Research Article |
Corresponding author: Dmitry A. Kapustin ( dima_kapustin@outlook.com ) Academic editor: Kalina Manoylov
© 2021 Dmitry A. Kapustin, Anton M. Glushchenko, John P. Kociolek, Maxim S. Kulikovskiy.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Kapustin DA, Glushchenko AM, Kociolek JP, Kulikovskiy MS (2021) Encyonopsis indonesica sp. nov. (Bacillariophyceae, Cymbellales), a new diatom from the ancient lake Matano (Sulawesi, Indonesia). PhytoKeys 175: 1-11. https://doi.org/10.3897/phytokeys.175.61044
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A new species, Encyonopsis indonesica, is described from the ancient lake Matano, Sulawesi island, Indonesia. The morphology of this species was studied by means of light and scanning electron microscopy. E. indonesica has a remarkable valve ultrastructure. The valve surface is ornamented with numerous longitudinal siliceous ribs and siliceous verrucae. Valve face delineated from the mantle by a thickened marginal ridge. Raised sterna border the raphe branches. Raphe is distinctly undulate with distal ends hooked strongly to the ventral side. The only similar species to E. indonesica is Amphora dissimilis described from New Caledonia. Comparison of both taxa is given and A. dissimilis is transferred to Encyonopsis. The taxonomic placement of both taxa is evaluated, and the phenomenon of external siliceous ornamentation is discussed.
ancient lake, diatoms, Indonesia, morphology, SEM, taxonomy
The genus Encyonopsis Krammer was established during a comprehensive revision of cymbelloid diatoms by
Relatively recently the genus Kurtkrammeria
The Malili lakes are located in the mountains of Central Sulawesi and are composed of five tectonic lakes, namely, Matano, Mahalona, Towuti, Lontoa (also known as Wawontoa) and Masapi (
The aim of this paper is to describe a new Encyonopsis species based on light and scanning electron microscopy, detail its unusual morphology, and discuss its generic placement.
An epilithic sample containing Encyonopsis indonesica was collected from Lake Matano in 2010 (02°28.433'S, 121°15.710'E). With a Hanna multiparameter probe meter (HANNA HI98128), the temperature was recorded as 28.5 °C, pH as 8.53, and conductivity as 177 μS∙cm–1.
The sample was heated in concentrated hydrogen peroxide (~37%) to dissolve the organic matter. It was then rinsed with deionized water four times at 12 h intervals. After decanting and filling with deionized water up to 100 ml, the suspension was spread on to coverslips and left to dry at room temperature. Permanent diatom slides were mounted in Naphrax. Light microscopic (LM) observations were performed with a Zeiss Scope A1 microscope equipped with an oil immersion objective (100×/n.a.1.4, differential interference contrast [DIC]) and Zeiss Axio-Cam ERc 5s camera. Valve ultrastructure was examined by means of a JSM-6510LV scanning electron microscope (Papanin Institute for Biology of Inland Waters RAS, Borok, Russia). For scanning electron microscopy (SEM), parts of the suspensions were fixed on aluminum stubs after air-drying. The stubs were sputter coated with 50 nm of gold.
Family Cymbellaceae Kützing
Genus Encyonopsis Krammer
(here designated): MHA 01105. Fig.
Indonesia, Island of Sulawesi, Lake Matano, 02°28.433'S, 121°15.710'E, leg. I.I. Ivanov, 14.XI.2010.
The specific epithet refers to the type locality from Indonesia.
LM (Fig.
SEM (Figs
A–F Encyonopsis indonesica sp. nov. (SEM). External view A–D whole valves showing morphological variability in external ornamentation E, F central area with dorsally deflected proximal raphe ends. Note the thickened marginal ridge, longitudinal ribs and verrucae on the valve surface. Scale bars: 2 µm (A, D), 2.5 µm (B, C), 1 µm (E, F).
A–F Encyonopsis indonesica sp. nov. (SEM). External view A central area B, C valve ends. Note a hyaline area along the raised sternum D a part of a raphe with transapical ribs on the valve surface E, F valve ends with strongly hooked distal raphe fissures. Scale bars: 1 µm (A, C, D, E), 2 µm (B), 0.5 µm (F).
A–G Encyonopsis indonesica sp. nov. (SEM). Internal view A–C whole valve D, E central area with rounded or elongated areolae located in a transapically elongated grooves F, G valve ends with typical helictoglossa. Note a thin, plate-like silica thickening present between helictoglossa and apex. Scale bars: 2 µm (A, C), 2.5 µm (B), 1 µm (D, E), 0.5 µm (F, G).
Encyonopsis indonesica is very similar to Amphora dissimilis described from New Caledonia (
Morphological and morphometric comparisons among Encyonopsis indonesica and E. dissimilis.
Taxon | Valve shape | Valve / ends | Raphe | Valve length, µm | Valve width, µm | Striae in 10 µm | Areolae in 10 µm |
---|---|---|---|---|---|---|---|
Encyonopsis indonesica | semi-lanceolate | cuneate to rostrate | undulate | 17–29 | 3–4 | 34–36 | 50 |
Encyonopsis dissimilis | semi-lanceolate | cuneate | filiform, proximal ends are abruptly curved dorsally to form an arc at the valve center | 29–40 | 4.6–5.4 | 18–20 | no data |
The authors initially had some doubts when placing Amphora dissimilis in Amphora (
We agree that Amphora dissimilis does not belong to this genus. Taking into account the remarkably similar morphology between Encyonopsis indonesica and Amphora dissimilis we propose to transfer the latter species to Encyonopsis:
Encyonopsis dissimilis (Metzeltin & Krammer) Kapustin, Kulikovskiy & Kociolek, comb. nov.
Basionym: Amphora dissimilis Metzeltin & Krammer in
In terms of valve outline, the degree of asymmetry about the apical axis might suggest we assign Encyonopsis indonesica and E. dissimilis to Cymbellopsis Krammer rather than to Encyonopsis. All species of the genus Cymbellopsis have distinctly dorsiventral valve outlines whereas the species of the genus Encyonopsis have only slightly dorsiventral valve outlines. However, in Cymbellopsis taxa possess an intermissio of Type 1, similar to what is seen in Encyonema silesiacum (
Remarkably, many endemic diatoms from Lake Matano, e.g. Celebesia distinguenda (Hustedt) Kapustin, Kulikovskiy & Kociolek, Cymbella eunotioformis Kapustin, Kociolek & Kulikovskiy, C. densigranulata Kapustin, Kociolek & Kulikovskiy, Gomphonema matanense Kapustin, Kociolek & Kulikovskiy and Encyonopsis indonesica are additionally ornamented with siliceous outgrowths, ridges, granules, or spines (
Authors are grateful to the staff of the Interlaboratory Centre of Electron Microscopy of the Papanin Institute for Biology of Inland Waters, RAS, for technical assistance. Publication is based on research carried out with financial support by Russian President Foundation (МД-1446.2020.4) and by framework of the state assignment (theme АААА–А19–119041190086–6) for finishing manuscript.