Paramecium O. F. Muller, 1773 , , ,
Synonym; Paramaecium O. F. Muller (ref. ID; 1618)

[ref. ID; 2014]
Medium- to large sized ciliate (120-300 um long), ovoid, elongate, foot- or cigar-shaped. The anterior end may be rounded or obliquely truncated and the posterior rounded or conical. The shape is rather asymmetrical due to the presence of an oblique depression, the oral groove, running from the apex of the cell to about the middle of the body on the ventral surface. The oral aperture is located at the posterior end of the oral groove. While the oral groove is prominent and easily seen the aperture is rarely visible without staining the cell with silver. Inside the buccal cavity there is a comparatively small undulating membrane on the right and 2 membranelles called peniculi lying alongside each other. Membranelle M3 comprise four rows of kinetosomes which diverge centrally to form a structure known as a quadrulus. Somatic ciliation is complete and uniform with 1, 2 or 3 hexagonal units. There are both pre- and post-oral sutures and trichocysts present. 1 to many (commonly 2) contractile vacuoles present which may be served by radiating canals. Cytoproct on the ventral surface located sub-orally. Macronucleus ovoid to reniform in shape, usually centrally located with variable number of micronuclei close by. Locomotion characteristically vigorous and spiralling anticlockwise. Wenrich (1928). The species of Paramecium are still in a state of flux. The classical species P. aurelia has recently been subdivided into 14 sibling species by Sonneborn (1975) and Gates, Powelson and Berger (1974) and Gates and Berger (1976) have discussed the morphological separation of these species. Vivier (1974) also reviews the classically named species.
Quote; Colin R. Curds, Michael A. Gates and David McL. Roberts "British and other freshwater ciliated protozoa Part II Ciliophora: Oligohymenophora and Polyhymenophora" Cambridge University Press, 1983 (ref. ID; 2014)

[ref. ID; 7435]
The molecular diversity within the D2 domain of the 23S ribosomal RNA molecules of Paramecium. (ref. ID; 7435)


Paramecium aurelia Ehrenberg, 1838 (ref. ID; 1335, 1622, 1629, 2245) or 1848 (ref. ID; 3116) reported year? (ref. ID; 1618)
Syn; Paramecium aurelia Dujardin, 1841
Description; Two small vesicular micronuclei, a massive macronucleus; two contractile vacuoles on aboral surface; posterior end more rounded that P. caudatum; in fresh water. (ref. ID; 1618)
Measurements; 120-180 um long. (ref. ID; 1618)
Paramecium bursaria Ehrenberg (ref. ID; 1219, 1618) or (Ehrenberg, 1831) Focke, 1836 (ref. ID; 4611), (Ehrenberg) Focker, 1836 (ref. ID; 1335, 1622, 1629, 2245), (Ehrenberg) Focker, 1843 (ref. ID; 3116) reported author and year? (ref. ID; 3292)
Syn; Loxodes bursaria Ehrenberg, 1831 (ref. ID; 4611)
Description; Foot-shaped, more or less flattened; uniform ciliation except for a group of long caudal cilia; green with symbiotic zoochlorellae; a long broad vestibulum leads to the buccal cavity, the buccal ciliary apparatus is characterized by 2 "peniculi"; 1 compact micronucleus; 2 contractile vacuoles; numerous prominent trichocysts. (ref. ID; 1219)
Foot-shaped, somewhat compressed; green with zoochlorellae as symbionts; a compact micronucleus; a macronucleus; two contractile vacuoles; in fresh water. (ref. ID; 1618)
Measurements; Length 180-300 um. (ref. ID; 1219)
About 100-150 by 50-60 um. (ref. ID; 1618)
Paramecium calkinsi Woodruff, 1921 (ref. ID; 1335, 1622, 4611, 7399) reported year? (ref. ID; 1618)
Description; Foot-shaped; posterior end broadly rounded; two vesicular micronuclei; two contractile vacuoles; in fresh, brackish and salt water. (ref. ID; 1618)
Measurements; 100-150 by 50 um. (ref. ID; 1618)
Paramecium caudatum Ehrenberg, 1833 (ref. ID; 4488, 4611) or 1838 (ref. ID; 1219, 1622, 1629, 2245, 3116) reported year? (ref. ID; 1618, 3342, 3698, 5462) reported author and year? (ref. ID; 3292, 4064)
Syn; Paramecium aurelia O. F. Muller, 1786 (ref. ID; 1622)
Description; Cigar-shaped, posterior end bluntly pointed and with a group of long cilia, ciliation otherwise uniform; vestibulum long and slightly oblique; buccal cavity with one endoral membrane and 2 peniculi; 1 ellipsoid macronucleus and 1 compact micronucleus; 2 contractile vacuoles, each with radial canals, near the aboral surface, numerous trichocysts, which may discharge explosively, all over the body. (ref. ID; 1219)
With a compact micronucleus, a massive macronucleus; two contractile vacuoles on aboral surface; posterior end bluntly pointed; in fresh water. The most widely distributed species. (ref. ID; 1618)
Measurements; Length 90-150 um. (ref. ID; 1219)
180-300 um long. (ref. ID; 1618)
180-260 x 40-50 um. (ref. ID; 3342)
Paramecium duboscqui Chatton & Brachon, 1933 (ref. ID; 7399 redescribed paper) reported author and year? (ref. ID; 4830, 4903)
Description; The body shape with its rounded posterior end and broad anterior part is of the "bursaria type" (Wichterman 1986). The oral groove is broad and oblique, and the anterior-right part of the body extends and twists to the ventral side, so that the whole body is kidney-shaped in lateral view when the animal is moderately starved. The body surface is uniformly ciliated except for the three or four long caudal cilia at the posterior end. The body length of 30 randomly chosen, fixed specimens ranged from 80 to 150 um. (ref. ID; 7399)
[Argentophilic structures]: In silver-impregnated specimens, the pellicular pattern forms hexagons over most of the body surface. Rhomboids are restricted to the left side of the preoral suture, and quadrilaterals are restricted to both sides of the postoral suture and the right side of the preoral suture. The preoral suture, an argyrophilic line, forms a bow-shaped curve to the organisms left. The cytoproct occupies the posterior half of the postoral suture. Two contractile vacuole pores, one for each contractile vacuole, are visible on the dorsal surface. (ref. ID; 7399)
[Buccal apparatus]: The vestibulum is shallow and ends in the middle or a little above the middle of the body at the buccal overture. The endoral membrane lies along the entire right edge of the buccal overture, but from its origin to its middle, the endoral dikinetids are zig-zag or single file. From the middle to the end, the kinetosomes of the dikinetids are side by side. The anarchic field is clearly visible at the right of the posterior end of the endoral membrane. Two peniculi lie on the left wall of the buccal cavity; each contains four rows of kinetosomes. The posterior end of the dorsal peniculus does not turn to the ventral and right side although that of the quadrules does. (ref. ID; 7399)
[Stomatogenesis]: During cell fission, as in other species of Paramecium, the buccal pouch for the future opisthe originates from the anarchic field and the inner portion of the right wall of the vestibulum. Three nascent membranelles extend out of the vestibulum and lie on the somatic pellicle at the right of the postoral suture. After the new buccal cavity separates from the old, the two buccal apparatuses are juxtaposed. This stomatogenesis strongly resembles that of P. bursaria (Shi 1980). (ref. ID; 7399)
[Nuclear morphology]: One ellipsoid macronucleus is present just above the center of the cell. In protargol-stained interphase cells, the nucleoli in the macronucleus often aggregates into a coarse network. This network is identified as nucleolar because it stains as nucleoli do in other ciliate species not as microtubules or other supporting structures do. The number of micronuclei range from zero to six, but two micronuclei are usual. Of 1,000 cells from 10 stocks examined, 685 (68%) had two micronuclei. Micronuclei in interphase are vesicular and shaped like long spindles (ca. 5.1 um x 1.2 um in hematoxylin preparations and ca. 10.2 um x 3.2 um in protargol preparations. (ref. ID; 7399)
[Mating types]: By mixing evey two combinations among 46 stocks collected from the same place, only two mating types have so far been detected. They are designated as syngen 1 in this species. This is the first report of conjugation in this species. Whether there were other mating types and syngens in collections from other locations remain to be studied. (ref. ID; 7399)
[Trichocysts]: The subpellicular trichocysts are perpendicular to the surface and appear more conspicuous than in other species. In protargol preparations, the main body of the trichocyst is rather thick, and its width is nearly equal to one half of its length. The length of the tip is about two-fifths that of the main body. (ref. ID; 7399)
[Contractile vacuoles]: Both contractile vacuoles are vesicle-fed. Immediately after systole the vesicles expand. At diastole, fibrils supporting the walls of the contractile vacuole are visible in the living ciliate. Probably these correspond to the tracts of microtubules that spiral around the wall of the contractile vacuole in other species of Paramecium. (ref. ID; 7399)
[Swimming behavior]: In contrast to all other species of Paramecium except P. calkinsi, this ciliate characteristically spirals to the right on its long axis (clockwise) when swimming. There are two spiraling modes in swimming, and extremely narrow spiral at greatest speeds and a long spiral at average speeds. These figures indicate that the forward progress of P. duboscqui when it is swimming fastest may be slower than its forward progress when it is swimming at slower speeds. (ref. ID; 7399)
Remarks; Chatton and Brachon (1933) reported that they collected their strain from a sewer in Banyuls-sur-Mer in January and April in 1933. The collecting seasons and the habitats of the two strains are so similar that the phenomenon cannot be considered as accidental. The temperature of sewer water in winter and early spring in France should be at its lowest for the year. It thus seems clear that the French strain of P. duboscqui must also be adapted to lower temperatures. At least two species of Paramecium of the bursalia group, Paramecium polycaryum and Paramecium woodruffi, are rarely found, although P. polycaryum is worldwide in distribution. Paramecium duboscqui may not be a rare species at all. Its absence from collections may reflect the fact that fewer collections of protozoa are made in the wintertime. Paramecium duboscqui clearly belongs to the bursaria group based on its nearly body-shape, i.e. the truncated anterior end, the rounded posterior end, the dorso-ventral flattening, the terminal cytoproct, and the pattern of stomatogenesis (Shi 1980). Its characteristics led the authors to the conclusion that Woodruff (1921) is fully correct in his classification of the species of Paramecium into "aurelia" and "bursaria" groups. They are really two natural groups formed in the long proccess of phylogeny in Paramecium. The twist of the anterior body of P. duboscqui and its reniform outline in lateral view are unique among the species of the bursaria group. Swimming in a right spiral is a characteristic shared only by P. calkinsi. In its contractile vacuole structure, P. duboscqui resembles P. trichium, which also has vesicle-fed contractile vacuoles. These are the only species of Paramecium that lack collecting canals. Paramecium trichium also has an unusual nucleolar structure, not like that of P. duboscqui, but nucleoli "pocketed" in the surface of the macronucleus. This species is the smallest in the genus, but some strains are large enough to overlap with P. duboscqui size range. It has a subcylindrical body, a single micronucleus, and a complex mating system. The morphological and breeding differences between these two species are significant enough to separated them. The right spiral swimming of P. calkinsi is a characteristic shared by P. duboscqui, but P. calkinsi has a buccal overture below the center of the body, compared to P. duboscqui buccal overture at or above the midline. It is euryhaline and can be found in freshwater ponds as well as marine tide pools. The breeding system of P. duboscqui, one syngen and two mating types, is like those of P. polycaryum and P. woodruffi, but more collections and breeding studies of these three species may well turn up other syngens as it did in P. calkinsi. It seems unlikely, however, that the breeding systems in these species will ever approach the complexity of the breeding systems of P. bursaria and P. trichium with their many syngens and multiple mating types. (ref. ID; 7399)
Temperature restrictions; Many collections from Majia Ditch were made year round for 14 years. Winter in Harbin is from November to March, and the water temperature in the shallow water at the edge of the ditch drops below 10 degrees C. Paramecium duboscqui was collected only at these temperatures. It was collected frequently during winter, but when water temperature rose to 15 degrees C, it disappeared. Where it summers is unknown, and even in winter, it did not appear in collections from other sites. (ref. ID; 7399)
Type locality; Collected from running water in Majia Ditch, Harbin, China, the overall length of which is more than 30 km. Industrially polluted water and domestic sewage drain into its upper reaches, and it empties into the Songhua Riber in Harbin city proper. (ref. ID; 7399)
Type materials; The slides of the type-specimens and the living strains are preserved in the Laboratory of Protozoology in Harbin Normal University. (ref. ID; 7399)
Paramecium jenningsi Diller & Earl, 1958 (ref. ID; 1618) reported author and year? (ref. ID; 3813, 4064)
Description; Resembles P. aurelia in general morphology; two micronuclei larger than those of P. aurelia; macronuclear anlagen with long persisting chromatinic centers. (ref. ID; 1618)
Measurements; 115-218 um long. (ref. ID; 1618)
Paramecium multimicronucleatum Powers & Mitchell, 1910 (ref. ID; 1335, 1622) reported year? (ref. ID; 1618) reported author and year? (ref. ID; 3292, 3990)
Description; 3-7 contractile vacuoles; four or more vesicular micronuclei; a single macronucleus; in fresh water. (ref. ID; 1618)
The somatic kinetosomes, single or double, appear as small dark granules; issuing from them is a kinetodesmal (Kd) fiber that runs anteriorly and to the right of the kinety, overlapping with more anteriorly located fibers to form a single kinetosomes are more closely spaced and the kinetodesmata are thicker by virtue of being formed by a larger number of overlapping Kd fibers. (ref. ID; 3990)
Measurements; The largest species, 200-330 um long. (ref. ID; 1618)
Paramecium nephridiatum V. Gelei, 1925 (ref. ID; 1622, 4903, 7486)
Description; The cell shape with its rounded posterior end, and broad anterior part is of the "bursaria" type (Wichterman 1986) or "woodruffi" type according to Jankowski (1969). The oral opening is situated a little anterior to the middle of the cell. The cell surface is uniformly ciliated except for several long caudal cilia located close to the posterior end of the dorsal side, but not on the top. The abundant subpellicular trichocysts are distributed uniformly. Specimens were about 145 x 47 um long in vivo but shrank 10% after the silver nitrate impregnation. In silver-impregnated specimens, there were ~ 38 rows of ventral kineties and ~ 35 dorsal kineties. The preoral suture is distinct, but the postoral suture is very obscure. The cytoproct is situated in the posterior third. The vestibular zone is conspicuous and is terminated by the distinctive shape of the buccal opening. Two peniculi and open quadrulus are located on the dorsal and left wall of the buccal cavity. The endoral membrane is situated along the entire right edge of the buccal opening but its dikinetids are not recognizable in all specimens. It has 15 dikinetids on the average. The buccal cavity size various around 30 um. On the dorsal side of the body the contractile vacuole pores are very distinctive both on impregnated specimens as well as in living cells. Usually, both contractile vacuoles have more than one pore each, typically two or three. However, we have found two stocks (WCh-1 and WS-12) where one of the contractile vacuoles quite often (up to 50% ) had only one pore. Both contractile vacuoles usually have 8-14 collecting canals, ten on average. Numerous crystals were very often found in the cytoplasm, but their quantity and location varied, probably depending on the culture conditions. During cell division, the anterior daughter cell (proter) more closely resembled the maternal cell than the opisthe which, at first, looks highly similar to some other peniculines. The nuclear apparatus is located in the anterior part of the cell. One slightly ellipsoid or ovoid macronucleus, ~ 30 x 36 um in living cell and ~ 17 x 23 um in stained cells, on average, resides just anterior to the equator of the cell. In Feulgen-stained cells the macronucleus has a very intense colour. The three to four spherical micronuclei of the "endosomal" type (Fokin 1997), ~ 3 um in diam. (on average) are distributed irregularly along the anterior part of cell. Endocytobiotic bacteria are often found in the cytoplasm (Fokin 1989) and can also be found in the perinuclear space and in the macronucleus (Fokin 1989, Fokin and Sabaneyeva 1997). The species is characterized by a binary mating type system. Using more than 20 stocks from different localities, two unambiguous mating types have been detected. The old macronucleus fragments before the separation of the conjugants. The new macronuclear anlagen are four in number. Selfing in stock cultures takes place on rare occasions. (ref. ID; 7486)
Swimming behavior; During swimming this species spirals on its long axis in both directions (Fokin 1987). We could no find any simple triggers (food, time) for changing this swimming direction. Typically, "left spiral swimmers" and "right spiral swimmers" were present at the same time in the culture. During the several years of investigation of this trait there was some preference of the cells from the same stocks to spiral in the left direction. (ref. ID; 7486)
Remarks; Gelei (1925) described a new species of Paramecium, Paramecium nephridiatum, based on the material which he had found in his laboratory aquarium. This population was in fact a mixture of the new species and Paramecium caudatum (Gelei 1938). This was the reason why some features of the new ciliate were similar to P. caudatum so that no one recognized this new species in nature, though reference to P. nephridiatum was made by Kahl (1931) and Kalmus (1931). Gelei (1938) redescribed the species from a native population (Tisza River, Szeged, Hungary) using a "clean culture". For unknown reasons, this new description did not attract the attention of protozoologists and in all subsequent reviews, P. nephridiatum was considered a nonvalid species (Vivier 1974; Wichterman 1953, 1986) even when the article of Gelei (1938) was listed in the references. Only once was P. nephridiatum mentioned in a short abstract as a species living in Florida, USA (Bovee 1983), although characters of the species were not listed in this publication. Since 1983, one of us (S. F) has repeatedly collected a species of Paramecium with multiple contactile vacuole pores, which is a distinctive trait of P. nephridiatum, although it was considered for a time as a feature of Paramecium woodruffi (Agamaliev 1983; Fokin 1986), Jankowski (pers. commun.). (ref. ID; 7486)
Occurrence and ecology; A number of stocks of P. nephridiatum were isolated from the sea shores of northern Europe: the North, Baltic, White, and Barents Sea coasts. It was detected during sampling in Woods Hole, MA, USA, Atlantic Ocean and on Sakhalin Island, Sea of Okhotsk. The salinity of these samples varied from 1.5-32 o/oo. The species was also found in a fresh-water body in Jerusalem Zoo, Israel. Samples were taken mainly during the summer, from mid-April (Wood Hole) to November (North Sea coast). Sampling of the same wild population of P. nephridiatum (Sredny Island, White Sea, Russia) has been repeated every year since 1990 to observe long-time changes in the population, as well as the euryhaline ability of the species. This population, as well as the euryhaline abiliy of the species. This population was present at salinities from 4-35 o/oo and in the temperature range from 10-25 degrees C. Very often the populations of P. nephridiatum occurred at the lower limit of oxgen concentrations. They were mainly feeding on bacteria. In the same samples these other ciliates were usually found: Prorodon sp., Frontonia marina, Metopus sp., P. calkinsi, P. woodruffi, and sometimes P. duboscqui. (ref. ID; 7486)
Paramecium polycaryum Woodruff, 1923 (ref. ID; 1335, 1622) reported year? (ref. ID; 1618), Woodruff & Spencer, 1923 (ref. ID; 7399) reported author and year? (ref. ID; 191, 4903)
Description; Form similar to P. bursaria; two contractile vacuoles; 3-8 vesicular micronuclei; in fresh water. (ref. ID; 1618)
Measurements; 70-110 um long. (ref. ID; 1618)
Paramecium putrinum Claparede & Lachmann, 1858 (ref. ID; 1622, 1629) 1859 (ref. ID; 4611) reported year? (ref. ID; 1219, 1618)
Description; Similar to P. bursaria but without zoochlorellae; macronucleus elongated, kidney-shaped; 1 micronucleus; only 1 contractile vacuole; no trichocysts (Lepsi, 1926; Kahl, 1930) Records of P. putrinum are scanty, and it is in fact doubtful whether the species is valid. This problem is of some saprobiological interest since Liebmann (1962) classified P. putrinum as a polysaprobic indicator organism. On the other hand, Sramek-Husek (1954) failed to find any specimens of P. putrinum during his saprobiological studies in Czehoslovakia; all representatives of the genus Paramecium that he found in the more heavily polluted zones were referable to P. trichium. Therefore, Sramek-Husek submitted that the polysaprobic "P. putrinum" of earlier authors is really P. trichium Stokes. P. putrinum sensu Liebmann has 2 contractile vacuoles, both shown with radial canals; P. putrinum sensu Liebmann was recorded from the sludge of polluted reservoirs, dammed rivers, lakes etc., in the upper zone of trickling filters, sewage drains, and in floating tufts of Sphaerotilus. Taxonomic studies of "P. putrinum" and P. trichium are thus urgently required. (ref. ID; 1219)
Similar to P. bursaria, but a single contractile vacuole and an elongated macronucleus; no zoochlorellae; in fresh water. (ref. ID; 1618)
Measurements; About 130 um long (ref. ID; 1219)
80-150 um long. (ref. ID; 1618)
Paramecium sonneborni Aufderheide, Daggett & Nerad, 1983 (ref. ID; 4061 original paper)
See; Paramecium aurelia complex
Description; [Body morphology]: The shape of the cell body from a cloned population of organisms grown at maximum rate at 27 degrees C is typical for that of the P. aurelia complex with the exception that the posterior end of most cells is pointed, bearing a superficial resemblance to Paramecium caudatum. Two contractile vacuole are present. (ref. ID; 4061)
[Nuclear morphology]: One macronucleus is present, ca. 70 um long, showing the prolate spheroid shape characteristic of all species of Paramecium. In interphase cells, the macronucleus is ventral and anterior to the oral apparatus, as is also usual with paramecia. Two vesicular micronuclei are consistently present. Many micronuclei show a concentric arrangement of the chromatin, while others have chromatin dispersed in a coarse reticulum. Twenty micronuclei examined in 12 living cells, using phase-contrast optics, have a mean diameter of 4.9 um (+/- 0.18 SE), with a range of 3.5-6.7 um. (ref. ID; 4061)
[Sexual behavior]: Both conjugation and autogamy have been observed, and two macronuclear anlagen are seen after fertilization. Two mating types have been identified. Mating-type determination appears to be karyonidal, although cytoplasmic determination has not been completely ruled out. Mating-reactive cells of this organism will not react with mating-reactive cells of any of the other 14 species assignable to the aurelia complex. These is no apparent diurnal cycle. (ref. ID; 4061)
[Further remarks]: The life expectancy of clones of our new species is relatively long compared to other species in the aurelia complex. Clones are viable for at least 250 generations. No endosymbionts have been detected in the species. (ref. ID; 4061)
Etymology; The new species has been named Paramecium sonneborni n. sp. in honor of the late Dr. Tracy M. Sonneborn of Indiana University. (ref. ID; 4061)
Type locality; College Station, Texas (Lat. 30 degrees 37'55''N, Long. 96 degrees 18'15''W). (ref. ID; 4061)
Type-specimens; Holotype and paratype slides (Nos. USNM31926 and 31927) have been deposited in the Ciliate Type Slide Collection, Smithsonian Institution, Washington, D.C. Paratype specimens remain in the collection of the senior author. (ref. ID; 4061)
Type culture; Paramecium sonneborni stock TAMU:0580:1 ATCC 30995) (ref. ID; 4061)
Measurements; Maximum body length of 26 fixed, silver-impregnated specimens ranged from 130 to 186 um, with a mean length of 154.4 um (+/- 2.9 SE). Maximum body width of the 26 cells ranged from 39 to 64 um, with a mean width of 50.3 um (+/- 1.3 SE). (ref. ID; 4061)
Paramecium trichium Stokes, 1885 (ref. ID; 1335, 1622, 2245, 7399) reported year? (ref. ID; 1219, 1618, 3342, 3698) reported author and year? (ref. ID; 191, 646, 7447)
Description; Body shape highly variable, more or less ellipsoid, somewhat flattened; ciliation uniform except for a group of long caudal cilia; vestibulum and buccal equipment similar to those of P. bursaria; 1 macronucleus; 1 compact micronucleus; 2 contractile vacuole, each with a convoluted outlet; unlike other members of its genus, P. trichium has a contractile vacuole without radial canals but with tributary vacuoles; numerous trichocysts all over the body; posterior part of the body more or less filled with dark granules. According to Sramek-Husek (1954), P. pseudoputrinum Baumeister is referable to P. trichium. (ref. ID; 1219)
Oblong, somewhat compressed; a compact micronucleus; two contractile vacuoles deeply situated, each with a convoluted outlet; in fresh water. (ref. ID; 1618)
[Morphology of the non-dividing (morphostatic) cells]: Throughout this paper, the directions right and left will be described according to the definition of Ng and Frankel (1977) as ".., right and left refer to the observer's right and left, assuming that he stands inside the animal so that his anterior-posterior axis coincides with that of the animal, and keeps turning around his longitudinal axis to face the surface of the animal," unless otherwise indicated. (ref. ID; 7447)
Basal bodies: In the anterior 3/4 to 4/5 of the cell surface, almost all cortical units possessed two closely spaced basal bodies (2BB), while each unit of the remaining region included one basal body (1BB). These units, hereafter, will be called 2BB units and 1BB units, respectively. In the 1BB unit region, paired basal bodies were not usually observed, while 1BB unit were often sporadically distributed over the 2BB unit region. Each unit usually included one parasomal sac (Ps), although in several units Ps could not be detected by the Chatton-Lwoff method. (ref. ID; 7447)
Kinetodesmal fibers: Kinetodesmal (Kd) fibers arose close to the single basal body in 1BB units and to the posterior one of the paired basal bodies in 2BB units, and always extended forward and along the right side of the kinety. The Kd fiber of the 2BB unit was approximately 3-5 um in length, while their length in 1BB units tended to be slightly shorter than in 2BB units. (ref. ID; 7447)
Kineties: When a paramecium is observed from its anterior pole, kineties are numbered clockwise with reference to the postoral suture (PO). Kinety No. 1 (K1) has a few cortical units and extends rearward along the right side of PO from the posterior margin of the buccal cavity (BC); and enumeration of kineties proceeds to the cell's right (viewer's left). Thus, the kinety on the left side of PO is No. n (Kn), with n taking the value of the total number of kineties. There are two or three rows of single basal bodies in the slender narrow (SN) region lying between kinety No. 3 (K3) and the paroral membrane (PM), which is a file of 16 to 25 closely packed paired basal bodies. However, we could not determine whether they consisted of the same components as the other cortical units, and therefore were anterior portions of kinety No. 1 and 2, or not. Furthermore, there were two short kineties just anterior to the SN region. The left one of these included two or three 2BB units and the other included three or six 2BB units. We also could not determine whether these were K1 and K2. In some species of paramecia, a permanent anarchic field has been described in the comparable area (Frankel 1989, Hufnagel 1969, Patterson 1981). However, we could not find such a field in P. trichium. Twenty specimens is which almost all basal bodies could be traced in eight representative kineties from Kn-9 to Kn-16 were obtained by the Chatton-Lwoff method. The number of 2BB and 1BB units was examined in these representative eight kineties. In these kineties, the mean number (+/- SD) of 2BB, 1BB, and total units per kinety was 27.60 +/- 3.45 (range 18-38), 6.67 +/- 1.83 (3-12), and 34.27 +/- 3.85 (25-43) (n = 160 kineties) respectively, although each kinety tended to contain slightly more units that its right-hand neighbor. (ref. ID; 7447)
Polygonal cortical ridges: When deciliated paramecia were fixed with Parducz's fixative and were observed by scanning electron microscopy, their cell surfaces were seen to be covered with a regularly arranged meshwork of polygonal cortical ridges. Since a territory bounded by the polygonal cortical ridges was regarded as a cortical unit, longitudinal rows of these territories were considered to correspond to kineties. In these deciliated paramecia, one or two remnant stub(s) of cilium(a) existed in each depression area of the cortical units. In the ventral surface of a deciliated cell, the oral groove region was covered with cortical units containing two remnant stubs of cilia (2C), although the most anterior cortical unit of each kinety on the right side of preoral suture (PR) possessed only one remnant stub of cilium (1C). Since this region consisted of 2BB units, the units of the region will be called two cilia-bearing-basal-body units (2C-2BB unit). In contrast, the remainder of the cell surface was covered with cortical units containing only one remnant stub of cilium (1C). The posterior 1/4 to 1/5 of the cell surface was covered with 1BB units and the remainder consisted of 2BB units, so that these units could be named 1-cilium-1-basal-body (1C-1BB) just and 1-cilium-2-basal body (1C-2BB) units, respectively. Also, several non-ciliated cortical units were sporadically distributed in the one cilium unit region. In the 1C-2BB unit region, two-cilia units were sometimes observed in non-deciliated cells. For comparison with the results from the analyses of silver impregnated specimens, the number of two-cilia units, one-cilium units, no-cilium units, and total units per kinety were examined in eight representative kineties from Kn-9 to Kn-16. In these kineties, the mean number (+/- SD) of two-cilia, one-cilium, no-cilium, and total cortical units per kinety was 8.71 +/- 1.52 (range 5-13), 27.31 +/- 2.62 (20-34), 0.14 +/- 0.62 (0-4) and 36.16 +/- 2.32 (29-42) (n = 160 kineties), respectively. (ref. ID; 7447)
[Reorganization of cortical structures during cell division]: The reorganization of cortical structures during cell division could be classified for convenience into five stages according to morphological characters.
Stage 1. When the cell surface was observed by scanning electron microscopy, appearance of a bare area was the first recognizable sign of morphogenetic events prior to cytokinesis. This unciliated, relatively flattened, area is located just posterior to the oral apparatus. This area formed as a result of the disappearance of cilia and polygonal cortical ridges in the posterior parts of kineties from K1 to K6, although we could not determine whether the cilia are resorbed into the cytoplasm or detached from the cell surface. On the other hand, in cells stained by the Chatton-Lwoff method, proliferation of basal bodies in the posterior part of SN region was the first visible morphogenetic event. Subsequently, in the posterior portion of K3 to K6, boundaries of cortical units gradually became obscure, and basal bodies rapidly proliferated. These basal bodies formed a long slender anarchic field parallel to the longitudinal axis of the cell. However, we could not determine whether these basal bodies of the anarchic field bore cilia or not, and also could not clarify the timing and spatial relationships between the sequential morphogenetic events visualized by the silver impregnation technique and the appearance of the bare area observed by scanning electron microscope. (ref. ID; 7447)
Stage 2. In the fully extended anarchic field, basal bodies were progressively arranged in the three files from the posterior end to the anterior end of the field as well as from the right side to the left side of the field. Each of the files was made up to four longitudinal rows of basal bodies. Of these, the right-most file was a primordium of the quadrulus and the remaining two were those of peniculi of the prospective posterior daughter cell. Since the deciliation technique used in this study could not detach the cilia of the anarchic field, it was found by scanning electron microscopic observation of deciliated cells that most, if not all, basal bodies of the oral primordium bore cilia at this stage. The beginning of fission line formation is another remarkable morphogenetic event of this stage. In each of several 1C-2BB units located along the equatorial right ventral region near the oral primordium, pre-existing Kd fibers were shortened and a new basal body was added just anterior to the paired basal bodies. In some species of paramecia, it has been reported that all old Kd fibers are resorbed and entirely new ones are formed prior to cytokineties (Fernandez-Galiano 1978, Iftode et al. 1989). However, in P. trichium we could not observe such a resorption of old Kd fibers. The fission line began to be formed as a discontinuity between such morphologically changed cortical units and unchanged units anterior to these altered units in each of kineties. The zone of discontinuity appeared at the right anterior region of the oral primordium. Then fission line formation rapidly progressed clockwise when the paramecium was observed from its apical pole. With the progression of fission line formation, a shortening of the preexisting Kd fiber and an addition of a basal body immediately anterior to the paired basal bodies occurred in cortical units that were located in the 1C-2BB region posterior to the fission line. Late in this stage, the triplet basal bodies of each cortical unit began to separate from each other and a new short Kd fiber appeared in each of the anterior two basal bodies of the unit. These sequential morphogenetic events progressed toward the posterior from the fission line as well as to the right side from the PO. By the end of this stage, the posterior margin of this morphogenetically changing area reached approximately to the middle of the 1C-2BB region, located to the right of the PO. In the remainder of the cell surface, visible morphogenetic changes had not yet occurred at the end of this stage. (ref. ID; 7447)
Stage 3. The formation of a second fission line was one of the most remarkable aspects in this stage. The second fission line appeared as a discontinuity in each kinety, formed in the same manner as the first fission line, along the equatorial zone of the cell surface region to the left of the oral primordium. The disruption of kineties sequentially propagated to the left from the Kn: the formation of this fission line progressed counterclockwise when the paramecium was observed from the apical pole of the cell. This fission line encountered the first one on the dorsal surface, and they then joined to become a single fission line. As a result, the region anterior to the fission line became the cell surface of the prospective anterior daughter cell, while the region posterior to the fission line became the prospective posterior daughter cell. Gillies and Hanson (1968) noted that "the fission line appears at the (cell's) left posterior end of the (oral) anlage and during stage III develops around the cell, passing dorsally and then returning ventrally to the (cell's) right anterior side of the anlage." This mode of fission line formation was never observed in our paramecia. To determine whether preexisting cortical units were equally distributed to both presumptive daughter cell surfaces by the formation of the fission line, in Chatton-Lwoff silver-impregnated stage-3 cells the number of cortical units per kinety was examined in eight representative kineties from Kn-9 to Kn-16, comparable with those of vegetative morphostatic cells. The posterior daughter cell surface received, significantly, one or two more units than the anterior surface (t-test, p < 0.02). (ref. ID; 7447)
Stage 4. Formation of the new buccal cavity for the prospective posterior daughter cell and constriction of the fission furrow along the fission line began to occur at this stage. In the prospective posterior daughter cell, differentiation of three oral membranelles, the two peniculi and a quadrulus, for the new oral apparatus had been completed by this stage and these ciliated structures were arranged on the cell surface to the posterior right of the old mouth parts. Then, a slit-like bare area appeared between the right most membranelle and an anarchic strip that consisted of many basal bodies randomly and closely distributed, located the right side of the membranelles. Subsequently, this bare are began to invaginate from the cell surface while extending in area. With the development of the buccal cavity (BC), the three membranelles sank and migrated to their final position along the left wall of the cavity. A new paroral membrane (PM) was differentiated at the left edge of the anarchic strip during the final stage of the BC formation. Another remarkable morphogenetic property of this stage was the appearance of cytospindle-like structures (Cohen and Beisson 1988, Cohen et al. 1982, Delgado et al. 1990, Fleury and Laurent 1995, Frankel 1989, Iftode et al. 1989, Jerka-Dziadosz et al. 1992), which could only be visualized by the Fernandez-Galiano method. They appeared as discontinuous wavy lines in the spaces between kineties early during this stage. Then, the developed to continuous wavy lines by the end of this stage. (ref. ID; 7447)
Stage 5. The morphogenetic events of the prospective posterior daughter cell surface were almost completed except for a new PR formation by the start of this stage. In the prospective anterior daughter cell surface the remaining morphogenetic events progressed rapidly from the fission furrow to the anterior pole of the cell and were completed by the end of this stage. Furthermore, in the 2C-2BB unit region the Kd fiber of each unit extended again to its final length without either proliferation of units or new cortical-component formation. With the progression of these morphogenetic events, the contractile ring rapidly contracted and finally divided the mother cell to two newborn daughter cells. (ref. ID; 7447)
Examined material; Clone 4B-1 (mating type IV) of the ciliate Paramecium trichium. This clone, which was esatblihsed in January 1991, is one of the F1 progeny of a crossbetween stocks OM4(IV) and MMB(III), which were kinely provided by Dr. Toshikazu Kosaka, Hirosima University. The clone 4B-1 was sexually mature and did not show any sign of senility during the course of this work. (ref. ID; 7447)
Measurements; Length 50-120 um. (ref. ID; 1219)
50-105 (80-90) um long. (ref. ID; 1618)
80-110 x 45-60 um. (ref. ID; 3342)
Paramecium woodruffi Wenrich, 1928 (ref. ID; 1335, 1618, 1622, 4611, 7399) reported author and year? (ref. ID; 4903)
Description; Similar to P. polycaryum; two contractile vacuoles; 3-4 vesicular micronuclei; brackish water. (ref. ID; 1618)
Measurements; 150-210 um long. (ref. ID; 1618)