Notohymena quadrinucleata Foissner, 2016
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publication ID |
https://doi.org/10.1080/00222933.2025.2498720 |
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persistent identifier |
https://treatment.plazi.org/id/2C3B905F-0A03-4D2A-FE78-FA24FD02C29B |
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treatment provided by |
Plazi |
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scientific name |
Notohymena quadrinucleata Foissner, 2016 |
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Notohymena quadrinucleata Foissner, 2016
( Figures 1–4 View Figure 1 View Figure 2 View Figure 3 View Figure 4 ; Tables 1, 2)
Improved diagnosis (based on original description and the present redescription) Body size in vivo 80–135 × 30–45 μm; elliptical to elongate-elliptical. Invariably four macronuclear nodules, 0–5 micronuclei. Cortical granules yellowish, or citrine, 0.7–1.0 μm
across. Eighteen fronto-ventral-transverse cirri; right marginal cirral row starts far subapically. Four dorsal kineties and two dorsomarginal rows, three caudal cirri. Adoral zone of membranelles 28.9–45.7% of body length, composed of 26–32 membranelles. Buccal cavity deep, narrow; conspicuous buccal horn present. Cyst surface wrinkled, contains lipid droplets and single macronuclear nodule.
Material deposited
Ten voucher slides with protargol-impregnated specimens have been deposited at the Protozoology Section (National Zoological Collections), Zoological Survey of India, Kolkata, India, with the following accession numbers: Pt. 6049–6056, 6062, 6106.
Description of Indian population
Body size in vivo 90–135 × 30–45 μm (n = 9) and ~90 × 30 μm (n = 24) after protargol impregnation, shrinkage of ~15% in both length and width was observed due to protargol preparation ( Table 1). Body shape elliptical to elongate-elliptical or slightly ovate, dorso-ventrally flattened up to 3:1. Nuclear apparatus slightly left of cell midline ( Figures 1 View Figure 1 (B, H), 2(A, F); Table 1). Four macronuclear nodules in line; anterior nodule behind proximal end of adoral zone of membranelles; studded with nucleoli. Two to five globular micronuclei close to macronuclear nodules. Contractile vacuole slightly anterior of mid-body at left cell margin ( Figures 1 View Figure 1 (A), 2(A)). Cortex flexible, with loose rows of citrine granules ~0.7 μm diameter ( Figures 1 View Figure 1 (C), 2(B)). Cytoplasm with moderate lipid droplets ( Figures 1 View Figure 1 (B), 2(A)) and numerous colourless crystals ( Figures 1 View Figure 1 (E), 2(C)) of varying shapes, ~2.4 μm diameter, scattered in postoral body portion. Food vacuoles 5–13 μm across, present throughout cytoplasm ( Figures 1 View Figure 1 (A, B), 2(A)). Moves by creeping at bottom of culture petri dishes.
Ventral ciliature follows pattern similar to Oxytricha species, with 18 ordinarily sized fronto-ventral-transverse cirri ( Figures 1 View Figure 1 (A, B, D, G–j), 2(A, D, E); Table 1). Three frontal cirri ~12 μm long in vivo; buccal cirrus positioned ~4 μm posterior of anterior end of paroral membrane. Postoral cirri closely spaced; four or five transverse cirri (mostly five), ~20 μm long in vivo, projecting distinctly beyond body outline. Marginal cirri ~8–10 μm long in vivo; right row begins ~18 μm from anterior body end, left marginal row extends posteriorly to body midline ( Figures 1 View Figure 1 (A, G–I), 2(A, D)). Four dorsal kineties and two dorsomarginal rows ( Figures 1 View Figure 1 (J), 2(E); Table 1). Three caudal cirri located at posterior ends of dorsal kineties 1, 2, and 4, respectively ( Figures 1 View Figure 1 (J), 2(E); Table 1).
Adoral zone 29–39%, averaging 33% of body length in protargol preparations; composed of ~29 membranelles with longest bases ~5.3 μm ( Figures 1 View Figure 1 (A, B, G–I), 2(A, D); Table 1). Buccal cavity narrow but deep; conspicuous buccal horn present, covering part of adoral zone and extending as membranellar scutum ( Figures 1 View Figure 1 (B, D), 2(A)). Buccal lip narrow, featuring typical Notohymena undulating membranes. Paroral membrane ~16 μm long; endoral membrane ~14 μm long, extending into pharynx and optically intersecting at mid-buccal cavity.
A declining population frequently undergoes reorganisation, leading to variability in the number of macronuclear nodules (ranging from one to several, primarily two) and resulting in shape distortion.
Resting cysts
Two-week-old resting cysts ~40 μm in diameter; surface wrinkled. Cyst wall and wrinkled surface ~1.5 μm and ~2.0 μm thick, respectively ( Figure 1 View Figure 1 (F)). Cyst contents near wall, consisting of lipid droplets and a single macronuclear nodule.
SSU rRNA gene sequence and phylogeny
The SSU rRNA gene sequence of Notohymena quadrinucleata Indian population was deposited in GenBank under accession number PV659386. The new sequence is 1675 bp in length and has a GC content of 45.8%. Phylogenetic trees based on SSU rRNA gene sequences using BI and ML analyses had similar topologies; therefore, only the BI tree is presented here ( Figure 5 View Figure 5 ). Phylogenetic analyses consistently place Notohymena quadrinucleata within the oxytrichids, clustering within a clade that includes two other Notohymena species ( N. gangwonensis and N. antarctica ), Apoterritricha lutea Kim et al., 2014 , Australocirrus shii (Shi et al., 1997) Kumar and Foissner, 2015 , Neokeronopsis asiatica Foissner et al., 2010 and Neokeronopsis aurea Foissner and Stoeck, 2008 .
Divisional morphogenesis
Divisional morphogenesis follows typical Notohymena pattern (for details see Berger 1999) with the difference in the formation of oral primordium. The parental adoral zone of membranelles remains unchanged for the proter, while that of the opisthe is formed from the oral primordium, which originates near transverse cirrus II/1 ( Figure 3 View Figure 3 (a)). The oral primordium proliferates by utilising postoral ventral cirri, leading to anlage formation for the opisthe. In total, six parental cirri (II/2, III/2, IV/2, IV/3, V/3, and V/4), along with the paroral and endoral, are involved in forming six anlagen for both the proter and the opisthe ( Figures 3 View Figure 3 (A–D), 4(A, B)). Anlage I of the opisthe gives rise to the leftmost frontal cirrus and undulating membranes. In the proter, the parental undulating membranes partially disintegrate to form anlage I, which subsequently generates the first frontal cirrus and undulating membranes. Cirri II/2, III/2, and IV/3 possibly contribute to the formation of anlagen II, III, and IV of the proter. Anlage V of the proter is formed by the splitting of anlage V of the opisthe ( Figure 3 View Figure 3 (E)). However, it remains unclear whether anlage VI of the proter is also formed by the splitting of anlage VI of the opisthe ( Figures 3 View Figure 3 (D, E), 4(B)). The anlagen for both the proter and the opisthe split into the characteristic 1:3:3:3:4:4 cirral pattern, resulting in the formation of 18 fronto-ventral-transverse cirri ( Figures 3 View Figure 3 (F, G), 4(C)).
The marginal primordia arise at each of two levels by ‘within-row’ primordia formation, utilising one or two of the parental cirri at each level. The primordia elongate by incorporating six to nine parental cirri and subsequently differentiate into new marginal rows. The remaining parental marginal cirri are resorbed ( Figures 3 View Figure 3 (F–H), 4(C, D)).
On the dorsal surface, three primordia are formed within-row from dorsal kineties 1, 2 and 3 at two levels (one set for the proter and one for the opisthe). The third dorsal primordium fragments in the middle, giving rise to the third and fourth kineties. Two dorso-marginal rows develop near the right marginal row and subsequently shift to the dorsal surface. Three caudal cirri are formed at the posterior ends of the first, second, and fourth dorsal kineties ( Figures 3 View Figure 3 (F–I), 4(C, D, F)).
Nuclear division follows the typical process observed in oxytrichids. In middle dividers, the macronuclear nodules fuse into a single mass, which undergoes two divisions to produce the characteristic four nodules in late dividers ( Figures 3 View Figure 3 (F, J), 4(C, E)). The micronuclei divide mitotically in the usual manner.
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