang Provence: Tianmu Mountains, Tianmu Canyon, 30° 21’ 56” N, 119° 28’ 35” E, 655 m
a s.l., W. Zhang, s.n. (holotype: SHOU!, slide ZW-ZheJ 0023, illustrated in Fig. 3).
Etymology:—Oricymba tianmuensis is named after the type locality.
Observations:—A very different individual with odd striae was observed in our study (Figs 19–21). The outline
of valve, raphe course, and number of striae in 10 µm all conform to conditions of “normal” individuals. It is interesting
that the striae show a strong tendency to become biseriate, with circular, lateral elongate or irregularly triangular
areolae (Figs 20, 21).
Discussion
Oricymba tianmuensis differs from other known species within the genus by valve outline and the size and shape of
the axial and central areas (Table 1). Oricymba tianmuensis differs in valve outline from other Oricymba species in
that it possesses a more distinctly gibbous central part of the valve. The new species also possesses bluntly cuneate
apices. These features found in O. tianmuensis differ from all other known species of the genus (Jüttner et al. 2010,
Kulikovskiy et al. 2015) (Table 1).
A number of other taxa also resemble O. tianmuensis in LM. Cymbella neuquina Frenguelli (1942: 163) and
C. neuquina var. fastigata (Krasske 1949: 86) Krammer, Maidana & Díaz Villanueva (2002: 341) found in Pehuén
district (Maidana et al. 2002) are more or less similar in shape, especially at the apices, but these are more strongly
dorsiventral with 2–4 sitgmata in the central area. Small valves of O. tianmuensis are similar in shape to Cymbopleura
schmidtii (Grunow in Schmidt et al. 1875: pl. 9) Stenger-Kovács (2011: 216) found in Lake Balaton (Stenger-Kovács
et al. 2011), but C. schmidtii lacks the central area and stigmata, and has radiate striae at the center. Some valves of O.
tianmuensis are similar in shape to Cymbella orientalis Lee, Gotoh & Chung (1993: 100) found in Korea and Japan
(Lee et al. 1993), however, valve margins of C. orientalis taper gradually from the valve centre towards the poles, and
the central area is unilateral, lacking or with a shortened central striate on the dorsal side.
Oricymba has a limited biogeographic distribution; it is unknown outsid Asia. While a limited biogeographic
distribution is relatively rare for freshwater diatom genera, a few with limited distributions include, e.g., genera from
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262 Phytotaxa 236 (3) © 2015 Magnolia Press
TABLE 1. Differences between species of the genus Oricymba.
Oricymba tianmuensis O. japonica O. subaequalis O. latirotundata O. subovalis O. perjaponica O. voronkinae
Reference this study Jüttner et al. 2010 Jüttner et al. 2010 Jüttner et al. 2010 Jüttner et al. 2010 Kulikovskiy et al. 2015 Kulikovskiy et al.
2015
Valve shape linear-lanceolate,
symmetrical or
slightly dorsiventral,
distinctly gibbous
central part of the
valve tapering
towards the bluntly
cuneate poles
lanceolate,
dorsiventral, margins
gradually tapering
towards rounded
poles
lanceolate, almost
symmetrical, rounded,
subrostrate poles
lanceolate, slightly
dorsiventral, margins
gradually tapering
towards the broadly
rounded poles
linear-lanceolate to
elliptic-lanceolate,
slightly dorsiventral,
rounded poles
rhomboid-lanceolate,
not dorsiventral,
narrowly rounded poles
narrow lanceolate,
with moderately
arched valve margins
gradually tapering
towards the rounded,
slightly protracted
poles
Valve length
(μm)
28–74 30–55 33–43 54–71 25–55 38–58 27–49
Valve width
(μm)
11–15 9–13 9–11 13–16 9–11 12–15 8–11
Number of
striae in 10 μm
7–9 7–10 9–11 7–9 8–11 8–9 9–10
Length/width
ratio, median
3.0–4.8, 3.6 2.7–4.7, 3.8 3.3–4.3, 3.8 3.6–5.0, 4.0 2.5–5.6, 3.5 not given not given
Number of
areolae in 10
μm
20–25 20–25 25–30 23–30 25–30 not given ca. 20
Raphe
structure
slightly lateral,
undulate
slightly lateral,
undulate
slightly lateral,
undulate
slightly lateral,
slightly undulate
slightly lateral,
undulate
slightly lateral,
undulate
slightly lateral,
undulate
Axial area lanceolate lanceolate lanceolate broadly lanceolate lanceolate linear-lanceolate lanceolate- lanceolate
Central area rhombic-lanceolate,
asymmetrical, <1/2
valve width
rhombic-lanceolate,
asymmetrical, <1/2
valve width
rhombic-lanceolate,
asymmetrical, <1/2
valve width
rhombic-lanceolate,
slightly asymmetrical,
<1/2 valve width
rhombic-lanceolate,
asymmetrical, <1/2
valve width
rhombic-lanceolate,
asymmetric, <1/2 valve
width
rhombic-lanceolate,
slightly asymmetric,
<1/2 valve width
Striae slightly radiate,
moderately radiate
near poles
slightly radiate,
moderately radiate
near poles
dorsal: almost parallel
at centre, moderately
radiate towards poles;
ventral: moderately
radiate
slightly radiate,
moderately radiate
near poles
almost parallel at
centre, slightly to
moderately radiate
towards poles
radiate, moderately,
radiate at poles
parallel to slightly
radiate
NEW CYMBELLOID SPECIES FROM CHINA Phytotaxa 236 (3) © 2015 Magnolia Press 263
FIGURES 22–25. Oricymba tianmuensis, SEM. Internal view of a whole valve. 24. Internal view of valve centre showing internal stigma
openings. 25. Internal view of the pole with helictoglossae and apical pore field. Scale bars = 20 μm (Figs 22, 23) and 5 μm (Figs 24, 25).
ancient lake systems, including Lake Baikal (see Kulikokskiy et al. 2012 for over ten new genera described from
that lake), Afrocymbella Krammer (2003: 129) from East African Rift Valley Lakes and Tetralunata Hamsher et al.
(2014: 361) from Lake Toba in Indonesia, genera from South America such as Perinotia Metzeltin & Lange-Bertalot
(2007: 188), as well as Tibetiella Li et al. (2010: 329) from Tibet, Sichuania Li et al. (2009: 688) from Sichuan
province, China, and Gomphosinica Kociolek et al. (2015: 178), described from lakes and other habitats from China
and northern localities in the USA (Kociolek et al. 2015). It would appear that Asia harbors many endemic freshwater
diatom genera and, given the relatively unknown nature of the flora in this region, future work is likely to uncover
other unique taxa.
Oricymba tianmuensis was found on the remnant leaves and stones from the type locality, together with
Achnanthidium minutissimum (Kützing 1833: 578) Czarnecki (1994: 157), Cymbella affinis Kützing (1844: 80),
Gomphonema parvulum (Kützing 1844: 33) Kützing (1849: 65), G. minutum (Agardh 1827: 629) Agardh (1831: 34),
G. gracile Ehrenberg (1838: 217), Cocconeis pediculus Ehrenberg (1838: 194), Brachysira microcephala (Grunow
1867: 19) Compère (1986: 26) and several at present unidentified species of Fragilaria and Encyonema.
To date, the new species O. tianmuensis is only known from the type locality. Compared to other Oricymba
species, O. tianmuensis occupies a different habitat. Oricymba subaequalis Jüttner, Krammer & Cox (2010: 411)
and O. subovalis Jüttner, Krammer & Cox (2010: 415) were both found in standing water (Jüttner et al. 2010), but
O. tianmuensis was found in running water, although three of them were favored by low ionic contents. Oricymba
latirotundata Jüttner & Van de Vijver in Jüttner et al. (2010: 414) was only found at a high elevation location (2840 m,
Jüttner et al. 2010), but O. tianmuensis was found in a relatively low elevation location (655 m). Oricymba japonica
has a wide geographical distribution in China; this species is commonly observed in freshwater habitats of Jiangsu,
Anhui, Jiangxi, Hubei, Chongqing, Sichuan, Guizhou, and Yunnan provinces, as well as in the Tibet region (sometimes
even found in alkaline lakes) (Shi 2013). Oricymba tianmuensis is present in the eastern part of China, within a
subtropical region, which enlarges the geographical distribution of Oricymba species.
Further investigations in the Tianmu Mountain region, or China generally, are needed to establish a more
comprehensive view of Oricymba species’ ecology and biogeography.
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264 Phytotaxa 236 (3) © 2015 Magnolia Press
Acknowledgements
We thank two anonymous reviewers for helpful comments and suggestions.
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... Oricymba perjaponica (Krammer & Lange-Bertalotin Krammer 2002: 64) Kulikovskiy et al. (2015: 127) and O. voronkinae Glushenko et al. in Kulivoskiy et al. (2015: 127) were collected from Laos and Cambodia. Recently, Zhang et al. (2015) and Zhang et al. (2016) described two additional species, O. tianmuensis W. Zhang & Y. L. Li (2015: 258) and O. xianjuensis Zhang & Kociolek (2016: 135), from Zhejiang province, southeast China. ...
... They differ from one another, however, in that O. rhynchocephala has proportionately more narrow valves, clearly rostrate poles and more sparse areolae density (19-23 in 10 μm), giving the valves a different appearance as compared to the Nepalese species. The features found in O. rhynchocephala are compared to all other known species of the genus in Table 1 (Jüttner et al. 2010, Kulikovskiy et al. 2015, Zhang et al. 2015, Zhang et al. 2016. The original description of the genus (Jüttner et al. 2010) indicated that the internal proximal raphe ends were covered by an internal flap of silica, and some subsequent descriptions (e.g. ...
... The original description of the genus (Jüttner et al. 2010) indicated that the internal proximal raphe ends were covered by an internal flap of silica, and some subsequent descriptions (e.g. Zhang et al. 2015Zhang et al. , 2016 also documented that feature in their descriptions, even though no images showed the presence of internal proximal raphe. Kulikovskiy et al. (2015, e.g. ...
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... Oricymba perjaponica (Krammer & Lange-Bertalotin Krammer 2002: 64) Kulikovskiy et al. (2015: 127) and O. voronkinae Glushenko et al. in Kulivoskiy et al. (2015: 127) were collected from Laos and Cambodia. Recently, Zhang et al. (2015) and Zhang et al. (2016) described two additional species, O. tianmuensis W. Zhang & Y. L. Li (2015: 258) and O. xianjuensis Zhang & Kociolek (2016: 135), from Zhejiang province, southeast China. ...
... They differ from one another, however, in that O. rhynchocephala has proportionately more narrow valves, clearly rostrate poles and more sparse areolae density (19-23 in 10 μm), giving the valves a different appearance as compared to the Nepalese species. The features found in O. rhynchocephala are compared to all other known species of the genus in Table 1 (Jüttner et al. 2010, Kulikovskiy et al. 2015, Zhang et al. 2015, Zhang et al. 2016. The original description of the genus (Jüttner et al. 2010) indicated that the internal proximal raphe ends were covered by an internal flap of silica, and some subsequent descriptions (e.g. ...
... The original description of the genus (Jüttner et al. 2010) indicated that the internal proximal raphe ends were covered by an internal flap of silica, and some subsequent descriptions (e.g. Zhang et al. 2015Zhang et al. , 2016 also documented that feature in their descriptions, even though no images showed the presence of internal proximal raphe. Kulikovskiy et al. (2015, e.g. ...
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... Tetralunata (Hamsher et al. 2014) and Celebesia ( Kapustin et al. 2017) have been described from Indonesia, and Antiquonema (Karthick & Kociolek, in press) is known from India. Oricymba ( Kulikovskiy et al. 2015;Zhang et al. 2015Zhang et al. , 2016 and Edtheriotia (Xie & Qi 1984;Kociolek et al. 2016) are also found in Southeast Asia, whereas Gomphosinica (Kociolek et al. 2015b) is a disjunct between China and western North America. Williams & Kociolek (2017) discussed the unique components of Australasian freshwater diatom communi- ties, focusing on Eunotiales. ...
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Species from the genus Oricymba are studied from freshwater ecosystems of Vietnam and Laos. Three species were found in Vietnam, namely O. japonica, O. subovalis and O. perjaponica comb. nov. The two last species are new taxa for the diatom flora of Vietnam. A new species is described from Laos, O. voronkinae sp. nov., and its morphology is documented with light and scanning electron microscopy. Oricymba voronkinae sp. nov. represents the first documented occurrence of the genus Oricymba in Laos. Our findings provide new information about the morphology and species distribution of the genus Oricymba in Indochina. We discuss the systematic position of Oricymba within the Cymbellales. Key words: diatoms, Oricymba, new species, morphology, distribution, Vietnam, Laos