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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Rhabdoaskenasia

Rhabdoaskenasia Krainer & Foissner, 1990 (ref. ID; 4352 original paper)

Order Haptorida (ref. ID; 7040)

[ref. ID; 4352]
Diagnosis; Mesodiniidae with circumoral kinety composed of dikinetids giving rise to nematodesmata which form a distinct basket (rhabdos). Kineties of equatorial and pre-equatorial belt composed of single files of basal bodies, those of subequatorial belt composed of two basal bodies each. (ref. ID; 4352)
Etymology; The name refers to the distinct rhabdos and to the similarity to Askenasia. Feminine gender. (ref. ID; 4352)
Remarks; The general plan of Rhabdoaskenasia is very similar to that of Askenasia. However, the distinct rhabdos and the single filed kineties of the equatorial kinety belt indicate that this similarity might be only superficial, resulting from convergent evolution. The rhabdos of Rhabdoaskenasia is in fact highly similar to that of many haptorids (Foissner 1984, Foissner & Foissner 1985, 1986). However, Rhabdoaskenasia lacks the dorsal brush, which is the main character defining the members of the order Haptorida (Foissner & Foissner, 1988). Rhabdoaskenasia should therefore not be included in this order. It probably belongs to the order Pseudoholophryidae, as indicated by its extrusomes. However, the general reorganization is too close to that of Askenasia to justify such a major shift without electron microscopic evidence. (ref. ID; 4352)
Type species; Rhabdoaskenasia minima n. sp. (ref. ID; 4352)
  1. Rhabdoaskenasia minima Krainer & Foissner, 1990 (ref. ID; 4352 original paper, 4612, 4613) reproted author and year? (ref. ID; 7040)

Rhabdoaskenasia minima Krainer & Foissner, 1990 (ref. ID; 4352 original paper, 4612, 4613) reproted author and year? (ref. ID; 7040)

Diagnosis

Size in vivo 20-35x18-30 um. Conical. Macronucleus reniform. Two types of club-shaped extrusomes. Single contractile vacuole. (ref. ID; 4352)

Descriptions

Cell constricted at cell equator and subapically at oral are, which has distinct centrally depressed bulge. Postequatorial portion globular, posterior pole with very short knob. Single macronucleus in rear end of cell. Chromatin bodies large, globular. Single, spherical micronucleus. Contractile vacuole subequatorial, excretory canal about 2 um in diameter. Anterior extrusomes 8-9 um long, arrayed around rhabdos. Comprising club-shaped posterior part about 5x1 um in size and needle-like, distally curved anterior part about 3.5 um in length. Posterior extrusomes 7-8 um long, scattered in rear end, comprising slender bat-shaped posterior part about 5x0.5 um in size and curved needle-like anterior part about 3 um in length. Both types strongly reminiscent of the extrusomes of Paraenchelys wenzeli, a haptorid genus (Foissner 1984). Pellicle firm resulting in fairly constants cell form, withstanding extended coverslip pressure. Cytoplasm pale green, sparsely filled with lithosome-like inclusions. Bacteria (spirills) attached to anterior portion. No terminal vacuole observed. The PKB-kineties with oblong basal bodies are associated with obliquely oriented fibers. The SKB-kineties are interconnected by transverse fibers. Circumoral kinety composed of paired, barren basal bodies of equal size. Curved transverse fibers originate from inner basal bodies, extending radially toward cytostome. Nematodesmata originate from outer basal bodies, forming distinct rhabdos extending to the cell's center. (ref. ID; 4352)

Etymology

"minima" (lat. small) refers to the small size. (ref. ID; 4352)

Type location

Excavated groundwater ponds near Graz (Styria, Austria). (ref. ID; 4352)