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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Novistrombidium

Novistrombidium Song & Bradbury, 1998 (ref. ID; 4918)

Order Strombidiida Jankowski, 1980: Family Strombidiidae Faure-Fremiet, 1970 (ref. ID; 4918)

[ref. ID; 4918]
Improved diagnosis; Strombidiidae with left portion of dextrally spiralled girdle kinety posterior to oral primordium. Ventral kinety longitudinal. (ref. ID; 4918)
Comparison with related genera; Song & Bradbury (1998) defined Novistrombidium as "Strombidiide with incomplete girdle kinety around equatorial area that is conspicuously opened with a large ventral gap, through which ventral kinety extends". The course of the girdle kinety is diverse in strombidiids (e.g. Alekperov 1985; Montagnes and Lynn 1988; Montagnes et al. 1988; Lynn and Gilron 1993; Petz et al. 1995; Agatha and Riedel-Lorje 1997). Thus, there might be transitions between Strombidium (horizontal girdle kinety) and Novistrombidium (dextrally spiralled girdle kinety). In the latter, the oral primordium develops above the left portion of the girdle kinety, while it develops below this portion in Strombidium, where this ciliary row migrates posteriorly below the oral primordium during ontogenesis (S. constrictum with its unique position of the girdle kinety near posterior cell end might represent an exception). This migration, respectively, the relative position of the left kinety portion and the oral primordium are thus better distinguishing features than the course of the girdle kinety alone. Although there are differences between the original description of S. testaceum by Anigstein (1913) and the redescription by Song and Bradbury (1998), especially in the presence of a ventral kinety, the redescription is regarded as authoritative till contrary results give evidence for the existence of S. testaceum sensu Anigstein (1913). Novistrombidium differs from Strombidium in the location of the oral primordium (anterior vs. posterior to left portion of girdle kinety). This results in a different ontogenetic behavior of this kinety portion: it remains below the oral primordium in Novistrombidium, while it migrates posteriorly underneath the oral primordium in Strombidium. Thus, Strombidium recapitulates the dextrally spiralled girdle kinety of Novistrombidium during ontogenesis, indicating that it is apomorphic. (ref. ID; 4918)
  1. Novistrombidium apsheronicum (Alekperov & Asadullayeva, 1997) Agatha, 2003 (ref. ID; 4918 redescribed paper)
  2. Novistrombidium testaceum (ref. ID; 4918)

Novistrombidium apsheronicum (Alekperov & Asadullayeva, 1997) Agatha, 2003 (ref. ID; 4918 redescribed paper)

Improved diagnosis

Size ~75x50 um in vivo and ~64x42 um after protargol impregnation. Cell broadly obconical and up to 2:1 dorsoventrally flattened; with peristomial collar. Macronucleus question mark-shaped Micronucleus globular. On average 15 anterior and 11 ventral membranelles. Girdle kinety comprises ~45 dikinetids, ventral kinety ~21. Extrusomes attached to cortex in an arc on posterior dorsal side and a question mark-shaped pattern surrounding cell, acicular and ~20x0.7 um in size. (ref. ID; 4918)

Redescription

Size 60-95x45-55 um in vivo, usually ~75x50 um, and 51-80x39-49 um, usually 64x42 um after protargol impregnation. Cell obconical to broadly obconical, widest underneath zone of anterior membranelles, dorso-ventrally flattened up to 2:1, anterior end truncate and slanted leftwards, with thin peristomial collar, posterior end pointed; often deformed by engulfed food organisms. Macronucleus roughly question mark-shaped, i.e. commences near right cell margin and extends parallel to zone of anterior membranelles to left cell margin, where it curves posteriorly; occasionally, constricted in mid-portion; C-shaped in two of 83 specimens. Nucleoli 1-3 um across after protargol impregnation. Micronucleus close to right end of macronucleus, ~7 um across in vivo, but only 2 um in protargol preparations, where it is difficult to recognize due to similar-sized nucleoli. No contractile vacuole observed. Extrusomes ("trichite") attachment sites arranged in two rows distinctly separate from girdle kinety, frequently impregnated with protargol. Anterior row roughly question mark-shaped, i.e. commences close underneath first anterior membranelles and extends parallel to membranellar zone across dorsal site to middle of ventral membranellar zone, where it curves posteriorly approaching middle of ventral kinety; attachment sites laterally and dorsally in clusters of 13-15 extrusomes each in a shallow depression, ventrally forming a stripe of alternating sites in the anterior portion and aligned sites in the posterior. Posterior row of extrusome attachment sites in shallow furrow on posterior quarter or fifth of dorsal side, commences near posterior end of ventral kinety and extends in a flat arc rightwards to girdle kinety. Resting extrusomes acicular, attached to cortex with rounded end, 18-22x0.7 um in anterior row, while probably shorter in posterior; ejected extrusomes were not investigated. Cytopyge near posterior end. Cortical platelets cover cell underneath anterior row of extrusome attachment sites, polygonal and 1-5 um across, conspicuous in vivo and even in some protargol-impregnated specimens. Posterior cell surface occasionally covered by some 1-2 um long bacterial rods. Cytoplasm colourless, contains lipid droplets 2-5 um across mainly in anterior cell portion and food vacuoles with remnants of up to 60 um long filamentous algae. Swims rapidly in spirals. Somatic cilia arranged in a girdle and a ventral kinety extending in shallow furrows, fusiform and ~2.5 um long in vivo, rod-shaped and 1-1.6 um in scanning electron micrographs. Girdle kinety commences ~35% back from anterior cell end on right side, extends obliquely across dorsal and left half of ventral side, approaching at an acute angle end of ventral kinety in posterior seventh of cell. On average 45 girdle dikinetids each with a commonly-sized left cilium and a ~0.4 um long right cilium. Ventral kinety commences in centre of ventral side, extends through gap formed by girdle kinety, and terminates near posterior sixth of right side; composed of ~21 dikinetids each with a commonly-sized anterior cilium and a ~0.4 um long posterior cilium. Oral apparatus occupies anterior end of cell, consists of a paroral membrane on inner wall of buccal lip and a membranellar zone. Membranellar zone distinctly open ventrally, bipartited into an anterior portion of ~15 membranelles and a ventral portion of ~11 membranelles; the two portions are not separated. Anterior membranelles ~10 um wide, each comprises three rows of basal bodies with cilia up to 30 um long. Protargol-affine structures, probably fibres, extend between anterior membranelles. Intermembranellar ridges ~4 um wide and distinct, especially on dorsal side, with a globular and an ellipsoidal granule in, or on, proximal portion in protargol preparations and occasionally a blister on distal portion in scanning electron micrographs. Ventral membranelles in oblique, shallow groove, composed of cilia ~15 um long; bases ~7 um wide, somewhat irregular distally and composed of three rows of basal bodies, except for the two posteriormost membranelles which probably comprise only two rows. Numerous blisters on oral cilia in scanning electron micrographs, probably preparation artifacts as not recognized in vivo and protargol slides. Paroral membrane on inner wall of buccal lip, composed of probably bare basal bodies as no cilia recognizable in scanning electron micrographs. Pharyngeal fibres insert at eccentric oral cavity, distinct in vivo and protargol preparations, where they are ~7 um long. (ref. ID; 4918)

Comparison with original description and similar species

The species description by Alekperov and Asadullayeva (1997) is based on live and silver-impregnated material. Data about extrusomes are lacking and there is a discrepancy between the morphometrics and the line drawing of an impregnated cell concerning the number of ventral membranelles (16-17 mentioned, 13 drawn; cp. Fig.9). Accordingly, the differences between the Caspian Sea and the Saudi Arabian specimens in the structure and length of the ventral kinety (with ~60 ciliated monokinetids and extending to posterior cell end, as estimated figure 9 vs. 10-17 dikinetids each with one distinct cilium and terminating ~14% back from end) and the number of anterior membranelles (10 vs. 14-17) are not thought to be significant, and the two populations are regarded as conspecific. Novistrombidium apsheronicum differs from M. testaceum, as described by Song and Bradbury (1998), Lei et al. (1999), and Modeo et al. (2003), in the ratio of cell length to width (1.3-1.8:1 vs. 0.95-1.0:1), the course of the anterior row of extrusomes (question mark-shaped vs. C-shaped and almost horizontal), and the location of the micronucleus (close to right end vs. near junction of macronucleus segments). Although scattered extrusomes were observed in the posterior cell portion of N. testaceum, they apparently do not form an additional row like that in N. apsheronicum (Song and Bradbury 1998; Lei et al. 1999; Modeo et al. 2003). Two insufficiently-known Strombidium species have a similar ciliary pattern and are thus possibly congeneric but differ from N. apsheronicum in the nuclear apparatus; S. ioanum (2-4 macronuclear nodules; Lynn and Gilron 1993) and S. grande Levander, 1894 sensu Czapik (1976; globular macronucleus). (ref. ID; 4918)