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PubMedDate not supplied

Divisional morphogenesis in Uroleptus caudatus (Stokes, 1886), and the relationship between the Urostylidae and the Parakahliellidae, Oxytrichidae, and Orthoamphisiellidae on the basis of morphogenetic processes (Ciliophora, Hypotrichida).

Morphogenetic processes during division in Uroleptus caudatus (Stokes, 1886) are described using protargol impregnation. As is typical for the family Urostylidae Bütschli, 1889, zigzag midventral cirri develop, but contrary to most species of this family the adoral membranelles of the proter are not renewed during division and two dorsomarginal kineties develop. These two atypical features occur in only two other species of the Urostylidae (Uroleptus musculus, Holosticha diademata), and in all species of the family Parakahliellidae Eigner. 1997, and in many of the Oxytrichidae Ehrenberg, 1838. Membranelles are also not renewed in the Orthoamphisiellidae Eigner, 1997. This shows that these three atypical members of the family Urostylidae are those which are most closely related to the other three hypotrichous families named above. The highly distinct zigzag midventral cirri clearly separate the family Urostylidae from the other three hypotrichous families. These cirri are used together with new morphogenetic features for a revised family diagnosis. The analysis of the Urostylidae revealed that during division all species of the family Urostylidae develop their cirral patterns, including the two rightmost ventral anlagen, in separate areas for each proter and opisthe. Thus, "long primary primordia" are absent in the Urostylidae. This is similar to the morphogenetic pattern by which the family Parakahliellidae is defined ("neokinetal 1") indicating that the Urostylidae are more closely related to the Parakahliellidae than to either the Oxytrichidae or to the Orthoamphisiellidae. All 68 detailed descriptions of divisional morphogenesis in species of the Hypotrichida are analyzed now in this and two former papers. As a result all these species can be assigned or at least recognized to be closely related to one of the following four families: to the Orthoamphisiellidae ("within-row" anlagen), to the Oxytrichidae ("neokinetal 3" anlagen), to the Parakahliellidae ("neokinetal 1" anlagen), and to the distinctly different Urostylidae ("midventral" anlagen). Thus, all Hypotrichida can most probably be assigned after morphogenetic investigation to one of the four families.

Animals↗
PubMed2006

Morphology and cell division of the oxytrichids Architricha indica nov. gen., nov. sp., and Histriculus histrio (Müller, 1773), Corliss, 1960 (Ciliophora, Hypotrichida).

The oxytrichid ciliate Architricha indica nov. gen., nov. sp., isolated from the river Yamuna, Delhi, shows a new combination of characters. It possesses a flexible body, 18 frontal-ventral-transverse (FVT) cirri, 3 right and 2 left marginal cirral rows, 6 dorsal bristle rows and 3 caudal cirri (CC). The FVT cirri arise from 6 primordia, which utilize 6 parental cirri in their origin as is typical of Oxytricha species. Multiple marginal rows (MMR) develop through 5 independent marginal primordia arising "within-row", 1 in each parental marginal row. All the 5 marginal rows are thus morphogenetically active. Such a mode of formation of MMR has not been recorded among oxytrichids and has necessitated separation of A. indica at the generic level. Histriculus, on the other hand, has well-known characteristics, viz. rigid body, confluent marginal rows and absence of CC. The morphogenesis of Histriculus histrio has been described by Berger and Foissner [1997. Cladistic relationships and generic characterization of oxytrichid hypotrichs (Protozoa, Ciliophora). Arch. Protistenkd. 148, 125-155]. Reinvestigation of very early stages of development revealed that (i) the FVT cirral primordia utilize kinetosomes from 5 parental FVT cirri, (ii) the primordium II of the proter is of a composite origin: kinetosomes from the oral primordium merge with the primordium II that originates from the buccal cirrus II/2 and (iii) the FVT primordia V and VI for the 2 daughter cells arise sequentially from the parental cirrus V/4. Thus, the genus Histriculus exhibits a new combination of characters with respect to the origin of FVT cirri, an additional pattern to be added to the known 6 patterns of FVT development in oxytrichids [Berger and Foissner, 1997; Berger, H., 1999. Monograph of the Oxytrichidae (Ciliophora, Hypotrichida), Kluwer Academic Publishers, Dordrecht/Boston/London].

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PubMedDate not supplied

Redescription of Phacodinium metchnikoffi (Ciliophora, Hypotrichida): general morphology and taxonomic position.

Living and stained specimens of Phacodinium metchnikoffi, collected near Madrid, Spain, were studied under light microscopy. Infraciliature was stained using a silver-impregnation procedure. The somatic infraciliature is composed of a relatively small number of discontinuous kinetics, formed by groups of few kinetosomes (pallets). The buccal ciliature is composed of an adoral zone of membranelles and a paroral formation otherwise unknown in ciliates, with many short kineties, which lie on a rigid stem. We propose that P. metchnikoffi is a primitive hypotrich and, consequently, we present a new classification system for hypotrichs.

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PubMed1991

Molecular evolution in hypotrichous ciliates: sequence of the small subunit ribosomal RNA genes from Onychodromus quadricornutus and Oxytricha granulifera (Oxytrichidae, Hypotrichida, Ciliophora).

The small subunit ribosomal RNA (16S-like rRNA) coding regions of the hypotrichous ciliates Onychodromus quadricornutus and Oxytricha granulifera were amplified using polymerase chain reaction techniques. Complete sequences were determined for the amplified genes and compared to those of other ciliated protozoa. In phylogenetic trees inferred using distance matrix methods oxytrichids are not seen as a cohesive phylogenetic group. Oxytricha nova is most closely related to Stylonychia pustulata in a lineage that also includes O. quadricornutus. This phylogeny contradicts phylogenetic schemes in which Onychodromus is considered to be a primitive hypotrichous ciliate and suggests that O. nova was misidentified as members of the genus Oxytricha.

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PubMed2006

Phylogenetic position of the marine ciliate, Certesia quadrinucleata (Ciliophora; Hypotrichia; Hypotrichida) inferred from the complete small subunit ribosomal RNA gene sequence.

The complete small subunit rRNA (SSrRNA) gene sequence of the rare marine hypotrich, Certesia quadrinucleata Fabre-Domergue, 1885, was determined, and found to be 1752 nucleotides long. The phylogenetic position of this species was deduced using distance matrix, maximum parsimony and maximum likelihood methods. Certesia was consistently demonstrated to be a member of the Aspidisca-Euplotes group and clearly exhibits a very close relationship to the well-known genus Euplotes (99% Bay, 99% LS, 99% NJ, 99% MP). The phylogenetic trees further suggest that: (1) Uronychia and Diophrys, traditionally placed in the family Uronychiidae, branch earlier and share a closer relationship to each other than to other hypotrichs; (2) taxa in Gastrocirrhidae, represented by Euplotidium arenarium, might be an "ancestral" group among "traditional" hypotrichs.

Animals↗
PubMed2006

A new investigation of the marine ciliate, Trachelostyla pediculiformis (Cohn, 1866) Borror, 1972 (Ciliophora, Hypotrichida), with establishment of a new genus, Spirotrachelostyla nov. gen.

The morphology and infraciliature of the type species of the ciliate genus Trachelostyla, T. pediculiformis (Cohn, 1866) Borror, 1972, collected from the Bohai Sea near Tianjin, north China, were investigated using live observation and protargol impregnation. The Chinese population corresponds well with the original description, as follows: size about 80-150 x 20-30 microm in vivo; body dorsoventrally flattened and non-spiral; outline elongate, with anterior region conspicuously narrowed while posterior not; on average 14 macronuclear nodules, two micronuclei and 42 adoral membranelles; 16-24 cirri in left and 21-31 in right marginal row. In total 18 frontoventral-transverse cirri: constantly 11 cirri in frontal area and two ventral ones together with five enlarged transverse cirri (TC). Three inconspicuous caudal cirri (CC); six dorsal kineties with prominent cilia. The literature on T. pediculiformis is critically reviewed, showing that the descriptions so far do not agree very well. To clarify the taxonomic status of this species, the population from the Chinese coast of the Bohai Sea is designated as a neotype. The small subunit rRNA gene was sequenced for the neotype and the molecular phylogenetic tree basically supports the establishment of the family Trachelostylidae Small & Lynn, 1985. Based on the data obtained, the genus Trachelostyla Borror, 1972 is redefined thus: dorsoventrally flattened trachelostylids, body non-spirally twisted and elongate, with peristomal region conspicuously narrowed; ciliature generally in 11:2:5:3 pattern, i.e. 11 cirri in frontal region, two ventral cirri located anterior to five TC, three CC present; one left and one right row of marginal cirri not confluent posteriorly. A new genus Spirotrachelostyla nov. gen. is proposed to include the taxa which were previously assigned to Trachelostyla but characterized by spirally twisted, spindle-like body shape and a variable number of cirri in the peristomal area. Three new combinations are suggested: Spirotrachelostyla spiralis (Dragesco & Dragesco-Kernéis, 1986) nov. comb. [basionym: Trachelostyla spiralis Dragesco & Dragesco-Kernéis, 1986], S. tani (Hu & Song, 2002) nov. comb. [basionym: T. tani Hu & Song, 2002] and S. simplex (Kahl, 1932) nov. comb. [basionym: Stichotricha simplex Kahl, 1932].

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PubMedDate not supplied

The behavior of the doublet of Oxytricha bifaria (Ciliata, Hypotrichida): a contribution to the understanding of this enigmatic form.

The tracks of normal organisms of Oxytricha bifaria and of stage IA, IB, II, III, IV and V doublets were studied to test the hypothesis that the doublet might function as a dispersal form. Stage IA, the only stage to swim, swims straight with only rare interruptions; its rate of mobility (Rmo = 443 micro/s) is roughly twice that of singlets (Rmo = 218 micro/s). Stage IA doublets swim in three-dimensional movement which enables them to be carried away by water currents. The other stages seem to represent passage back towards the normal singlet form. The ethological evidence reported here together with other results already published supports the working hypothesis that the doublet of O. bifaria is a dispersal form suggests that the doublet might well represent a special fourth differentiation state of this species in addition to pairs, giants, and cysts.

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PubMedDate not supplied

Cold microgradients elicit adaptive behavior in isotropically cooled, inert populations of Oxytricha bifaria (Ciliophora, Hypotrichida).

To complete our investigations on the oriented behavioral response of isotropically cooled, inert populations of Oxytricha bifaria to a warm thermal gradient, their physiological potentialities under cold microgradient conditions arising at 8.5 degrees C were studied. We monitored the behavior of the experimental populations, both at the level of the passing cold wave front, and afterwards when the thermal gradient stabilized, evaluating (i) their distribution in general, (ii) their relative centroids, (iii) the percentage of both backward creeping and immobile ciliates, and (iv) the numerical indices and rates of their creeping tracks. At the arrival of the cold wave front, the oxytrichas react immediately to the thermal stimulus, creep backwards at very high velocity along uninterrupted linear tracks, and thus move away from the cooling source. No specific behavioral response was ever observed in the static microgradient conditions. At 8.5 degrees C, despite their inertness, the ciliates are still able to behave adaptively, reacting immediately and orientatedly, once a directional factor (the cold-repelling thermal gradient) arises in an isotropic environment. This is similar to their behavior in the symmetric warm attracting thermal gradient.

Adaptation, Physiological↗
PubMedDate not supplied

Redescription of Psilotricha acuminata Stein, 1859 and revisions of the genera Psilotricha and Urospinula (Ciliophora, Hypotrichida).

Psilotricha acuminata was described by Stein in 1859 as the type species of the ciliate genus Psilotricha Stein, 1859. The ciliate has rarely been found since, and its infraciliature has never been described with the aid of silver-impregnation techniques. We have found P. acuminata Stein, 1859 in soil samples from upland grassland in Scotland (U.K.). Living and healthy organisms of P. acuminata are oblong in outline, and dorso-ventrally compressed. They closely resemble ciliates of the genus Euplotes. The main morphological features used for identification of P. acuminata are the very long and sparse cirri, and the two macronuclei. When the ciliate crawls, the cirri appear stiff and directed backwards. Specimens observed from the ventral side have a protruding anterior end, a rounded or acuminate posterior pole, and a "beak-like" projection to the left side of the posterior end. The ciliate shares characters with the Euplotidae (body shape and reduced ciliature) and with the Oxytrichidae (marginal rows, macronuclei, reduced number of transverse cirri). Because the arrangement of the silver-impregnated infraciliature was unknown, and as the only description of the ciliate was that of Stein (1859a, b), the genus Psilotricha became confused with other hypotrich genera, especially Urospinula Corliss, 1960. Here we provide a full redescription of P. acuminata based on living and silver-impregnated specimens, and a revision of the genera Psilotricha Stein, 1859 and Urospinula Corliss, 1960. We resurrect the genus Urospinula, and give an emended diagnosis for both genera. The species now included within the genus Psilotricha are P. acuminata Stein, 1859 (type species); Psilotricha viridis (Penard, 1922) Kahl, 1932; and Psilotricha geleii (Gelei, 1954) Stiller, 1974. Psilotricha viridis sensu Kahl, 1932 and Psilotricha dragescoi Grolière, 1975 are considered incertae sedis.

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