Platessa strelnikovae (Bacillariophyta), a new species ...

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Nova Hedwigia, Beiheft 143, p. 239–244 Stuttgart, July 2014

Platessa strelnikovae (Bacillariophyta), a new species from Maine and Vermont lakes, USA Mihaela D. Enache1*, Marina Potapova2 & Eduardo A. Morales3 1

New Jersey Department of Environmental Protection, Office of Science, Trenton, New Jersey 08625, USA 2 Academy of Natural Sciences, 1900 Benjamin Franklin Parkway, Philadelphia, Pennsylvania 19103, USA 3 Herbario Criptogámico, Universidad Católica Boliviana San Pablo, Av. Gral. Galindo s/n, P.O. Box 5841, Cochabamba, Bolivia * Corresponding author: [email protected]

With 23 figures Abstract: A new species, Platessa strelnikovae Enache, Potapova & E.Morales is described from modern and subfossil lake sediments from the Northeastern United States. This species is placed in the genus Platessa Lange-Bertalot based on biseriate striae and absence of terminal raphe fissures. The new species is easily distinguishable from other Platessa species by its valve shape and the presence of a depression in the central area of the rapheless valve; depression that none of the other Platessa species described in the literature thus far have. The new species was found in sediment samples from circumneutral, low conductivity and mesotrophic lakes from Maine and Vermont. Key words: Diatoms, Bacillariophyta, Platessa strelnikovae sp. nov., North America, United States

Introduction The genus Platessa was recently established by Lange-Bertalot (Krammer & Lange-Bertalot 2004). Representatives of Platessa are monoraphid diatoms that live as single cells or form short chains. The frustules of Platessa are only slightly flexed in contrast to most other monoraphid diatoms. The raphe valve is concave and the rapheless valve is convex, while the raphe lacks terminal fissures. The striae are biseriate, although some species, such as Platessa montana (Krasske) Lange-Bert., P. lutheri (Hust.) Potapova, and P. kingstonii Potapova have uniseriate striae on the raphe valve (Krammer & Lange-Bertalot 2004, Potapova 2012a, b); one species, P. ziegleri (Lange-Bert.) Lange-Bert., has uniseriate striae on both valves, and another, P. bahlsii Potapova, has multiseriate striae (Krammer & Lange-Bertalot 2004, Potapova 2012c). Many currently known Platessa species, such as P. hustedtii (Krasske) Lange-Bert., P. conspicua (Mayer) Lange-Bert., P. holsatica (Hust.) Lange-Bert. and P. lutheri are cosmopolitan, while P. kingstonii Potapova, and P. stewartii (R.M.Patrick) Potapova have been reported so far only from North America (Hustedt 1933, Krammer & Lange-Bertalot 2004, Potapova 2010, 2012b, d). Here we describe a new species of Platessa that was found in sediment cores collected from circumneutral, low conductivity, mesotrophic lakes in Maine and Vermont, northeastern United States of America. Materials and methods The new Platessa species was found in top (modern) and bottom (sub-fossil) samples of sediment cores collected in the course of the Environmental Protection Agency National Lake Assessment project in the summer of 2007 (Table 1). © 2014 J. Cramer in der Gebr. Borntraeger Verlagsbuchhandlung, Stuttgart, Germany

DOI 10.1127/1438-9134/2014/011

www.borntraeger-cramer.de

1438-9134/2014/011 $ 1.50

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M.D. Enache, M. Potapova & E.A. Morales

The sediment samples were treated with nitric acid and permanent slides were prepared using the synthetic mounting medium Naphrax®, following the protocols in Charles et al. (2002). For light microscopy (LM) we used a Zeiss Axio Imager microscope equipped with differential interference contrast optics and oil immersion 100X objective with a numerical aperture of 1.4. Digital images were captured by an AxioCam MRm digital camera. For scanning electron microscopy (SEM), cleaned material was dried on aluminum stubs, which were sputter-coated with Pt-Pd and observed under a Zeiss Supra 50 VP FE SEM (Carl Zeiss, Jena, Germany) at an accelerating voltage of 10 kV. Terminology used to describe valve structure follows Anonymous (1975), Ross et al. (1979), and Krammer & LangeBertalot (2004).

Table 1. Locations and water quality characteristics of lakes where Platessa strelnikovae. was recorded (Cond. – conductivity; TP – total phosphorus).

Latitude

Longitude

Cond. (μS cm-1)

pH

TP (μg L-1)

Lake name

State

Marshfield Pond

Vermont

44.33

–72.33

39

6.90

20

Hudson Pond

Maine

46.17

–69.00

26

7.40

20

Female Pond

Maine

45.75

–69.22

35

7.05

13

Results Platessa strelnikovae Enache, Potapova & E.Morales sp. nov. Figs 1–16 LM, Figs 17–23 SEM DESCRIPTION: Valves broadly elliptical with rounded, sometimes slightly protracted apices, 6–7 μm wide, 11–19 μm long. In girdle view, raphe valve concave, rapheless valve convex. Raphe valve with narrow, straight axial area, widening towards rhomboid central area. Raphe straight with simple endings. Terminal raphe fissures are absent. Axial area on rapheless valve broad, rhomboid with one-sided horseshoe depression extended to the valve margin. Striae radiate, 14–17 in 10 μm. HOLOTYPE: Here designated, circled specimen on slide ANSP GC 58991, Academy of Nat. Sci., Philadelphia. The holotype specimen is illustrated in Figs 1–2. ISOTYPES: Here designated, circled specimens on slide ANSP GC58992, Academy of Natural Sciences, Philadelphia (This isotype specimen is illustrated in Figs 3 and 4) and CANA 86153, Canadian Museum of Nature, Ottawa. This Isotype specimen is illustrated in Figs 5 and 6. TYPE LOCALITY: Marshfield Pond, (41.848’ N, 71.787’ W), Vermont, USA. Surface sediment sample ANSP NLS00265 (type material), collected by Environmental Protection Agency (EPA) staff, September 7, 2007. ETYMOLOGY: This species is dedicated to Nina Ivanovna Strelnikova.

Discussion Platessa strelnikovae differs from its congeners by the relatively large size and the shape of the central area on the rapheless valve with a characteristic horseshoe depression similar to that found in Planothidium species (Figs 1, 3, 5, and 7–11). The SEM observations show that this species differs from Planothidium species by having biseriate striae with areolae arranged in a quincunx pattern (Fig. 22). The external openings of the areolae in the new species have a more or less reniform shape due to a siliceous projection that protrudes from the periphery

Platessa strelnikovae, a new species from Maine and Vermont lakes, USA

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Figs 1–16. Platessa strelnikovae sp. nov. Type material, Marshfield Pond, Vermont. LM. Raphe (Figs 2, 4, 6, and 12–16) and rapheless (Figs 1, 3, 5, and 7–11) valves. Figs 1–2. Holotype specimen (ANSP GC58991). Figs 3–4. Isotype specimen (ANSP GC58992). Figs 5–6. Isotype specimen (CANA86153). Scale bar = 10 μm.

toward the center of the areola. The striae in Planothidium are multiseriate and areolae are round (Krammer & Lange-Bertalot 2004). The hymenate occlusions of areolae in Platessa strelnikovae (Fig. 23) are similar to those in Planothidium species, but such occlusions are characteristic of the entire family Achnanthidiaceae (Krammer & Lange-Bertalot 2004) and thus, they do not add information on the phylogenetic relationships at the genus level. The raphe of the new species is narrow, straight, with simple distal and proximal endings (Figs 17, 18), similar to other Platessa species, while in Planothidium the raphe has terminal fissures curved to the secondary side of the valve.

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Figs 17–20. Platessa strelnikovae sp. nov. Type material, Marshfield Pond, Vermont. SEM. Fig. 17. External view of raphe valve. Fig. 18. Internal view of raphe valve. Fig. 19. Internal view of rapheless valve. Fig. 20. External view of rapheless valve. Scale bar = 5 μm.

Platessa strelnikovae is easily distinguishable from other relatively large-celled Platessa species, such as P. bavarica Lange-Bertalot & Hofmann, P. montana, P. stewartii and P. hustedtii (Krammer & Lange-Bertalot 2004, Potapova 2010, 2011). Platessa bavarica has rapheless valve with a very broad, elliptical axial area and a very narrow transverse central area in the raphe valve (Krammer & Lange-Bertalot 2004). Platessa montana differs by rhombic-elliptic valve shape with round to rectangular central area on raphe valve and narrower, lanceolate axial area on rapheless valve and denser striae (18–24 vs, 14–17 in P. strelnikovae) (Krammer & LangeBertalot 2004). Platessa hustedtii has more parallel valve margins with an elliptic central area on raphe valve and denser striae (17–22 vs. 14–17 in Platessa strelnikovae) (Krammer & LangeBertalot 2004, Potapova 2011). Platessa stewartii has narrow axial areas and relatively narrow transverse central areas on both valves (Potapova 2010). None of the previously described Platessa species display a horseshoe-shaped depression in the central area of the rapheless valve. This depression makes Platessa strelnikovae somewhat similar to Planothidium lanceolatum (Bréb. ex Kütz.) Lange-Bert., but the latter has narrow axial area and more distant striae (12–15 in 10 μm) (Krammer & Lange-Bertalot 2004). Acknowledgements We acknowledge the use of the Centralized Research facilities in the College of Engineering at Drexel University, Philadelphia.

Platessa strelnikovae, a new species from Maine and Vermont lakes, USA

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Figs 21–23. Platessa strelnikovae sp. nov. Type material, Marshfield Pond, Vermont. SEM. Fig. 21. Oblique view of frustule. Fig. 22. External openings of areolae. Fig. 23. Internal view of valve surface showing areolae occluded by hymens. Scale bars = 5 μm (Fig. 21), 1 μm (Figs 22–23).

References Anonymous (1975): Proposals for a standardization of diatom terminology and diagnoses. – Nova Hedwigia 53: 323–354. Charles, D.F., Knowles, C. & Davis, R.S. (2002): Protocols for the analysis of algal samples collected as part of the U.S. Geological Survey National Water-Quality Assessment Program. Report No 02–06. – Acad. Nat. Sci., Philadelphia. Hustedt, F. (1933): Die Kieselalgen Deutschlands, Österreichs und der Schweiz unter Berücksichtigung der übrigen Länder Europas sowie der angrenzenden Meeresgebiete. – In: Rabenhorst, L. (ed.), Kryptogamen Flora von Deutschland, Österreich und der Schweiz. Akad. Verlagsgesell. Leipzig, 7: 321–432.

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Krammer, K. & Lange-Bertalot, H. (2004): Bacillariophyceae. 4. Teil: Achnanthaceae. Kritische Ergänzungen zu Navicula (Lineolatae) und Gomphonema. – In: Ettl, H., Gärtner, G., Gerloff, J., Heynig, H. & D. Mollenhauer (eds.), Süsswasserflora von Mitteleuropa, 2(4), p. 1–459. Second Edition. Gustav Fischer Verlag, Stuttgart. Potapova, M. (2010): Platessa stewartii. – In: Diatoms of the United States. Retrieved March 11, 2013, from http://westerndiatoms.colorado.edu/taxa/species/planothidium_stewartii Potapova, M. (2011): Platessa hustedtii. – In: Diatoms of the United States. Retrieved March 11, 2013, from http://westerndiatoms.colorado.edu/taxa/species/platessa_hustedtii Potapova, M. (2012a): Platessa lutheri. – In: Diatoms of the United States. Retrieved March 11, 2013, from http://westerndiatoms.colorado.edu/taxa/species/platessa_lutheri Potapova, M. (2012b): Platessa kingstonii. – In: Diatoms of the United States. Retrieved March 11, 2013, from http://westerndiatoms.colorado.edu/taxa/species/platessa_kingstonii Potapova, M. (2012c): Platessa bahlsii. – In: Diatoms of the United States. Retrieved March 11, 2013, from http://westerndiatoms.colorado.edu/taxa/species/platessa_bahlsii Potapova, M. (2012d): New species and combinations in monoraphid diatoms (family Achnanthidiaceae) from North America. – Diatom Res. 27: 29–42. doi:10.1080/0269249X.2011.644636 Ross, R., Cox, E.J., Karayeva, N.I., Mann, D.G., Paddock, T.B.B., Simonsen, R. & Sims, P.A. (1979): An amended terminology for the siliceous components of the diatom cell. – Nova Hedwigia 64: 513–533.