(Discospirina tenuissima)

Almennt

Discospirina tenuissima (Carpenter, 1870)

Discospirina tenuissima (Carpenter, 1870) - sensu Gooday, A.J. et al 2013. The ecology and biogeography of Discospirina tenuissima (Foraminifera) in the Atlantic and Indian Oceans. Deep-Sea Resarch II, vol. 98, pt. B, pp. 301-314 (https://doi.org/10.1016/j.dsr2.2012.05.001): p.302, figs. 4-10.  

Description: Test is a nearly circular and flat disk, but is slightly concave or undulating in occasional specimens; the test is extremely thin (≈ 0,03 mm) and retains a nearly uniform thickness at all developmental stages. The surface is smooth, except for faint sutural lines. Walls are extremely thin, clearly revealing the internal structure of the test, comprising numerous radial partitions, subdividing a chamber into numerous chamberlets. The partitions are regularly placed between any two adjacent apertures of the previous chamber and extend closely towards the inner side of the apertural faces (septa), thus forming a continuous peripheral passage (annular canal) between the chamberlets.  

The embryonic apparatus consists of a globular proloculus and planispirally coiled undivided tube of 2-3 windings (cornuspiran stage), followed by 3 - 9 septate, tubular and planispirally coiled chambers (spiroloculine stage); then up to 3 short and broad, non-tubular chambers (peneropline stage, which is missing in some specimens); next are 2-5 flaring or flabelliform chambers and finally several annular chambers, up to 18 in the largest specimen at hand.

The flaring flabelliform and annular chambers, which collectively constitute almost the entire test,

Initially, the aperture is a simple opening, but the flabelliform and annular chambers have multiple apertures, forming simple row of circular to ovate apertures along the edge of the test.

The largest specimen is 16 mm in diameter, but most are 4 - 8 mm. About 280 specimens were picked from 50 of the 1031 Bioice samples that were checked for forams.

Diagnosis: The semi-transparent, disc shaped and extremely thin test, revealing clearly the internal compartments, makes this species quite distinct from all other foraminferan species in Icelandic waters.

Gudmundur Gudmundsson, IINH (gg@ni.is)

Útbreiðslukort

Myndir

Höfundur

Guðmundur Guðmundsson 2018

Biota

Tegund (Species)
(Discospirina tenuissima)