Fottea X:X | DOI: 10.5507/fot.2025.007

Widespread and homologous life-history traits within the Rhopalodiales (Bacillariophyceae)

Heidi Abresch1, Mark B. Edlund2*, Scott R. Miller1
1 Division of Biological Sciences, University of Montana, Missoula, Montana, USA
2 St. Croix Watershed Research Station, Science Museum of Minnesota, Marine on St. Croix, Minnesota, USA, *Corresponding author e-mail: medlund@smm.org

Significant changes have been proposed for the order Rhopalodiales, including subsuming Rhopalodia O.Müll. into Epithemia Kütz. to maintain monophyly and recognition of the genus Tetralunata Hamsher et al. However, hesitancies about adopting these higher-level classifications remain. We report widespread and homologous internal valve and life history traits as evidence to guide higher-level classification within the Rhopalodiales. We provide the first reports of internal valve formations in five species and show examples from six species representing multiple branches in the Rhopalodiales: Epithemia (Rhopalodia) gibba (Ehrenb.) Kütz., Epithemia adnata (Kütz.) Bréb., Epithemia turgida (Ehrenb.) Kütz., Epithemia argus (Ehrenb.) Kütz., Epithemia catenata Schvarcz, Stancheva et Steward, and Epithemia reicheltii Fricke. This observation, along with shared, unique cell development and life history traits including endosymbiosis and sexual reproduction, should be considered in phylogenetic revisions.

Keywords: diatoms, Epithemia, Innenschalen, internal valves, life history, Rhopalodia, spheroid bodies

Received: April 29, 2025; Revised: June 11, 2025; Accepted: June 16, 2025; Prepublished online: September 3, 2025 

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    References

    1. Abresch, H.E.; Miller, S.R. & Bell, T. (2021): Evolution of metabolism in nitrogen-fixing endosymbionts of Epithemia. - In: 26th International Diatom Symposium, Abstracts. - p. 48, Yamagata, Japan.
    2. Abresch, H.E.; Bell, T. & Miller, S.R. (2024): Diurnal tran­scriptional variation is reduced in a nitrogen-fixing di­a­tom endosymbiont. - The ISME Journal: p.wrae064. Go to original source...
    3. Cholnoky, B.J. (1928): Über mehrfache Schalenbildung bei Anomoeoneis sculpta. - Hedwigia 68: 297-310.
    4. Cocquyt, C.; Kusber, W.-H. & Jahn, R. (2018): Epithemia hirudiniformis and related taxa within the subgenus Rhopalodiella subg. nov. in comparison to Epithemia subg. Rhopalodia stat nov. (Bacillariophyceae) from East Africa. - Cryptogamie, Algologie 39: 35-62. Go to original source...
    5. Cox, E.J. (1996): Identification of freshwater diatoms from live material. - 158 pp., Chapman & Hall, London, New York.
    6. Davidovich, N. & Davidovich, O. (2022): Diatoms with studied sexual reproduction. - Fottea 22: 292-296. Go to original source...
    7. DeYoe, H.R.; Lowe, R.L. & Marks, J.C. (1992): Effects of nitrogen and phosphorus on the endosymbiont load of Rhopalodia gibba and Epithemia turgida (Bacillariophyceae). - Journal of Phycology 28: 773-777. Go to original source...
    8. Edlund, M.B. & Stoermer, E.F. (1993): Resting spores of the freshwater diatoms Acanthoceras and Urosolenia. - Journal of Paleolimnology 9: 55-61. Go to original source...
    9. Edlund, M.B. & Stoermer, E.F. (1997): Ecological, evolutionary, and systematic significance of diatom life histories. - Journal of Phycology 33: 897-918. Go to original source...
    10. Edlund, M.B.; Stoermer, E.F. & Taylor, C.M. (1996): Aulacoseira skvortzowii sp. nov. (Bacillariophyta), a poorly understood diatom from Lake Baikal, Russia. - Journal of Phycology 32: 165-175. Go to original source...
    11. Geitler, L. (1927): Häutung bei einer pennaten Diatomee. - Österreichische Botanische Zeitschrift 76: 98-100. Go to original source...
    12. Geitler, L. (1932): Der Formwechsel der pennaten Diatomeen (Kieselalgen). - Archiv für Protistenkunde 8: 289-296.
    13. Geitler, L. (1970): Die Entstehung der Innenschalen von Amphiprora paludosa unter acytokinetischer Mitose. - Österreichische Botanische Zeitschrift 118: 591-596. Go to original source...
    14. Geitler, L. (1971): Die inäquale Teilung bei der Bildung der Innenschalen von Meridion circulare. - Österreichische Botanische Zeitschrift 119: 442-446. Go to original source...
    15. Geitler, L. (1973): Auxosporenbildung und Systematik bei pennaten Diatomeen und die Cytologie von Cocconeis-Sippen. - Österreichische Botanische Zeitschrift 122: 299-321. Go to original source...
    16. Geitler, L. (1977): Zur Entwicklungsgeschichte der Epithemiaceen Epithemia, Rhopalodia und Denticula (Diatomophyceae) und ihre vermutlich symbiotischen Sphaeroidkorper. - Plant Systematics and Evolution 128: 259-275. Go to original source...
    17. Geitler, L. (1980): Zellteilung und Bildung von Innenschalen bei Hantzschia amphioxys und Achnanthes coarctata. - Plant Systematics and Evolution 136: 275-286. Go to original source...
    18. Hamsher, S.E.; Graeff, C.L.; Stepanek, J.G. & Kociolek, J.P. (2014): Frustular morphology and polyphyly in freshwater Denticula (Bacillariophyceae) species, and the description of Tetralunata gen. nov. (Epithemiaceae, Rhopalodiales). - Plant Ecology and Evolution 147: 346-365. Go to original source...
    19. Hargraves, P.E. (1983): Diatom resting spores: significance and strategies. - In: Fryxell, G.A. (ed.): Survival strategies of the algae. - pp. 49-68, Cambridge University Press, Cambridge.
    20. Howard, K. & Morales, E. (2012): Fragilariforma nitzschioides. Diatoms of North America. Retrieved June 24, 2021 from https://diatoms.org/species/fragilariforma_nitzschioides.
    21. Hustedt, F. (1927): Die Kieselalgen Deutschlands, Österreichs und der Schweiz mit Berücksichtigung der übrigen Länder Europas sowie der angrenzenden Meeresge­beite. - In: Rabenhorst, L. (ed.): Kryptogramen-Flora von Deutschland, Österreich und der Schweiz, Bd. 7, Teil 1, Lieferung 1 - pp. 1-272, Akademische Ver­lagsgesellschaft Geest und Portig K.-G., Leipzig.
    22. Jahn, R.; Kusber, W.-H. & Cocquyt, C. (2017): Differentiating Iconella from Surirella (Bacillariophyceae): typifying four Ehrenberg names and a preliminary checklist of the African taxa. - PhytoKeys 82: 73-112. Go to original source...
    23. Kaczmarska, I. & Ehrman, J.M. (2021): Enlarge or die! An auxospore perspective on diatom diversification. - Organisms Diversity & Evolution 21: 1-23. Go to original source...
    24. Kaczmarska, I.; Poulíèková, A.; Sato, S.; Edlund, M.B.; Idei, M.; Watanabe, T. & Mann, D.G. (2013): Propo­sals for a terminology for diatom sexual reproduction, auxospores and resting stages. - Diatom Research 28: 263-294. Go to original source...
    25. Kamakura, S.; Mann, D.G.; Nakamura, N. & Sato, S. (2021): Inheritance of spheroid body and plastid in the raphid diatom Epithemia (Bacillariophyta) during sexual reproduction. - Phycologia 60: 265-273. Go to original source...
    26. Kociolek, J.P. & Herbst, D.B. (1992): Taxonomy and distribution of benthic diatoms from Mono Lake, Califor­nia, USA. - Transactions of the American Microscopical Society 111: 338-355. Go to original source...
    27. Kociolek, J.P. & Stoermer, E.F. (1991): Taxonomy and ultrastructure of some Gomphonema and Gomphoneis taxa from the upper Laurentian Great Lakes. - Canadian Journal of Botany 69: 1557-1576. Go to original source...
    28. Kociolek, J.P.; Greenwood, M.; Rogers, D.; Hamsher, S.E.; Miller, S.; Li, J.; Chang, A.G. & Taylor, J. (2024a): Light and scanning observations on a Denticula species reported from South Africa and endemism of the diatom genus Tetralunata (Rhopalodiales, Bacillariophyceae). - Phytotaxa 652: 284-292. Go to original source...
    29. Kociolek, J.P.; Greenwood, M.; Hamsher, S.E.; Miller, S. & Li, J. (2024b): Valve ultrastructure of Rhopalodia constricta (W. Smith) Krammer (Rhopalodiales, Bacillariophyceae) and a consideration of its systematic placement. - Diatom Research 39: 51-60. Go to original source...
    30. Kociolek, J.P.; Williams, D.M.; Hamsher, S.; Miller, S. & Li, J. (2024c): Studies on type material from Kützing's diatom collection VIII. Species assigned to the ge­nera Epithemia Brébisson ex Kützing and Rhopalodia O.Müller. - Diatom Research 39: 159-186. Go to original source...
    31. Kociolek, J.P.; Sala, S.E.; Guerrero, J.; Uyua, N.; Hamsher, S.E.; Miller, S.; Li, J. & Borsa, T. (2025a): Valve ultrastructure, systematics and diversity of the Rhopalodiales. I. Introduction and consideration of morphological groups within the genus Epithemia Brébisson ex Kützing. - Nova Hedwigia 1-77. Go to original source...
    32. Kociolek, J.P.; Ruppert, R.; Hamsher, S.E.; Greenwood, M.; Miller, S.R.; Li, J. & Taylor, J.C. (2025b): A consideration of Epithemia reicheltii (Rhopalodia­les, Bacillariophyceae) and the description of two new species of the genus. - Phycologia: 1-8. DOI: https://doi.org/10.1080/00318884.2025.2503038 Go to original source...
    33. Krasske, K. (1927): Diatomeen deutscher Solquellen und Gra­derwerke. - Archiv für Hydrobiologie 18: 252-272.
    34. Liebisch, W. (1929): Experimentelle und kritische Untersu­chun­gen über die Pektinmembran der Diatomeen un­ter besonderer Berücksichtigung der Auxosporenbil­dung und der Kratikularzustände. - Zeitshrift für Botanik: 1-64.
    35. Liu, Q.; Wu, W.; Wang, J.; Feng, J.; Lv, J.; Kociolek, J.P. & Xie, S. (2017): Valve ultrastructure of Nitzschia shanxiensis nom. nov., stat. nov. and N. tabellaria (Bacillariales, Bacillariophyceae), with comments on their systematic position. - Phytotaxa 312: 228-236. Go to original source...
    36. Loescher, J.E.H. (1972): Diatoms from a native Iowa prairie. - MS Thesis, Iowa State University.
    37. Mann, D.G. & Edlund, M.B. (2024): The ecology of diatom reproduction. - In: Maidana, N.; Licursi, M. & Morales, E. (eds): Diatom ecology: From molecules to metacommunities. - pp. 59-84, Scrivener Publishing LLC, Beverly, MA, USA. Go to original source...
    38. Mann, D.G.; Trobajo, R.; Sato, S.; Li, C.; Witkowski, A.; Rimet, F.; Ashworth, M.P.; Hollands, R.M. & The­riot, E.C. (2021): Ripe for reassessment: A synthesis of available molecular data for the speciose diatom family Bacillariaceae. - Molecular Phylogenetics and Evolution 158: p.106985. Go to original source...
    39. Mizuno, M. (2008): Evolution of centric diatoms inferred from patterns of oogenesis and spermatogenesis. - Phycological Research 56: 156-165. Go to original source...
    40. Moulin, S.L.; Frail, S.; Braukmann, T.; Doenier, J.; Steele-Ogus, M.; Marks, J.C.; Mills, M.M. & Yeh, E. (2024): The endosymbiont of Epithemia cle­men­tina is specialized for nitrogen fixation wi­thin a photosynthetic eukaryote. - ISME Communications 4: p.ycae055.
    41. Müller, O. (1899): Bacillariaceen aus den Natronthälern von El Kab (Ober-Aegypten). - Hedwigia 38: 274-288.
    42. Nakayama, T.; Ikegami, Y.; Nakayama, T.; Ishida, K; I­nagaki, Y. & Inouye, I. (2011): Spheroid bodies in rhopalodiacean diatoms were derived from a single endosymbiotic cyanobacterium. - Journal of Plant Research 124: 93-97. Go to original source...
    43. Round, F.E.; Crawford, R.M. & Mann, D.G. (1990): The Diatoms: Biology & morphology of the genera. - 747 pp., Cambridge University Press, Cambridge.
    44. Ruck, E.C. & Kociolek, J.P. (2004): Preliminary Phylogeny of the Family Surirellaceae (Bacillariophyta). - Bibliotheca Diatomologica 50: 1-236.
    45. Ruck, E.C.; Nakov, T.; Alverson, A.J. & Theriot, E.C. (2016a): Nomenclatural transfers associated with the phylogenetic reclassification of the Surirellales and Rhopalodiales. - Notulae Algarum 10: 1-4.
    46. Ruck, E.C.; Nakov, T.; Alverson, A.J. & Theriot, E.C. (2016b): Phylogeny, ecology, morphological evolution, and reclassification of the diatom orders Surirellales and Rhopalodiales. - Molecular Phylogenetics and Evolution 103: 155-171. Go to original source...
    47. Rybak, M.; Kochman-Kêdziora, N. & Pêczu³a, W. (2020): Diversity of the Rhopalodiaceae diatoms (Bacilla­riophyta) on macrophytes of different architecture in small and shallow oxbow lakes (SE Poland). - Journal of Ecological Engineering 21: 164-173. Go to original source...
    48. Schmid, A.-M.M. (2009): Induction of resting-spores in the pennate diatom Navicula (Craticula) cuspidata by uncoupling of the cell and plastid cycles. - Nova Hedwigia 135: 85-101.
    49. Schvarcz, C.R.; Wilson, S.T.; Caffin, M.; Stancheva, R.; Li, Q.; Turk-Kubo, K.A.; White, A.E.; Karl, D.M.; Zehr, J.P. & Steward, G.F. (2022): Overlooked and widespread pennate diatom-diazotroph symbioses in the sea. - Nature Communications 13: 799. Go to original source...
    50. Sicko-Goad L.; Stoermer E.F. & Kociolek J.P. (1989): Diatom resting cell rejuvenation and formation: time course, species records and distribution. - Journal of Plankton Research 11: 375-389. Go to original source...
    51. Sims, P.A. (1983): A taxonomic study of the genus Epithemia with special reference to the type species E. turgida (Ehrenb.) Kütz. - Bacillaria 6: 211-235.
    52. Sims, P.A.; Mann, D.G. & Medlin, L.K. (2006): Evolution of the diatoms: insights from fossil, biological and molecular data. - Phycologia 45: 361-402. Go to original source...
    53. Spaulding, S.A.; Potapova, M.G.; Bishop, I.W.; Lee, S.S.; Gasperak, T.S.; Jovanoska, E.; Furey, P.C. & Edlund, M.B. (2021): Diatoms.org: supporting taxo­nomists, connecting communities. - Diatom Research 36: 291-304. Go to original source...
    54. Stancheva, R. (2006): Distribution of resting spores of Eunotia soleirolii and Meridion circulare var. constrictum (Ba­cillariophyta) in sediments of peat bogs from Mt. Cen­tral Sredna Gora, Bulgaria - In: Ognjanova-Rume­no­va, N. & Manoylov, K. (eds): Advances in Phycological Studies. - pp. 111-121, Pensoft, Sofia and Moscow.
    55. Stevenson, R.J. (1984): Procedures for mounting algae in a syrup medium. - Transactions of the American Mi­croscopical Society 103: 320-321. Go to original source...
    56. Thaler, F. (1972): Beitrag zur Entwicklungsgeschichte und zum Zellbau einiger Diatomeen. - Österreichische Botanische Zeitschrift 120: 313-347. Go to original source...
    57. Vigneshwaran, A.; Liu, Y.; Kociolek, J.P. & Karthick, B. (2021): A new species of Epithemia Kützing (Bacillariophyceae, Rhopalodiales) from the Mula River, Western Ghats, India, with comments on the phy­loge­netic position of Rhopalodia and Epithemia. - Phyto­taxa 489: 171-181. Go to original source...
    58. Von Stosch, H.-A. & Fecher, K. (1979): "Internal thecae" of Eunotia soleirolii (Bacillariophyceae): development, structure and function as resting spores. - Journal of Phycology 15: 233-243. Go to original source...

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