notulae algarum no. 81 algarum no. 81.pdf · notulae algarum no. 81 (15 november 2018) issn...

Notulae algarum No. 81 (15 November 2018) ISSN 2009-8987

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Is Trieres Ashworth & E.C. Theriot 2013 (Bacillariophyta) a superfluous redescription of Microtheca Ehrenberg 1838? W.-H. Kusber, Botanic Garden and Botanical Museum Berlin, Freie Universität Berlin, Königin-Luise-Str. 6-8, D-14195 Berlin, Germany (corresponding author: [email protected]) O. Skibbe, Botanic Garden and Botanical Museum Berlin, Freie Universität Berlin, Königin-Luise-Str. 6-8, D-14195 Berlin, Germany R. Jahn, Botanic Garden and Botanical Museum Berlin, Freie Universität Berlin, Königin-Luise-Str. 6-8, D-14195 Berlin, Germany Ehrenberg (1838) published a new monotypic genus name Microtheca among many other new names in his famous work “Infusionsthierchen”. Ehrenberg’s drawings show similarities to species of the much later diatom genus name Trieres Ashworth & E.C. Theriot (in Ashworth et al. 2013). Accordingly, Williams et al. (2017) proposed the rejection of Ehrenberg’s genus and species name. One argument for rejection was the lack of type specimens or authentic specimens deposited by Ehrenberg at BHUPM. Our aim was to seek relevant specimens to unravel the identity of the genus Microtheca, and, if possible, to typify Microtheca octoceras (Ehrenberg) Ehrenberg, the type of the name of the genus according to Turland et al. (2018: Art. 9, Rec. 9A). For an account of our methods and work on the Ehrenberg collection see Jahn & Kusber (2004). On 2 July 1832, Ehrenberg gave a presentation entitled “Dritter Beitrag zur Erkenntniss grosser Organisation in der Richtung des kleinsten Raumes” at the Akademie der Wissenschaften, Berlin. The subject matter discussed was the occurrence of highly organized aquatic microorganisms. Ehrenberg divided these into two groups, which he named “Räderthierchen (Rotatoria)” and “Magenthierchen (Polygastrica)”. The first taxon is now referred to the Rotifera Cuvier, 1817, a phylum of animals, but the second consisted of what are now various protozoa, algae and bacteria. Two years later, Ehrenberg (1834) published his revised and slightly extended studies including new genera, species, and copper plates depicting some of these taxa. He included the description of an unusual marine rotifer from Kiel Harbour (Baltic Sea), Anurea ? octoceras without publishing an image, but documenting it by hand drawings stored in his collection and housed today in the Museum für Naturkunde Berlin as BHUPM 787. The date of observation (in Berlin) was 23 October 1832 where Ehrenberg studied a seawater sample from Kiel Harbour sent by Dr Michaelis. Ehrenberg’s habit was to put miscellaneous observations of each species on the same drawing sheet. The first observation was usually placed on the top left of the page with the intention of leaving room for further additions. Details of the first locality and date were normally placed at the bottom right, later observations being added here or directly next to additional figures. The size, given as fraction of a Paris line (= 2256 µm), is normally given at the bottom on the left side. Early drawing sheets give the scientific name near the bottom in the centre. Accordingly, we reconstructed the drawing (BHUPM 787) as of October 1832 by removing later additions from the scanned image. Fig. 1 shows drawing sheet 787 depicting Anurea ? octoceras, the size (“testa sine spinis 1/24” [size without spines 96 µm]), the locality (“ex Mari baltico 23 Oct. 1832”), and the observations corresponding to the first description. The length, including “spines”, was published in Ehrenberg (1834) as 1/18” [125 µm]. On drawing sheet BHUPM 787, Ehrenberg depicted four cells, later recognised as diatoms, all in girdle view. One of them is in lateral view because the valve is elliptical in shape. The other three are in the normal view of microscopic preparations. The yellow-brownish cells show chloroplasts and a cruciform darker structure in the centre around the nucleus as can be seen in living cells (e.g., Hoppenrath et al. 2009: fig. 41a for Odontella regia (M.Schultze) Simonsen). One cell is empty. No ledge between the mantle of the valve (as found in


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Trieres mobiliensis (Bailey) Ashworth & E.C.Theriot) and the girdle is depicted. No valve structures are shown, suggesting that the valve was very smooth as in Trieres chinensis (Greville) Ashworth & E.C.Theriot). Ehrenberg’s drawing shows four “spines” at each valve. The outer “spines” are elevations of ocelli. The acute tip does not correspond with the modern light microscopical image. This may be due to the restricted magnification of Ehrenberg’s 1832 microscope. However, the acute tip suggests that elevations and ocelli are very thin, as depicted by Ashworth et al. (2013) for species of Trieres. The two “spines” in between both elevations are longer than the elevations with ocelli, up to twice as long. These longer spines are external rimoportula tubes (Ashworth et al. 2013, Lavigne et al. 2015). The relative distance of these tubes to the elevations with ocelli can be measured as distance between tube and elevation divided by the valve diameter (RD), which means the distance between both elevations. RD in Microtheca octoceras is 0.17-0.33, mean= 0.29 (n=12). Compared with the lectotype of Biddulphia chinensis Greville (≡ Odontella chinensis (Greville) Grunow, ≡ Trieres chinensis (Greville) Ashworth & E.C. Theriot, incorrectly altered to ‘sinensis’), designated by Hendey (1964) as BM 2998, the relative distance is much larger. The lectotype as depicted by Willams (1988: 18, pl. 24: fig. 3) shows only one edge with a short elevation and ocellus and an external rimoportula tube which can be studied. RD of the type of Biddulphia chinensis is just 0.06. This is in good agreement with modern documentations of the species (Hendey 1964, Pankow 1990, Snoeijs & Balashova 1998, Hoppenrath et al. 2009, Ashworth et al. 2013), an important component of Baltic marine plankton (Hällfors 2004, as Odontella sinensis). It is thus clear from the morphological evidence that the nomenclatural types of Microtheca (see below) and Trieres do not represent the same species. Because Microtheca octoceras was not considered by Ashworth et al. (2013), the main question is whether or not Trieres is congeneric with Microtheca. Accordingly, we compared Microtheca octoceras from the Baltic Sea in Germany with Trieres regia (M.Schultze) Ashworth & E.C.Theriot. The basionym of the latter taxon was described by Schultze (1858) from Helgoland, North Sea as Denticella regia and is recognised also in recent identification manuals (Drebes 1974, Hoppenrath et al. 2009, as Biddulphia regia and Odontella regia, respective) for the North Sea. The published images by Schultze (1858) looks similar to Ehrenberg’s drawings of Microtheca octoceras. There is no evidence that Schultze (1858) who cited mainly Ehrenberg (1854) consulted the Ehrenberg collection or the publications of Ehrenberg (1834, 1836, 1838). RD in Denticella regia varies between 0.18 and 0.25, x̅ = 0.23 (n=12) which is close to Microtheca octoceras. There is thus no morphological evidence that Denticella regia and Microtheca octoceras are distinct species. Becoming more and more interested in diatoms, Ehrenberg must have realized subsequently that his uncertain Anurea actually was a new coloured genus of Polygastrica (protists). As a result, he used the binary designation “Microtheca octoceras” in Ehrenberg (1836). At this time, the designation “Microtheca” was not valid, and thus “Microtheca octoceras” was also invalid (Turland et al. 2018: Art. 35.1).


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Fig. 1. Ehrenberg’s drawing BHUPM 787. Reconstructed content by the authors as of October 1832 (compare Fig. 2). Prior to the publication of his Infusionsthierchen, Ehrenberg, was not able to study the organism again. He published (Ehrenberg 1838) the genus and species name Microtheca octoceras (as ‘octoceros’) validly and supplemented it by copper plate engravings based on his earlier drawings (see Fig. 1). Although he accepted the genus and species, he was aware that further investigations of Microtheca were necessary. He included a short note under Denticella Ehrenberg (1838): “Auch Microtheca ist für Denticella zu vergleichen” (“Microtheca should be reinspected with regard to Denticella”, our translation). Its classification as a desmid by Ehrenberg, resulting seemingly from his perception of it as being analagous to chain-forming desmids such as Desmidium swartzii C.Agardh ex Ralfs, might be one important reason why later diatomists overlooked Ehrenberg’s name. Ehrenberg (1838: 164) also gave an incorrect plate citation “Tafel XII, Fig. X.” rather than “Tafel XI, Fig. X”. This mistake later spread; for example, VanLandingham (1971: 2279) included Microtheca octoceras in his diatom catalogue but copied the wrong plate citation from Ehrenberg’s text and noted “Desmid!” for the species and “Probably not a diatom genus; composed of desmids, etc.!”. This latter note is only correct for Ehrenberg’s plate XII, which does not include Microtheca. Ralfs (1848), who studied Ehrenberg’s works in detail, did not include the genus and species in his (later starting point book) British Desmidieae.


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Fig. 2. Ehrenberg’s drawing BHUPM 787 as currently stored in BHUPM. The drawing represents the content as of 1839, except of the label “787” on the right top. In 1839, Ehrenberg tried to reinvestigate Microtheca octoceras using living material sent by Dr Michaelis from Cuxhaven (North Sea). Three drawn cells, a small chain of two cells, also in lateral view show similarities with Zygoceros mobiliensis Bailey (≡ Odontella mobiliensis (Bailey) Grunow, ≡ Trieres mobliensis (Bailey) Ashworth & E.C.Theriot) as Williams et al. (2017) have previously stated. However, even though Williams et al. (2017) did not find the species on mica preparations at BHUPM, Ehrenberg had deposited a specimen as the basis for his species.


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Figs 3-6. BHUPM 540118-6 (Trockenpräparate II. Polygastrica CXVIII) Mica unlabelled, “Microtheca octoceros (granulata)” according to the taxonomic index housed in BHUPM. 3-5. Odontella sp., one cell in different planes. 3. Horns and two spines in focus. 4. Valve with pores and fine structure of the girdle in focus. 5. Cell with complete spines. 6. Microtheca (= Trieres) sp. with weakly silicification and thin horns. Scale bars: 3-4: 10 µm, 5: 100 µm, 6: 50 µm. The Ehrenberg collection consists of a relatively small collection of species “Trockenpräparate” and a large collection in geographical order (Lazarus & Jahn 1998, Jahn & Kusber 2004). “Trockenpräparate” are arranged in two sections, “I Rotatoria” including the genus Anurea, and “II Polygastrica” mostly unicellular protists. The specimens indexed as Anurea are lacking Anurea ? octoceras. But “II Polygastrica” includes Microtheca octoceras (granulata). The index is lacking any further information. We hoped to discover whether this specimen is the original material from Kiel Harbour (Baltic Sea) or later material from Cuxhaven (North Sea). Previously, we were able to find exactly those diatoms and dinoflagellate specimens that Ehrenberg had depicted (e.g., Jahn et al. 2004, Kusber & Jahn 2009, Elbrächter et al. 2018) but in this case we failed. No cell of the Kiel material could be unambiguously identified; therefore, this preparation most likely represents the Cuxhaven material. The cell in the centre of the mica (Figs 3-5) features a heavily silicified cell, in contrast to species of Trieres, for example, as can be seen in SEM micrographs of the species (e.g., Ashworth et al. 2013, Lavigne et al. 2015). Ehrenberg’s specimen was identified as Odontella granulata (Roper) R.Ross according to identification manuals for the North Sea (Drebes 1974, Hoppenrath et al. 2009). This cell shares the orientation (Fig. 3) of spines with Zygoceros mobiliensis Bailey (≡ Trieres mobliensis (Bailey) Ashworth & E.C.Theriot) and Ehrenberg’s drawings as of 1839, but has thick elevations with ocelli like Denticella aurita (Lyngbye) Ehrenberg (≡ Diatoma auritum Lyngbye, ≡ Odontella aurita (Lyngbye) C.Agardh). Ehrenberg’s drawings of Denticella aurita differ by the insertion of spines and the clearly transversal valve face (BHUPM drawing 387). Beside the heavily silicified cell this mica also includes, only partly visible due to detritus, a weakly silicified planktonic form which is clearly Trieres in the sense of Ashworth et al. (2013), compare with Microtheca octoceras (Fig. 6). Williams et al. (2017) considered that Ehrenberg’s name and drawings required interpretation by an epitype specimen. We were able to find a specimen in the Ehrenberg collection, but after a thorough study we must conclude, that this specimen is not suitable for interpreting Ehrenberg’s taxon. Our studies of the original drawing revealed, that with Anurea ? octoceras Ehrenberg described the first species which is now included in Trieres. This makes Trieres a superfluous name, because it includes the type of the name of Microtheca. Our study supplements the studies of Ashworth et al. (2013) and Williams et al. (2017). The question remains if it is “wiser” (Willams et al. 2017) to reject Microtheca Ehrenberg and its type Microtheca octoceras (Ehrenberg) Ehrenberg or simply to


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accept that Microtheca has priority over Trieres. Molecular and ultrastructural results should be linked to the 19th-century species best classified under Microtheca. The genus Microtheca shares with the description of Trieres weakly silicified frustules (an adaptation to planktonic life) with large pervalvar distance elongated with ocelli at the apices and opposed rimoportulae with external tubes on the valve face. None of these micro morphological details, shown by Ashworth et al. (2013) with SEM images, can be seen in Ehrenberg’s drawings and preparations: the wall-like projection running between the ocelli and the alveolate valves with conspicuously finely perforated vela arrayed in box-like sections and single, circular foramen on the valve interior. These fine structures, as well as the molecular identity can only be expected for Microtheca octoceras. However, this is also true for the other 19th-century species included in Trieres by Ashworth et al. (2013). Microtheca Ehrenberg, Infusionsthierchen: 164. 1838. Type (by monotypy): Microtheca octoceras. Microtheca octoceras (Ehrenberg) Ehrenberg, Infusionsthierchen, 164. 1838. ≡ Anurea ? octoceras Ehrenberg in Physikalische Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin 1833: 199, 1834. - Microtheca octoceras (Ehrenberg) Ehrenberg in Abhandlungen der Physikalisch-Mathematischen Klasse der Königlichen Akademie der Wissenschaften zu Berlin 1834: 540 adnot., table III,1836, nom. inval. (Turland et al. 2018, Art. 35.1). Type locality: Kiel (Germany), Baltic Sea, “Seewasser der Ostsee von Kiel”, gathering [most likely] Oct. 1832, sent by Dr Michaelis to Berlin where Ehrenberg studied a live sample on 23 October 1832. Lectotype (designated here): BHUPM drawing no. 787 part (the part which can be considered original material is given as our Fig. 1). Images of this part were used for publication on plate XI: X in Ehrenberg (1838). Registration: http://phycobank.org/100396 = Denticella regia M.Schultze in Archiv für Anatomie, Physiologie und wissenschaftliche Medicin1858: 341, pl. XIII; figs 11, 12, 1858. ≡ Trieres regia (M.Schultze) Ashworth & E.C.Theriot in Ashworth et al., Journal of Phycology 49: 1221. 2013. Type locality (of Denticella regia): Helgoland (Germany), North Sea. We wish to thank David Lazarus for allowing access to the Ehrenberg Collection. The nomenclatural work is granted by the Deutsche Forschungsgemeinschaft (DFG) [PhycoBank, JA 874/8-1]. The manuscript was improved by Michael Guiry and Luc Ector; the comments by Wm. J. Woelkerling were invaluable for the taxonomic assessment of Ehrenberg’s observations and our nomenclatural conclusions. Ashworth, M.P., Nakov, T. & Theriot, E.C. (2013). Revisiting Ross and Sims (1971): toward a

molecular phylogeny of the Biddulphiaceae and Eupodiscaceae (Bacillariophyceae). Journal of Phycology 49(6): 1207-1222.

Drebes, G. (1974). Marines Phytoplankton. Eine Auswahl der Helgoländer Planktonalgen (Diatomeen, Peridineen) pp. 1-186. Stuttgart: Thieme Verlag.

Ehrenberg, C.G. (1834). Dritter Beitrag zur Erkenntniss grosser Organisation in der Richtung des kleinsten Raumes. Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin 1833: 145-336, pls I-XI.

Ehrenberg, C.G. (1836). Das Leuchten des Meeres: neue Beobachtungen nebst Übersicht der Hauptmomente der geschichtlichen Entwicklung dieses merkwürdigen Phänomens. Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin 1834: 411-575.


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Ehrenberg, C.G. (1838). Die Infusionsthierchen als vollkommene Organismen: Ein Blick in das tiefere organische Leben der Natur. pp. i-xviii, [1-4], 1-547, pls I-LXIV. Leipzig: Verlag von Leopold Voss.

Ehrenberg, C.G. (1854) Mikrogeologie. Das Erden und Felsen schaffende Wirken des unsichtbar kleinen selbstständigen Lebens auf der Erde. Atlas. Pp. 1-374, pls. 1-40. Leipzig: Verlag von Leopold Voss.

Elbrächter, M., Hoppenrath, M., Jahn, R. & Kusber, W.-H. (2018). Stability of the generic names Alexandrium Halim and Gessnerium Halim at risk because of Peridinium splendor-maris Ehrenberg, the first documented bloom of Alexandrium (Dinophyceae). Notulae Algarum 60: 1-6.

Hällfors, G. (2004). Checklist of Baltic Sea phytoplankton species (including some heterotrophic protistan groups). Baltic Seas Environment Proceedings 95: [1]-208. Online at http://www.helcom.fi/Lists/Publications/BSEP95.pdf

Hendey, N.I. (1964). An introductory account of the smaller algae of British coastal waters. Part V: Bacillariophyceae (diatoms). Ser. IV (part 5) pp. [i]-xxii, 1-317. Great Britain: Ministry of Agriculture, Fisheries and Food, Fishery Investigations. Her Majesty’s Stationery Office, London.

Hoppenrath, M., Elbrächter, M. & Drebes, G. (2009). Marine phytoplankton. Selected microphytoplankton species from the North Sea around Helgoland and Sylt. pp. [1]-264, figs 1-87. Stuttgart: E. Schweizerbart'sche Verlagsbuchhandlung.

Jahn, R. & Kusber, W.H. (2004). Algae of the Ehrenberg collection - 1. Typification of 32 names of diatom taxa described by C.G. Ehrenberg. Willdenowia 34(2): 577-595, 1 table.

Jahn, R., Kusber, W.-H., Medlin, L.K., Crawford, R.M., Lazarus, D., Friedl, T., Hepperle, D., Beszteri, B., Hamann, K., Hinz, F., Strieben, S., Huck, V., Kasten, J., Jobst, A. & Glück, K. (2004). Taxonomic, molecular and ecological information on diatoms: The information system AlgaTerra. Proceedings of the International Diatom Symposium 17: 121-128.

Kusber, W.-H. & Jahn, R. (2009). The last chapter of the Discoplea story. Studi Trentini di Scienze Naturali 84: 105-110.

Lavigne, A.S., Sunesen, I. & Sar, E.A. (2015). Morphological, taxonomic and nomenclatural analysis of species of Odontella, Trieres and Zygoceros (Triceratiaceae, Bacillariophyta) from Anegada Bay (Province of Buenos Aires, Argentina). Diatom Research 30(4): 307-331.

Lazarus, D. & Jahn, R. (1998). Using the Ehrenberg Collection. Diatom Research 13(2): 273-291. Pankow, H. (1990). Ostsee-Algenflora. pp. 1-648, 153 pl. in text, VI pl. at end. Jena: Fischer. Ralfs, J. (1848). The British Desmidieae. pp. [i]-xxii, [i], [1]-226, pls I-XXXV. London: Reeve,

Benham & Reeve. Schultze, M. (1858). Innere Bewegungserscheinungen bei Diatomeen der Nordsee aus den

Gattungen Coscinodiscus, Denticella, Rhizosolenia. Archiv für Anatomie, Physiologie und Wissenschaftliche Medicin Jahrgang 1858: 330-342, pl. 13: figs 1-5.

Snoeijs, P. & Balashova, N. (1998). Intercalibration and distribution of diatom species in the Baltic Sea The Baltic Marine Biologists Publication No. 16e. Vol. 5 pp. 1-144, 1 fig, 6 tables, 101 plates. Uppsala: Opulus Press.

Turland, N.J., Wiersema, J.H., Barrie, F.R., Greuter, W., Hawksworth, D.L., Herendeen, P.S., Knapp, S., Kusber, W.-H., Li, D.-Z., Marhold, K., May, T.W., McNeill, J., Monro, A.M., Prado, J., Price, M.J. & Smith, G.F., editors (2018). International Code of Nomenclature for algae, fungi, and plants (Shenzhen Code) adopted by the Nineteenth International Botanical Congress Shenzhen, China, July 2017. Regnum Vegetabile, Vol. 159. pp. [i]-xxxviii, 1-253. Glashütten: Koeltz Botanical Books.

Vanlandingham, S.L. (1971). Catalogue of the fossil and recent Genera and Species of Diatoms and their Synonyms. Part IV. Fragilaria through Naunema. Lehre: Verlag von J. Cramer.

Williams, D.M. (1988). An illustrated catalogue of the type specimens in the Greville diatom herbarium. Bulletin of the British Museum (Natural History), Botany 18: 1-148.


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Williams, D.M., Sims, P.A., Ashworth, M. & Theriot, E.C. (2017). (2561–2562) Proposals to reject the names Microtheca and Anuraea octoceras (M. octoceras) (Bacillariophyceae). Taxon 66(6): 1466-1467.

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