Morphologic Variability in Fasciculated Diatoms as Exemplified by Thalassiosira Tumida (Janisch) Hasle, Comb. Nov.

  1. George A. Llano and
  2. I. Eugene Wallen
  1. Grethe R. Hasle1,
  2. Berit R. Heimdal1 and
  3. Greta A. Fryxell2

Published Online: 14 MAR 2013

DOI: 10.1029/AR017p0313

Biology of the Antarctic Seas IV

Biology of the Antarctic Seas IV

How to Cite

Hasle, G. R., Heimdal, B. R. and Fryxell, G. A. (1971) Morphologic Variability in Fasciculated Diatoms as Exemplified by Thalassiosira Tumida (Janisch) Hasle, Comb. Nov., in Biology of the Antarctic Seas IV (eds G. A. Llano and I. E. Wallen), American Geophysical Union, Washington, D. C.. doi: 10.1029/AR017p0313

Author Information

  1. 1

    Institute of Marine Biology B, University of Oslo, Oslo 3, Norway

  2. 2

    Department of Oceanography, Texas a & M University, College Station, Texas 77843

Publication History

  1. Published Online: 14 MAR 2013
  2. Published Print: 1 JAN 1971

ISBN Information

Print ISBN: 9780875901176

Online ISBN: 9781118664551

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Keywords:

  • Coscinodiscus inflatus Karsten;
  • Coscinodiscus tumidus;
  • Diatoms;
  • Pleomorphism;
  • Thalassiosira inflata;
  • Thalasslosira turnida

Summary

Coscinodiscus inflatus Karsten is an antarctic, weakly silicified species with valve areolae arranged in sectors; Coscinodiscus tumidus Janisch is another antarctic, coarsely silicified species with valve areolae in straight tangential or eccentric curved rows. Cells that could be classified as these two species and also cells having one valve from each of them were found mixed in colonies of Thalassiosira type. Light- and electron-microscope examinations of valves of both species found in the same samples demonstrated the presence of many central apiculi, numerous apiculi located both close to the valve margin and in the rest of the valve, and 3–5 labiate processes in the weakly as well as in the coarsely silicified valves. Coscinodiscus inflatus and C. tumidus are therefore regarded as conspecific and, because of the appearance in colonies produced by long threads emerging from central apiculi and connecting the cells, are transferred to the genus Thalassiosira. According to the rule of priority, the name should be Thalassiosia tumida (Janisch) Hasle comb. nov. A diagnosis including previous studies and our observations is presented.

Our own observations on materials collected in antarctic and subantarctic waters and the records of species conspecific with T. tumida, either according to literature or our own opinion, indicate T. tumida as a southern circumpolar species of a wide latitudinal range.

A possible general relationship between degree of silicification and valve areola pattern is discussed with reference to observations of other Thalassiosira species grown in unialgal cultures.