Stereonema

Stereonema Foissner & Foissner, 1993 (ref. ID; 5727 original paper)

[ref. ID; 5727]
Diagnosis; Medium-sized (20-30 um) Spironemidae with kineties in indistinct furrows and terminating near mid-body. Posterior end with distinct tail. Cortex soft and slightly plicate; cells deformable but acontractile. (ref. ID; 5727)
Remarks; Stereonema differs from Spironema by the inability to perform euglenoid movement. Like in Hemimastix, even extreme stimuli (strong cover glass presseur, heat) do not induce metaboly. It is, however, clearly separate from Hemimastix by the shorter kineties, the reduced epiplasm and the simpler organization of the flagellar furrows. (ref. ID; 5727)
Etymology; Stereonema is of Greek derivation. "Stereo" means stiff, and "nema" means stick; Stereonema therefore denotes a "stiff stick". (ref. ID; 5727)
Type species; Stereonema geiseri n. sp. (ref. ID; 5727)

Stereonema geiseri Foissner & Foissner, 1993 (ref. ID; 5727 original paper)

Stereonema geiseri Foissner & Foissner, 1993 (ref. ID; 5727 original paper)

Diagnosis

In vivo 20-30x5-8 um. Body lanceolate with tail about 1/4 of cell length. Capitulum inconspicuous. Kineties with about 12 flagella each. Nucleus roundish. (ref. ID; 5727)

Descriptions

Light microscopy: Shape rather constant, in broad axis view distinctly lanceolate, in short axis view fusiform; anterior end more distinctly flattened than posterior half; tail straight or obliquely bent. Nucleus near or slightly above centre of thickened portion of body. Contractile vacuole near base of tail, surrounded by bleb-like vesicles. Several tiny (0.8x0.3 um), rod-like inclusions in anterior cell portion, corresponding to posterior compartment of extrusomes. Flagella 6 um long, rather rigid, beat asynchronously. Food vacuoles roundish, contain single bacteria. Many colourless, refractile, ellipsoid inclusions 0.5-2 um in size scattered throughout cytoplasm; very likely, these are condensed food vacuoles. Movement very slow, trembling, cannot swim. (ref. ID; 5727)
Electron microscopy: Cortical plates as in Spironema terricola, i.e. slightly plicate, but tapering epiplasm without osmiophilic sheet; some regions with serrate structures (striation) between microtubules and epiplasm or cell membrane, respectively. Mean diameter of flagella 332 nm (range 300-364 nm, n=7), axonemes 205 nm (185-223 nm, n=7), basal bodies 184 nm (180-200 nm, n=5), membranous sacs 89 nm (77-117 nm, n=5); mean length of basal bodies 179 nm (175-182 nm, n=5). Extrusomes about 4x0.23 um in size, barely recognizable in light microscope, anchored in epiplasm along kineties and in capitulum. Anterior extrusome compartment ("nail") with thick granular centre, tip bipartite by two bulbous dilations, posterior end club-shaped, i.e. much simpler than in S. terricola and H. amphikineta, and not separated by electronlucent zone from granular content of posterior extrusome compartment. Anterior end of posterior extrusome compartment with single bulbous dilation as in H. amphikineta. Food vacuoles with bacteria, membrane residues and electron-dense masses, the latter probably corresponding to the conspicuous ellipsoid inclusions seen in the light microscope. (ref. ID; 5727)

Etymology

This new species is dedicated to the Bavarian entomologist Dr. Remigius Geiser in appreciation of his help in nomenclatural problems. (ref. ID; 5727)

Type location

River Amper about 2 km downriver from the sewage plant at Geiselbullach, east of Furstenfeldbruck, Bavaria, Germany, 48 degrees 13'N, 11 degrees 21'E. (ref. ID; 5727)

Occurrence and ecology

Occasionally found in the Aufwuchs (periphyton) of meso-saprobic rivers in Germany and Austria (Amper near Munich, Ager near Linz). (ref. ID; 5727)

Type specimens

Fig.38-42. No permanent slides available. (ref. ID; 5727)