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Raphidiophrys minuta
From Siemensma, 1991

Raphidiophrys minuta Nicholls, 1985

Diagnosis: Cells 10-15 µm in diameter (excluding scales). Scale layer 2-5 pm thick and noticeably clustered along beaded axopodia up to 50 µm long. Scales circular, to circular-ovate in outline, 2-6 µm in diameter. Scales are patterned with alternately long and short, wavy, radially dis­posed ribs; the long ones are 2 to 4 times longer than the short ones and extend from the scale margin to the centre of the scale. Scales lack a folded rim.

Ecology: Collected in the plankton of West Twin Lake, Ontario, Canada, 1979.

Remarks: Raphidiophrys minuta scales differ from those of other species with similar ornamentation by their lack of a marginal folded rim. Also the radial ribs originate from the scale centre, not from a median axis as in R. intermedia, R. elegans, and R. orbicularis.

I found this very small heliozoan in a sample from the Laegieskamp, the Netherlands (2016). It radiates some stiff axopodia each with 3-4 prominent extrusomes. It might be R. minuta.
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