Parameciom boetschlii, Krenek & Berendonk & Fokin, 2015

Krenek, Sascha, Berendonk, Thomas U. & Fokin, Sergei I., 2015, New Paramecium (Ciliophora, Oligohymenophorea) congeners shape our view on its biodiversity, Organisms Diversity & Evolution (New York, N. Y.) 15 (2), pp. 215-233 : 219-220

Parameciom boetschlii sp. nov.

Size in vivo was up to 200×55 μm, usually 190 ×52 μm (Figs. 1–3). The average size of fixed and impregnated cells was 174.5±7.0×48.8±4.7 μm (Figs. 4, 5). The number of cilia rows amounted to 70–85 (77.5±3.6 on average). The buccal cavity (BC) size was 31.1±1.6 μm which is 0.18 of the body length only ( Table 2). The buccal overture (BO), ellipsoidal in shape, was located a bit forward to the anterior end from the cell’ s equator and has a normal composition of buccal ciliature–quadrilus, two peniculi and endoral membrane (Figs. 4, 6). Two contractile vacuoles (CV) had usually two and sometimes three pores (PCV) each, but no collecting canals (Figs. 1, 2, 5, 7, 14–16). The cytoproct started relatively far from BO, close to the posterior end of the cell (Figs. 3, 4, 8). The cortex contained numerous uniformly distributed trichocysts (Figs. 9, 12, 13) that were classically spindleshaped and about 5–6 μm long in resting condition. The ellipsoidal or oval macronucleus (MA) (21.1± 2.0 ×41.4 ±

Data based on Chatton–Lwoff silver impregnated cells. Macro- and micronuclei were measured from Feulgen-stained ciliates. Measurements in micrometers

x arithmetic mean, SD standard deviation, Min minimum, Max maximum, CV coefficient of variation in percentage, n number of cells investigated

2.9 μm on average) was situated close to the cell’ s equator ( Table 2, Figs. 1, 9, 10). A single ellipsoidal micronucleus (MI) had sizes of 2.5–3.2 × 5.5–6.0 μm (2.9 ± 0.9× 5.8 ± 1.8 μm on average) and was usually located close to the MA or in its depression ( Table 2, Figs. 1, 9, 10, 12). This single MI is of the compact morphological type, but the chromatin of the nucleus always looked fine and homogenous without any achromatin cape (Figs. 9, 10). The general cell form was intermediate, between the classical cigar shape and those of P. woodroffi, which is posteriorly rounded and to some extent dorsoventrally compressed (Figs. 1–5). The width-to-length ratio was 0.28. When undisturbed, the cells were slowly moving or gliding along substrate using typical cilia beating. During the normal swimming procedure, the cells rotated both clockwise and counter-clockwise ( Table 2, Figs. 1–8, 9–16, and 17–22).

Using artificial treatment of the culture with KCl, acriflavine and Ca-poor conditions ( Miyake 1968), conjugation could be induced (Fig. 17). In the prophase of the first meiotic division, the MI does not manifest a clear parachote stage; however, this species apparently has no crescent MI stage as well (Fig. 18). Exchange of pronuclei started before the old MA break down. The old MA became fragmented only after the first synkaryon division. The number of old MA fragments was always quite small (15–25) and of diverse dimensions and forms (10–25 μm; Figs. 20–22). The three consecutive synkaryon divisions resulted in four MA anlagen and four further MI (Figs. 19–22), but only one of the generative nuclei survived in progeny.

Despite many attempts, we did not succeeded in establishing stable monoclonal cultures, but the ciliate could be maintained as a multi-clonal population on rice grain medium. Other food sources such as lettuce medium inoculated with E. aerogenes or medium with the freshwater micro-alga Chlorogoniom sp. never served as a proper medium for P. boetschlii sp. nov. Unfortunately, the stock culture died off after 2 years of maintenance under laboratory conditions.