Gocevia obscura
Gocevia obscura
Gocevia obscura, 52 and 43 µm, the same specimen

 

Gocevia obscura (Penard, 1902)

 

Diagnosis: amoeba more or less spherical in shape, with a central granular hump, partly or completely surrounded by a distinct hyaline margin; surface with a heavy covering of refractive mineral grains, which individually are clear or yellowish but give the cuticle a blackish appearance; cuticle is in rest spherical or ovoid; hyaline zone often irregular in outline with conical or digiform subpseudopodia and trailing filaments; cells uninucleate. Cysts observed.

Dimensions: Penard (1902): 25-30 µm, active up to 50 µm; Hoogenraad & De Groot (1940): 67-100 µm; my measurements 43-66 µm.

Ecology: fresh water, in sediments of clear water. Spiegelplas, Kootwijk, The Netherlands, Weser, Germany. Not common, but probably easily overlooked in its resting form. The species easily multiplies in wet mounts kept in a humidity chamber.

Remarks: the dense layer of mineral grains is supposed to be a flexible protection for the amoeba. The membrane resembles at first sight the shell of a Pseudodifflugia species.
This amoeba was described by Penard (1902) as Cochliopodium obscurum and placed in the genus Gocevia by Valkanov (1932). The name Gocevia obscurum is not correct and should be replaced by Gocevia obscura (Hoogenraad & De Groot, 1940).

 

Gocevia obscura
Gocevia obscura
Gocevia obscura
Gocevia obscura
Gocevia obscura, 67 µm, the same specimen changing within a minute
Gocevia obscura
Gocevia obscura
Gocevia obscura
The same specimen with different plasma shapes
Gocevia obscura
Gocevia obscura
Cell 35 µm in diameter and 23 µm high (bar = 10 µm)
Gocevia obscura
Drawing by Penard, in Faune Rhizopodique du Bassin de Léman, 1902
Gocevia obscura
Gocevia obscura, 58 µm
Gocevia obscura
Gocevia obscura, 66 µm