Spathidium polynucleatum ( Foissner et al., 2002 ) Jang & Vďačný & Shazib & Shin, 2017

Jang, Seok Won, Vďačný, Peter, Shazib, Shahed Uddin Ahmed & Shin, Mann Kyoon, 2017, Linking morphology and molecules: integrative taxonomy of spathidiids (Protista: Ciliophora: Litostomatea) from Korea, Journal of Natural History 51 (17 - 18), pp. 939-974 : 956-959

Spathidium polynucleatum ( Foissner et al., 2002) comb. nov.

( Figures 8 (a–g) and 9(a–l); Table 2)

Epispathidium polynucleatum Foissner et al., 2002: 312 , figs 70a–m, 329a–u

Description of a Korean population

Body size 135–210 × 20–40 µm in vivo, usually about 155 × 30 µm; not contractile but very flexible. Shape narrowly to very narrowly spatulate with a length:width ratio of 3.8– 6.8: 1 in vivo and 2.7–6.1:1 after protargol impregnation; oral region inconspicuously set off from cylindrical trunk because neck only slightly narrowed; anterior end about as wide as broadest post-oral body portion; posterior end rounded ( Figures 8 (a,d–f) and 9 (a,b,h–j); Table 2). Nuclear apparatus scattered throughout trunk and composed of 29–50 macronuclear nodules and 13–34 micronuclei. Macronuclear nodules oblong and about 4.5–17.0 × 3.0–6.5 µm in size after protargol impregnation; nucleoli small, globular, evenly distributed over macronuclear nodules, well recognisable after protargol impregnation. Micronuclei globular and about 1.5–2.0 µm in diameter in protargol preparations ( Figures 8 (d) and 9(e,h–j)). A single contractile vacuole at posterior end, about 13 µm across during diastole ( Figure 9 (b)). Extrusomes attached to oral bulge and scattered throughout cytoplasm: oral extrusomes rod-shaped, sometimes slightly curved, 8–10 × 0.5 µm in size, do not impregnate with the protargol method used; developing cytoplasmic extrusomes fusiform, 6.5–9 µm long, middle globular part about 1.2–2.8 µm wide, impregnate deeply with the protargol method used ( Figures 8 (b,c) and 9(d,f,l)). Cortex very flexible, contains about four granule rows between adjacent kineties; granules ordinarily to narrowly spaced, 0.5 µm across in vivo; covered with epibiotic, 2 µm-long bacteria ( Figures 8 (g) and 9(c,g)). Cytoplasm colourless, packed with macronuclear nodules, developing fusiform extrusomes, and 2–8-µm-sized lipid droplets ( Figures 9 (a,d,e)). Movement relatively slow, either gliding on microscope slide or swimming by rotation about main body axis.

Cilia 8–11 µm long in vivo, spaced ordinarily except for five to seven densely spaced basal bodies in curved anterior kinety portion. On average 24 equidistant, ordinarily spaced meridional ciliary rows anteriorly curved distinctly dorsally on right side while curved slightly to distinctly ventrally on left side. Dorsal brush dikinetidal; three-rowed, isostichad; middle row slightly longer than right and left row; dikinetids more narrowly spaced in anterior (1 µm) than posterior (2–2.5 µm) brush portion ( Figures 8 (d–f) and 9(k); Table 2).

Oral bulge occupies ordinarily oblique anterior body end, distinctly set off from body proper and comparatively thick ( Figure 9 (a)). Circumoral kinety at base of oral bulge, continuous, composed of narrowly spaced and perpendicularly oriented dikinetids associated with nematodesmata, forming easily recognisable bundles in some protargol-impregnated specimens ( Figures 8 (d–f) and 9(i,j)).

Comparison with original description and remarks

The Korean population matches well the Namibian type population and Australian population with regard to body size and shape, macronuclear and extrusome pattern, as well as the number of somatic ciliary rows ( Foissner et al. 2002). Conspecificity is thus beyond reasonable doubt. Because its oral ciliary pattern is in transition between

Spathidium - and Epispathidium -like, as already mentioned by Foissner et al. (2002), and because it clusters with other Spathidium species in molecular phylogenies, we suggest transferring this species to the genus Spathidium .

Figures

Figure 8. Spathidium polynucleatum from life (a, c, g) and after protargol impregnation (b, d–f). (a) Right side view of a representative individual; (b) developing cytoplasmic extrusomes, 4–8 µm long; (c) oral extrusomes, 8–10 µm long; (d, e) right and left side view of ciliary pattern and nuclear apparatus of a representative specimen; (f) dorsal view of ciliary pattern in anterior body portion; (g) cortical granulation. CG, cortical granules; CK, circumoral kinety; DB, dorsal brush; MA, macronuclear nodules/macronucleus; MI, micronuclei/micronucleus; OB, oral bulge; SC, somatic cilia; SK, somatic kinety/somatic kineties. Scale bars: a, d, e = 100 µm; f = 30 µm.