Pseudomaryna
Pseudomaryna Foissner, 2003 (ref. ID; 4915 original paper)
[ref. ID; 4915]
Diagnosis; Small, bacteriophagous Colodidae with oral opening near mid-body and preorally widely projecting left side ciliary rows, producing a spatulate (preoral) suture, that is, a bare stripe extending from anterior to posterior body end right of oral opening. Vestibulum of ordinary size, conical, pharyngeal fibres directed posteriorly. Left wall of vestibulum overhangs right. Right oral polykinetid composed of few, slightly disordered kineties. (ref. ID; 4915)
Remarks; Pseudomaryna differs from the colpodid genera described in Foissner (1993) and Foissner et al. (2002) mainly by the ciliary pattern: the left side preoral kineties extend to the right side of the cell causing the preoral suture to become located to the right of the oral opening and to continue into the postoral body region. Thus, a broad, unciliated stripe extends whole body length to the right of the oral apparatus, while the preoral suture is narrower and extends between the anterior end of the body and the oral opening the in Colpoda and most marynids. Maryna antarctica Foissner, 1993 has a very similar mouth location and somatic ciliary pattern as P. australiensis, and is thus transferred to the new genus: Pseudomaryna antarctica (Foissner, 1993) nov. comb. Unfortunately, the transfer is not entirely certain because the direction of the pharyngeal fibres is not recognizable in the slides of M. antarctica. (ref. ID; 4915)
Etymology; Composite of the Greek adjective pseudo (false) and the generic name Maryna. Feminine gender. (ref. ID; 4915)
Type species; Pseudomaryna australiensis nov. spec. (ref. ID; 4915)
- Pseudomaryna australiensis Foissner, 2003 (ref. ID; 4915 original paper)
Diagnosis
Size about 45x30 um in vivo. Body reniform and closely covered with a thin mineral envelope. Macronucleus near dorsal anterior body end, with single central nucleolus. On average 17 ciliary rows, first preoral kinety conspicuously convex because distinctly shortened posteriorly. Left oral polykinetid cuneate, composed of an average of 6 ciliary rows. Resting cyst globular and smooth, covered with the mineral envelope of the trophic cell. (ref. ID; 4915)
Descriptions
Size 35-60x20-35 um, usually near 45x30 um, slightly flattened laterally, no diagonal (postoral) groove. Specimens often highly refractive, that is, opaque and dark at low magnification (< /_ x100) due to the mineral envelope and many compact food vacuoles. Shape basically reniform due to a more or less distinct indentation near mid-body, that is, in oral area; in detail, however, highly variable, viz., ellipsoidal (when oral bay indistinct), Metopus-like (when broader preorally than postorally), Colpoda maupasi-like (when narrower preorally than postorally), or indistinctly dumb-bell-like; rarely fusiform with very irregular mineral envelope. Macronucleus in anterior body half, usually even in anterior dorsal third of cell, a curious location found in only a few other colpodids, viz., Dragescozoon terricola, Kreyella minuta, and Orthokreyella schiffmanni (Foissner 1993; Foissner et al. 2002); hyaline and thus difficult to recognize even with interference contrast optics, except for the more compact central nucleolus, another rare feature present only in Colpoda steinii, C. formisanoi, Dragescozoon terricola, Pseudokreyella terricola, P. australis, and Microdiaphanosoma terricola (Foissner 1993; Foissner et al. 2002). Micronucleus not found. Contractile vacuole in rear body end, with single excretory pore in pole centre. Cortex flexible, specific cortical granules (mucocysts) not recognizable, covered by a 1-2 um thick, brownish "mineral envelope" appearing as a bright, rough layer separated from pellicle by a distance of about 0.5 um in living and prepared cells and with an opening over the oral area. Mineral envelope compact, composed of 1-2 um-sized, irregular mineral particles embedded in a slimy matrix to which environmental debris and bacteria adhere and which stains pink with methyl green-pyronin; mineral inclusions similar to clay particles common in the environment and to minute, cytoplasmic crystals conspicuously sparkling under interference contrast optics, quite similar to those shown by Foissner et al. (2002) in micrograph 421y of Maryna namibiensis. Cytoplasm colourless, in most cells packed with 4-10 um-sized food vacuoles containing tightly packed bacterial rods or their loosely dispersed indigestible remnants. Swims rapidly by rotation about main body axis; never rests. Cilia about 8 um long in vivo, paired, except for barren anterior basal body of dikinetids in rear third; no elongated caudal cilia; arranged in an average of 17 rows more densely ciliated anteriorly than posteriorly, especially on left side of cell. Ciliary rows in Colpoda pattern modified by the genus-specific, spatulate preoral suture, which is not above but right of oral opening and thus extends, as spatula-handle, to posterior body end between right side and postoral kineties. Right side ciliary rows indistinctly sigmoidal, first two to three rows slightly shortened anteriorly producing, together with the gradually shortened left side preoral rows, a roundish, bare anterior pole area, that is, the spatula of the preoral suture. Preoral ciliary rows conspicuous because numerous an distinctly convex, extend transversely over ventral, side and spiral posteriorly on left and dorsal side of cell; first preoral kinety above oral opening especially distinct because very densely ciliated and almost semicircular, that is, shortened posteriorly. Invariably four postoral ciliary rows, leftmost and rightmost row extend to upper mouth margin almost touching first preoral kinety, oral area thus surrounded by a key-hole shaped kinety pattern. Oral apparatus in flat indentation slightly underneath mid-body, posterior margin of left ciliary field 62% distant from anterior body end on average. Vestibulum broadly conical and small, that is, about 6 um wide and deep, a bundle of pharyngeal fibres originates at proximal end and extends to rear body end. Left oral polykinetid cuneate, composed of an average of six slightly convex rows becoming longer distally; cilia only about 3 um long and thus not forming a beard as in Colpoda steinii. Right oral polykinetid crescentic, composed of four slightly disordered kineties and a row of about 10 dikinetids proximally. Silverline pattern colpodid throughout, irregularly meshed only in bare regions, that is, in preoral suture and around excretory pore of contractile vacuole. A tree-shaped silverline pattern extends in left vestibular wall. (ref. ID; 4915)
Cysts and life cycle
Unfortunately, pure culture trials failed. Thus, all observations and the proposed life cycle are from specimens as obtained with the non-flooded Petri dish culture, which was air-dried and rewetted three times to simulate the flood-pulses typical for the habitat. Accordingly, the life cycle could be not elucidated in full details, for instance, whether every fission product forms a resting cyst after some growth, or can undergo another round of division before resting encystment. Pseudomaryna australiensis divides exclusively in thin-walled reproductive cysts with up to four offspring, and produces thick-walled resting cysts, as common in small colpodids (Foissner 1993). Both cyst types retain the brownish mineral envelope of the trophic cell, but cyst and envelope can be separated by mild cover glass pressure. Resting cysts globular and 26 um across on average, wall colourless, smooth, and about 1 um thick; cytoplasm with some 2-3 um-sized crystals and many opaque globules 1-5 um across. Pseudomaryna australiensis becomes abundant already 20-30 hr after rewetting the sample and encysts after one or two days, even if the sample is undisturbed. The same has been observed in some marynid colpodids from temporary pools. This indicated that P. australiensis has a marynid life cycle and is an r-selected organism, as are colpodids in general (Foissner 1993), adapted to the floodplain environment in that is quickly excysts and reproduces when the flood comes, and encysts when other organisms and potential predators become abundant; the mineral envelope may be an additional shelter. (ref. ID; 4915)
Remarks
Pseudomaryna australiensis differs from Maryna antarctica Foissner, 1993, combined with Pseudomaryna above, by body size (35-60x20-35 um vs. 25-35x20-25 um), the structure of the macronucleus (with vs. without central nucleolus), the mineral envelope (present vs. absent), the number (about 17 vs. 11) and arrangement of the ciliary rows (first preoral kinety conspicuous vs. inconspicuous; second and third preoral kinety in parallel vs. V-like spread anteriorly), and the structure of the left oral polykinetid (composed of an average of 6 vs. 8 rows becoming longer vs. shorter distally). These constitute quite a number of differences, suggesting that further species exist. Of course, P. australiensis resembles several small Colpoda species, especially small-sized specimens of the Colpoda cucullus group, which have a similar body shape as the specimens of P. australiensis. However, all Colpoda spp. lack a mineral envelope and have a different ciliary pattern. (ref. ID; 4915)
Etymology
Named after the country in which discovered. (ref. ID; 4915)
Type location
Soil from Murray River floodplain near the town of Albury, waterside of Ryans road, Australia, 37 degrees S, 147 degrees E. (ref. ID; 4915)
Type specimens
1 holotypes slide each with silver nitrate (Chatton-Lwoff method) and protargol-impregnated specimens and 4 paratype slides have been deposited in the Biology Centre of the Museum of Upper Austria, Linz (LI), Austria. Relevant specimens are marked by black ink circles on the coverglass. (ref. ID; 4915)