Morphometry of modern Chlorococcales and fossil Leiosphaeridia (algae)

 

The size is not a sole diagnostic character. Anyhow related modern taxa of the rank of genus as well as species seem to have a limited size range and measurements may be important features for determination of modern algae.

The size distribution in Leiosphaeridia may be compared to vegetative stages of modern unicellular Chlorococcales. The knowledge of size relations between vegetative cells and resting cysts is too fragmentary for comparisons.

For comparisons of dimensions among taxa a “size difference” value (SD) may be calculated as the size range value in per cent of the minimum size value (Lindgren 1981).

size


Figure 1
A. Cumulative diagram showing size differences in 49 genera of the Chlorococcales. Size difference of Leiosphaeridia is indicated by an L.
B. Cumulative diagram showing size differences in 257 species of the Chlorococcales (curve C), and in 55 species of Leiosphaeridia (curve L).
The size difference is calculated as the size range value in per cent of the minimum value. (From Stockholm Contrib. Geol., 38(1): 8, figure 1)


In 49 genera of the Chlorococcales tabulated from Philipose (1967) the size difference varies between SD = 4 and SD = 5400, with a median value of SD = 250 (fig. 1A). Only in six genera the size difference exceeds SD = 1000, and only in two it exceeds SD = 4000. Specimens of Ankistrodesmus Corda 1838 emend. Ralfs 1848 (seven species) range from 3 µm to 165 µm (SD = 5400), and specimens of Chlorococcum Fries 1820 (three species) range from 2 µm to 109 µm (SD = 5350).

In Leiosphaeridia the size range is recorded as 8—440 µm. The size difference is SD = 5400.

Thus the size difference for genus Leiosphaeridia is extremely high, but not quite impossible for a natural taxon. In described species of Leiosphaeridia, however, the size range is far more restricted than in modern Chlorococcales (fig 1B).

In 257 species of the Chlorococcales, also tabulated from Philipose (1967), the size difference in vegetative cells ranges between SD = 4 and SD = 1163, with a median value of SD = 100. 13.6 % of the difference values exceed SD = 200 and 4.7 exceed SD = 350.

In 55 species of Leiosphaeridia (including Protoleiosphaeridium) the size difference ranges from SD = 3 to SD = 203, with a median value of SD = 58.

The values of the size differences are summarized in table I

 


Table I
Size differences in modern Chlorococcales and fossil Leiosphaeridia

 

Number 

 

 

 

 

Size difference 

 

 

 

 

of taxa 

 

 

 

 

Minimum 

 

 

 

Maximum 

 

 

 

Median 

 

 

 

Mean 

 

 

 

Genera             
Chlorococcales

49

 

 

 

 

4

 

 

 

5400

 

 

 

250

 

 

 

557

 

 

 

Leiosphaeridia 

1

 

 

 

   

5400

 

 

 

   
             
Species             
Chlorococcales

257

 

 

 

 

4

 

 

 

1163

 

 

 

100

 

 

 

128

 

 

 

Leiosphaeridia 

55

 

 

 

 

3

 

 

 

203

 

 

 

58

 

 

 

62

 

 

 

 The size difference is calculated as the size range value in per cent of the minimum value.

 

 

 

 

  

 

 

 

 

  

BACK TO


Morphology and taxonomy
Botanical affinities
Diagnostic features in modern algae
  FORWARD TO


Genus Leiosphaeridia
Distribution of Leiosphaeridia

References

Lindgren, S., 1981.
Remarks on the taxonomy, botanical affinities, and distribution of leiospheres. (Summary in Russian) Stockholm Contrib. Geol., 38(1): 1—20. Stockholm. ISBN 91-22-00500-5. ISSN 0585-3532. — Buy at the lowest prices among books in Sweden.
Philipose, M.T., 1967.
Chlorococcales. Indian Counc. Agric. Res., New Delhi. 365 p.

 

 

Web Link

Steiner, M., 1997. Chuaria circularis Walcott 1899 — “megasphaeromorph acritarch” or prokaryotic colony? Acta Universitatis Carolinae, Geologica, 40: 645—665. Prague.


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One Response to Morphometry of modern Chlorococcales and fossil Leiosphaeridia (algae)

  1. […] TO Morphology and taxonomy Botanical affinities Diagnostic features in modern algae Morphometry of modern and fossil algae Genus Leiosphaeridia Distribution of […]

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