Spathidium securiforme Kahl, 1930

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 : 961-968

Spathidium securiforme Kahl, 1930 stat. nov.

( Figure 12 (a–e))

Spathidium amphoriforme var. securiforme Kahl, 1930: 166 , fig. S. 160, 28

Epispathidium amphoriforme var. securiforme – Foissner, 1987a: 224 (combining author) Description of a Korean population

Because our attempts at protargol impregnation failed, the following description is based only on in vivo observations. Body size 165 × 65 µm; not contractile but flexible. Shape spatulate with a length:width ratio of about 2.5:1; oral area flattened laterally and separated from trunk by a more or less indistinct neck; oral bulge conspicuously convex in lateral view, wider than mid-body, extends over slightly inclined anterior body end; posterior end rounded ( Figure 12 (a)). Macronucleus a tortuous, slightly nodulated strand extending in trunk ( Figure 12 (b,c)). Micronuclei not recognisable. A single contractile vacuole at posterior body end ( Figure 12 (a)). Two types of extrusomes attached to oral bulge and scattered throughout cytoplasm: type I rod-shaped, sometimes slightly curved, 10–14 × 0.5 µm, usually 12 × 0.5 µm in size; type II more numerous in oral bulge than type I, oblong, straight or slightly curved, with rounded ends, 4–6 × 0.5 µm, usually 5 × 0.5 µm in size ( Figure 12 (d,e)). Cytoplasm colourless, contains lipid globules and both types of extrusomes ( Figure 12 (a–e)). Dorsal brush inconspicuous because bristles only up to 3 µm long.

Comparison with original description and remarks

The Korean population matches the original description in terms of stout body shape, very conspicuous oral region that is distinctly wider than the broadest postoral body portion, the tortuous, strand-like macronucleus, and the inconspicuous dorsal brush. However, the Korean population is much smaller (165 µm vs 200–300 µm) and exhibits two types of oral bulge extrusomes. Because type II extrusomes can be easily overlooked due to their comparatively small size, we assume that the Korean population is conspecific with Kahl’ s variety. Moreover, on the basis of our phylogenetic analyses, we suggest elevating Kahl’ s variety to species level and tentatively assigning this species to the genus Spathidium .

Family BRYOPHYLLIDAE Jankowski, 1980

Genus Apobryophyllum Foissner, 1998

Apobryophyllum schmidingeri Foissner and Al-Rasheid, 2007

( Figures 13 (a–r), 14(a–n) and 15(a–j); Table 2)

Apobryophyllum schmidingeri Foissner and Al-Rasheid, 2007: 211 , figs 16–51 Apobryophyllum schmidingeri – VďaČný et al., 2011: 512 (18S rRNA gene sequence) Apobryophyllum schmidingeri – VďaČný et al., 2012: 398 (ITS region sequence)

Description of a Korean population

Body size 110–185 × 50–80 µm, usually near 145 × 65 µm in vivo and 97–220 × 45– 105 µm with an average size of about 170 × 70 µm after protargol impregnation; not contractile but flexible ( Table 2). Shape lanceolate to narrowly lanceolate with an average length:width ratio of 2.2: 1 in vivo and 2.4:1 after protargol impregnation; oral area and anterior body portion leaf-like flattened and hence hyaline; ventral margin convex while dorsal margin sigmoidal and usually concave in anterior body third, rarely both margins undulating; right side flat, left side usually vaulted ( Figures 13 (a–g,i–l), 14 (a–g) and 15(a–d,f); Table 2). Nuclear apparatus scattered throughout body, except for the flattened cell portion. Number of macronucleuar nodules highly variable (i.e. ranging from 25 to 73); individual nodules globular to oblong and about 12 × 7.5 µm in size after protargol impregnation; nucleoli small and rounded. About 8–28 micronuclei distributed among or attached to macronuclear nodules, globular and about 3.5 µm in diameter after protargol impregnation ( Figures 13 (a,i–l,o,p), 14(k) and 15(a–f,i); Table 2). Contractile vacuole subterminal to terminal and usually slightly shifted to dorsal side ( Figures 13 (a–d,m) and 14(a,i)). Extrusomes attached to oral bulge and scattered throughout cytoplasm; form a conspicuous, highly refractive fringe along whole oral bulge; individual extrusomes have a ‘torn’ appearance (i.e. anterior end tapered while posterior end rounded), often slightly to distinctly curved; oral extrusomes do not impregnate with the protargol method used while developing cytoplasmic stages impregnate deeply; type II absent or not recognisable ( Figures 13 (a–g,m,n) and 14(a,h– l)). Cytoplasm colourless, studded with macronuclear nodules, extrusomes, and 2–9-µmsize lipid droplets. Glides slowly on microscope slide.

Cilia 8–10 µm long in vivo, arranged in about 25 equidistantly spaced rows, forming the typical Bryophyllum -like pattern ( Figure 13 (q,r)). Almost all ciliary rows of left side differentiated in anterior body third into a conspicuous dorsal brush: dorsal-most row composed of few dikinetids anteriorly, followed by narrowly spaced tail monokinetids extending almost to posterior body end; all other brush rows heteromorphic – that is, composed of dikinetids bearing brush bristles and monokinetids bearing ordinary cilia ( Figures 13 (q) and 15(g)). Brush bristles of ventral-most rows slightly inflated and of similar length (about 3.0 µm), while anterior bristle of dikinetids about half as long as posterior bristle in middle brush rows; monokinetidal tail bristles oblong and only 1.5 µm long ( Figures 13 (h,q) and 14(l–n)).

Oral bulge extends from anterior body end over entire ventral side to curve around posterior body end. Circumoral kinety extends at base of oral bulge, composed of narrowly spaced dikinetids ( Figure 13 (p–r)). Nematodesmata not recognisable in vivo or after protargol impregnation.

Comparison with original description

The Korean population matches the original description in Foissner and Al-Rasheid (2007) almost perfectly. The single difference is the assumed absence of type II extrusomes in Korean specimens. However, we cannot exclude that they were only overlooked because they were overlaid by a dense fringe of highly refractive and massive type I extrusomes. Indeed, according to Foissner and Al-Rasheid (2007), type II extrusomes are difficult to recognize because they are inconspicuous and only 2 × 0.3 µm in size.

Figures

Figure 12. Spathidium securiforme from life. (a) Right side view of a representative individual; (b, c) optical sections showing tortuous macronuclear strand; (d) detail of anterior body portion showing type I (arrows) and type II (arrowheads) extrusomes attached to oral bulge; (e) optical section showing type I (arrows) and type II (arrowheads) extrusomes scattered throughout cytoplasm. MA, macronucleus. Scale bars: a = 100 µm; b, c = 10 µm; d, e = 5 µm.