Contraction of the body frequent and in most cases a tail region became apparent on shortening. Anterior region bulbous and rounded; nuclear apparatus large. (ref. ID; 2316)
Only slightly flattened laterally. Grey to blackish in dissecting and bright-field microscope due to innumerable, 4x2 um sized, refractile (crystalline?) inclusions in head and trunk. Shape of fully extended specimens slenderly fusiform with neck distinctly separate from head and cylindroid trunk; no tail, i.e. posterior region only slightly tapering and narrowly rounded. Head about 300 um wide, claviform, at one side obliquely truncate, conspicuous because distinctly wider and darker than neck due to many ellipsoid inclusion described above; oral bulge inconspicuous, about 3 um high, difficult to recognize because indistinctly separate from head and also filled with ellipsoid inclusions, surface flat or slightly depressed in centre. Slightly contracted cells fusiform, fully contacted specimens about 350 um long in vivo, ampulliform or banana-shaped and with distinct or indistinct head; glabrous stripe neither protruding nor distinctly tuberculate. Macronuclei globular, form conspicuous, about 20 um sized cluster in vivo, possibly a capsule, in centre of trunk; each nucleus usually contains two large nucleoli and one or two cuboid or hexagonal protein crystals, which do not stain with protargol. Micronuclei globular, in centre of macronuclear cluster. No contractile vacuole. Cortex highly flexible, about 1-2 um thick, forms large columnar tubercles between and many small claviform blisters along ciliary rows in contracted specimens. Cortical granules about 0.6 um in diameter, colourless arranged in broad stripes between kineties and in narrowly spaced rows in glabrous stripe; stain red with methylgreen-pyronin but are not extruded. Cytoplasm packed with ellipsoid inclusions as described above, many fat globules and clear vacuoles, and some 2-3 um sized irregular crystals. Movement like in other trachelocercids, i.e. elegantly gliding and winding between sand grains and organic debris. (ref. ID; 2267)
Infraciliature: The somatic and oral infraciliature of T. ditis is very similar to that of T. sagitta. All important differences concern morphometric characteristics, and features recognizable only in live specimens and described above, emphasizing the need for morphometry and live observation for a correct identification of trachelocercid ciliates. Thus, Foissner et al. refrain from a complete description of the infraciliature, which would be a repetition of that given for T. sagitta, and refer to the detailed figures and figure explanations. Nevertheless, a few features are different or were seen clearly only in this species, and are thus described in some detail. The somatic ciliation of T. ditis is highly variable. In some specimens it is very similar to that described for T. sagitta, while others have both basal bodies of the dikinetids ciliated throughout, especially in the kineties right of the glabrous stripe. The anterior end of the somatic kineties is distinctly curved or almost straight, bearing only 1-3 more narrowly spaced (condensed) dikinetids. These dikinetids lack the posterior cilium, as in all other trachelocercids. The glabrous stripe is relatively narrower in T. ditis than in T. sagitta, i.e. occupies only one quarter or less of the body width, corresponding to an area occupied by 1-2 kineties. Highly interesting specializations were found in the bristle kinety bordering the glabrous stripe. In three specimens it was clearly recognizable, obviously because this species lacks a tail, that the bristle kinety curves around the posterior end of the organism, emphasizing Foissner et al. interpretation that it is a single row extending around the glabrous stripe. Furthermore, a special fibre, associated with the ciliated basal body of the dikinetids and directed laterally towards the somatic kineties, was observed in some excellently prepared specimens. Accordingly, this fibre shows the same peculiar polarity as the ciliation of the bristle dikinetids, i.e. it originates from the posterior basal body along the right side of the glabrous stripe and from the anterior basal body along its left side. The number of dikinetids comprising the circumoral kinety is much more variable in T. ditis than in T. sagitta. Likewise, their arrangement is more variable which is, however, possibly a preparation artifact. In most specimens the dikinetids form a continuos row, while more or less distinct fragments are recognizable in others. Scanning electron micrographs revealed that the oral dikentids have only one basal body ciliated, possibly the posterior. Interestingly, the circumoral cilia and those at the anterior end of the somatic kineties are frequently partially or completely lost by the preparation procedure. (ref. ID; 2267)
Measurements
Size of fully extended specimens in vivo about 800-1,000x40-50 um, highly flexible and contractile, size and shape thus poorly preserved and highly variable in protargol slides. (ref. ID; 2267)
Trachelocerca geopetiti is a large contractile vermiform ciliate, reaching 1800 um in length when extended. Its nuclei are united into a single compact group, about 40 um large, which lies in the medium region of the body. We found two varieties of T. geopetiti which were similar in vivo but differed as to the number of individual nuclei in the group. Specimens of the first variety had four large, tightly packed macronuclei in peripheral position, and to micronuclei in the centre of the nuclear group. Those of the second variety showed eight small and more loosely arranged peripheral macronuclei, and four central micronuclei, also of smaller size. Most natural populations were mixtures of both varieties. The large macronuclei of the first variety contained numerous nucleoli and several (up to 10) strongly Feulgen positive chromocentres; the macronuclei of the second variety contained a smaller number of both components. Otherwise, the morphological and cytochemical pecularities of the nuclei of the varieties proved rather similar, and they will be further considered together. The electron microscope reveals no special structures holding the nuclei together in the group. The nuclear group is externally surrounded with usual cytoplasm which, like in all Karyorelictida, contains many mitochondria, small dictyosomes and lage lacunes of the smooth endoplasmic reticulum. The central cavity of the nuclear group contains few mitochondria, no dictyosomes, but many flattened vesicles of the smooth endoplasmic reticulum which are often arranged concentrically around the micronuclei, virtually encapsulating them. More peripherally, some agranular cisternae widen into lacunae which occupy the clearance between the micro- and the macronuclei. (ref. ID; 7583)
Examined material
The material on T. geopetiti has been collected at the Black sea beaches: in September 1971 and July 1977 near Sebastopol (Crimea, USSR), in August-September 1976 and June-July 1979 near Primorsko and Sozopol (Bulgaria). (ref. ID; 7583)
[ref. ID; 2267]
Greyish in dissecting and bright-field microscope. Fully extended specimens filiform with anterior end posterior third gradually tapering, neck and tail this indistinctly separate from trunk. Head claviform, conspicuous because distinctly wider than neck and dark to black at low magnification (< /_ x100) due to many about 3x2 um sized, refractile (crystalline?) inclusions; oral bulge hyaline, about 3 um high, surface flat or slightly depressed in centre. Distal end of tail pointed and distinctly curved, sometimes almost rectangularly bent. Fully contracted specimens about 250x50 um in vivo, banana-shaped, convex side with glabrous stripe distinctly protruding and tuberculate; partially contracted cells elongate-fusiform, highly resembling Muller's figures. Macronuclei globular, form distinct cluster, possibly a capsule, in centre of cell; contain small and large nucleoli and often a tetragonal protein crystal which does not stain with protargol. Micronuclei globular, in centre of macronuclear cluster. No contractile vacuole. Cortex highly flexible, about 1 um thick, forms columnar tubercles in contracted specimens. Cortical granules globular, about 1 um in diameter, colourless, arranged in narrow stripes right of ciliary rows and tightly spaced rows in globrous zone. Movement like in other trachelocercids, i.e. elegantly gliding and winding between sand grains and organic debris. (ref. ID; 2267)
Somatic infraciliature: The surface of T. sagitta is densely ciliated, leaving blank a rather wide zone, the glabrous stripe, extending the whole body length in the midline of the left side. The cilia, which are rather stiff and can be spread, are about 10 um long and arranged in longitudinal rows which are distinctly separate from the circumoral ciliature and extend between flat cortical crests. The anterior end of the ciliary rows has condensed. i.e. more narrowly spaced dikinetids and is slightly curved to their right. The ciliary rows are gradually shortened anteriorly in the neck region left of the glabrous stripe and posteriorly, where the body narrows to the tail, on both sides of the stripe. In other words, an anterior and posterior secant system are formed on the left surface of the neck and tail where 5-6 kineties about to the left branch of the bristle kinety. Thus, the head, neck, and tail have about one third less kineties than the trunk. The ciliary rows neighbouring the right branch of the bristle kinety are unshortened anteriorly, i.e. extend parallel to the glabrous stripe. The distances between the ciliary rows decrease slightly from right to the left, i.e. those forming the anterior secant system are more narrowly spaced than those right of the glabrous stripe. The entire infraciliature consists of dikinetids which, however, have a highly specialized ciliation. The dikinetids are rotated 20-30 degrees counter-clock-wise to the kinety axis and associated with conspicuous, overlapping postciliary microtubule ribbons, which originate from the posterior basal body of the dikinetids and form a thick, strongly impregnated postciliodesma right of each ciliary row. A thin, sharply impregnated fibre, very likely a subkinetal microtubule ribbon, extends underneath each ciliary row. Only the anterior basal body of the dikinetids is ciliated, except in the distal neck region of the right side, where both are ciliated. In other words, the posterior cilium is lacking in the dikinetids of all kineties neighbouring the bristle kinety, in the condensed dikinetids at the anterior end of the head kineties, and in all trunk and tail dikinetids. The contractile apparatus of T. sagitta consist of a myoneme close to the left of each kinety. The distinctiveness of the myonemes varies highly, depending on preparation conditions; frequently they are partially or completely unstained. The myonemes are flattened ribbon-like and extend the whole length of the kineties, but are wider (thicker) in the trunk than in the tail and head region. No myonemes were found in the glabrous stripe in any of the species investigated. Likewise, all myonemes observed were unbranched, i.e. did not contact each other. The globrous stripe, which extends along the whole length of the body, is narrow in the head region and widens, respectively narrow, gradually on the neck and tail. Its full width on the trunk corresponds to an area occupied by 1-2 kineties, i.e. approximately on third of body width. The glabrous stripe is rather flabby and becomes tuberculate when the cell contracts. It is bordered by the bristle kinety which consists, like the ordinary ciliary rows, of dikinetids having about 15 um long, rather stiff cilia. However, the bristle kinety is easily distinguished from ordinary somatic ciliary rows because its dikinetids are more irregularly and loosely arranged and either lack or have very inconspicuous postciliary microtubule ribbons too small to be recognized with the light microscope. Furthermore, the bristle kinetids have a unique ciliation, most parsimoniously explained by the assumption that they belong to a single kinety extending along the stripe margins, quite similar to the left lateral kinety of the loxodids. Both ends of the bristle kinety are very close together subapically and terminally in the midline of the glabrous stripe. The dikinetids along the right margin of the glabrous stripe have the posterior basal body ciliated, whereas the dikinetids along the left margin of the glabrous stripe have the anterior basal body ciliated. Nonciliated granules are scattered within the bristle kinety in the trunk region. In the best preparations, the ciliated dikinetids are composed of three granules forming minute triangles. The additional (third) granule is directed to the somatic kineties. (ref. ID; 2267)
Oral infraciliature: the oral infraciliature of T. sagitta is very simple and consists of a single, dikinetidal circumoral kinety extending in the flat furrow separating the oral bulge from the head. The circumoral kinety is very likely composed of about 8 small fragments, as indicated by small gaps, 1-2 dikinetids wide, and the bundled arrangement of the nematodesmata. The dikinetids have, very likely, only the posterior basal body ciliated and are associated with a distinct nematodesma. The nematodesmata of each dikinetidal fragment unite to small bundles extending posteriorly underneath the anterior end of the somatic kineties. (ref. ID; 2267)
Measurements
Size of fully extended specimens in vivo about 1,000x30 um, highly flexible and contractile, size and shape thus poorly preserved and highly variable in protargol slides; trunk flattened up to 2:1. (ref. ID; 2267)
