Research Article |
Corresponding author: Bart Van de Vijver ( bart.vandevijver@meisebotanicgarden.be ) Academic editor: Christine Cocquyt
© 2024 Bart Van de Vijver, Wolf-Henning Kusber, Ingrid Jüttner, Tanja M. Schuster, David M. Williams.
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:
Van de Vijver B, Kusber W-H, Jüttner I, Schuster TM, Williams DM (2024) Revision of the Staurosirella leptostauron complex (Staurosiraceae, Bacillariophyta) in Europe with the description of three new species. Plant Ecology and Evolution 157(2): 174-201. https://doi.org/10.5091/plecevo.119907
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Background and aims – Small-celled araphid diatoms form an important part of the diatom flora in our rivers and lakes. Although several of these species are frequently reported, their correct taxonomic identity is often obscured due to a lack of good knowledge of the original (type) material.
Material and methods – Several historical (nineteenth century) original samples were retrieved from different European and North American diatom collections. The samples have been analysed using light (LM) and scanning electron microscopy (SEM).
Key results – Staurosirella crux comb. nov., based on Ehrenberg’s Navicula crux, proved to be the oldest valid name for Staurosirella harrisonii, the latter now being considered a younger synonym. A new European species, S. neorhomboides sp. nov., is described to replace the name S. rhomboides, now considered a younger synonym of S. leptostauron. The North American populations of S. rhomboides and S. martyi differ sufficiently from the type populations and are described as new species: S. moralesii sp. nov. and S. manoyloviana sp. nov. The new combination Staurosirella informis comb. nov. is proposed for a taxon described in 1856 from the French Pyrenees as Odontidium informe. Staurosirella leptostauron turns out to be insufficiently described and is now documented for further use.
Conclusion – The analysis of the original (type) material corrected several taxonomic errors and better characterised the morphology of several commonly observed Staurosirella species.
araphid diatoms, Bacillariophyceae, new species, Staurosirella, type material
The diatom genus Staurosirella D.M.Williams & Round (Staurosiraceae, Bacillariophyta) was described in 1987 by Williams and Round, split from the catch-all genus Fragilaria Lyngb. (
At present, Staurosirella includes more than 50 published names (
During the past two years, intensive taxonomic research based on the analysis of historical samples from several European diatom collections, such as the Van Heurck collection (BR, Belgium), the Ehrenberg collection (BHUPM, Germany), the Kützing collection (BM, United Kingdom), and the Grunow collection (W, Austria), revealed major inconsistencies in the identification of common European Staurosirella taxa, clearly demonstrating the need for a more detailed revision of historical type material as it was successfully done in the past for other diatom genera such as Pinnularia, Brachysira, Ulnaria, and Eunotia (e.g.
One of the most iconic and characteristic Staurosirella species in Europa, mainly due to its typical cruciform valve outline, is Staurosirella leptostauron (Ehrenb.) D.M.Williams & Round. In 1854, Christian Gottfried Ehrenberg (1795–1876) originally published it as Biblarium leptostauron Ehrenb. from a sample named ‘Silbergrauer Polierschiefer von Cassel’, a city in central Germany, and illustrated this new species with two small line drawings (
In 2006, Morales and Manoylov analysed a large number of Staurosirella populations from several North American rivers (
In this paper, we analyse the original (type) material of several Staurosirella species commonly reported in Europe. The material included the original Ehrenberg material for Navicula crux Ehrenb. and Biblarium leptostauron, and samples kept in BR from the collections of William Smith and the Scottish botanist George A. Walker Arnott (1799–1868) for Odontidium harrisonii and its var. β, as well as Odontidium informe W.Sm. Additionally, type material from the Grunow collection in Vienna (W) for Fragilaria harrisonii var. dubia var. rhomboides, and fossil material collected by Héribaud from the Auvergne for Opephora cantalense Hérib. and O. martyi Hérib. kept in BM were also investigated. In addition, the original slide and material used to illustrate S. rhomboides and S. martyi in
In this study, a large number of historical samples from various European diatom collections was brought together to clarify the taxonomic identity of the S. leptostauron complex. Table
A subsample of each of the selected materials was prepared for LM and SEM observations following the method described in van der Werff (1955). Small volumes of subsamples were cleaned by adding 37% H2O2 and subsequently heated to 80°C for about 1–2 h. The reaction was completed by addition of saturated KMnO4. Following digestion and rinsing by centrifugation (three times 10 minutes at 4500 × rpm), the resulting cleaned diatom material was diluted with distilled water to avoid excessive concentrations of diatom valves and an aliquot was placed on a slide and mounted in Naphrax®. Slides were analysed using an Olympus BX53 microscope at ×1000 magnification (UPLanFL N 100× objective, N.A. 1.30), equipped with Differential Interference Contrast (Nomarski) optics and the Olympus UC30 Imaging System. For each taxon, the number of specimens, measured at random on the type slide, is indicated (n = X). To assess the associated diatom flora in each sample, at least 200 valves were enumerated and identified on random transects.
Sample | Locality | Investigated taxon | Collection date | Collector | Collection | Collection number |
Ehrenberg sample 2726 | Polirschiefer bei Cassel, Germany | Navicula crux, Biblarium leptostauron | ? | C.G. Ehrenberg | BHUPM | BHUPM s.n. |
Smith s.n. | Hull, United Kingdom | Odontidium harrisonii | 15 Jan. 1854 | R. Harrison | BR | BR-4685 |
Grunow s.n. | Moosach near Munich, Germany | Fragilaria harrisonii var. rhomboides | ? | A. Grunow | BR, W | BR-4819, W0164841 |
Kützing 921 | Moosach near Munich, Germany | Fragilaria harrisonii var. rhomboides | ? | ? | BR | BR-4820 |
Smith s.n. | Cauterets, Gave de Lizez, France | Odontidium informe | Jul. 1856 | W. Smith | BR | BR-4821 |
Smith s.n. | Gave de la Reine, France | Odontidium informe | Jul. 1856 | W. Smith | BR | BR-4822 |
Walker Arnott S445 | Redesdale, Hermits Well, United Kingdom | Odontidium informe | Aug. 1856 | R.K. Greville | BR | BR-4823 |
Smith s.n. | Burnham, Norfolk, United Kingdom | Odontidium harrisonii var. β | 1 Jan. 1854 | Mr. Brookes | BR | BR-4824 |
Smith s.n. | Lough Derg, County Clare, Ireland | Odontidium harrisonii var. β | 24 Jul. 1854 | W. Smith | BR | BR-4825 |
Morales s.n. | Willow Creek, Waushara, Wisconsin, United States | Staurosirella moralesii, S. manoyloviana | 1993 | ? | ANSP, BR | ANSP G.C 100049b, BR-4826 |
Jüttner s.n. | Killen Burn, Highland, Scotland, United Kingdom | Staurosirella neorhomboides | ? | I. Jüttner | BR | BR-4827, slide 435 |
Grunow 552 | Stienitz See, Berlin, Germany | Fragilaria harrisonii var. dubia | ? | Amic. Reinhardt | BR, W | BR-4828, W0164812, W0164813 |
Héribaud s.n. | Dépôt de Neussargues, Cantal, France | Opephora martyi | 1901? | P. Marty | BR | BR-4829 |
Héribaud s.n. | Dépôt de Joursac, Cantal, France | Opephora cantalense | 1903? | M.J. Pagès-Allary? | BM | BM 68398 |
Smith s.n. | Ormesby, Norfolk, United Kingdom | Staurosirella martyi | 10 Apr. 1853 | M. Bridgeman | BR | BR-4830 |
For SEM analysis, parts of the oxidised suspensions were filtered through a 5 µm Isopore™ polycarbonate membrane filter (Merck Millipore). Filters were air-dried and pieces were affixed to aluminium stubs. The stubs were sputter-coated with a platinum layer of 10 nm and studied using a ZEISS Ultra scanning electron microscope at 3 kV and 6 mm working distance (Natural History Museum, United Kingdom). Additional observations were preformed using a JEOL-JSM-7100F field emission scanning electron microscope, operated at 2 kV and 4 mm working distance (Meise Botanic Garden, Belgium). Slides, samples and stubs analysed in this study are stored at the BR collection (Meise Botanic Garden, Belgium). Figures were prepared using Photoshop CS5.
Terminology used for the description of the various structures of the siliceous cell wall is based on
For typification of the new species, we chose to use the entire sample as the holotype following Article 8.2 of the International Code of Nomenclature for algae, fungi, and plants (
Based on the morphological analysis of the selected (historical and recent) populations, we propose important taxonomic changes in the genus Staurosirella, which alter the generally accepted ideas of some taxa considerably and may therefore not meet with universal approval. Commonly used names such as Staurosirella harrisonii, S. dubia, and S. rhomboides should no longer be used, as they represent more recent synonyms of other taxa. Others, such as S. martyi, represent different taxa. Based on their valve outline, two groups can be recognized: a first group with (almost) isopolar cruciform/rhomboid valves and a second with heteropolar, ovoid to clavate valve outlines.
Ehrenberg originally described Navicula crux (
Staurosirella crux (Ehrenb.) Van de Vijver & Kusber comb. nov., LM micrographs taken from the original Ehrenberg sample 2726 (Polirschiefer bei Cassel, Germany). A. Original drawing 2348 from the Ehrenberg Collection (Berlin, Germany). B–E. LM pictures of valves in valve face view from the original mica conserved in BHUMP, Berlin, Germany. F–H. LM pictures of prepared unmounted Ehrenberg material. Scale bar = 10 µm.
Staurosirella crux (Ehrenb.) Van de Vijver & Kusber comb. nov., LM and SEM micrographs taken from the original Smith type material for Odontidium harrisonii (BR-4685, Hull, United Kingdom). A. LM picture of a frustule in girdle view. B–M. LM pictures of valves in valve face view in decreasing length. N. SEM external view of a complete valve. O. SEM external detail of the footpole showing the large apical pore field. P. SEM external detail of part of the central area with the marginal spines, the large virgae and the vimines. Q. SEM internal view of a complete valve. Scale bar = 10 µm (A–N, Q), 1 µm (O–P).
Staurosirella crux (under the name Fragilaria harrisonii or Staurosirella harrisonii) has been considered by some authors as a synonym of the more commonly known Staurosirella leptostauron (Ehrenb.) D.M.Williams & Round (
The search for S. leptostauron in Ehrenberg’s sample 2726 was not successful (contrary to S. crux). Due to the usage of Canada balm by Ehrenberg, the marked parts of the deposited mica were obscured and Ehrenberg’s specimens of this species could not be identified. Ehrenberg’s drawings, based on his own observations, show two different valves, one without striae and one with striae (Fig.
When
Staurosirella informis (W.Sm.) Van de Vijver comb. nov., LM and SEM micrographs taken from the original Smith material (BR-4821, Cauterets, Gave de Lizez, France). A. Original drawing from
Staurosirella leptostauron (Ehrenb.) D.M.Williams & Round, LM and SEM micrographs taken from Grunow’s Moosach sample (BR-4819, Moosach, Germany). A. Published images in
Odontidium harrisonii var. β was first mentioned in
Staurosirella moralesii Van de Vijver, Jüttner & D.M.Williams sp. nov., LM micrographs taken from the type material (ANSP G.C 100049b, Willow Creek, United States). A–Z. LM pictures of valves in valve face view in decreasing length. Note the change in valve outline in the smaller valves. Scale bar = 10 µm.
In their analysis of the Odontidium species described by
In Europe, several populations were identified as Staurosirella rhomboides based on
Staurosirella moralesii Van de Vijver, Jüttner & D.M.Williams sp. nov., SEM micrographs taken from the type material (ANSP G.C 100049b, Willow Creek, United States). A–C. SEM external view of three complete valves, showing the variation in the shape and size of the sternum, the differences in shape and size in apical pore field between head- and footpole. D. SEM internal view of a complete valve. E–F. SEM view of the valvocopula with the fimbriate extensions in oblique and frontal view. Scale bar = 10 µm.
Staurosirella neorhomboides Van de Vijver & Jüttner sp. nov., LM and SEM micrographs taken from the type material (BR-4827, Killen Burn, United Kingdom). A. LM picture of a frustule in girdle view. B–AG. LM pictures of valves in valve face view in decreasing length. AH–AJ. SEM external view of several valves, clearly showing the irregular spines and papillae on the valve margins. AK. SEM internal view of a complete valve. AL. SEM view of the broad valvocopula with the fimbriate extensions. Scale bar = 10 µm (A–AI, AK–AL), 1 µm (AJ).
Analysis of the type material of Odontidium informe (Fig.
It is possible that Fragilaria leptostauron var. woerthensis A.Mayer (
One taxon, often considered morphologically closely related to S. leptostauron, but with a heteropolar, ovoid valve outline, is Staurosirella dubia, first described as Fragilaria harrisonii var. γ dubia
Heteropolar valves similar to S. dubia are often reported as Staurosirella martyi in the literature. For instance, LM images in
Our analyses of the type material of both S. dubia and S. martyi revealed, however, that both species share a large number of common morphological features, such as the absence of marginal spines, a heteropolar valve shape, the shape of the apical pore field, and an apical depression at the headpole. Larger valves in the fossil type material of Staurosirella martyi (Figs
We also investigated the type population of Opephora cantalense (Fig.
Round proposed the new genus Martyana Round for Opephora martyi, based on the absence of an apical pore field at the headpole, the presence of a step at the headpole, the absence of spines, and the structure of the areolae and striae (
Staurosirella martyi (Hérib.) E.Morales & Manoylov, LM and SEM micrographs taken from the epitype material (BR-4828, Grunow sample 552, Stienitz See, Berlin, Germany). A. Original drawing from the Grunow Collection in W. B. LM picture of a frustule in girdle view. C–V. LM pictures of valves in valve face view in decreasing length. W–X. SEM external view of several valves. Y. SEM girdle view of a valve and its connected valvocopula. Z. SEM internal view of an entire view. Scale bar = 10 µm.
Staurosirella martyi (Hérib.) E.Morales & Manoylov, LM micrographs taken from the original material for Opephora cantalense Hérib. (C–J) and O. cantalense var. capitata (K–U) (BM68398, Dépôt de Joursac, Cantal, France). A–B. Original drawings from
Comparison table of all Staurosirella species discussed in this paper. Figures: figures in this paper; Suppl. materials: supplementary materials related to this paper.
Staurosirella crux | Staurosirella informis | Staurosirella leptostauron | Staurosirella moralesii | Staurosirella neorhomboides | Staurosirella martyi | Staurosirella manoyloviana | |
Figures | 1, 2 | 3 | 4 | 5, 6 | 7 | 8–11 | 12–13 |
Suppl. materials | 1, 2A–J, 3A–B | 4 | 2K–Z, 3C–F, 5–7 | 8 | 9 | ||
Length (µm) | 10–36 | 15–22 | 15–23 | 10–40 | 5–20 | 9–38 | 15–70 |
Width (µm) | 7–24 | 7–9 | 10–16 | 5–9 | 3.5–7.0 | 5–10 | 8–10 |
Valve outline | cruciform in larger valves becoming subovoid to rhomboid in smaller specimens | isopolar, rhombic-lanceolate in larger valves, more strictly lanceolate in smaller specimens | distinctly cruciform throughout its entire cell cycle | almost isopolar, with a slightly larger footpole, rhombic throughout the entire cell diminution series | weakly heteropolar, slightly broader headpole, more acute footpole, rhombic-lanceolate to strictly lanceolate and elliptical | heteropolar, larger valves with clear constriction between valve middle and headpole, smaller valves ovoid in shape | distinctly heteropolar, ovoid in shape throughout the entire cell diminution series |
Sternum | rather wide, linear to weakly lanceolate | moderately broad, lanceolate, slightly widened near the centre | broad, distinctly lanceolate, widened near the valve centre, often showing irregular markings | variable, moderately broad, mostly lanceolate, to narrow and linear in some valves | variable, moderately broad, lanceolate, slightly widened near the centre to very narrow, linear | narrow to moderately broad, linear to lanceolate | narrow, linear, very rarely lanceolate |
Spines | irregular, rudimentary, grouped as verrucae-like structures | irregularly shaped on the virgae | flattened, irregularly shaped, blunt, on the virgae | large, flattened marginal, on the virgae | single or double, irregular, on the virgea | absent | absent |
Apical pore field | very large, equal in size on both apices, composed of a large number of parallel rows of very small, slit-like pores | present on both apices, equal in size and shape, composed of at least 7 long rows of small, rounded pores, covered occasionally by small silica plates | present on both apices, clearly different in size and shape, giving the valves an heteropolar appearance | present on both apices, larger at the footpole, composed of at least 7 long rows of small, rounded pores, covering the entire foot pole, smaller on the headpole | present on both apices, larger at the footpole, composed of at least 7 long rows of small, rounded pores, covered by distinct, silica plates | at footpole very large, composed of > 8 long rows of small, rounded to squarish pores, much smaller at headpole, restricted to a few small pores | present on both apices, much larger on the footpole, composed of 5– 7 long rows of small, rounded pores |
Striae in 10 µm | 5–6 | 6–7 | ca 9 | 7–8 | 9–10 | 6–7 | 5–6 |
Striation pattern | alternating, radiate to weakly curved | weakly radiate | parallel to weakly radiate at the centre, becoming more radiate towards the apices | parallel in the middle, becoming weakly radiate at the apices | weakly radiate throughout the entire valve | parallel in the middle becoming gradually weakly radiate towards the apices | alternating, parallel throughout to weakly radiate towards the apices |
Lineolae in LM | clearly discernible | occasionally weakly discernible | only very rarely discernible | not discernible | not discernible | often discernible | clearly discernible |
An analysis of the type material of S. martyi (and the populations identified as S. dubia) also indicated that the populations used to illustrate these species in
Staurosirella manoyloviana Van de Vijver, Jüttner & D.M.Williams sp. nov., LM micrographs taken from the type material (ANSP G.C 100049b, Willow Creek, United States). A–B. LM pictures of two frustules in girdle view. C–T. LM pictures of valves in valve face view in decreasing length. Note the change in valve outline in the smaller valves. Scale bar = 10 µm.
Staurosirella manoyloviana Van de Vijver, Jüttner & D.M.Williams sp. nov., SEM micrographs taken from the type material (ANSP G.C 100049b, Willow Creek, United States). A. SEM view of a frustule in girdle view. B. SEM view of the valvocopula with the fimbriate extensions. C–D. SEM external view of two complete valves. E. SEM internal view of a complete valve. Scale bar = 10 µm (C–E), 5 µm (A–B).
The results of our study highlight the importance and even necessity of including historical material in taxonomic studies of diatoms. Although phycologists in the nineteenth century, such as Ehrenberg and Grunow, usually made very accurate drawings, comparison between these drawings and LM observations is not always easy and misinterpretations can occur, leading to incorrect identifications, taxonomic drift, and/or shoehorning new populations into historical names. It is therefore crucial that taxonomic analyses, especially those involving taxonomic changes (new combinations, transfers, and synonymies), include the revision of original material, when it is available. A better analysis and documentation of historical material is the basis for avoiding making incorrect or incomplete taxonomic interpretations. Historical diatom collections, such as the Grunow collection in Vienna (W), have become more accessible, facilitating the search for these materials (
Table
Navicula crux
Ehrenb. (basionym), Die Infusionsthierchen als vollkommene Organismen. Ein Blick in das tiefere organische Leben der Natur: 184. 1838. (
Biblarium crux
(Ehrenb.) Ehrenb. (
Odontidium harrisonii
W.Sm. (
Dimeregramma harrisonii
(W.Sm.) Ralfs (
Fragilaria harrisonii
(W.Sm.) Grunow (
Diatoma harrisonii
(W.Sm.) Cleve (
Rhaphoneis harrisonii
(W.Sm.) O’Meara (
Staurosira harrisonii
(W.Sm.) Grunow (
Nematoplata harrisonii
(W.Sm.) Kuntze (
Staurosirella lata
Levkov et al. (
Staurosirella harrisonii
(W.Sm.) E.Morales & C.E.Wetzel (
Germany, Polierschiefer bei Cassel, Ehrenberg BHUPM drawing sheet 2348, BHUPM sample 2726.
BHUPM 420310 ε w ‘Cassel’ (Kasten = case 42, Buch = folder 3, mica strip 10 ε white ring) (designated here), specimen illustrated as our Fig.
BHUPM s.n., specimen illustrated as our Fig.
GERMANY • Polierschiefer bei Cassel; Ehrenberg sample 2726, Ehrenberg [icon!] drawing sheet 2348; BHUPM • Moosach near München; Grunow sample s.n., Moosach W0164841 [filed as Staurosira harrisonii under Odonti[di]um harrisonii in the general collection], slide BR-4819; W, BR • Moosach near München; Kützing sample 921, slide BR-4820; BR.
UNITED KINGDOM • Hull; 15 Jan. 1854; Smith sample s.n., slide BR-4685; BR.
Frustules in girdle view rectangular, solitary. Valve outline cruciform in larger valves becoming subovoid/rhomboid in smaller specimens, usually showing a rather irregular valve outline. Larger valves subtly heteropolar with one apex slightly wider than the opposite one, becoming distinctly heteropolar in the lower end of the size range. Apices not protracted, broadly rounded. Central inflations broadly rounded with a broad base. Valve dimensions (n = 30): length 10–36 µm, width 7–24 µm. Sternum rather wide, linear to weakly lanceolate. Striae narrower than the virgae, alternating, radiate to weakly curved, 5–6 in 10 µm. Individual lineolae in the striae usually well discernible in LM. Figures
Valve surface uneven. Virgae with clearly raised transapical ridge. Striae uniseriate, composed of long, apically elongated areolae (= lineolae). Vimines broader than the areolae, becoming shorter towards the sternum and on the valve mantle. Spines irregular, rudimentary, grouped as verrucae-like structures on the valve face/mantle junction, located on the virgae in pit-like, shallow depressions. Apical pore fields very large, present on both apices, with both pore fields almost equal in size. Pore fields composed of a large number of parallel rows of very small, double, slit-like pores. Internally, valve surface more or less flat, with broad virgae and depressed series of areolae. Volae on the striae bifurcate, emerging from the longer inner side of the vimines. Figure
The lectotype population was observed in a fossil sample (Polierschiefer = layered diatomaceous earth) collected in the surroundings of Cassel, a town in central Germany (Hesse, Germany). According to
Odontidium informe
W.Sm. (basionym), Annals and Magazine of Natural History, second series 19: 10, plate II, fig. 12a–c. 1857. (
Gave de Lizez, Cauterets, Pyrenees Mountains, France, Jul. 1856.
BR-4821 (designated here), slide made from Smith sample Gave de Lizez. Figure
FRANCE • Cauterets, Gave de Lizez; William Smith sample Gave de Lizez, slide BR-4821; BR • Gave de la Reine; William Smith sample Gave de la Reine, slide BR-4822; BR.
UNITED KINGDOM • Redesdale, Hermits Well; Aug. 1856; leg. R.K. Greville; Walker Arnott sample S445, slide BR-4823; BR.
Frustules rectangular in girdle view, solitary, but occasionally forming short band-like chains. Valves isopolar, rhombic-lanceolate in larger valves, becoming more strictly lanceolate in smaller specimens. Apices not protracted, cuneately to broadly rounded. Valve dimensions (n = 20): length 15–22 µm, width 7–9 µm. Sternum moderately broad, lanceolate, slightly widened near the centre. Striae not broader than the virgae, weakly radiate throughout the entire valve, 6–7 in 10 µm. Areolae occasionally weakly discernible in LM (e.g. Fig.
Sternum and vimines externally raised above the striae. Weakly raised parallel ridges present on the virgae. Single or double, irregularly shaped spines present on the virgae, with a large number of small granules present between the spines on virgae and vimines. Striae composed of linear, slit-like areolae, separated by thin vimines. Areolae diminishing in length near the sternum. Apical pore fields present on both apices, equal in size and shape, composed of at least 7 long rows of small, rounded pores, covered occasionally by small silica plates. Valvocopula very large, plain, with distinct fimbriae. Internal areola occlusions formed by finely branched volae. Figure
The type population was found in a sample from the Gave de Lizez, a stream in the French Pyrenees (region de Bigorre, Haute-Pyrenées, France). The sample is dominated by Achnanthidium gracillimum (F.Meister) Lange-Bert., A. trinode Ralfs, Brachysira neoexilis Lange-Bert., Denticula tenuis, Fragilaria perdelicatissima Lange-Bert. & Van de Vijver, Staurosirella neopinnata, and Staurosira tabellaria (W.Sm.) Leud.-Fortm., together with several species of Cymbella, Delicata, and Gomphonema. According to
Biblarium leptostauron
Ehrenb. (basionym) (
Fragilaria harrisonii var. β rhomboides
Grunow (
Fragilaria leptostauron
(Ehrenb.) Hust. (
Fragilaria leptostauron var. rhomboides
(Grunow) Hust. (
Staurosirella rhomboides
(Grunow) E.Morales & Manoylov (
Staurosira leptostauron
(Ehrenb.) Kulikovskiy & Genkal (
Germany, Polierschiefer bei Cassel, Ehrenberg BHUPM drawing sheet 2347, BHUPM sample 2726.
Moosach near Munich, Grunow Moosach sample s.n., material conserved at BR! and W!.
BHUPM drawing sheet 2347 “Cassel.” (designated here by Kusber & Van de Vijver), valve original annotated in black colour “10. δ.bl.”, subsequently annotated in red colour “31” [icon!], the image represents a specimen on Mica BHUPM 420310 δ r that could not be found during the recent studies at BHUPM. The lectotype here selected was published in
BR-4819 (designated here by Van de Vijver for the above lectotype), slide made from the Grunow Moosach sample s.n. Figure
W0164841 (designated here by Schuster & Van de Vijver for the above lectotype), raw Grunow Moosach material s.n. at W.
GERMANY • Polierschiefer bei Cassel, Ehrenberg sample 2726, [icon!] drawing sheet 2347; BHUPM • Moosach near München; Grunow Moosach sample s.n., slide BR-4819; BR • Moosach near München; Kützing sample 921, slide BR-4820; BR.
UNITED KINGDOM – England • Burnham, Norfolk; William Smith sample; 1 Jan. 1854; leg. Mr. Brookes; slide BR-4824; BR • Redesdale, Hermits Well; Walker Arnott sample S445; Aug. 1856; leg. R.K. Greville; slide BR-4823; BR.
IRELAND • William County Clare; Smith sample Lough Derg; 24 Jul. 1854; leg. W. Smith; slide BR-4825; BR.
As the search for S. leptostauron in Ehrenberg’s sample 2726 was not successful, the following morphological description is based on the epitype material from Moosach.
Frustules in girdle view rectangular, impossible to get into focus entirely due to protruding central parts. Valves isopolar to weakly heteropolar with weakly narrower footpole (Fig.
Valve face not flat, showing clear topography with raised virgae and sternum and depressed striae. Distinct short, parallel ridges present on the virgae, in line with the vimines separating the linear areolae. In eroded valves, ridges less prominently present to even absent. Sternum often irregularly raised. Large, flattened, irregularly shaped marginal blunt spines placed on the virgae. Numerous, irregular, often very small granules present on the virgae between the spines and the vimines. Apical pore fields present on both apices, clearly different in size and shape, giving the valves an heteropolar appearance. Pore field at the footpole composed of more than 8 long rows of small, rounded to squarish pores. At the headpole, pore field smaller, with a maximum of 5–6 short rows of small pores. Observations of valve interior in the Moosach material showing typical finely branched volae (Fig.
The Moosach population is quite diverse and dominated by taxa such as Achnanthidium exile (Kütz.) Heib., Cocconeis pseudothumensis, Denticula kuetzingii Grunow, D. tenuis Kütz., Ellerbeckia arenaria (Moore) Dorofeyuk & Kulikovskiy, Eunotia alkalibiontica Lange-Bert., Grunowia tabellaria (Grunow) Rabenh., Odontidium mesodon (Ehrenb.) Kütz., Staurosirella neopinnata E.Morales et al., S. leptostauron (Ehrenb.) D.M.Williams & Round, and various species of Delicata, Cymbella, and Gomphonema. This species composition is often found in oligo- to mesotrophic, calcium-bicarbonate enriched, alkaline conditions (
Willow Creek, Waushara, Wisconsin, USA Western Lake Michigan Drainage study Unit, 1993 (ANSP G.C 100049b).
ANSP G.C 100049b (Academy of Natural Sciences, Philadelphia). Figure
UNITED STATES • Willow Creek, WI; sample ANSP G.C 100049b, material kept at The Academy of Natural Sciences, Philadelphia, new slide deposited as BR-4826; BR, ANSP.
Valves almost isopolar, with a slightly larger footpole, rhombic throughout the entire cell diminution series. Larger specimens more elongated than smaller, more compact valves. Apices acutely rounded, not protracted. Valve dimensions (n = 25): length 10–40 µm, width 5–9 µm. Sternum variable, moderately broad, mostly lanceolate, to narrow and linear in some valves (Fig.
Valve face irregular with weakly raised virgae bearing parallel very low ridges. Series of large, flattened marginal spines present on the virgae, due to erosion often split into several parts (Fig.
The species is named after the late Dr Eduardo A. Morales (University of Evora, Portugal) who suddenly passed away in May 2023. Eduardo was a world-renowned specialist of the taxonomy and morphology of small-celled araphid genera and described many species in the genera Staurosirella.
The Willow Creek sample is entirely dominated by several species of Staurosirella. Apart from S. moralesii, S. ovata E.Morales & Manoylov and S. manoyloviana had high relative abundances. However,
Killen Burn, Highland, Scotland, UK.
BR-4827 (Meise Botanic Garden, Belgium), slide made from original Killen Burn material. Figure
Slide 435 (University of Antwerp, Belgium).
UNITED KINGDOM – Scotland • Killen Burn, Highland; slide BR-4827; BR.
Frustules rectangular in girdle view, solitary (Fig.
Sternum and virgae externally raised above the striae. Weakly raised parallel ridges present on the virgae. Single or double, irregularly shaped spines present on the virgae, with a large number of small granules present between the spines on virgae and vimines. Striae narrower than the virgae, composed of linear, slit-like areolae, separated by thin vimines. Areolae diminishing in length near the sternum. Both apices not depressed. Apical pore fields present on both apices, on the footpole larger than on the headpole. On the footpole, pore field composed of at least 7 long rows of small, rounded pores, covered by small, but distinct, silica plates. Valvocopula very large, plain, with distinct fimbriae. Internal areola occlusions formed by finely branched volae. Figure 7AH–AK.
The specific epithet refers to Staurosirella rhomboides (now considered a synonym of S. leptostauron), the name that was used in the past to identify this species.
The sample from Killen Burn is dominated by species of Achnanthidium, Navicula lanceolata (C.Agardh) Ehrenb., N. tripunctata, Planothidium reichardtii Lange-Bert. & Werum, and Tabellaria flocculosa (Roth) Kütz. with Cocconeis pseudothumensis, Frustulia vulgaris (Thwaites) De Toni, Gomphonema exilissimum (Grunow) Lange-Bert. & E.Reichardt, Navicula gregaria Donkin, Planothidium lanceolatum (Bréb.) Lange-Bert., and Reimeria sinuata (W.Greg.) Kociolek & Stoermer showing lower abundances. According to
Opephora martyi
Hérib., 1902 (basionym) (
Fragilaria harrisonii var. γ dubia
(
Staurosira harrisonii var. dubia
(Grunow) Cleve (
Opephora martyi var. capitata
Hérib. (
Opephora cantalense
Hérib. (
Opephora cantalense var. capitata
Hérib. (
Fragilaria mutabilis f. martyi
(Hérib.) A.Cleve (
Martyana martyi
(Hérib.) Round (
Fragilaria martyi
(Hérib.) Lange-Bert. (
Staurosirella leptostauron var. dubia
(Grunow) Edlund (
Staurosira martyi
(Hérib.) Lange-Bert. (
Staurosirella dubia
(Grunow) E.Morales & Manoylov (
Staurosira dubia
Grunow, nom. inval. (
Dépôt de Neussargues, sample collected between the train station and L’Allagnon (
Grunow sample 552, “zwischen Aegagropila Sauteri aus dem Stienitz See bei Berlin” (Leg. amic. Reinhardt), material conserved at W! Two samples of cleaned material (W0164812 and W0164813, the latter sampled) are filed in the general collection under Fragilaria intermedia.
BR-4829, slide made from Héribaud sample Dépôt de Neussargues. Figure
BR-4828, slide made from Grunow sample 552. Figure
FRANCE • Dépôt de Neussargues, sample collected between the train station and l’Allagnon, Cantal, France; slide BR-4829; BR • Dépôt de Joursac, Cantal, France, slide Collection Tempère & Peragallo (2e edition) BM 68398; BM • zwischen Aegagropila Sauteri aus dem Stienitz See bei Berlin; leg. amic. Reinhardt; Grunow sample 552, slides BR-4828, W0164812 and W0164813; BR, W.
UNITED KINGDOM • Ormesby, Norfolk; 10 Apr. 1853; leg. M. Bridgeman, Smith sample s.n., slide BR-4830; BR.
Frustules rectangular in girdle view, solitary, band-like colonies at present not observed. Valves heteropolar, larger valves with clear constriction between valve middle and headpole, smaller valves ovoid in shape. Headpole broadly rounded, and more acute footpole. Valve outline lanceolate in larger valves, elliptic to elliptic-lanceolate in smaller valves. Valve dimensions (n = 40): length 9–38 µm, width 5–10 µm. Sternum narrow to moderately broad, linear to lanceolate. Striae broad, wider than the virgae, parallel in the middle becoming gradually weakly radiate towards the apices, 6–7 in 10 µm. Individual areolae often discernible in LM (Fig.
Headpole clearly depressed. Sternum and vimines externally weakly raised above the striae. Areolae linear, slit-like, separated by narrow vimines, the latter occasionally interconnected subdividing the areolae in two or three smaller areolae. Spines absent. Apical pore field at footpole very large, composed of more than eight long rows of small, rounded to squarish pores, extending from valve face to mantle. Apical pore field much smaller at headpole, restricted to a compact group of a few small pores. Internally, small pseudoseptum present at footpole contrary to headpole lacking pseudoseptum. Internal areola occlusions eroded due to age of material (Miocene), making observations not possible. Valvocopula very large, plain, open. Figure
Willow Creek, Waushara, Wisconsin, USA, Western Lake Michigan Drainage study Unit, 1993 (ANSP G.C 100049b).
ANSP G.C 100049b (Academy of Natural Sciences, Philadelphia). Figure
UNITED STATES • Willow Creek, WI; sample ANSP G.C 100049b, material kept at The Academy of Natural Sciences, Philadelphia, new slide made BR-4826; BR.
Frustules rectangular in girdle view, solitary or in pairs, band-like colonies at present not observed. Valves distinctly heteropolar, ovoid in shape throughout the entire cell diminution series. Larger valves slightly more elongated. Headpole not protracted, broadly rounded. Footpole more acutely rounded. Valve dimensions (n = 20): length 15–70 µm, width 8–10 µm. Sternum narrow, linear, very rarely lanceolate. Striae as broad as, or narrower than the virgae, alternating, parallel throughout to weakly radiate towards the apices, 5–6 in 10 µm. Individual areolae clearly discernible in LM. Figure
Observations based on
The species is named after Prof. Dr Kalina Manoylov (Georgia College, USA), co-author of
The Willow Creek sample is entirely dominated by several species of Staurosirella. Apart from S. manoyloviana, S. ovata and S. moralesii had high relative abundances, with S. manoyloviana being the least abundant.
Ms Myriam de Haan and Mrs Petra Ballings are thanked for their help with the SEM analyses. Mrs Laura Aycock and Dr Marina Potapova are thanked for their help in retrieving the Willow Creek material from the Academy of Natural Sciences in Philadelphia. Dr David Lazarus and Dr Johan Renaudie are thanked for providing access to the Ehrenberg collection in Berlin.
Staurosirella crux (Ehrenb.) Van de Vijver & Kusber comb. nov., LM micrographs taken from Grunow’s Moosach sample (BR-4819, Moosach, Germany). A–E. LM pictures of valves in valve face view in decreasing length. F. SEM external view of a complete valve. G. SEM internal view of a complete valve. Scale bar = 10 µm.
Staurosirella crux (Ehrenb.) Van de Vijver & Kusber comb. nov. (A–J, left specimen), and S. leptostauron (Ehrenb.) D.M.Williams & Round (J–Z, right specimen). LM micrographs taken from Kützing’s Moosach sample 921 (BR-4820, Moosach, Germany). A–J. LM pictures of valves in valve face view in decreasing length of S. crux. J–Z. LM pictures of valves in valve face view in decreasing length of S. leptostauron. Scale bar = 10 µm.
Staurosirella crux (Ehrenb.) Van de Vijver & Kusber comb. nov. (A–B), and S. leptostauron (Ehrenb.) D.M.Williams & Round (C–F). SEM micrographs taken from Kützing’s Moosach sample 921 (BR-4820, Moosach, Germany). Note the structural differences between both species. A. SEM external view of a complete valve of S. crux. B. SEM internal view of a complete valve of S. crux. C–D. SEM external view of two complete valves of S. leptostauron. E. SEM view of the valvocopula with the fimbriate extensions. F. SEM internal view of a complete valve of S. crux. Scale bar = 10 µm.
Staurosirella informis (W.Sm.) Van de Vijver comb. nov. LM and SEM micrographs taken from Walker Arnott’s sample S445 (BR-4823 Redesdale, Hermits Well, United Kingdom). A. LM picture of three connected frustules in girdle view. B–T. LM pictures of valves in valve face view in decreasing length. U. SEM external view of a complete valve. V. SEM external detail of the valve apices of a complete frustule. W. SEM external view of the valve apex showing the apical pore field. X. SEM internal view of a complete valve. Scale bar = 10 µm (A–U, W–X), 5 µm (V).
Staurosirella leptostauron (Ehrenb.) D.M.Williams & Round, LM and SEM micrographs taken from Smith’s original sample for Odontidium harrisonii var. β (BR-4824, Burnham, United Kingdom). A. Original drawing from
Staurosirella leptostauron (Ehrenb.) D.M.Williams & Round, LM and SEM micrographs taken from Smith’s original sample for Odontidium harrisonii var. β (BR-4825, Lough Dern, United Kingdom). A. Original drawing from
Staurosirella leptostauron (Ehrenb.) D.M.Williams & Round, LM and SEM micrographs taken from Walker Arnott’s sample S445 (BR-4823, Redesdale, Hermits Well, United Kingdom). A–O. LM pictures of valves in valve face view in decreasing length. P. SEM external view of a complete valve. Q. SEM internal view of an entire valve. Scale bar = 10 µm.
Staurosirella moralesii Van de Vijver, Jüttner & D.M.Williams sp. nov., LM micrographs taken from the type material (ANSP G.C 100049b, Willow Creek, United States). A–L. LM pictures of several very large valves. Scale bar = 10 µm.
Staurosirella martyi (Hérib.) E.Morales & Manoylov, LM and SEM micrographs taken from Smith’s material of Ormesby (BR-4830, Ormesby, United Kingdom). A–B. LM pictures of two frustules in girdle view. C–Z. LM pictures of valves in valve face view in decreasing length. AA. SEM external view of a complete valve. AB. SEM external detail of the footpole showing the large apical pore field. AC. SEM internal view of an entire valve. AD. SEM view of the valvocopula with the fimbriate extensions. Scale bar = 10 µm (A–AC), 1 µm (AD).