Antetetmemena minima ( Kumar et al., 2016) Omar & Jung, 2024

Omar, Atef & Jung, Jae-Ho, 2024, Disentangling the stylonychine ciliates (Ciliophora: Hypotricha): the establishment of two new genera using an integrative taxonomic approach, Zoological Journal of the Linnean Society (zlae 144) 202, pp. 1-40 : 20-22

Antetetmemena minima ( Kumar et al., 2016) comb. nov.

( Figs 10–12 ; Table 1 )

2009 Stylonychia bifaria (Stokes, 1887) Berger 1999 —Küppers, Claps and Lopretto, Rev. Mex. Biodivers. 80:583, figs 3A–C, 6B; table 3 [misidentification; brief description of Argentina population, one voucher slide (MLP35) was deposited at Colección de Invertebrados from the Museo de La Plata, Argentina].

2016 Tetmemena bifaria minima nov. subspec. – Kumar, Bharti, Quintela-Alonso, Shin and La Terza, Eur. J. Protistol. 56:212, fig. 8, table 2 [establishment of a new subspecies; one slide ( NHMUK 2015.5 .21.1) containing the holotype and many paratype specimens were deposited at the Natural History Museum , London, UK].

2021 Tetmemena bifaria minima Kumar et al. 2016 —Omar and Jung, J. Spec. Res. 10:308, fig. 10 [brief redescription; two voucher slides (NNIBRPR20120 and NNIBRPR20121) were deposited at the Nakdonggang National Institute of Biological Resources, South Korea].

Morphological description of the Korean population: This population was described only briefly by Omar and Jung (2021). In the present study, we are providing a detailed description of the same population including the ontogenetic aspect, because it has been assigned to the new genus Antetetmemena . Size 85–110 μm × 30–45 μm in vivo (N = 5) and 60–87 μm × 27–43 μm after protargol impregnation. Body ellipsoid, anterior end narrowly rounded and truncated to left, posterior end rounded in vivo and slightly truncated to right after protargol impregnation; frontal area of Tetmemena pustulata type, i.e. narrowed and bearing frontal cirri; body margins parallel and straight, sometimes only slightly convex or concave. Length:width ratio 1.8–2.4:1, on average 2.1:1 ( Figs 10A–C , 11A–D ). Nuclear apparatus commences at ~27% of body length and ends at ~74%. Invariably two macronuclear nodules and one or two micronuclei. Individual macronuclear nodules broadly ellipsoidal, usually in the midline of the body, size in vivo 12–18 μm × 8–12 μm. Micronuclei usually attached to macronuclear nodules, spherical, ~5 μm across ( Figs 10C , 11D ). Contractile vacuole in mid-body near left cell margin; at end of diastole ~10 μm across. Collecting canals not observed ( Fig. 10A ). Cortex rigid and colourless; cortical granules lacking. Cytoplasm hyaline, studded with lipid droplets, refractive crystals throughout cell, and food vacuoles 6–10 μm across containing bacteria and flagellates ( Figs 10A , 11A, B ). Cells usually crawl on the bottom of the culture dish or rarely swim by spiralling around long body axis.

Cirral pattern of Antetetmemena minima oxytrichid, i.e. 18 FVT cirri arranged as follows: three frontal cirri in middle of frontal area, with cilia ~22 μm long in vivo; one buccal cirrus with cilia ~20 μm long in vivo; four frontoventral cirri arranged in V-shaped pattern with cilia 20 μm long in vivo; three postoral cirri in inverted L-shape pattern, with cilia as long as those of frontoventral cirri, cirrus IV/2 distinctly anterior to level of cirrus V/4; two obliquely arranged pretransverse cirri, with cilia as long as those of postoral cirri; and five transverse cirri arranged in two groups, two right and three left, subterminal, projecting from posterior body end except for the leftmost cirrus, which ends at rear body margin, ~25 μm long in vivo ( Figs 10A, B , 11C ). Marginal cirri each ~17 μm long. Right marginal row commences subapically at ~16% of body length and ends posteriorly at ~94% of body length, composed of 11–15 cirri. Left marginal row commences at ~43% of body length and ends at posterior body end, composed of 9–12 cirri. Gap between posterior ends of marginal rows distinctly shifted to right ( Figs 10A, B , 11C ).

Six dorsal kineties, including two dorsomarginal ones, with bristles ~3–4 μm long in vivo. Kineties 1–3 bipolar, not curved anteriorly, possessing 17–19, 13–18, and 13–14 dikinetids, respectively. Kinety 4 distinctly shortened anteriorly, i.e. commences at ~28% of body length and possesses 7–13 dikinetids. Dorsomarginal kineties 1 and 2 extend posteriorly over ~40% and 25% of cell length and possess 6–8 and 3–5 dikinetids, respectively. Three caudal cirri, ~25 μm long in vivo, distinctly shifted to the right, one each at end of kineties 1, 2, and 4 ( Figs 10C , 11D ).

Adoral zone occupies 39%–48% of body length and is composed of 23–26 membranelles. Distal end of adoral zone commences at ~8% of body length on right side (DE-value 0.19 on average). Cilia of membranelles ~20 μm long in vivo, bases of largest membranelles ~4 μm wide after protargol impregnation. Buccal cavity, i.e. transverse distance between anterior end of paroral membrane and opposite adoral membranelle on left side, 5–10 μm wide and narrowing posteriorly ( Figs 10A, B , 11C ). Undulating membranes in slightly curved Stylonychia pattern. Paroral membrane commences anterior to buccal cirrus at ~19% of body length, with a length of ~11 μm in protargol-impregnated specimens, and extends to near end of buccal vertex. Endoral membrane commences posterior to anterior end of paroral membrane at ~16% of body length, with a length of ~12 μm after protargol impregnation, and extends to end of buccal vertex. Membranes at the midline of the body, cilia ~8 μm long. Pharyngeal fibres extend obliquely to right body margin ( Figs 10A, B , 11C ).

Morphogenesis: The ontogenesis of Antetetmemena minima is identical to that of Apostylonychia baugilensis in all respects ( Fig. 12 ).

Figures

Figure 10. Antetetmemena minima from life (A) and after protargol impregnation (B, C). A, ventral view of a representative specimen showing the elliptical body and the adoral zone of membranelles occupying <50% of body length.B, C, ventral (B) and dorsal (C) views of a voucher specimen showing the body shape, the undulating membranes, which are parallel and slightly curved, the transverse cirri in two distinctly separated groups (dotted ellipses), the infraciliature, and the nuclear apparatus. Note that the frontal cirri are not shifted to the right. Abbreviations:1–4, dorsal kineties; AZM, adoral zone of membranelles; BC, buccal cirrus; CC, caudal cirri; DM1, DM2, dorsomarginal kineties; EM, endoral membrane; FC, frontal cirri; FVC, frontoventral cirri; LMR, left marginal row; MA, macronuclear nodules; MI, micronucleus; PF, pharyngeal fibres; PM, paroral membrane; PTVC, pretransverse cirri; PVC, postoral cirri; RMR, right marginal row; TC, transverse cirri.Scale bars: 30 μm in A; 20 μm in B, C.

Figure 11.Antetetmemena minima from life (A, B) and after protargol impregnation (C, D). A, B, ventral views showing the elliptical body. C, D, ventral (C) and dorsal (D) views of a voucher specimen showing the body shape, the undulating membranes, the transverse cirri in two distinctly separated groups, the infraciliature, and the nuclear apparatus. Abbreviations:1–4, dorsal kineties; AZM, adoral zone of membranelles; BC, buccal cirrus; CC, caudal cirri; DM1, DM2, dorsomarginal kineties; FC, frontal cirri; FVC, frontoventral cirri; LMR, left marginal row; MA, macronuclear nodules; MI, micronucleus; PM, paroral membrane; PTVC, pretransverse cirri; PVC, postoral cirri; RMR, right marginal row; TC, transverse cirri. Scale bars: 30 μm in A, B; 20 μm in C, D.

Figure 12. Antetetmemena minima after protargol impregnation.A, ventral view of an early divider showing the apokinetal origin of the oral primordium left to the leftmost transverse cirrus. B, ventral view of a late early divider showing the origin of anlage III of the proter from cirrus III/2, anlagen IV–VI from cirrus IV/3, and the origin of anlagen V and VI of the opisthe from cirrus V/4. C, D, ventral (C) and dorsal (D) views of a middle divider, showing the formation of all anlagen and the intrakinetal origin of marginal (arrowheads) and dorsal anlagen.E, F, ventral (E) and dorsal (F) views of a late divider, showing the differentiation of cirri, the fragmentation of dorsal kinety 3, the formation of a single macronucleus, and the new caudal cirri formation.G, H, ventral (G) and dorsal (H) views of a late divider showing the migration of cirri to their final positions and the division of the nuclear apparatus. Abbreviations: 1A–4A, dorsal kineties anlagen; CC, caudal cirri; DM1, DM2, dorsomarginal kineties; I–VI, frontal–ventral–transverse anlagen; OP, oral primordium. MA, macronuclear nodules; MI, micronuclei.Scale bars:20 μm.