back to first page Piona rotundoides
Piona cf. rotundoides underside with details 14-07-2015
Piona cf. rotundoides
♀ - 1.5 mm

The underside of the specimen of the photos that are shown on the first page about this species. Hover the mouse cursor over the photo, to reveal sketchy indications of signature details (on a touchscreen, tap the photo).

I cannot identify this mite with certainty down to the species. The length of this female specimen, almost 1.5 mm, is greater than the maximum stated in some works (1250 µm, Smit, 2018; Gerecke ea, 2016). However, Besseling (1964) gives a length of up to 1650 µ for 'Piona (Pusillopiona) forma rotundoides'.

The genital plates have a wide crescent shape and carry many acetabula, I count about 38 on the right plate (that is the left plate in the photo). The shape and number of acetabula may be correct for P. rotundoides. Two other species, P. pusilla and P. obturbans, have similar plates with acetabula, but P. pusilla and P. obturbans have slightly fewer acetabula (Smit 2018; Gerecke ea, 2016) Besseling (1964) gives even fewer acetabula for P. pusilla. Another similar species, P. disparillis, we can exclude. because the tops of the genital plates run more or less parallel to the bottom sides (so it's more like a horizontal U-shape) and there are many more acetabula: about 2x 60 according to Viets (1936), more than 55 per plate according to Smit (2018) . This specimen has a curious orange color in the acetabula, I don't know why.

The bars indicate lengths of 100 µm. The length of the median edge of the fourth epimer must be at least 155 µm according to Smit (2018) em Gerecke et al (2016). Difficult to see if that applies here, because the seams between the third and fourth epimers do not clearly extend to the middle.

The lower detail section shows a number of features related to the plates around the excretory pore (e.p.). I keep the fields marked with S on the overlay for the glandula where the accompanying hairs are close to or on. The excretory pore ("anus") indicated by ep lies between the hairs, the triangle e.p. with the lower glandular gland g is isosceles (a=b, c is larger) and not equilateral, as in P. obturbans. (Smit in Macrofaunanieuwsmail 95 - 2010, see below).


Smit, H., 2010 Mites en concepttable Piona soorten. Macrofaunanieuwsmail 95, 14 december 2010

More on the watermites BIBLIOGRAPHY.

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© G.H. Visser 20-07-2015
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