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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Paraurostyla

Paraurostyla Borror, 1972 (ref. ID; 2014, 2129)

Class Polyhymenophora: Subclass Spirotricha: Order Hypotrichida: Suborder Stichotrichina: Family Urostylidae (ref. ID; 2014)

[ref. ID; 2014]
Elongate, ellipsoidal body with several to many rows of ventral cirri, 2 marginal rows and clearly differentiated frontal cirri, the anterior most of which are often large. Transverse cirri present. AZM moderate, approximately a third of the body length. Usually 2 macronuclei but sometimes more with a variable number of micronuclei. Several species have been described. Genus erected by Borror (1972) to separate certain species of Urostyla with a different morphogenetic pattern. In these, the ventral rows arise from the differentiation of longitudinal streaks of kinetosomes. Jankowski (1979) advocates two subgenera, one of which, Onychodromopsis Stokes, 1887 (see: Pleurotricha) may be a valid genus. Borror (1979) transferred this genus to the Oxytrichidae.
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; 3925]
My observations of this genus corroborate published descriptions of morphogenesis in Paraurostyla which differs markedly from that of Urostyla; there are no midventral cirri, nor the urostylid fronto-buccal-field. Similarities with Amphisiella and Oxytricha suggest the need for transfer of Paraurostyla to the Oxytrichidae. (ref. ID; 3925)
  1. Paraurostyla buitkampi Foissner, 1982 (ref. ID; 662 original paper)
  2. Paraurostyla hymenophora (Stokes) (ref. ID; 3809) reported author and year? (ref. ID; 191)
  3. Paraurostyla macrotoma Foissner, 1982 (ref. ID; 662 original paper)
  4. Paraurostyla pulchra Buitkamp (ref. ID; 2365 original paper)
  5. Paraurostyla terricola Buitkamp (ref. ID; 2365 original paper)
  6. Paraurostyla viridis (Stein, 1859) Borror, 1972 (ref. ID; 4488, 4609) reported year? (ref. ID; 5462 Parurostyla misspelling?) reported author and year? (ref. ID; 1629)
    Syn; Urostyla viridis Stein, 1859 (ref. ID; 4609, 5462)
  7. Paraurostyla weissei (ref. ID; 191, 1629, 3925, 4260, 4471, 4970, 7308, 7575, 7580, 7581, 7675)
  8. Paraurostyla weissei (Stein, 1859) (ref. ID; 3764) reported year? (ref. ID; 3809) or (Stein, 1859) Borror, 1972 (ref. ID; 4488, 4609, 7423) reported year? (ref. ID; 5462 Parurostyla misspelling?)
    Syn; Urostyla weissei Stein, 1859 (ref. ID; 4609, 5462)
  9. Paraurostyla weissei Wirnsberger et al., 1985 (ref. ID; 4719)

Paraurostyla hymenophora (Stokes) (ref. ID; 3809) reported author and year? (ref. ID; 191)

Descriptions

The left anterior quadrant of the organisms' ventral surface (the oral region) is composed of the adoral zone of membranelles (AZM) on the left and extending beyond the cell's anterior limit, and the 2 undulating membranes (UMs) on the right. These 2 sets of structures converge posteriorly to meet at the cytostome. The remainder of the ventral ciliature is comprised of cirri divided into 4 groups: (A) The left and right marginal cirri (LMC and RMC), forming an apparently continuous single row from the level of the collar region of the AZM on the right side, around the posterior end and up the left margin of the cell to a point just anterior and left of the cytostome. (B) The 6 prominent frontal cirri (FC) are located immediately posterior to the collar region of the AZM and numbered couterclockwise starting with the anterior left most cirrus. FC #1 differs from the other 5 FC in that it is differentiated from the anterior end of the undulating membrane primordium; it is thus more appropriately called a buccal cirrus. (C) Near the posterior end of the cell are found the 6 (occasionally 7) transverse (anal) cirri, which are numbered from right to left. (D) Between the frontal and transverse cirri, at a right-to-midventral location, are the 2 ventral cirral rows, which extend from an area just posterior to the collar region of the AZM to an area anterior to the transverse cirri. The right row (ventral row #1) is composed of more cirri than the left row, but the range of variation in the absolute number of cirri is not known. In addition to the 2 ventral cirral rows, at least 1, sometimes as many as 4, postcytostomal cirri (PC) are found to the left of ventral row #2 and posterior to the cytostome. Occasionally, ectopic cirri were observed at various locations on the ventral surface. Observation of cirri at the light and transmission electron microscopic level reveals that within the ventral and marginal rows they have a common structure. Each parallelogram-shaped cirrus is composed of hexagonally packed kinetosomes within a fibrillar network and basket, a feature described previously for other hypotrich species. The number of kinetosomes per cirrus is highly variable with 12 (2x6) being most common; however, 24 (4x6) have been observed as an upper limit. Each row appears to possess the same degree of variability, with no obvious localization of the cirri possessing the larger kinetosomal numbers. Each cirrus within the row has 3 large microtubular bundles which extend from the distal margins of the fibrillar cirral basket. The anterior and left microtubular bundles are both ~8 um in length, whereas the posterior microtubular bundle is only ~2 um. The postciliary microtubules presumably contribute (at least partially) to the posterior microtubular bundle. The location and size of these microtubular bundles correspond closely to the "fiber" arrangements reported previously for the marginal cirri of Gastrostyla steinii Engelmann, Stylonychia mytilus (O.F. Muller, 1773) and Onychodromas grandis Stein, 1859. Additionally, some cirri within each of these rows have a striated fiber attached to the posterior-proximal cirral limit. The distribution of cirri possessing this fiber, its length and function are unknown, although it is presumably homologous to those reported in Oxytricha, Gastrostyla and Stylonychia. In contrast to cirri within the marginal and ventral rows, the pentagonal-shaped frontal cirri have many more hexagonally packed kinetosomes (~50-65/cirrus) within the fibrillar basket. Further, the microtubular bundles associated with the cirri are unique; the anterior bundles radiate as discrete bundles from the entire anterior limit of the fibrillar basket and attached to the collar membranelles located ~4 um away. The posterior microtubular bundle is attached to the posterior limit of the fibrillar basket and tapers posteriorly for a distance of ~6 um. No microtubular bundle, corresponding to the left microtubular bundle on ventral and marginal cirri, is present on frontal cirri. The dorsal ciliature is composed of 6 kineties of dorsal bristles and posteriorly coated caudal cirri. The 3rd row of bristles is discontinuous, being divided into 2 segments which meet mid-dorsally. The extent of polymorphism and the morphogenesis of the dorsal surface were not studied. Paraurostyla hymenophora was observed to encyst. (ref. ID; 3809)

Paraurostyla weissei (ref. ID; 191, 1629, 3925, 4260, 4471, 4970, 7308, 7575, 7580, 7581, 7675)

Descriptions

Congugation morphologenesis, zygocyst morphogenesis. (ref. ID; 7308)
Ultrastructural study of formation and morphologenetic movements of ventral ciliary primordia. (ref. ID; 7575)
Ultrastructural study of formation of the adoral zone of membranelles. (ref. ID; 7580)
Ultrastructural study of formation of the preoral membranelles. (ref. ID; 7581)
Ultrastructural study of morphogenesis of dorsal bristles and caudal cirri. (ref. ID; 7676)

Paraurostyla weissei (Stein, 1859) (ref. ID; 3764) reported year? (ref. ID; 3809) or (Stein, 1859) Borror, 1972 (ref. ID; 4488, 4609, 7423) reported year? (ref. ID; 5462 Parurostyla misspelling?)

Synonym

Urostyla weissei Stein, 1859 (ref. ID; 4609, 5462)

Descriptions

The body of P. weissei is elongated, 150-200 um in length, and laterally flexible. The oral region is ~1/4th the length of the body. A well developed adoral zone of membranelles and a double undulating membrane are present. Ventral cirri occur in numerous rows. Six frontal cirri and 5-8 transverse cirri are also present. Dorsal ciliature is sparse. The micronuclei are spherical with a diameter of ~5 um. Most organisms contain 4 or 6 micronuclei, although individuals with as few as 2 or as many as 8 have been observed. Macronuclei are elongated, ranging in length from 20-30 um. Two or 3 macronuclei are present in each organism. (ref. ID; 3764)
  • Vegetative Cyst: P. weissei has the ability to encyst in response to such unfavorable conditions as starvation or temperature extremes. The resulting cysts are somewhat smaller than nonmotile exconjugants and are bounded by an extremely durable extracellular wall which has a stellate appearance. These cysts require no external food source and can withstand temperature extremes and dehydration for prolonged periods. Cysts dried onto filter paper and stored at 4 degrees C remain viable for many months. Vegetative organisms "hatch" from such cysts within a few days of return to normal culture conditions. (ref. ID; 3764)

    Remarks

    The species generates an anlage (the anterior anlagen-part of N1) in the rightmost ventral cirral row nine. This row develops as usual side by side with the second rightmost ventral row eight. Most cirri of row nine migrate as fronto-terminal cirri or to use it synonym, as the anterior segment of the amphisiellid cirral row (ACR) anteriorly and are positioned upon the row eight. This gives in interphase the impression of one nearly body long cirral row, as it develops in some lowly evolved oxytrichids. The dorsal kinety that is adjacent to the left marginal row also develops in an unusual way: the anlagen develop their streaks not within, but right of the old kinety. Two within anlagen develop probably in individuals with a longer row seven, instead of one within and one de novo anlage. (ref. ID; 7423)