Choanocystis rotundata

 

From Siemensma, 1991

Choanocystis rotundata (Nicholls, 1983) Siemensma & Roijackers, 1988

Diagnosis: Scales of two types. Spine-scales 3-12 µm long, usually slightly bent in the proximal one-quarter to one-half of their length. Spine shaft hollow, 0.12-0.2 µm in diameter, seated eccentrically at the base of a cleft in an ovate to circular base plate 1-1.3 µm in diameter. Base plate with a marginal rim. Apex of the spine shaft abruptly cut off at right angles without taper but with 12-20 minute marginal rounded teeth about 0.015 µm high. Plate-scales elliptical 3.5 x 1.5-2.5 µm, patternless except for an axial thickening positioned in the middle of the scale about two-thirds the length of the scale and a maximum width of about 0.15 µm in the midregion.

Remarks: The base plates of the spine-scales of A. rotundata are similar to those of A. perpusilla Petersen et Hansen; however, A. perpusilla spines are only 3-4 µm long and have a marked bifurcation at their apices.

Distribution: Canada. Freshwater.

Recent posts

Cryptodifflugia key 2

1 Shell is distinctly compressed laterally 2 – Shell is not compressed or slightly compressed laterally 7 2 Oval aperture C. compressa angustioris – Circular

Read More »

Campascus cyphoderiformis

Campascus cyphoderiformis – After Chardez et Gaspar, 1984 Campascus cyphoderiformis  Chardez et Gaspar, 1984 Diagnosis: Test very clear, hyaline, consisting of endogenous scales of 1.2

Read More »

Campascus insterstitialis

Campascus interstitialis – After Golemansky, 1981 Campascus interstitialis  Golemansky, 1981 Diagnosis: Test elongated, in the shape of a bottle with a curved, colorless, transparent and

Read More »

Campascus triqueter

Campascus triqueter – After Penard, 1899 and 1891 Campascus triqueter  Penard, 1899 Diagnosis: Test brownish or yellowish, build of organic material embedded with a large

Read More »

Campascus bidens

Campascus bidens – After Krascheninnikov, 1923 Campascus bidens Krascheninnikov, 1923 Diagnosis: Test as C. minutus, but with, in ventral view, two small tooth-like projections, facing

Read More »

Campascus dentatus

Campascus dentatus – After Edmondson and Kingman, 1913 Campascus dentatus Edmondson and Kingman, 1913 Diagnosis: Shell of yellowish, chitinoid material similar in general outline to

Read More »