Urotricha Claparede & Lachmann, 1857 (ref. ID; 3540, 3690) or 1859 (ref. ID; 2013, 4298, 4613, 7243)
Class Kinetofragminophora: Subclass Gymnostomata: Order Prostomatida: Suborder Prorodontina: Family Prorodontidae (ref. ID; 2013)
Order Prostomatida: Family Prorodontidae (ref. ID; 4701)
Order Prorodontida: Family Urotrichidae (ref. ID; 7287)

Synonym Balanitozoon Stokes (ref. ID; 1618)

[ref. ID; 2013]
Body shape ovoid to spherical. Oral aperture apical, cytopharynx supported by trichites. Somatic cilia uniform but longitudinal kineties only extend part way down the cell so that the posterior body quarter is free from cilia with the exception of one or more caudal cilia. There are 1 or 2 circlets of double cilia surrounding the oral aperture (peribuccal cilia) and a dorsal brush consisting usually of 3 or 4 short lines of paired cilia. Macronucleus spherical to ovoid, usually centrally situated. One or more contractile vacuoles in the posterior cilia-free zone. Some species with trichocysts.
Quote; Colin R. Curds "British and other freshwater ciliated protozoa Part I Ciliophora: Kinetofragminophora" Cambridge University Press, 1982 (ref. ID; 2013)


Urotricha agilis Stokes, 1886 (ref. ID; 3540) reported year? (ref. ID; 1618, 1629, 3698) or (Stokes, 1886) Kahl, 1930 (ref. ID; 4488, 4611, 4613)
Syn; Balanitozoon agile Stokes, 1886 (ref. ID; 4611, 4613)
Description; Body small; swimming as well as leaping movement; standing fresh water with sphagnum. (ref. ID; 1618)
Measurements; Body about 15-20 um long. (ref. ID; 1618)
Urotricha armata Kahl, 1927 (ref. ID; 1335, 1619, 1629, 2316, 3540, 4611, 4613)
See; Urotricha platystoma (ref. ID; 4613)
Syn; Urotricha corlissiana Song Weibo & Wilbert, 1989 (ref. ID; 4611); Urotricha platystoma Stokes, 1886(?) (ref. ID; 1619, 3540)
Description; This organism 45 um in length matched the description of U. armata however the body shape was not as oval as Kahl (1927, 1930) and Dragesco (1960) described but was rather periform in shape, resembling U. synuraphaga Kahl, 1927. In all other respects it resembled U. armata including the possession of a caudal cilium. (ref. ID; 2316)
Urotricha cyrtonucleata Martin & Montagnes, 1993 (ref. ID; 7287 original paper) reported author and year? (ref. ID; 4613)
Diagnosis; The following diagnosis is based on observations of over 30 protargol-stained specimens from Indian Arm, B.C. Single elongate macronucleus positioned around oral cavity. Somatic infraciliature, 46-52 kineties that run from anterior to posterior part of cell. Circumoral ciliature, 32-36 oblique dikinetids. Three adoral organelles: AO1, two rows of 5-6 kinetosomes; AO2 and AO3, both two rows of 8-9 kinetosomes. (ref. ID; 7287)
Description; Cell ovoid, 45 um (38-53) long and 32 um (27-43) wide. Each somatic kinety consists of 35-40 monokinetids. Three somatic kineties do not extend completely to cell anterior, leaving a space anteriorly where 3 adoral organelles (AO1, AO2 and AO3) are located. These organelles comprise what was formerly known as the brosse. Pharyngeal fibers line oral cavity and run from entrance of oral cavity down ~1/4 of cell's length. Macronucleus extended length of 35-50 um. Posterior zone absent of ciliature except for ~3 caudal cilia. (ref. ID; 7287)
Generic position and comparison with related species; Morphological characteristics used to distinguish members of the genus Urotricha include number of somatic kineties; arrangement and number of kinetosomes forming the adoral organelles; number of short kineties behind the adoral organelles; peribuccal infraciliature; number of caudal cilia and macronuclear shape (Martin-Gonzalez et al., 1985). Kahl's review of the genus lacked silver-stained preparations, resulting in poor detail of infraciliature necessary for comparisons. Separation of the Indian Arm specimen from species described in the older literature relies on macronuclear shape differences alone. The elongate macronuclear of U. cyrtonucleata distinguishes it from the spherical and ovoid nuclei of all others in the genus. Many Urotricha species have since been described or redescribed using silver-staining techniques. Several species share characteristic similar to those of Urotricha cyrtonucleata with respect to size, shape and infraciliature: U. armata (Kahl, 1927) Dragesco et al., 1974, U. ovata Kahl, 1927, U. puytoraci Dragesco et al., 1974, U. faurei Dragesco et al., 1974, U. sphaerica Groliere, 1977, U. apsheronica Alekperov, 1984, and U. castalia Munoz et al., 1987. Urotricha cyrtonucleata has three adoral organelles, distinguishing it from U. armata and U. faurei, which possess six and four, respectively. Urotricha sphaerica, U. apsheronica and U. ovata, which possess 59-61, 60 and 28-34 somatic kineties, respectively, differ from U. cyrtonucleata, which has 46-52. In addition, none of the latter five species has the same number of short kineties abutting the adoral organelles as U. cyrtonucleata. Although similar to U. cyrtonucleata with respect to somatic ciliature, U. puytoraci and U. castalia have fewer pairs of kinetosomes making up the peribuccal ciliature. Furthermore, the number of kinetosomes comprising the adoral organelles of the latter two species differ from those observed for U. cyrtonucleata. (ref. ID; 7287)
Etymology; The specific epithet, cyrtonucleata (kyrtos, Gr., meaning arched or curved) derives from the shape of the macronucleus. (ref. ID; 7287)
Type locality; Shallow marine waters (top 5 m; salinity of 22-25 o/oo) of Indian Arm, B.C., Canada (latitude 49 degrees 22'N, longitude 122 degrees 55'W), taken February 1990. (ref. ID; 7287)
Deposition of type material; A holotype of Urotricha cyrtonucleata has been marked on a slide of protargol-impregnated cells (from this field study) and has been deposited in the Ciliate Type Specimen Slide Collection, USNM 43113, U.S. Natural History Museum, Smithsonian Institution, Washigton, DC, USA. (ref. ID; 7287)
Urotricha farcta Claparede & Lachmann, 1858 (ref. ID; 1619, 1629, 2245, 3115, 3540, 4671) or 1859 (ref. ID; 4488, 4611, 4613) reported year? (ref. ID; 1219, 1618, 3342) reported author and year? (ref. ID; 7141, 7243)
Syn; Balanitozoon gyrans Stokes, 1887 (ref. ID; 1618, 1619, 3540, 4613); Urotricha Minkewickzi Schout, 1906 (ref. ID; 1619, 3540); Urotricha parvula Penard, 1922 (ref. ID; 1618, 1619, 3540, 4613)
Description; Body conical; uniform ciliation except in the posterior region which is without cilia except for 1 oblique caudal cilium; cytostome at anterior pole, surrounded by small flaps; 1 spherical macronucleus located in the anterior half of cell; 1 micronucleus; 1 contractile vacuole near the posterior end. (ref. ID; 1219)
Algivorous ciliates. (ref. ID; 7141)
Measurements; Length 20-30 um. (ref. ID; 1219, 1618)
22-33 um. (ref. ID; 3342)
Urotricha matthesi matthesi Krainer, 1995 (ref. ID; 4613 redescribed paper)
Description; 1) Size in vivo 30-45 x 20-40 um. 2) Body ovoid to ellipsoidal with unciliated posterior portion indistinctly to distinctly narrowed and set off plug-like from body proper. 3) Macronucleus ellipsoidal, eccentric in mid-body. 4) Contractile vacuole in posterior end, eccentric, with single excretory pore distinctly outside area occupied by caudal cilia. 5) Extrusomes rare and tiny, rod-shaped, according to original description about 4 um long, according to original illustration only about 1.3 um long. 6) 28-35, usually about 32 meridional ciliary rows shortened posteriorly by about 20%. 3-4 circularly arranged caudal cilia about half as long as body. 7) Oral opening at anterior end of cell, oral basket inconspicuous in vivo. Undulating membrane circular, consists of short, paired cilia forming digitate processes (oral flaps) around oral opening. 5-6 serially and obliquely arranged adoral organelles (brosse) each composed of 2-4 dikinetids. 8) Movement conspicuous, that is, periods of fast forward swimming interrupted by wide jumps at irregular intervals. (ref. ID; 4613)
Comments; Foissner & Pfister (1997) reinvestigated the type slides. They fond several major discrepancies to Krainer's description and figures: (1) some specimens have a distinctly narrowed posterior body portion, indicating that the plug is more distinct in vivo than described and figured by Krainer; (2) the excretory pore of the contractile vacuole is not within but distinctly outside the area occupied by the caudal cilia as, for example, in Urotricha pelagica; (3) the ciliary rows are shorter than described, that is, terminate in the posterior quarter, as is usual; (4) in 3 out of 9 specimens the basal bodies are as regularly spaced as in other Urotricha species; (5) there are not 4-5 or 2-4 caudal cilia, as stated by Krainer, but 3-4; (6) there are not 5 adoral organelles, but 5 or 6 as also shown in one of Krainer's figure. Furthermore, the length of the extrusomes (unfortunately not recognizable in the type slides) differs greatly in the figure (1.3 um) and description (4 um). These data are included in the following differential diagnosis. Investigation of further populations recommended. The subspecies Urotricha matthersi tristicha is conical and invariably has only 3 adoral organelles. Also easily confused with U. castalia (6 um long extrusomes in posterior end, 4-10 caudal cilia, 34-50 ciliary rows). Urotricha venatrix, U. valida, U. pelagica, and U. apsheronica are larger and, more importantly, have prominent, fusiform somatic extrusomes, producing a conspicuous peripheral fringe in live specimens, Urotricha multisetosa and U. faurei lack sometimes extrusomes. (ref. ID; 4613)
Urotricha ondina Munoz, Tellez & Fernandez-Galiano, 1989 (ref. ID; 4298 original paper) reported author and year? (ref. ID; 191)
Description; The cells of U. ondina are oval and measure 19-40 um long by 16-35 um wide. Each shows a round macronucleus (9 um diam.) and a single rounded micronucleus (3 um diam.). The somatic infraciliature consists of 23-26 kineties that run meridionally from the anterior zone to the posterior part of the cell, leaving a large zone free of cilia except for a long caudal cilium. Three of the somatic kineties are shorter than the rest and leave a space where 3 adoral organelles (AO1, AO2 and AO3) are located. They correspond to what was formerly known as the brosse; AO1 is formed by 2 rows of 3 or 4 kinetosomes each; AO2 has an anterior row of 3 kinetosomes and a posterior row of 2 or 3 kinetosomes, and AO3 is more reduced with only 2 rows of 2 kinetosomes or only 1 kinetosome in the last row. The somatic meridional kineties have from 9 to 16 kinetosomes each, with the exception of 2 of the short kineties below the adoral organelles: Kn-2 has from 5 to 9 kinetosomes and Kn-1 has from 8 to 12 kinetosomes. Kinety n, although shorter in length than the rest of the meridional kineties has also from 9 to 16 kinetosomes, but the kinetosomes at its anterior end are more closely packed. Kinety Kn-3 is the long kinety at the left of the adoral organelles and is the one that bears the caudal cilium. The kinetosomes of the somatic kineties bear a kinetodesmal fiber and have also an associated structure that might correspond to the parasomal sac. The paroral infraciliature (PO) is formed by 12-16 pairs of obliquely disposed ciliated kinetosomes. In some specimens, we observe fibers running from each pair of kinetosomes of the paroral to the lumen of the buccal opening, and in other cases these fibers join the contiguous fiber at their left, lining the buccal cavity in a circle. These fibers correspond to the bundles of microtubules described by de Puytorac & Grain (1972) and were identified as transverse microtubules by the same authors (1976), but the recent work of Huttenlauch & Bardele (1987) in Coleps suggests they are postciliary microtubules. In some preparations, the argyrome impregnates and appears as a rectangular net in the ciliated part of the cell and irregularly polygonal at the posterior naked zone. We have not observed somatic extrusomes in this species. (ref. ID; 4298)
[Morphogenesis]: The first sign of morphogenesis observed in U. ondina is the proliferation of the kinetosomes of the somatic kineties at the equatorial zone. At first this proliferation simultaneous in all kineties, but soon it is apparent that the first kinety and the 3 short kineties (Kn, Kn-1 and Kn-2) below the adoral organelles proliferate more actively than the rest of the somatic kineties. They will participate in the formation of the new paroral infraciliature and adoral organelles of the opisthe. At an early stage, the stomatogenic kineties break in the middle and the newly formed kinetosomes move to the left, forming groups of kinetosomes between the kineties. These kinetosomes lack kinetodesmal fibers. Kineties Kn-1 and Kn-2 proliferate more actively than kineties K1 and Kn. The most anterior kinetosomes formed by proliferation of kineties Kn-2 and Kn-1 - generally 7 pairs of kinetosomes - group together forming a horizontal band. Below this band (B1), the rest of the kinetosomes formed by the proliferation of kineties Kn-2 and Kn-1 will organize in a new horizontal band (B2) parallel to the band previously formed. The primordia of adoral organelles 1 and 2 will organize from the left ends of band 1 and 2, respectively. The third adoral organelle of the opisthe possibly is formed from a pair of kinetosomes of band 1 or band 2 that migrates posteriorly and lies below adoral organelle 2. During this time, the proliferation of kineties Kn and K1 produces a certain number of pairs (12-15) of kinetosomes that will eventually organize in a circle to form the major part of the paroral. Also, some pairs of kinetosomes at the right of band 1 seem to contribute to the formation of the paroral infraciliature by migration to the right. Along this proliferation, there are more pairs of kinetosomes than are needed to form the paroral of the opisthe and consequently, they will disappear afterwards. At this stage we can observe, in some specimens, an equatorial furrow at the site of division of the cell. The pairs of kinetosomes that will form the paroral rotate and dispose in a circle, moving while the adoral organelles move backwards lying below the paroral. In this last stage of division, the pairs of kinetosomes of the paroral appear associated with long fibers. When the cell divides, the last kinetosomes of kinety Kn-3 of the proter migrates downwards and will lie at the posterior pole giving rise to the caudal cilium. Division of both nuclei takes place at the end of stomatogenesis. The micronucleus divides first and the macronucleus divides slightly later when the primordia of the paroral and adoral organelles are already formed. (ref. ID; 4298)
Comments; The features of the infraciliature that permit us to distinguish different species of Urotricha are: (1) number of somatic kineties, (2) number of pairs of kinetosomes of the paroral, (3) number and position of kinetosomes of the adoral organelles and (4) number of caudal cilia. The number of kinetosomes per kinety is, in our experience, slightly variable in the same population but shows more diversity in different populations. Another feature which in some cases may be diagnostic in the presence or absence of extrusomes. In our studies on sliver-impregnated specimens, only the presence of extrusomes can be determined; their absence can not be definitively established as it can depend on the fixation. In the case of U. ondina, however, were numerous impregnated specimens have been observed, extrusomes have never appeared. Morphological characters such as size or shape are also used as diagnostic features, but they should not be considered definitive by themselves either. In many species of Urotricha, size shows important variations, and sometimes it differs by 20 um in a population in which the maximum size is 35 um as in the case of U. nais (Munoz, Tellez & Fernandez-Galiano 1987). This new species of Urotricha can be compared with the organism originally described as U. ovata by Kahl (1930-1935) and in the work of Gelei (1953) and de Puytorac & Grain (1972); however, these descriptions do not describe some of the details of the infraciliature that probably could permit us to differentiate between these 2 organisms. More recent description of U. ovata by Groliere (1977) and Foissner (1979) do not correspond to the species we describe here. The U. ovata described by Groliere (1977) has a larger number of somatic kineties and a greater number of kinetosomes forming the paroral infraciliature. This is surprising since we find that very frequently, the number of pairs of kinetosomes of the paroral in most species of Urotricha is approximately half the number of somatic kineties. Urotricha ondina can be differentiated from the U. ovata described by Foissner (1979) by the position of the buccal cavity, which is subapical in U. ovata, and in the number of short kineties, which according to his drawing seem to be 2 instead of 3. Also the adoral organelles are smaller, according to his figures. Urotricha ondina can also be compared with U. macrostoma described by Foissner (1983), but this species has 2 caudal cilia and U. ondina has only 1. Also the adoral organelles are larger in U. macrostoma, and this species has extrusomes. We have compared our organism with the figures of the species U. vitrea, described by Martin-Gonnzalez et al. (1985) and find that they are similar in size, in the number of adoral organelles (although they vary somewhat), and in the number of caudal cilia. There are, however, some significance differences: the buccal cavity is smaller in U. vitrea and even more important, the short kineties of U. vitrea, 3 in number as in U. ondina, do not correspond to the same kineties. In U. ondina, the short kineties are kineties Kn, Kn-1 and Kn-2, and all of them participate in formation of the new oral structure while in U. vitrea the short kineties are kineties Kn-1, Kn-2, and Kn-3. (ref. ID; 4298)
Urotricha simonsbergeri (ref. ID; 4613 original paper)
Diagnosis; Size in vivo about 100 x 75 um. Bursiform to broadly ellipsoidal with sparsely ciliated posterior body potion evenly rounded. Macronucleus broadly ellipsoidal. Somatic extrusomes narrowly ovate, 5 um long, form distinct peripheral fringe; oral extrusomes rod-shaped, 8 um long. 92 ciliary rows, 25 scattered caudal cilia, and 57 circumoral dikinetids on average. Brosse prominent, enklitoloph-dexiotrop, consists of a series of about 16 minute, oblique rows. (ref. ID; 4613)
Description; 1) Size in vivo 70-120 x 60-100 um, usually about 100 x 75 um. 2) Body slightly bursiform to broadly cylindroidal, well-fed specimens almost globular, posterior portion evenly and broadly rounded, that is, not set off plug-like from body proper. Very fragile, difficult to preserve, prepared specimens thus stouter than live ones. 3) Macronucleus eccentrically in mid-body, broadly ellipsoidal (1.5:1), with many globular and ellipsoidal nucleoli. One micronucleus. 4) Contractile vacuole subterminal, distinctly eccentrical on ventral side slightly right of adoral organelles, with 1 (rarely 2 or 3) excretory pore at margin of ciliated/unciliated body potion. 5) Extrusomes numerous and clearly recognizable in live and silver carbonate-impregnated specimens: type 1 in and around oral opening, about 8 um long, rod-shaped; type 2 between ciliary rows, produces conspicuous peripheral fringe, about 5 x 1 um, narrowly ovate. 6) 73-109, usually about 92 meridional ciliary rows shortened posteriorly by only about 10%; unciliated posterior body portion thus inconspicuous. About 25 slightly elongated (15 um vs. 10 um somatic cilia), rather stiff caudal cilia scattered in posterior pole area. 7) Oral opening at anterior end of cell, comparatively large and thus conspicuous. Oral basket trumpet-shaped and extending to mid-body. Undulating membrane circular, consists of about 3 um long, paired cilia forming an average of 57 inconspicuous digitate processes (flaps) around oral opening each flap accompanied by an extrusome at cytostomial side. Brosse (adoral organelles) enklitoloph-dexiotrop (somatic ciliary rows abut to brose only right side), composed of conspicuous series of 12-20 (mean = 16) minute, obliquely arranged rows separated from each other by distinct ridges; individual organelles small and decreasing in length posteriorly, composed of 1-8 dikinetids having about 3 um long, almost immobile cilia. 8) Movement inconspicuous, that is, does not jump like most congeners, but swims moderately fast by rotation about main body axis. (ref. ID; 4613)
Comments; Urotricha simonsbergeri has several outstanding characteristics, which might justify considering it as type of a new genus. However, a definite generic character could not be found because the species looks like a combination of Urotricha and Bursellopsis. The brosse (many short, oblique rows) and the oral flaps (two short cilia associated with an extrusome) indicate that it is a true Urotricha, whereas other features (fragility; large, trumpet-shaped oral basket; oral flaps inconspicuous, do not form a dome; ciliary rows end unequally anteriorly and posteriorly) are reminiscent of Bursellopsis or occur in both Urotricha and Bursellopsis (irregularly arranged caudal cilia; lack of brosse plate; ordinary movement, that is, not jumping). Urotricha simonsbergeri is easily identified, both in vivo and after silver impregnation, by the conspicuous series of adoral organelles. As concerns size, shape, caudal cilia, and movement, there are several very similar species, for instance U. venatrix (3 large, particularly arranged adoral organelles), Bursellopsis truncata (3 longitudinally arranged adoral organelles), and Holophrya discolor Ehrenberg, 1833 (3 longitudinally arranged adoral organelles, different cortex pattern). Thus the species-specific series of adoral organelles, which is easily recognizable with interference contrast optics, is required of identification. (ref. ID; 4613)
Dedication; We dedicate this new species to Prof. Dr. Peter Simonsberger, head of the Electron Microscopy Department at the Institute of Zoology, Salzburg University, for his help and support over many years. (ref. ID; 4613)
Type location; Pelagial of a eutrophic, artificial pond and Salzburg University Austria (47 degrees 47'N, 13 degrees 40'E) (ref. ID; 4613)
Type slides; Three slides (1 holotype, 2 paratypes) with protargol-impregnated specimens and 1 holotype slide with Chatton-Lwoff sliver nitrate-impregnated specimens have been deposited in the Oberosterreichische Landesmuseum in Linz (LI), Austria. (ref. ID; 4613)
Urotricha vitrea Martin-Gonzalez, Serrano & Fernandez-Galiano, 1985 (ref. ID; 7243 original paper) reported author and year? (ref. ID; 4298)
Description; Urotricha vitrea n. sp. is a freshwater ciliate, spherical in shape. The body size is very variable, ranging from 46 to 27 um in length and 43 to 26 um in width. The nuclear apparatus consists of a spherical macronucleus placed it the anterior half of the body and a voluminous spherical micronucleus close to it. The somatic infraciliature is made up to 20-23 meridian kineties that delimit an unciliated area at the posterior end where there is a long caudal cilium. Each somatic kinety consists of 15-20 kinetosomes. The arrangement of these kinetosomes is not homogeneous but the distance between two adjacent kinetosomes of the same kinety decreases according to a postero-anterior grandient. Close to the left posterior zone of each somatic kinetosome there is an argentophilic granule, probably a parasomal sac. The brosse is located in a depression at the anterior part of the body and consists of three short double kinetal segments with 4, 3, and 2 kinetosomes, respectively. This structure interrupts three somatic kineties at their anterior ends so these kineties have fewer kinetosomes than the other meridians. The circumoral infraciliature is made up of 13-16 oblique pairs of kinetosomes that encircle the cytostome. There is also a ring of tubular tricocysts along the edge of this permanent buccal overture. Urotricha vitrea n. sp. has only a single contractile vacuole located in the posterior third of the body, which opens by a pore close to the posterior end of the somatic kinety located just to the right of the three dorsal somatic kineties that are shorter than the others. Each somatic kinetosome bears a thick kinetodesmal fiber, as does the caudal kinetosome which also has transverse fiber and a long postciliary fiber. There are many refractile vesicles (likely lipidic) arranged randomly in the cytoplasm of this species. We also found a large number of long mitochondria, some of them parallel to the somatic kineties and the others at the unciliated posterior end. (ref. ID; 7243)
Conjugation process; [Conjugant union and cortical phenomena]: The union of conjugants in pairs occurs at the ventral zones of the body and involves four somatic kineties of each cell. The anterior parts of these kineties beak down and later disappear. Therefore it is usual to observe somatic kinetal segments in the exconjugants of U. vitrea. This union, including a part of both circumoral infraciliatures, extends from the anterior end of the body to the posterior zone where the somatic kineties finish, without reaching the unciliated posterior end. There is no variation in any of the fibrillar systems associated with the somatic kinetosomes of both cells during the conjugation process. (ref. ID; 7243)
[Nuclear changes]: The nuclear phenomena being soon after the conjugants union. In early meiotic prophase I, each micronucleus becomes more voluminous and moves away from its respective macronucleus. In a later stage of meiotic prophase I, a condensation of the micronuclear genetic material takes place and the chromosomes begin to appear in a radial arrangement. Later on, these chromosomes group together in the typical image of the "parachute stage"; their ends converge on a more dense, small chromatin body. Two haploid nuclei originate as a result of this reductional first pregametic micronuclear division; one of these appears near the anterior end and the other one at the intermediate third of the body. Each of these nuclei undergoes a second maturation division, which produces four nuclear derivates. Three of these nuclei degenerate and the other one takes part in the third matulation division (postmeiotic division), giving rise to the stationary and the migratory pronuclei in each conjugant. As result of the exchange of pronuclei and subsequent fusion of each one with the stationary pronucleus of the other partner, a voluminous synkaryon is formed in each conjugant. This spherical synkaryon undergoes a mitotic division that results in two diploid nuclei. During this first division of the synkaryon, the conjugants separate progessively so the subsequent divisions take place in the exconjugants. The four nuclear derivates from the second postzygotic mitosis are of the same size. Two of them, which are never sister nuclear, degenerate. The other two nuclei undergo a third mitotic division and give rise to four nuclei. Two of these nuclei increase in size and become macronuclear anlagen and the other two differentiate into micronuclei. During the first partitioning of the exconjugant, one micronucleus and one macronuclear anlage segregate to each daughter cell. (ref. ID; 7243)
Remarks; We have observed nutritional polymorphism phenomena; there is a great variation in size which depends on the amount and kind of food consumed. We believe that body size is not an essential systematic character for identification of the species members of the genus Urotricha. Our species has an oblique pair of kinetosomes at the posterior end of the body with only one caudal cilium. This characteristic differentiates it from U. armata Kahl, 1927 (Dragesco et al. 1974), U. obliqua Kahl, 1931, U. venatrix Kahl, 1930-1935 (Dragesco et al. 1974), U. pelagica Kahl, 1930-1935, and U. puytoraci and U. faurei (Dragesco et al. 1974), as all of these species have several caudal cilia or several unciliated kinetosomes and one caudal cilium at the posterior end of the body. Urotrica vitrea n. sp. can be distinguished from U. baltica Czapik and Jordan, 1976 because the latter lives in marine habitats and has a high number of somatic kineties, and the arrangement of the kinetosomes in the brosse is quite different. In the same way, the number of somatic kineties in U. sphaerica Groliere, 1977 (59-61 kineties) is also higher than that found in U. vitrea n. sp. In addition, we have observed differences in the number of pairs of kinetosomes that compose the peribuccal infraciliature (26 pairs in U. sphaerica, 13-16 pairs in U. vitrea) and in the arrangement of the kinetosomes in the brosse (U. sphaerica has 17-25 pairs of kinetosomes distributed in oblique kinetal segments in contrast to 4, 3, and 2 pairs in U. vitrea). The morphology of U. farcta (Dragesco et al. 1974) and U. ovata (Groliere, 1977) seem to be very similar to that of U. vitrea. However, these are several relevant differences between them. The number of somatic kineties is 28-30 in U. farcta and the kinetosomes of one kinety are far apart. Besides, this species has a very reduced brosse, with 3-4 single or double kinetosomes disposed obliquely. Finally, U. ovata as redescribed by Groliere (1977) differs from our species in the number of somatic kineties, which is higher in U. vitrea and the peribuccal infraciliature has more pairs of kinetosomes. Urotricha ovata described by de Puytrac and Grain (1972) is 30 um long, has 20 somatic kineties, and a circumoral infraciliature consisting of 12 pairs of ciliated kinetosomes. These authors do not give any data on the number of kinetosomes and their arrangement in the brosse; the number of somatic kineties interrupted by this structure; nor the size, shape, and location of the macronucleus. Thus it is very difficult to determine if U. vitrea and U. ovata are the same species. The conjugant union in U. vitrea involves a wide area of the body surface, which covers several somatic kineties and a part of both circumoral infraciliatures. We have not found any bibliographic references to these characteristics of conjugation in other species within the Prorodontidae, although our own observations of Coleps hirtus (Colepidae) indicate that the union in this ciliate involves the circumoral cilia and does not modify the prebuccal and somatic infraciliatures. As occurs in most of the ciliates studies (see Raikov 1972) there are three maturation divisions in U. vitrea. In this species, as in Didinium nasutum (Prandtl, 1906), the "parachute stage" is a characteristic of meiotic prophase I. Nevertheless, it is not typical of the order Prostomatida since in C. hirtus (personal observations) we have observed the "crescent stage". With regard to the synkaryon division, the reconstruction process of the nuclear apparatus is more complex than in Prorodon griseus (Tannreuther, 1926) and C. hirtus. The conjugation process in this species only has one synkaryon division. In Didinium nasutum (Prandtl, 1906) the conjugation includes two synkaryon division, but in this case there are five types of reconstruction of the nuclear apparatus. Urotricha vitrea can be defined as type III according to the nuclear reconstructions of Raikov (1972), but it represents a new subtype because two products of the second postzygotic division degenerate. (ref. ID; 7243)