Stauroforma exiguiformis

Taxon ID: 252
Author: Lange-Bertalot    
Synonym: Fragilaria virescens var. exigua, Fragilaria exigua, Fragilaria exiguiformis



Click any image to enlarge...
LM image scalebar = 10 µm = pixels not measured     



Observations: Bart Van de Vijver
Length: 7-33µm
Width: 2,5-4,5µm
Striae: 19-26 striae in 10µm


Valves elliptical, narrow-linear to lanceolate, sometimes heteropolar with broadly rounded to slightly subcapitate apices (L 7-33µm, W 2,5-4,5µm, 19-26 striae in 10µm). Striae are opposite, consisting of one row of circular areolae. Marginal spines present or absent at the end of each interstria. Apical porefield, when present, consists of a group of small pores. No relationship between presence/absence of apical porefields and/or marginal spines was found. Sternum narrow or absent.

Morphology: Araphid




Present in many samples but in low numbers, without a clear preference for standing or running water. Highest abundancies were reached in small shallow pools. pH-optimum 6,4. No difference in ecology was found between spinose and non-spinose forms. Fairly common in wet mosses (optimal F-value around IV) and wet soils.South Georgia (Van de Vijver & Beyens 1996, 1997a), Kerguelen (Le Cohu 1999), South Orkney Islands (Jones et al. 1993, Oppenheim 1990, Oppenheim & Greenwood 1990, Oppenheim & Patterson 1990).Le Cohu (1999) discussed the difference between S. exiguiformis and S. inermis Flower, Jones & Round, a second Stauroforma species that has been split from S. exiguiformis based on the absence of marginal spines and the presence of an apical porefield. He concluded by regrouping both taxa in S. exiguiformis. After examination of quite a lot of frustules from our 'Crozet population', we agree with Le Cohu (1999). As in his paper, valves with both marginal spines and (vestiges of) an apical porefield have been observed.



Other sites with Stauroforma exiguiformis

  • Ile de la Possession (moist habitats), Crozet Archipelago

Original Type Description

Author: Lange-Bertalot

Original Description:


New combination

Author: Flower, Jones & Round 1996



Index Nominum Algarum (INA):

  • Original
  • If an INA link is available, it will be shown above
  • The INA is a bibliographic reference "card file" for algal taxonomy, containing nearly 200,000 names of algae (in the broad sense).

See full publication info assembled for this website