Abstract
During an evaluation of the diatom diversity and water quality of a small brook near Morogoro (Tanzania), an unknown Planothidium species was observed that could not be identified using the currently available literature. The past 10 years, a large number of Planothidium species has been revised resulting in a better characterisation of some well-known taxa such as P. lanceolatum (Brébisson ex Kützing 1846: 247) Lange-Bertalot (1999: 287), P. frequentissimum (Lange-Bertalot 1993: 4) Lange-Bertalot (1999: 282) and P. delicatulum (Kützing 1844: 75) Round & Bukhtiyarova (1996: 353), but also in the description of a lot of new species (Compère & Van de Vijver 2009, Jahn et al. 2017, Kulaš et al. (2020), N’Guessan et al. 2014, Stancheva 2019, Stancheva et al. 2020, Van de Vijver et al. 2013, 2018, Wetzel et al. 2013, 2014, 2019). Several of these studies dealt with Planothidium species from the African Continent. Compère & Van de Vijver (2009) analysed and illustrated the type material of P. engelbrechtii (Cholnoky 1955: 16) Round & Bukhtiyarova (1996: 353), whereas N’Guessan et al. (2014) discussed the morphology and taxonomic history of two species formerly described by Carter & Denny in 1982: P. miotum (J.R.Carter & Denny 1982: 286) Lange-Bertalot (1999: 278) & P. piaficum (J.R.Carter & Denny 1982: 286) C.E.Wetzel & Ector (in N’Guessan et al. 2014: 460), completed with the description of P. comperei C.E.Wetzel et al. (in N’Guessan et al. 2014: 456), a new Planothidium species from Ivory Coast.
References
<p>Bąk, M. & Lange-Bertalot, H. (2014) Four small-celled <em>Planothidium</em> species from Central Europe proposed as new to science. <em>Oceanological and Hydrobiological Studies</em> 43 (4): 346–359. https://doi.org/10.2478/s13545-014-0152-9</p>
<p>Carter, J.R. & Denny, P. (1982). Freshwater algae of Sierra Leone III. Bacillariophyceae: Part (i) Diatoms from the River Jong (Taia) at Njala. In: Diatomaceae III, Fetschrift Niels Foged. <em>Beihefte zur Nova Hedwigia</em> 73: 281–331.</p>
<p>Cholnoky, B.J. (1955) Hydrobiologische Untersuchungen in Transvaal. I. Vergelichung der herbstlichen Algengemeinschaften in Rayton-vlei und Leeufontein. <em>Hydrobiologia</em> 7: 137–209.</p>
<p>Cleve, P.T. & Grunow, A. (1880) Beiträge zur Kenntniss der arctischen Diatomeen. <em>Kongliga Svenska Vetenskaps-Akademiens Handlingar </em>17 (2): 1–121.</p>
<p>Compère, P. & Van de Vijver, B. (2009) <em>Planothidium engelbrechtii</em> (Cholnoky) Round & Bukhtiyarova: Identity and lectotypification (Bacillariophyta). <em>Fottea</em> 9: 187–192. https://doi.org/10.5507/fot.2009.019</p>
<p>Czarnecki, D.B. (1994) The freshwater diatoms culture collection at Loras College, Dubuque, Iowa. In: Proceedings of the 11th International Diatom Symposium. <em>Memoirs of the California Academy of Sciences</em> 17: 155–174.</p>
<p>Danielidis, D.B. & Mann, D.G. (2003) New species and new combinations in the genus <em>Seminavis</em> (Bacillariophyta). <em>Diatom Research</em> 18 (1): 21–39. https://doi.org/10.1080/0269249X.2003.9705570</p>
<p>Grunow, A. (1878) Algen und Diatomaceen aus dem Kaspischen Meere. <em>In</em>: Schneider, O. (Ed.) <em>Naturwissenschaftliche Beiträge zur Kenntnis der Kaukasusländer, auf Grund seiner Sammelbeute</em>. Dresden Burdach, Dresden, pp. 98–132.</p>
<p>Hohn, M.H. & Hellerman, J. (1963) The taxonomy and structure of diatom populations from three eastern North American rivers using three sampling methods. <em>Transactions of the American Microscopical Society</em> 82 (3): 250–329.</p>
<p>Hustedt, F. (1949) Diatomeen von Sinai-Halbinsel und aus dem Libanon-Gebiet. <em>Hydrobiologia</em> 2: 24–55.</p>
<p>Jahn, R., Abarca, N., Gemeinholzer, B., Mora, D., Skibbe, O., Kulikovskiy, M., Gusev, E., Kusber, W.-H. & Zimmermann, J. (2017) <em>Planothidium lanceolatum</em> and <em>Planothidium frequentissimum</em> reinvestigated with molecular methods and morphology: four new species and the taxonomic importance of the sinus and cavum. <em>Diatom Research</em> 32 (1): 75–107. https://doi.org/10.1080/0269249X.2017.1312548</p>
<p>Kulaš, A., Gligora Udovič, M., Ector, L. & Van de Vijver, B. (2020) Analysis of the type material of <em>Achnanthes hauckiana</em> Grunow (Achnanthaceae, Bacillariophyceae). <em>Botany Letters</em> 167 (4): 439–452. https://doi.org/10.1080/23818107.2020.1808527</p>
<p>Kützing, F.T. (1844) <em>Die Kieselschaligen Bacillarien oder Diatomeen</em>. Nordhausen, pp. [i-vii], [1]–152.</p>
<p>Kützing, F.T. (1846) Kurze Mitteilung über einige kieselschalige Diatomeen. <em>Botanische Zeitung</em> 4 (14): 247–248.</p>
<p>Lange-Bertalot, H. (1993) 85 neue Taxa und über 100 weitere neu definierte Taxa ergänzend zur Süsswasserflora von Mitteleuropa, Vol. 2/1-4. <em>Bibliotheca Diatomologica</em> 27: 1–454.</p>
<p>Lange-Bertalot, H. (1999) Neue Kombinationen von Taxa aus <em>Achnanthes</em> Bory (sensu lato). <em>Iconographia Diatomologica</em> 6: 270–283.</p>
<p>Lange-Bertalot, H., Hofmann, G., Werum, M. & Cantonati, M. (2017) Freshwater benthic diatoms of Central Europe: over 800 common species used in ecological assessment. English edition with updated taxonomy and added species. Koeltz Botanical Books, Schmitten-Oberreifenberg, 942 pp.</p>
<p>Meister, F. (1932) <em>Kieselalgen aus Asien</em>. Gebrüder Borntraeger, Berlin, pp. [1]–56.</p>
<p>N’Guessan, K.R., Wetzel, C.E. Ector, L., Coste, M., C.Cocquyt, C., Van de Vijver, B., Yao, S.S., Ouattara, A., Kouamelan, E.P. & Tison-Rosebery, J. (2014) <em>Planothidium comperei</em> sp. nov. (Bacillariophyta), a new diatom species from Ivory Coast. <em>Plant Ecology and Evolution</em> 147 (3): 455–462. https://doi.org/10.5091/plecevo.2014.981</p>
<p>Østrup, E. (1903) Freshwater diatoms. In Flora of Koh Chang. Part VII. Contributions to the knowledge of the Gulf of Siam. Preliminary Report on Botany. Results Danish Expedition to Siam (1899–1900). <em>Botanisk Tidsskrift</em> 25 (1): 28–41.</p>
<p>Patrick, R.M. (1944) Estudo Limnologico e Biologico das Lagoas da regiao Litoranea Sul-Riograndense II. Some New Diatoms from the Lagoa dos Quadros. <em>Boletim do Museu Naciona, nova serie, botanica</em> 2: 1–6.</p>
<p>Round, F.E. & Bukhtiyarova, L. (1996) Four new genera based on <em>Achnanthes</em> (<em>Achnanthidium</em>) together with a re-definition of <em>Achnanthidium</em>. <em>Diatom Research</em> 11 (2): 345–361. https://doi.org/10.1080/0269249X.1996.9705389</p>
<p>Stancheva, R. (2019) <em>Planothidium sheathii</em>, a new monoraphid diatom species from rivers in California, USA. <em>Phytotaxa</em> 393 (2): 131–140. https://doi.org/10.11646/phytotaxa.393.2.4</p>
<p>Stancheva, R., Kristan, N.V., Kristan, W. B, III & Sheath, R.G. (2020) Diatom genus <em>Planothidium</em> (Bacillariophyta) from streams and rivers in California, USA: diversity, distribution and autecology. <em>Phytotaxa</em> 470 (1): 1–30. https://doi.org/10.11646/phytotaxa.470.1.1</p>
<p>Taylor, J.C., Harding, W.R. & Archibald, C.G.M. (2007) <em>An Illustrated Guide to Some Common Diatom Species from South Africa An Illustrated Guide to Some Common Diatom Species from South Africa</em>. WRC Report No TT 282/07. Water Research Commission, Pretoria, pp. 1–178 pls.</p>
<p>Van de Vijver, B., Wetzel, C., Kopalová, K., Zidarova, R. & Ector, L. (2013) Analysis of the type material of <em>Achnanthidium lanceolatum</em> Brébisson ex Kützing (Bacillariophyta) with the description of two new <em>Planothidium</em> species from the Antarctic Region. <em>Fottea</em> 13 (2): 105–117. https://doi.org/10.5507/fot.2013.010</p>
<p>Van de Vijver B., Wetzel, C.E. & Ector, L. (2018) Analysis of the type material of <em>Planothidium delicatulum</em> (Bacillariophyta) with the description of two new <em>Planothidium</em> species from the sub–Antarctic Region. <em>Fottea</em> 18 (2): 200–211. https://doi.org/10.5507/fot.2018.006</p>
<p>Wetzel, C.E., Van de Vijver, B., Hoffmann, L. & Ector, L. (2013) <em>Planothidium incuriatum</em> sp. nov. a widely distributed diatom species (Bacillariophyta) and type analysis of <em>Planothidium</em> <em>biporomum</em>. <em>Phytotaxa</em> 138 (1): 43–57. https://dx.doi.org/10.11646/phytotaxa.138.1.6</p>
<p>Wetzel, C.E., Van de Vijver, B., Kopalová, K., Hoffmann, L., Pfister, L. & Ector, L. (2014) Type analysis of the South American diatom <em>Achnanthes haynaldii</em> (Bacillariophyta) and description of <em>Planothidium amphibium</em> sp. nov., from aerial and aquatic environments in Oregon (USA). <em>Plant Ecology and Evolution</em> 147 (3): 439–454. https://doi.org/10.5091/plecevo.2014.1058</p>
<p>Wetzel, C.E., Van de Vijver, B., Blanco, S. & Ector, L. (2019) On some common and new cavum-bearing <em>Planothidium</em> (Bacillariophyta) species from freshwater. <em>Fottea</em> 19 (1): 50–89. https://doi.org/10.5507/fot.2018.016</p>
<p>Werum, M. & Lange-Bertalot, H. (2004) Diatoms in springs from Central Europe and elsewhere under the influence of hydrologeology and anthropogenic impacts. <em>Iconographia Diatomologica</em> 13: 3–417.</p>
<p>Carter, J.R. & Denny, P. (1982). Freshwater algae of Sierra Leone III. Bacillariophyceae: Part (i) Diatoms from the River Jong (Taia) at Njala. In: Diatomaceae III, Fetschrift Niels Foged. <em>Beihefte zur Nova Hedwigia</em> 73: 281–331.</p>
<p>Cholnoky, B.J. (1955) Hydrobiologische Untersuchungen in Transvaal. I. Vergelichung der herbstlichen Algengemeinschaften in Rayton-vlei und Leeufontein. <em>Hydrobiologia</em> 7: 137–209.</p>
<p>Cleve, P.T. & Grunow, A. (1880) Beiträge zur Kenntniss der arctischen Diatomeen. <em>Kongliga Svenska Vetenskaps-Akademiens Handlingar </em>17 (2): 1–121.</p>
<p>Compère, P. & Van de Vijver, B. (2009) <em>Planothidium engelbrechtii</em> (Cholnoky) Round & Bukhtiyarova: Identity and lectotypification (Bacillariophyta). <em>Fottea</em> 9: 187–192. https://doi.org/10.5507/fot.2009.019</p>
<p>Czarnecki, D.B. (1994) The freshwater diatoms culture collection at Loras College, Dubuque, Iowa. In: Proceedings of the 11th International Diatom Symposium. <em>Memoirs of the California Academy of Sciences</em> 17: 155–174.</p>
<p>Danielidis, D.B. & Mann, D.G. (2003) New species and new combinations in the genus <em>Seminavis</em> (Bacillariophyta). <em>Diatom Research</em> 18 (1): 21–39. https://doi.org/10.1080/0269249X.2003.9705570</p>
<p>Grunow, A. (1878) Algen und Diatomaceen aus dem Kaspischen Meere. <em>In</em>: Schneider, O. (Ed.) <em>Naturwissenschaftliche Beiträge zur Kenntnis der Kaukasusländer, auf Grund seiner Sammelbeute</em>. Dresden Burdach, Dresden, pp. 98–132.</p>
<p>Hohn, M.H. & Hellerman, J. (1963) The taxonomy and structure of diatom populations from three eastern North American rivers using three sampling methods. <em>Transactions of the American Microscopical Society</em> 82 (3): 250–329.</p>
<p>Hustedt, F. (1949) Diatomeen von Sinai-Halbinsel und aus dem Libanon-Gebiet. <em>Hydrobiologia</em> 2: 24–55.</p>
<p>Jahn, R., Abarca, N., Gemeinholzer, B., Mora, D., Skibbe, O., Kulikovskiy, M., Gusev, E., Kusber, W.-H. & Zimmermann, J. (2017) <em>Planothidium lanceolatum</em> and <em>Planothidium frequentissimum</em> reinvestigated with molecular methods and morphology: four new species and the taxonomic importance of the sinus and cavum. <em>Diatom Research</em> 32 (1): 75–107. https://doi.org/10.1080/0269249X.2017.1312548</p>
<p>Kulaš, A., Gligora Udovič, M., Ector, L. & Van de Vijver, B. (2020) Analysis of the type material of <em>Achnanthes hauckiana</em> Grunow (Achnanthaceae, Bacillariophyceae). <em>Botany Letters</em> 167 (4): 439–452. https://doi.org/10.1080/23818107.2020.1808527</p>
<p>Kützing, F.T. (1844) <em>Die Kieselschaligen Bacillarien oder Diatomeen</em>. Nordhausen, pp. [i-vii], [1]–152.</p>
<p>Kützing, F.T. (1846) Kurze Mitteilung über einige kieselschalige Diatomeen. <em>Botanische Zeitung</em> 4 (14): 247–248.</p>
<p>Lange-Bertalot, H. (1993) 85 neue Taxa und über 100 weitere neu definierte Taxa ergänzend zur Süsswasserflora von Mitteleuropa, Vol. 2/1-4. <em>Bibliotheca Diatomologica</em> 27: 1–454.</p>
<p>Lange-Bertalot, H. (1999) Neue Kombinationen von Taxa aus <em>Achnanthes</em> Bory (sensu lato). <em>Iconographia Diatomologica</em> 6: 270–283.</p>
<p>Lange-Bertalot, H., Hofmann, G., Werum, M. & Cantonati, M. (2017) Freshwater benthic diatoms of Central Europe: over 800 common species used in ecological assessment. English edition with updated taxonomy and added species. Koeltz Botanical Books, Schmitten-Oberreifenberg, 942 pp.</p>
<p>Meister, F. (1932) <em>Kieselalgen aus Asien</em>. Gebrüder Borntraeger, Berlin, pp. [1]–56.</p>
<p>N’Guessan, K.R., Wetzel, C.E. Ector, L., Coste, M., C.Cocquyt, C., Van de Vijver, B., Yao, S.S., Ouattara, A., Kouamelan, E.P. & Tison-Rosebery, J. (2014) <em>Planothidium comperei</em> sp. nov. (Bacillariophyta), a new diatom species from Ivory Coast. <em>Plant Ecology and Evolution</em> 147 (3): 455–462. https://doi.org/10.5091/plecevo.2014.981</p>
<p>Østrup, E. (1903) Freshwater diatoms. In Flora of Koh Chang. Part VII. Contributions to the knowledge of the Gulf of Siam. Preliminary Report on Botany. Results Danish Expedition to Siam (1899–1900). <em>Botanisk Tidsskrift</em> 25 (1): 28–41.</p>
<p>Patrick, R.M. (1944) Estudo Limnologico e Biologico das Lagoas da regiao Litoranea Sul-Riograndense II. Some New Diatoms from the Lagoa dos Quadros. <em>Boletim do Museu Naciona, nova serie, botanica</em> 2: 1–6.</p>
<p>Round, F.E. & Bukhtiyarova, L. (1996) Four new genera based on <em>Achnanthes</em> (<em>Achnanthidium</em>) together with a re-definition of <em>Achnanthidium</em>. <em>Diatom Research</em> 11 (2): 345–361. https://doi.org/10.1080/0269249X.1996.9705389</p>
<p>Stancheva, R. (2019) <em>Planothidium sheathii</em>, a new monoraphid diatom species from rivers in California, USA. <em>Phytotaxa</em> 393 (2): 131–140. https://doi.org/10.11646/phytotaxa.393.2.4</p>
<p>Stancheva, R., Kristan, N.V., Kristan, W. B, III & Sheath, R.G. (2020) Diatom genus <em>Planothidium</em> (Bacillariophyta) from streams and rivers in California, USA: diversity, distribution and autecology. <em>Phytotaxa</em> 470 (1): 1–30. https://doi.org/10.11646/phytotaxa.470.1.1</p>
<p>Taylor, J.C., Harding, W.R. & Archibald, C.G.M. (2007) <em>An Illustrated Guide to Some Common Diatom Species from South Africa An Illustrated Guide to Some Common Diatom Species from South Africa</em>. WRC Report No TT 282/07. Water Research Commission, Pretoria, pp. 1–178 pls.</p>
<p>Van de Vijver, B., Wetzel, C., Kopalová, K., Zidarova, R. & Ector, L. (2013) Analysis of the type material of <em>Achnanthidium lanceolatum</em> Brébisson ex Kützing (Bacillariophyta) with the description of two new <em>Planothidium</em> species from the Antarctic Region. <em>Fottea</em> 13 (2): 105–117. https://doi.org/10.5507/fot.2013.010</p>
<p>Van de Vijver B., Wetzel, C.E. & Ector, L. (2018) Analysis of the type material of <em>Planothidium delicatulum</em> (Bacillariophyta) with the description of two new <em>Planothidium</em> species from the sub–Antarctic Region. <em>Fottea</em> 18 (2): 200–211. https://doi.org/10.5507/fot.2018.006</p>
<p>Wetzel, C.E., Van de Vijver, B., Hoffmann, L. & Ector, L. (2013) <em>Planothidium incuriatum</em> sp. nov. a widely distributed diatom species (Bacillariophyta) and type analysis of <em>Planothidium</em> <em>biporomum</em>. <em>Phytotaxa</em> 138 (1): 43–57. https://dx.doi.org/10.11646/phytotaxa.138.1.6</p>
<p>Wetzel, C.E., Van de Vijver, B., Kopalová, K., Hoffmann, L., Pfister, L. & Ector, L. (2014) Type analysis of the South American diatom <em>Achnanthes haynaldii</em> (Bacillariophyta) and description of <em>Planothidium amphibium</em> sp. nov., from aerial and aquatic environments in Oregon (USA). <em>Plant Ecology and Evolution</em> 147 (3): 439–454. https://doi.org/10.5091/plecevo.2014.1058</p>
<p>Wetzel, C.E., Van de Vijver, B., Blanco, S. & Ector, L. (2019) On some common and new cavum-bearing <em>Planothidium</em> (Bacillariophyta) species from freshwater. <em>Fottea</em> 19 (1): 50–89. https://doi.org/10.5507/fot.2018.016</p>
<p>Werum, M. & Lange-Bertalot, H. (2004) Diatoms in springs from Central Europe and elsewhere under the influence of hydrologeology and anthropogenic impacts. <em>Iconographia Diatomologica</em> 13: 3–417.</p>