Lecythium spinosum (Penard, 1890)
Diagnosis: test membranous, ovoid or pyriform, in dorsal view circular or a little compressed, with numerous short curved spines, which are modifications of the membrane; aperture sub-terminal, oblique and pliable; nucleus granular, placed posteriorly; cytoplasm filling the test; filopodia numerous, simple or branched, sometimes anastomosing.
Ecology: aquatic vegetation (Hopkinson), sediments (Lauterborn). I have found one specimen in the sediments of a forest pond at Groeneveld, Baarn, the Netherlands, in 1981. I found some specimens again in the ooze of ditches in Den Treek (2012), Laegieskamp (2013) and Naardermeer (2015).
Dimensions: Lauterborn, Penard and Hopkinson: 45-70 µm long; my measurements: 37-68 µm long (n=11).
Remarks: This species has been described by Penard (1890) as Trinema spinosum and by Lauterborn (1901) as Plagiophrys armatus. Later Penard (1902) accepted the name Pamphagus armatus. Penard (1902) described this species as follows: ‘Body pocket-shaped. Membranous test with curved spines all over its surface. 45-70 µm.
The photomicrographs below were made by Francisco Pujente, Spain, and might represent L. spinosum:
According to Francisco, his sample comes from Parque La Albufera in Valencia in Spain, freshwater with moderate pollution. Water temperature approx. 18 º Celsius. The lake is fed by the river Turia and is in contact with the Mediterranean Sea through various channels. All around the lake are rice fields flooded with water for several months a year.