Abstract
The centric diatom Coscinodiscus variabilis, described by Joaquín Frenguelli for the coastal waters of Mar del Plata City (Buenos Aires, Argentina), was examined to review and elucidate its taxonomic position. The type material contained in the Frenguelli Collection was studied with light microscopy. The species has a particular and distinctive stellate pattern of hyaline rays on the valve face that helps in its initial identification and exhibits a remarkable morphological variation. The presence of a distinctive pseudonodulus, radial sectoring and circular valves support its transfer to the genus Actinocyclus as Actinocyclus ferrarioae nom. nov. The valve morphology of A. ferrarioae is described and compared to its original description and closely related taxa. We have estimated the rimoportulae density as a morphometric character for comparing morphologically similar Actinocyclus taxa. Since Frenguelli did not formally designate a holotype in the original description, we selected a lectotype and provide an expanded description of the species.
References
- Andrews, G.W. (1976) Miocene marine diatoms from the Choptank Formation, Calvert County, Maryland (Professional Paper No. 910). U.S. Geological Survey, 26 pp. https://doi.org/10.3133/pp910
- Barron, J.A. (2005) Scanning electron microscope studies of some early Miocene diatoms from the Equatorial Pacific Ocean with description of two new species, Actinocyclus jouseae Barron and Actinocyclus nigriniae Barron. Proceedings of the California Academy of Sciences 56: 639–655.
- Bradbury Platt, J.P. & Krebs, W.N. (1995) The diatom genus Actinocyclus in the Western United States (Professional Paper No. 1543-A-B). U.S. Government Printing Office, 73 pp. https://doi.org/10.3133/pp1543AB
- Castracane, F. (1886) Report on the diatomaceae collected by H.M.S. Challenger during the years 1873-1876. Report on the Scientific Results of the Voyage of H.M.S. Challenger during the years 1873–76. Botany 2 (part 4): 1–178.
- Corda, A.J.C. (1840) Observations microscopiques sur les animalcules des eaux thermales de Carlsbad. Almanach de Carlsbad (Prague) 10: 186–221.
- Desikachary, T.V. & Prema, P. (1987) Diatoms from the Bay of Bengal. In: Desikachary, T.V. (Ed.) Atlas of Diatoms, fasc. III. Madras Science Foundation, Madras, pp. 1–10, pls 222–331.
- Ehrenberg, C.G. (1837) Eine briefliche nachricht des Hrn. Agassiz in Neuchatel über den ebenfalls aus mikroskopischen Kiesel-Organismen gebildeten Polirschiefer von Oran in Afrika. vor. Bericht. Die zur Bekanntmachung geeinenten Verhandlungen der Königlich-Preussischen. Akademie der Wissenchaften zu Berlin, pp. 59–61. https://doi.org/10.1002/andp.18371160414
- Ehrenberg, C.G. (1843) Verbreitung und Einfluss des mikroskopischen Lebens in Süd- und Nord-Amerika. Abhandlungen der Königlichen Akademie der Wissenschaften zu Berlin 1841: 291–4457.
- Ehrenberg, C.G. (1854) Mikrogeologie. Das Erden und Felsen schaffende Wirken des unsichtbar kleinen selbstständigen Lebens auf der Erde. Leipzig: Verlag von Leopold Voss. 374 pp. https://doi.org/10.5962/bhl.title.118752
- Ferrario, M.E. (1984) Diatomeas Centrales de la Ría de Puerto Deseado (Santa Cruz, Argentina) II. S.O Coscinodiscaceae, Fam. Hemidiscaceae, Fam. Melosiraceaae. Revista del Museo de La Plata 13, Botánica 84: 267–289.
- Ferrario, M.E. & Galván, N.M. (1989) Catálogo de las diatomeas marinas citadas entre los 36° y los 60° S con especial referencia al Mar Argentino. Dirección Nacional del Antártico. Instituto Antártico Argentino. Buenos Aires. 327 pp.
- Frenguelli, J. (1928) Diatomeas del Océano Atlántico Frente a Mar del Plata (República Argentina). Anales del Museo Nacional de Historia Natural “Bernardino Rivadavia” 1: 497–572.
- Frenguelli, J. (1930) Diatomeas Marinas de la Costa Atlántica de Miramar (Provincia de Buenos Aires). Anales del Museo Nacional de Historia Natural “Bernardino Rivadavia” 36: 243–311.
- Gogorev, R.M. & Pushina, Z.V. (2015) The genus Actinocyclus (Bacillariophyta) in the Antarctic Ocean. Issues of Modern Algology. Bulletin 2015 (Special Issue): 35–37.
- Hasle, G.R. (1983) The marine planktonic diatoms Thalassiosira oceanica sp.nov. and T. partheneia. Journal of Phycology 19: 220–229.
- Harwood, D.M. & Maruyama, T. (1992) Middle Eocene to Pleistocene diatom biostratigraphy of Southern Ocean sediments from the Kerguelen Plateau, Leg 120. In: Wise, S.W., Schlich, R. et al. (Eds.) Proceedings of the Ocean Drilling Program, Scientific Results. College station, Texas (Ocean Drilling Program) 120: 683–733.
- Hasle, G.R. & Syvertsen, E.E. (1997) Marine Diatoms. In: Thomas, C.R. (ed.) Identifying Marine Phytoplankton. Academic Press Inc., pp. 5–385. https://doi.org/10.1016/B978-012693018-4/50004-5
- Hayashi, T., Saito-Kato, M. & Tanimura, Y. (2012) Actinocyclus nipponicus sp. nov. and A. bradburyii sp. nov. (Bacillariophyta) from Miocene lacustrine sediments of the proto-Japan Sea. Phycologia 51 (1): 98–112. https://doi.org/10.2216/11-17.1
- Kociolek, J.P. & Vouilloud, A.A. (2020) Hantzschia subandina Frenguelli (Bacillariophyceae): Morphology, status and typification, as well as the description of a new species of Nitzschia. Boletin de la Sociedad Argentina de Botánica 55: 521–534. https://doi.org/10.31055/1851.2372.v55.n4.29200
- Krasske, G. (1934) Die Diatomeenflora der hessischen Kieselgurlager. Sitzungsberichte Heidelberger Akademie der Wissenschaften 9: 3–26.
- Makarova, I.V. (1985) Combinationes taxorµm generis Actinocyclus Ehr. novae. Novitates Systematicae Plantarµm Non Vasculariµm 22: 96–99.
- Muller Melchers, P. (1959) Plankton diatoms of the Southern Atlantic Argentine and Uruguay coast. Comunicaciones Botánicas del Museo de Historia Natural de Montevideo 3 (38): 1–45.
- Ognjanova-Rumenova, N. & Buczkó, K. (2015) Taxonomical re-investigation of Sarmatian diatoms from NE Bulgaria, hosted in the Pantocsek Collection (Budapest). Geologica Balcanica 44 (1–3): 39–50. https://doi.org/10.52321/GeolBalc.44.1-3.39
- Rattray, J. (1890) A Revision of the Genus Coscinodiscus Ehrb., and some Allied Genera. Proceedings of the Royal Society of Edinburgh 16: 449–692. https://doi.org/10.1017/S0370164600006489
- Round, F.E., Crawford, R.M. & Mann, D.G. (1990) The diatoms biology and morphology of the genera. Cambridge: Cambridge University Press. 747 pp.
- Sar, E.A. (1996) Flora Diatomológica de Bahía San Antonio (Prov. de Río Negro, Argentina) O. Centrales I. Revista del Museo de La Plata, XIV, 106: 365–400.
- Sar, E.A., Sala, S.E., Sunesen, I., Henninger, M.S. & Montastruc, M. (2009) Catalogue of the genera, species, and infraspecific taxa erected by J. Frenguelli. Diatom Monographs 10: 1–419.
- Sar, E.A., Sunesen, I. & Hinz, F. (2008) Fine morphology of Coscinodiscus jonesianus and Coscinodiscus commutatus and their transfer to Coscinodiscopsis gen. nov. Diatom Research 23 (2): 401–421. https://doi.org/10.1080/0269249X.2008.9705766
- Simonsen, R. (1972) Über die Diatomeengattung Hemidiscus Wallich und andere Angehörige der sogenannten “Hemidiscaceae”. Veröffentlichungen des Instituts für Meeresforschung in Bremerhaven 13: 265–273.
- Simonsen, R. (1975) On the Pseudonodulus of the Centric Diatoms, or Hemidiscaceae reconsidered. In: Simonsen, R. (Ed.) Proceedings of the Third Symposium on Recent and Fossil Marine Diatoms, Kiel. Beihefte zur Nova Hedwigia 53: 83–98.
- 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. (eds.) (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. Glashütten: Koeltz Botanical Books, pp. [i]–xxxviii, 1–253. https://doi.org/10.12705/Code.2018
- Villarreal, T.A. & Fryxell, G.A. (1983) The Genus Actinocyclus (Bacillariophyceae): Frustule Morphology of a A. sagittulus sp. nov. and two related species. Journal of Phycology 19: 452–466. https://doi.org/10.1111/j.0022-3646.1983.00452.x
- Vouilloud, A.A. (2003) Catálogo de diatomeas continentales y marinas de Argentina. Asociación Argentina de Ficología, La Plata, Argentina, 308 pp.
- Wu, C., Williams, D.M., Peng, Z. & Chen, C. (2022) A distinctive stellate species of the genus Actinocyclus (Bacillariophyta) from Oligocene sediments in the central Pacific Ocean and its morphological significance. Phycologia 61 (2): 211–223. https://doi.org/10.1080/00318884.2022.2030192