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Polychaos dubium
Polychaos dubium, slender form, 200 µm

Polychaos dubium (Schaeffer, 1917)

In the early spring of 2012 and 2015 I found large number of specimens of Polychaos dubium in floating debris at several locations around the Naardermeer. These specimens were completely filled with food particles and large paired bodies, thus resembling a Pelomyxa species. Because they were filled with food particles, they probably didn’t show a more slender and palmate shape as is characteristic for Polychaos. At first sight these specimens are hard to distinguish from Pelomyxa, being broad and without pseudopodia and fully filled with food and debris. One specimen contained a large quartz particle. Only when they start to move, you can see that the monopodial form lacks the fountain streaming of Pelomyxa, though specimens which doesn’t adhere to the substrate, also show this fountain streaming.

Polychaos dubium
Polychaos dubium
Nucleus, 29 µm and uroid
Polychaos dubium
Locomotive form, 256 µm, with uroid (left), contractile vacuoles and numerous food particles.
Polychaos dubium
Stationary form; this specimen resembles a Pelomyxa with all its inclusions.
Polychaos dubium
Crystals in a specimen from the river Gard, France, 2019.
Polychaos dubium
Polychaos dubium
Paired bodies
Polychaos dubium
Polychaos dubium
Nucleus, aberrant form, 71 µm and nucleus 35 µm
Polychaos dubium
Polychaos dubium
Nucleus 44 µm, all four nuclei in specimens in the same sample.
Polychaos dubium
Detail with nucleus, contractile vacuole and characteristic uroid.
Polychaos dubium
Arrow points to the nucleus, 31 µm in diameter
Polychaos dubium
ca. 200 µm long
Polychaos dubium
Arrow points to the nucleus, 31 µm in diameter.
Polychaos dubium
Uroid with some longer villi.
Polychaos dubium
Polychaos dubium
Nucleus, with small ‘holes’ or lacunae in the nucleolar granules
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