Dicrateria gilva

Original description: Diagnosis: Cellula sphaeroidi subovatave; 2 flagellis cellulae diametro 3-4 plo longioribus, ex granulo basali distincto exsistentibus; chromatophoris fulvis pallidis, plerumque contrapositis; 2 vacuolis parvis non trepidantibus ubi inserta sunt flagella fere sitis; nucleo laterali propius polum ilium sito ex quo exsistunt flagella; cellulae mobili est diametros 5-8 µm; cysto diametros 7-7-5 µm..

Similar in form to the previous species [D. inornata], but shows several points of difference. The motile stage is larger, measuring 5-8 µm in diameter, and appears to have a slightly less rigid periplast (Text-figs. 63, 66). No stigma is developed, but two small non-contractile vacuoles, lacking in the previous species, are present near the point of origin of the flagella; the chromatophores are paler in colour and possess a faint greenish tinge (PI. I, fig. 3; Text-figs. 62-64).

The flagella, arising from one distant basal granule (or two adjacent granules), are three to four times the cell diameter in length and are therefore much longer than in the previous species; neither flagellum shows a plumate structure as far as could be seen from stained preparations. The movement of this organism differs also from that of D. inornata; there are alternate periods of movement and quiescence, but when swimming it shows fairly rapid movement with frequent change of direction. The position of the flagella when the cell is both in motion and at rest is the same as in D. inornata, but the flagella are more rigid when at rest than in the former species. This species is also phototactic in reaction.

Geological Range:
Last occurrence (top): within (-Ma, top in "Holocene" stage).
First occurrence (base): within (-Ma, base in "Holocene" stage).

Plot of occurrence data:

• Range-bar - range as quoted above, pink interval top occurs in, green interval base occurs in.
• Triangles indicate an event for which a precise placement has been suggested.
• (NB There is no histogram as there are no occurrence records for the taxon in the Neptune database) Parent: Dicrateria

Dicrateria gilva compiled by Jeremy R. Young, Paul R. Bown, Jacqueline A. Lees viewed: 15-8-2026 Taxon Search: Advanced Search Short stable page link: https://mikrotax.org/Nannotax3/index.php?id=20538 Go to Archive.is to create a permanent copy of this page - citation notes

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