Pseudoparamoeba

1. Pseudoparamoeba pagei (Sawyer, 1975) Page, 1979 (ref. ID; 2093 redescribed paper, 7710)
   See; Vexillifera pagei (ref. ID; 7757)

Pseudoparamoeba pagei (Sawyer, 1975) Page, 1979 (ref. ID; 2093 redescribed paper, 7710)

See

Descriptions

• Light-microscopy: Both locomotive and floating forms are so similar to the smaller Paramoeba species, especially P. pemaquidensis Page, 1970, that only Feulgen preparations were accepted as evidence that no parasome was present in any cells. The amoebae were then compared with Vexillifera strains, as the next most similar ones. It is in the light of comparisons with those two genera that the light-microscopical characters are described. These amoebae have varying, irregular shapes, but when they are advancing steadily the hyaloplasm is distinct, often very flattened and spread out anteriorly, sometimes in more elongated forms extending back along the sides. This hyaline sheet usually has an irregular edge, sometimes but not always with short, conical projections, generally 2 um or less long. Occasionally one of the projections elongates into a finely conical pseudopodium. Sometimes such a pseudopodium is carried back along the side, but that occurs much less often than in Vexillifera bacillipedes (freshwater) or Vexillifera armata (marine), and these amoebae consequently do not have the spiny appearance characteristic of those species. Commonly a long pseudopodium arises as an anterior prolongation from the granuloplasm, pushing through or above the hyaline zone. The result is a longitudinal ridge in the main cell mass, continuing for up to 7 um or so as a narrowly conical pseudopodium, hyaline at least where it is separate from the ridge of which it is a prolongation. Sometimes two or three such ridges and pseudopodia may form. It is by advance of the flattened hyaline region that the amoebae progresses, and when an amoeba is not actually advancing it commonly does not have an extensive flattened hyaline region but only anterior hyaline projections. The granular region is generally narrow and more elongated than the hyaloplasm. At any one time many amoebae in a preparation, though more or less in the locomotive form, may be stationary. This sluggishness probably accounts for much of the great variation in shape, probably also for differences in length/breadth ratios among strains as measured. These ratios are therefore of less significance than in more uniformly active amobae, since they are more variable within a strain. The locomotive rates of 10 amoebae of strain 246, at 21 degrees, were from 11 to 17 um per minute, or from 0.8 to 1.2 times their lengths. The typical floating form has a rounded central mass with very long, very fine, radiate, hyaline pseudopodia, whose tips may be difficult to see. The pseudopodia may be straight, bent, or curved like a whip in the distal region. They may have a length three times the diameter of the central mass, though they usually do not reach that length. In a fresh wet mount, it may be several minutes before such radiate forms appear. Sometimes only rounded cells with stubby projections were observed, but that seemed to happen only when the amoebae were full of food. The principal difference between this floating form and that of Paramoeba pemaquidensis is that the hyaline webbing which may form between pseudopodia bases in the latter has not been seen in the floating forms of P. pagei. The nucleus and its central nucleolus were often elongated during cytoplasmic flow. The appearance of mitotic stages was very similar in all three strains. The nucleolus disappears in prophase, and all metaphase figures lacked any nuclear membrane. Spindle fibres could be distinguished in some but not all metaphase figures. The most striking observation was the distinct, well-formed rings in which the chromosomes were organised during metaphase and anaphase, not commonly seen so distinctly in small amoebae. No centriole could be found; the cytoplasm distal to the chromosomes sets in telophase appeared hyaline, almost vacuolated, but not in the shape of a spherical vesicle. (ref. ID; 2093)
• Electron-microscopy: The surface of P. pagei is covered with many blister-like tubercles which appear at first to have little in common with the glycostyles of either Vexillifera or Vannella. However, sections of their proximal region, tangential to the cell surface, showed a distinct hexagonal base, and in a few the same arrangement of central tubule and radial septa seen in V. armata was found. These tubercle-like structure are therefore truncate glycostyles most similar towards their proximal ends to the glycostyles of Vexillifera but closing toward their distal ends in a dome-like fashion. The transition between hexagonal and more rounded regions, the latter without the six struts in its wall, is probably at the top of the basal layer of the surface coat. In most of the truncate glycostyles the dome appears to be complete, i.e., imperforate, but in a few there is a suggestion of an opening. Possibly the opening is present in all but more expanded at some times than other; the fact that it is indiscernible in most can hardly be an accident of sectioning. The diameter of the hexagonal basal region of each glycostyle is about 56 nm. The base of the dome-like region where it emerges from the basal layer of the surface coat varies from about 41 to 50 nm. Apparently the hexagonal region rises vertically to the beginning of the domed region. The total height from plasma membrane or the apex of the dome is about 33 nm. The maximum diameter of the apparent opening in the dome is less than 17 nm. Simple filaments about 140 nm long are also seen, irregularly distributed and often absent. Possibly these are not permanent, regular structures as those of Vannella but only threads pulled out by adhesion. The truncate glycostyles, like the more elongate structures of Vannella and Vexillifera, also appear to assist in capture of bacteria, which may be seen connected to the cell surface by threads, possibly pulled out by adhesion to the sticky material of the glycostyles or their contents. Vesicles containing no particulate matter but lined with a well-formed coating identical with the surface coat and possibly transporting membrane to the surface may be rather large and somewhat flattened. The mitochondria are of the usual type in amoebae, usually oval or elliptical, occasionally sausage-shaped, with tubular, anastomosing cristae. The maximum length measured was 0.8 um. No more than one Golgi body was found per cell, made up of about eight flattened, closely packed sacs or layers of sacs, with an over-all diameter slightly more or less than 1 um. All seen were close to the nucleus. The rough endoplasmic reticulum was in the form of small vesicles or flattened cisternae, some nearly 2 um long. The pseudopodia contained distinct longitudinal filaments. In some very narrow parts of pseudopodia, presumably at some distance from the cell mass, these filaments were distributed across the breadth of the pseudopodium. In the broader basal region of the pseudopodium they formed a core which might extend some distance into the cell mass. The pseudopodia seen in section probably were those of floating forms. The fine structure of the nuclei did not appear in any way unusual. (ref. ID; 2093)
• Cyst: No cysts have been found. (ref. ID; 2093)