Apostylonychia notophorides ( Foissner, 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 : 15-16

Apostylonychia notophorides ( Foissner, 2016) comb. nov.

( Figs 5–9 ; Table 1 )

2016 Stylonychia notophorides nov. spec. – Foissner (2016), Denisia 35:835, figs 283, 284 (original description).

Improved diagnosis (based on original description and our data): Body size 70–120 μm × 28–50 μm in vivo and 64–91 μm × 27–45 μm after protargol impregnation. Body obovate, widest at mid of adoral zone; length:width ratio 1.9–2.9:1. Two separate macronuclear nodules. Right marginal row composed of 9–16 cirri, left row of 9–12 cirri. Dorsal kinety 4 commences at the same level as kinety 3 or slightly shorter. Adoral zone occupies 42%–57% of body length after protargol impregnation and is composed of 24–32 membranelles. Resting cysts ~45 μm in vivo, with spines 4–7 μm wide at base and 5–10 μm long and fused macronuclear nodules.

Voucher material: Two voucher slides (NNIBRPR27178 and NNIBRPR27179) with protargol-impregnated specimens have been deposited in the Nakdonggang National Institute of Biological Resources, Korea. Two further voucher slides (GUC009426 and GUC009427) have been deposited in the Jung laboratory (J.-H. Jung) in Gangneung-Wonju National University.

Morphological description of the Korean population: Size 90–120 μm × 35–50 μm in vivo (usually ~110 μm × 45 μm, N = 14) and 64–91 μm × 27–45 μm after protargol impregnation. Body moderately obovate, widest in mid of adoral zone of membranelles, wide frontal area, scutum hyaline, rounded and slightly narrowed anteriorly, obliquely truncated to left, body margins gradually converging posteriorly, both right and left margin straight or slightly convex. Length:width ratio 1.9–2.6:1, on average 2.2:1 ( Figs 5A–C , 6A–F , 7A–E ). Nuclear apparatus commences at ~23% of body length and ends at ~72%. Invariably two macronuclear nodules and two micronuclei; cells with a single micronucleus observed only during division. Individual macronuclear nodules broadly ellipsoidal, in or slightly left of the midline of the body, in vivo 15–25 μm × 10–15 μm. Micronuclei usually attached to macronuclear nodules, spherical, ~4 μm across ( Figs 5C , 6F , 7A, B ). Contractile vacuole in mid-body at left cell margin; at end of diastole ~14 μm across. Collecting canals not recognizable ( Figs 5A , 6E, F ). Cortex rigid and colourless; cortical granules lacking. Cytoplasm hyaline, studded with lipid droplets, refractive crystals in posterior portion of cell, and food vacuoles ≤8 μm across containing bacteria, yeast, and occasionally ≤15 μm across containing flagellates and starch grains ( Figs 5A , 6A–H ). Usually crawling slowly on bottom of culture dish or swimming by spiralling around long body axis.

Cirral pattern of Apostylonychia notophorides usually in Stylonychia mytilus pattern, i.e. 18 FVT cirri arranged as follows: three enlarged frontal cirri distinctly shifted to right, i.e. right of the midline of the body, with cilia ~26 μm in vivo; one buccal cirrus with cilia ~21 μm in vivo; four frontoventral cirri arranged in V-shaped pattern with cilia 18 μm long in vivo; three postoral cirri in inverted L-shape pattern, with same length as frontoventral cirri, cirrus IV/2 placed more anteriorly than cirrus V/4; two obliquely arranged pretransverse cirri, with cilia ~20 μm long; and five transverse cirri arranged in two groups, two right and three left, subterminal, all cirri project from posterior body end, fringed distally, ~30 μm long in vivo ( Figs 5A, B , 6A, B, G , 7A, C, D, F ). Marginal cirri fine and of same length, ~18–20 μm long. Right marginal row commences subapically at ~14% of body length and ends posteriorly at ~94% of body length, composed of 10–15 cirri. Left marginal row commences at ~47% of body length and ends at ~98% of body length, composed of 9–12 cirri. Gap between posterior ends of marginal rows slightly shifted to the right ( Figs 5B , 6B , 7A, C, D ).

Six dorsal kineties, including two dorsomarginal ones, with bristles ~4 μm long in vivo. Kineties 1–3 bipolar, not curved anteriorly, possessing 22–26, 17–21, and 14–18 dikinetids, respectively; kinety 1 slightly shortened anteriorly, i.e. usually ~5 μm shorter than kineties 2 and 3 after protargol impregnation; kinety 4 slightly shortened anteriorly, i.e. ~7 μm shorter than kineties 2 and 3 anteriorly and possesses 10–16 dikinetids. Dorsomarginal kineties 1 and 2 extend posteriorly over about half and first quarter of cell length and possess 6–10 and 3–6 dikinetids, respectively. Three caudal cirri, ~35 μm long in vivo, slightly shifted to the right, one each at end of kineties 1, 2, and 4; left caudal cirrus usually straight or beating slower than the other two cirri ( Figs 5C , 6E, H , 7B, E, G, H ).

Adoral zone occupies 49%–57% of body length and is composed of 29–32 membranelles. Distal end of adoral zone commences at an average of 10% of body length on right side (DE-value 0.19 on average). Cilia of membranelles ~20 μm long in vivo, bases of largest membranelles ~5 μm wide after protargol impregnation ( Figs 5A , 6A–D , 7A, C, D ). Buccal cavity, i.e. the transverse distance between anterior end of paroral membrane and the opposite adoral membranelle on the left side, 11–16 μm wide and narrowing posteriorly. Undulating membranes at the midline of the body, cilia 9–10 μm long, in Stylonychia pattern, i.e. parallel or slightly overlapping. Paroral membrane commences anterior to buccal cirrus at ~22% of body length, with a length of ~16 μm in protargol-impregnated specimens, and extends to near end of buccal vertex. Endoral membrane commences posterior to anterior end of paroral at ~26% of body length, with a length of ~16 μm after protargol impregnation, and extends to end of buccal vertex. Pharyngeal fibres extend transversely to right body margin ( Figs 5A, B , 6A, B , 7A ).

Resting cysts: Cysts of Apostylonychia notophorides spherical, size including spines ~45 μm across in vivo. Wall hyaline, ~3–4 μm thick in vivo, ornamented by thick spines, 4–7 μm wide at base and each 5–10 μm long. Cytoplasm studded with lipid droplets; macronuclear nodules fuse to form a single macronuclear nodule in mature cysts ( Figs 6I, J , 7I, J ).

Morphogenesis: Apostylonychia notophorides divides in the same ontogenetic pattern as Apostylonychia baugilensis in all respects ( Figs 8A–H , 9A–D ).

Figures

Figure 5. Apostylonychia notophorides from life (A) and after protargol impregnation (B, C). A, ventral view of a representative specimen showing the obovate body with wide frontal area and frontal cirri shifted to right of the midline of the body, the distinctly narrowed posterior end, and the large adoral zone of membranelles. B, C, ventral (B) and dorsal (C) views of a voucher specimen showing the body shape, the undulating membranes in Stylonychia pattern, the frontal cirri located right of the midline of the body, the transverse cirri in two distinctly separated groups (dotted ellipses), 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; EM, endoral membrane; FA, frontal area; FC, frontal cirri; FVC, frontoventral cirri; LMR, left marginal row; MA, macronuclear nodules; MI, micronuclei; PF, pharyngeal fibres; PM, paroral membrane; PTVC, pretransverse cirri; PVC, postoral cirri; RMR, right marginal row; TC, transverse cirri. Scale bars: 30 μm.

Figure 6. Apostylonychia notophorides from life under differential interference contrast microscopy. A–F, ventral (A–D) and dorsal (E, F) views showing the obovate body shape with wide frontal area and narrowed posterior end, the transverse cirri (arrows), the location of the contractile vacuole (E, F), and the long caudal cirri (arrowheads). Note that dorsal kinety 4 is shortened anteriorly. G, ventral view showing the transverse cirri arranged in two groups (arrows). H, dorsal view showing the posterior portion of the body and the narrowly spaced caudal cirri slightly shifted to the right (arrowheads).I, J, optical section (I) and surface view (J) of mature cysts, showing the spines on the cyst wall (arrows) and the macronuclear nodule (asterisk). Abbreviations:1–4, dorsal kineties; AZM, adoral zone of membranelles; BC, buccal cirrus; BL, buccal lip, CV, contractile vacuole; DM1, DM2, dorsomarginal kineties; FA, frontal area; FC, frontal cirri; FV, food vacuoles; LMR, left marginal row; MA, macronuclear nodules; MI, micronuclei; RMR, right marginal row; S, scutum. Scale bars: 30 μm in A–H; 20 μm in I, J.

Figure 7. Apostylonychia notophorides after protargol impregnation (A, B) and in the scanning electron microscope (C–J). A, B, ventral (A) and dorsal (B) views of a voucher specimen, showing the body shape, the infraciliature, and the nuclear apparatus. C–E, ventral (C, D) and dorsal (E) views, showing the body shape, the frontal cirri shifted to right of the midline of the body, and the infraciliature. Arrowheads denote the caudal cirri, and arrows mark the transverse cirri arranged in groups. F, G, ventral (F) and dorsal (G) views showing the arrangement of transverse cirri (arrows) and the three narrowly spaces caudal cirri shifted to the right, each at the posterior end of kineties 1, 2, and 4 (arrowheads). H, dorsal view showing the anterior end of the dorsal kineties.I, J, surface views of mature cysts showing the spines (arrows). Abbreviations:1–4, dorsal kineties; AZM, adoral zone of membranelles; BC, buccal cirrus; CC, caudal cirri; DM1, DM2, dorsomarginal kineties; EM, endoral membrane; FA, frontal area; FC, frontal cirri; FVC, frontoventral cirri; LMR, left marginal row; MA, macronuclear nodules; MI, micronuclei; PM, paroral membrane; PTVC, pretransverse cirri; PVC, postoral cirri; RMR, right marginal row; TC, transverse cirri. Scale bars: 30 μm in A–E; and 10 μm in F–J.

Figure 8. Apostylonychia notophorides after protargol impregnation.A, B, ventral views of very early dividers show the apokinetal origin of the oral primordium left to the leftmost transverse cirrus. C, ventral view of an early divider, showing the dedifferentiation of cirrus IV/3 (double arrowhead). D, E, ventral view of an early divider, showing the formation of anlagen IV–VI of the proter from cirrus IV/3 and anlagen V and VI of the opisthe from cirrus V/4. F, G, ventral (F) and dorsal (G) view of a middle divider, showing the formation of anlage I of the proter from the paroral membrane, anlage II from the buccal cirrus, and anlage IV of the opisthe from cirrus IV/2, the formation of the right marginal anlagen (arrowheads), and the formation of dorsal kineties anlagen apokinetally at two levels in each dorsal kinety.H, ventral view of a middle divider showing the differentiation of anlagen into cirri and the extension of marginal anlagen (arrowheads). Abbreviations:1–4A, dorsal kineties anlagen; I–VI, frontal–ventral–transverse anlagen; OP, oral primordium. Scale bars: 20 μm.

Figure 9. Apostylonychia notophorides after protargol impregnation.A, B, ventral (A) and dorsal (B) views of a late mid-divider showing the complete formation of ventral cirri, the formation of dorsomarginal kineties (double arrowhead), and the extension of dorsal kineties’ anlagen. C, D, ventral (C) and dorsal (D) views of a late divider showing the migration of cirri to their final positions, the fragmentation of dorsal kinety 3 to form kinety 4, the new caudal cirri at the ends of kineties 1, 2, and 4 (arrowheads), and the division of the nuclear apparatus. Abbreviations:1–4, dorsal kineties; 1–3A, dorsal kineties anlagen; DM1, DM2, dorsomarginal kineties; EM, endoral membrane; I–VI, frontal– ventral–transverse anlagen; MA, macronuclear nodules; MI, micronuclei; PM, paroral membrane. Scale bars: 20 μm.