Paraflabellula

1. Paraflabellula hoguae (Sawyer, 1975) (ref. ID; 7710) reported author and year? (ref. ID; 7077)
2. Paraflabellula kudoi (Singh & Hanumaiah, 1979) n. comb. (ref. ID; 7710)
3. Paraflabellula reniformis (Schmoller, 1964) (ref. ID; 7710) reported author and year? (ref. ID; 7077)

Paraflabellula reniformis (Schmoller, 1964) (ref. ID; 7710) reported author and year? (ref. ID; 7077)

Descriptions

• Light microscopy: The locomotive form was typically flattened and flabellate. There was a well-developed anterior hyaline zone, often nearly half the total length of the amoeba, with an irregularly serrate anterior edge. The posterior region was densely granular, frequently with pronounced trailing filaments. The hyaloplasm often extended around the sides of the granuloplasm. The locomotive rates of ten amoebae (temperature 22 degrees C) were 18-42 um per min, or 0.8-1.9 times the length of the amoebae from a 7-day culture. The cell could change shape quickly, generally correlated with the speed of the amoeba. When advancing rapidly, the amoeba spread out in an oval with the breadth up to twice the length. If the speed decreased, the shape might transform to a triangular outline with the apex posterior. As the rate of locomotion decreased, the elongation could continue until a limax-like form was reached, with the length up to about twice the breadth. The anterior hyaline zone advanced in broad, wave-like eruptions which could involve up to one-third of the anterior edge. Superimposed upon these waves could be seen subpseudopodia with a basal diameter about 1 um and a length up to 4 um, tapering toward the tip but never sharply pointed or furcate. These subpseudopodia were most numerous when the amoeba was advancing rapidly, with a number up to about ten, originating not only from the anterior edge but also from the upper side of the hyaloplasm. The advancing edge of the amoeba overtook the subpseudopodia, often by filling in the space between them, and they never passed posteriorly to become uroidal filaments. Besides many small granules, the granuloplasm contained food vacuoles (digestive vesicles), each with a few bacteria, and some small, clear vesicles which were not seen to empty. The use of polarisers did not disclose any optically active inclusions. The nucleus was located in the anterior part of the granuloplasm, its quite distinct nucleolus surrounded by a clear, not very sharply defined space without a conspicuous limiting membrane. Both nucleus and nucleolus were spherical. Two amoebae of 25 (8 per cent) were binucleate. Page (1971) reported 3.5 per cent of Flabellula citata and 12.2 per cent of F. calkinsi to have supernumerary nuclei; most of these were binucleate. Uroidal filaments were formed by focal contacts of the cell surface with the substratum and might be drawn out to a length as long as or longer than that of the main cell mass. Several filaments were present at any one time and could originate from anywhere behind the anterior edge of the hyaloplasm but occurred most commonly as a tail from the posterior end of a fan-shaped amoeba. A uroidal filaments sometimes branched. The development of a bundle of uroidal filaments was often as follows: An amoeba which was advancing rapidly and thus had a broad hyaline zone suddenly slowed down and proceeded at an angle of nearly 90 degees to the original direction. During the re-organisation of the hyaloplasm and the granuloplasm, that part of the hyaloplasm located where a new posterior end would be formed adhered to the substratum, providing a fixed point around which the amoeba turned. The larger part of the original hyaloplasm went to the new anterior end of the amoeba, but the smaller part, which was attached to the substratum, was drawn out as the amoeba advanced, forming a bundle of filaments. If the speed of the amoeba increased, the filaments, loosened from the substratum, often recoiled and were drawn back into the granular cytoplasm. Such adhesive uroidal filaments also occur on Flabellula citata (Page 1971), where they are perhaps not quite so conspicuous. The floating form of the amoebae, formed on suspension in liquid, had a few to many radiate pseudopodia, whose length was three to five times the diameter of the rounded central mass. Each pseudopodium tapered to a fine tip. Measurements of ten floating forms from a 21-day culture were: diameter of central mass 5.2-12.9 um, mean 9.4 um; number of pseudopodia 2-11, mean 7; length of longest pseudopodium, 14.3-39.9 um, mean 27.1 um. The process of settling to the substratum could be observed in detail with the inverted microscope. Some amoebae attained the locomotive form quickly, but after four to five hours many were still in the floating form. This was in contrast to Flabellula citata, which could settle very quickly, often within five min. When an amoeba settled, it still had the stellate form, and withdrawal of the pseudopodia took up to five min. An imprint of a amorphous substance showing the stellate form of the amoeba when it first touched the substratum was regularly seen after the amoeba had moved away. When the locomotive form had been organised, an imprint of the same amorphous substance could be recognised where a uroid was formed but not outside the uroidal region. Such imprints were never seen when F. citata had settled. No convincing cysts or remnants of cysts were seen, a point to which attention was given because of the observations of Sawyer (1975) on pseudocysts of the similar Flabellula hoguae Sawyer, 1975. Amongst the stellate floating forms were many spheres containing granular cytoplasm and often also a nucleus. These spheres never transformed to locomotive forms. That they represented a dying stage could be seen by an increase in the proportion of such cells after 10-15 hr in the observation chamber. After 24 hr all amoebae in a chamber had transformed to spheres, in which Brownian movement, an indication of death, was observed. The viability of such spheres was investigated by isolating ten (diameter 6.9-12.7 um, mean 9.3 um), just washed from an agar plate, onto Cerophyl/seawater agar. As a control, ten single amoebae of normal locomotive form were isolated at the same time. After six weeks, no growth had occurred on any of the plates inoculated with spheres, but new clones had appeared on six of the ten plates inoculated with locomotive forms. When Flabellula citata was placed into such a chamber for observation with the inverted microscope, amoebae in great numbers and in the active locomotive form could be found for more than a week. (ref. ID; 7710)
• Electron microscopy: The cell coat outside the plasma membrane was very thin, ca. 5 nm or less in thickness, and only at high magnifications did it appear to consist in part of obscure blister-like elevations. No further surface differentiations were visible in amoebae fixed with the glutaraldehyde/OsO4 mixture in an ice bath. However, amoebae fixed with glutaraldehyde at 20 degrees C had peripheral lenticular bodies, just below the plasma membrane, resembling the collosomes of Rhizamoeba saxonica (Page 1980), though not as numerous. Amongst the larger cytoplasmic inclusions were mitochondria, digestive vesicles, and bacteria. Sausage-shaped mitochondria were up to approximately 1.5 um long; the more common elliptical profiles were about 0.8 or 0.9 um long. These had the usual tubular, branched cristae. Digestive vesicles were commonly small, their contents when identifiable consisting of one or two bacteria, though larger vesicles with more bacteria were sometimes found. Most sections contained few to many bacteria not enclosed in cytoplasm membranes. Their presence and the slow growth of cultures on agar of different salinities (ca. 17.0-25.5 0/00) suggested that a bacterial infection, rather than unsuitable salinity, might account for the low rate of multiplication. Similar infections have been observed in other species of amoebae, with indications of a retarding effect on population growth (Page 1980). The Golgi system consisted of numerous dictyosomes made up of four to five flattened saccules each, with a maximum width up to 0.6 um across the dictyosome. These bodies had no constant location and often occurred in groups of two or more. As many as nine were found in a section of only part of a cell. This large number of Golgi bodies may be connected with the conspicuous deposit of an amorphous substance on the substratum after the amoeba has settled, as described above in the light-microscopical observations. This relationship is suggested by the fact that the cell coat observed with the electron microscope is very thin though the Golgi system is generally associated with the secretion of such coats. The rough endoplasmic reticulum was also conspicuous, especially as flattened tracts sometimes more than 2.5 um long, though many small vesicles were also studded with ribosomes. Other small vesicles were sometimes concentrated along parts of the cell periphery, as in Flabellula citata (Page, 1980). While small groups of short filaments could sometimes be found in the cytoplasm, larger and longer tracts of fibrillar material were especially noticeable. A few longitudinal sections through the anterior hyaloplasm showed that these tracts extended far back into the hyaline lobopodium and forward into the short subpseudopodium. In some cases, as central subpseudopodium in Fig.9, the course of the fibrillar tract could not be traced at the level of sectioning all the way into the subpseudopodium. Such tracts were longer, thicker, and therefore more conspicuous in sections of floating forms, one of which is seen in Fig.10. The orientation of the tracts even deep within the cell in that figure suggest the directions of floating pseudopodia. Sections of pseudopodia of several floating forms contained similar longitudinally orientated material. Even in amoebae fixed with the appropriate glutaraldehyde procedure, neither cytoplasmic microtubules nor complex centriole-like bodies resembling those of the Acanthamoebidae (Bowers and Korn 1968; Page 1981) were found. The nucleus was highly irregular in shape, its envelope not supported by any internal fibrous lamina. The nucleolus, rather than being more or less homogenous and compact as in many small amoebae, had a looser appearance characterised by dense patches against a background not differing greatly from the general nucleoplasm. This appearance resembles that reported for Flabellula citata and Rhizamoeba saxonica (Page 1980) and some nuclei of Flabellula calkinsi (Page 1980), Acanthamoeba castellanii (Bowers and Korn 1968), and Protacanthamoeba caledonica (Page 1981). (ref. ID; 7710)

Examined materials