Oxytricha Granulifera Research Articles

A New Record of Oxytricha granulifera granulifera Foissner and Adam, 1983 (Protozoa, Ciliophora, Oxytrichidae) From a Hot Spring in Iceland, With Notes on Its Abnormal Form During Cultivation

We isolated a population of Oxytricha granulifera granuliferaFoissner and Adam (1983) from a hot spring in Iceland. The pure culture of this isolate was established at room temperature in the laboratory. This allowed for a detailed investigation, informed by integrated approaches, of the isolate’s morphology and morphogenesis, as well as molecular phylogeny. Results showed that the morphological and morphogenetic characteristics of the Iceland population are consistent with those of other populations. During the 3-year long period of laboratory cultivation, some abnormal individuals appeared repeatedly in the culture system. Interestingly, the morphological characteristics of these abnormal cells were rather stable, and were as follows: 1) body slender and elliptical-shaped; 2) remarkably shortened adoral zone and significantly reduced number of adoral membranelles; and 3) loss of undulating membranes. Resting cysts, binary fission and conjugate reproduction were not found in abnormal specimens. Although the morphology of abnormal individuals changed significantly, the sequences of the SSU rDNA of the normal and abnormal morphotypes were the same. Phylogenetic analyses showed that the two morphotypes clustered in a clade with other populations of O. granulifera granulifera.

Morphological and molecular characterization of Neogastrostyla aqua nov. gen., nov. spec. (Ciliophora, Hypotrichia) from River Yamuna, Delhi; comparison with Gastrostyla-like genera

A novel hypotrichous ciliate, Neogastrostyla aqua nov. gen., nov. spec. isolated from River Yamuna, Delhi, India, is described using morphological, morphometric and morphogenetic characters from live and stained cells supplemented with derivation of phylogenetic relationships using SSU rRNA gene. Neogastrostyla aqua nov. gen., nov. spec., is characterized by light yellow cortical granules present singly or in clusters of two to five, distributed randomly; parental adoral zone of membranelles retained unchanged for proter; Oxytricha-pattern of paroral and endoral; 25–27 frontal-ventral-transverse cirri including a distinct bipartite frontoventral row of composite origin; three dorsal kineties with no fragmentation of the third kinety, two dorsomarginal kineties, three caudal cirri, two macronuclear nodules and two or three micronuclei. Though Neogastrostyla aqua nov. gen., nov. spec. has a frontoventral row like Gastrostyla species, it differs distinctly in the combination of characters from Gastrostyla and other genera with Gastrostyla-like ventral ciliature (Protogastrostyla, Hemigastrostyla, Apogastrostyla and Pseudogastrostyla) particularly in the colour and distribution of cortical granules as well as arrangement and formation of ciliature. According to the phylogenetic analyses, Neogastrostyla aqua nov. gen., nov. spec. clustered consistently with Gastrostyla sp. Y2 (no description available), Oxytricha granulifera and Architricha indica as close neighbours.

A New Subspecies of Oxytricha granulifera (Hypotrichia: Oxytrichidae) from Mexico, with Notes on its Morphogenesis and Phylogenetic Position.

The genus Oxytricha Bory de Saint-Vincent in Lamouroux, Bory de Saint-Vincent and Deslongchamps, 1824 comprises about 38 species distributed worldwide and has been considered to be a nonmonophyletic group. Based on living observations, protargol preparations, and a small subunit ribosomal RNA (SSU rRNA) gene sequence, we describe a new subspecies Oxytricha granulifera chiapasensis n. subsp. This new taxon is morphologically characterized by undulating membranes basically in a Stylonychia-pattern, six dorsal kineties, size invivo ca. 60-120×20-40μm, 21-30 right and 21-31 left marginal cirri, 22-29 adoral membranelles, and spherical cortical granules arranged in longitudinal rows on the dorsal side. In terms of the SSU rRNA gene sequence, the new subspecies differs from populations of O.granulifera from GENBANK by 7-35 nucleotides. Phylogenetic analyses showed that Oxytricha granulifera gene sequences were nested into three groups, with the new subspecies included in one of them. Oxytricha granulifera chiapasensis n. subsp. is different from Oxytricha granulifera granulifera Foissner and Adam, 1983 and Oxytricha granulifera quadricirrata Blatterer and Foissner, 1988 based on: (i)undulating membranes in Stylonychia-pattern, (ii) formation of a sixth dorsal kinety during morphogenesis, (iii) the adoral membranelles number, and (iv)inhabiting freshwater habitats.

Morphogenesis of a saline soil ciliate Urosoma salmastra (Dragesco and Dragesco-Kernéis, 1986) Berger, 1999 with notes on the phylogeny of Urosoma (Ciliophora, Hypotrichia)

Morphogenesis in a population of Urosoma salmastra collected from saline soil in Weinan, China, was investigated using protargol staining. The main morphogenetic event that characterizes U. salmastra is the inclusion of cirrus III/2 in the formation of the frontoventra-transverse cirral anlagen. We also provide small subunit ribosomal DNA gene sequences for a population of U. salmastra and for two populations of U. emarginata. The molecular phylogeny indicates that Urosoma is not monophyletic, viz, U. emarginata branches separately from its congeners and the closest relative of U. salmastra is Oxytricha granulifera.

First report of predation of Giardia sp. cysts by ciliated protozoa and confirmation of predation of Cryptosporidium spp. oocysts by ciliate species.

Ciliated protozoa are important components of the microbial food web in various habitats, especially aquatic environments. These organisms are useful bioindicators for both environmental quality assessment and the wastewater purification process. The pathogenic parasitic protozoan species Giardia and Cryptosporidium represent a significant concern for human health, being responsible for numerous disease outbreaks worldwide. The predation of cysts and oocysts in 15 ciliate species from water and sewage samples collected in Campinas, São Paulo, Brazil were verified under laboratory conditions. The ciliated protozoan species were selected based on their mode of nutrition, and only bacterivorous and suspension-feeders were considered for the experiments. The species Blepharisma sinuosum, Euplotes aediculatus, Sterkiella cavicola, Oxytricha granulifera, Vorticella infusionum, Spirostomum minus, and Stentor coeruleus ingested cysts and oocysts, the resistance forms of Giardia spp. and Cryptosporidium spp., respectively. This is the first time that the ingestion of Giardia cysts by ciliated protozoa has been reported. These findings may contribute to a better understanding of the biological removal of these pathogens from aquatic environments.

Morphology and molecular phylogeny of an Indian population of Cyrtohymena citrina (Ciliophora, Hypotricha), including remarks on ontogenesis of Urosomoida-Notohymena-Cyrtohymena group

The oxytrichid ciliate Cyrtohymena citrina, isolated from a soil sample from India, is moderately flexible, measures about 105×35μm in life and possesses citrine cortical granules, mainly arranged around cirri and dorsal cilia. Morphology and ontogenesis was investigated using live observation and protargol impregnation, and 18S rDNA was sequenced. Ontogenesis of an Indian population of Urosomoida agilis was also investigated. All three genera included in the Urosomoida-Notohymena-Cyrtohymena group have long been characterized by the ontogenetic feature that “anlagen V and VI of proter originate de novo”. This ontogenetic feature has been considered as the sole synapomorphy and an important diagnostic feature of the group. Based on current observations on ontogenesis of C. citrina and U. agilis, and previous observations of C. shii, Notohymena saprai and N. australis, the aforesaid ontogenetic feature is no longer true for the group. Indian population of C. citrina clusters with C. muscorum, Paraurosomoida, Urosomoida, Notohymena and Paraurostyla, and is placed away from Oxytricha granulifera; all oxytrichids in the cluster show deviation(s) from any of the typical oxytrichid features like Oxytricha pattern undulating membrane, 18 frontoventral transverse cirri and fragmentation of dorsal kinety 3. Phylogenetic analyses supported non-monophyly of Cyrtohymena and other flexible-bodied oxytrichids.

Morphology and phylogenetic position of the oxytrichid ciliates, Urosoma salmastra (Dragesco and Dragesco-Kernéis, 1986) Berger, 1999 and U. karinae sinense nov. sspec. (Ciliophora, Hypotrichia)

The morphology and infraciliature of two hypotrichous ciliates, Urosoma salmastra and U. karinae sinense nov. sspec., were investigated for populations collected from the surface of intertidal gravel in the Huguang Mangrove Forest, Zhanjiang, China and the upper 10cm layer of soil in the Sangke Grass Land in the southern part of Gansu Province, China, respectively. Urosoma salmastra is characterized by its elongate-elliptical body with no tail-like structure; two macronuclear nodules; cortical granules colourless, less than 1μm across, and arranged in short rows; adoral zone occupying 25% of body length in vivo; paroral conspicuously short and located in front of endoral. Urosoma karinae sinense nov. sspec. is characterized by its elongate-elliptical body with no tail; 2–4 macronuclear nodules; cortical granules colourless, less than 1μm across, and arranged in short rows; adoral zone occupying 30% of body length in vivo; paroral shorter than, and located ahead of endoral. Phylogenetic analyses based on SSU rRNA gene sequence data suggest a close relationship between U. salmastra, U. karinae sinense nov. sspec. and Oxytricha granulifera within the Oxytrichinae assemblage.

Morphology and phylogenetic analysis of two oxytrichid soil ciliates from China, Oxytricha paragranulifera n. sp. and Oxytricha granulifera Foissner and Adam, 1983 (Protista, Ciliophora, Hypotrichia).

The morphology and infraciliature of two hypotrichous ciliates, Oxytricha paragranulifera n. sp. and Oxytricha granulifera Foissner and Adam, 1983, collected respectively from the surface of a sandy soil in the Huguang mangrove forest, Zhanjiang, China, and the surface of soil in a forest beside Ziwu Road, Xian, north-west China, were examined. O. paragranulifera n. sp. is characterized by an elongate body with slightly tapered anterior end, two macronuclear nodules and two micronuclei, paroral and endoral in Stylonychia-pattern, colourless cortical granules distributed in clusters or irregular short rows, adoral zone occupying 37 % of the body length, marginal rows almost confluent posteriorly, six dorsal kineties and three caudal cirri, caudal cirri and dorsal bristles almost indistinguishable when viewed in vivo. The well-known O. granulifera Foissner and Adam, 1983 was also redescribed and can be separated from the novel species by having cortical granules arranged along dorsal kineties and marginal rows on both sides (vs grouped in clusters as well as in short irregular rows), paroral and endoral in Oxytricha-pattern (vs in Stylonychia-pattern), macronuclear nodules obviously detached (vs adjacent) and a non-saline terrestrial habitat (vs saline terrestrial). The separation of these two taxa is also firmly supported by the molecular data, which show a significant difference between the two in their SSU rRNA gene sequences (similarity 97.1 %). Phylogenetic analyses based on SSU rRNA gene sequence data suggest a close relationship within the Oxytrichidae assemblage between O. paragranulifera n. sp. and O. granulifera.

Two Oxytrichid Ciliates, Cyrtohymena primicirrata and Oxytricha granulifera (Ciliophora: Sporadotrichida: Oxytrichidae) Unknown from Korea

This study reports the discovery of two oxytrichid ciliates, Cyrtohymena primicirrata (Berger and Foissner, 1987) and Oxytricha granulifera Foissner and Adam, 1983, in Jeju Island, Korea. The morphology of the two species was studied using live observation and protargol impregnation. These species are described as follows: Cyrtohymena primicirrata has a body size in live specimens <TEX>$90-140{\times}40-60{\mu}m$</TEX>, length : width ratio 2.3 : 1 on average; elongated and slender obovate in outline of body. Cortical granules are shiny yellow on the ventral and dorsal side. Adoral zone of membranelles (AZM) is covering about 48% of the cell with about 38 adoral membranelles. Arrangement of undulating membranes is ordinary Cyrtohymena pattern. Dorsal kineties is six rows with <TEX>$5{\mu}m$</TEX> long bristles. Oxytricha granulifera has a body size in live specimens <TEX>$90-115{\times}25-38{\mu}m$</TEX>, length : width ratio 3.31 on average; elongated ellipsoidal in outline of body. Cortical granules are colorless on the ventral and dorsal side. AZM is covering 28% of the cell length in vivo with about 24 adoral membranelles. Arrangement of undulating membranes is Oxytricha pattern. Dorsal kineties is five rows with about <TEX>$3{\mu}m$</TEX> long dorsal bristles.

A comparative fine structural and phylogenetic analysis of resting cysts in oligotrich and hypotrich Spirotrichea (Ciliophora)

So far, neither morphology nor gene sequences have provided a reliable classification of halteriid and hypotrichid spirotrichs. Thus, we performed a comparative study on the fine structure of the resting cysts in some representative species, viz., the oligotrichs Halteria grandinella and Pelagostrombidium fallax and the oxytrichid hypotrichs Laurentiella strenua, Steinia sphagnicola, and Oxytricha granulifera. Main results include: (i) there are three different, very likely non-homologous cyst surface ornamentations, viz., spines (generated by the ectocyst), thorns (generated by the mesocyst), and lepidosomes (produced in the cytoplasm); (ii) Halteria has a perilemma; (iii) Halteria, Meseres and Pelagostrombidium have fibrous lepidosomes, while those of Oxytricha are tubular; (iv) the cyst wall structure of Pelagostrombidium and Strombidium is distinctly different from that of halteriids and oxytrichids, which are rather similar in this respect; (v) cyst ornamentation does not provide a reliable phylogenetic signal in oxytrichid hypotrichs because ectocyst spines occur in both flexible and rigid genera. The new observations and literature data were used to investigate the phylogeny of the core Spirotrichea. The Hennigian argumentation scheme and computer algorithms showed that the spirotrichs are bound together by the macronuclear reorganization band, the subepiplasmic microtubule basket, and the apokinetal stomatogenesis. The Hypotrichida and Oligotrichida are united by a very strong synapomorphy, viz., the perilemma, not found in any other member of the phylum. Halteriid and oligotrichid spirotrichs form a sister group supported by as many as 13 apomorphies. Thus, the molecular data, which classify the halteriids within the core hypotrichs, need to be reconsidered.

Rigidothrix goiseri nov. gen., nov. spec. (Rigidotrichidae nov. fam.), a new “flagship” ciliate from the Niger floodplain breaks the flexibility-dogma in the classification of stichotrichine spirotrichs (Ciliophora, Spirotrichea)

Rigidothrix goiseri nov. gen., nov. spec. was discovered in soil from the Niger floodplain near to the town of Timbuktu, Republic of Mali. Its morphology, ontogenesis, and 18S rDNA gene sequence were studied with standard methods. Rigidothrix goiseri is very conspicuous in vivo because of its average size of 230×70 μm and a distinct tail. Further main characteristics include the rigid body; the conspicuous, stylonychid frontal area; the undulating membranes in Oxytricha pattern; a mighty adoral zone of membranelles not reorganized during ontogenesis; distinct midventral rows of which those of the opisthe develop right of the parental ones; and eight dorsal kineties, of which three develop intrakinetally and five are generated dorsomarginally. Rigidothrix goiseri possesses main characteristics of oxytrichine, stylonychine, and urostyline stichotrichs, specifically, it is the first rigid stichotrich with midventral rows, and thus it breaks the flexibility dogma. Distinct similarities with the genus Uroleptus and the CEUU hypothesis suggest that R. goiseri is more closely related to the oxytrichine than urostyline stichotrichs, in spite of the conspicuous midventral rows. This is also supported by the sequence data which show that R. goiseri is almost equally similar to both Oxytricha granulifera (95.88%) and Uroleptus gallina (94.93%), but fairly different from Urostyla grandis (92.7%). The main morphological peculiarities of R. goiseri show that it represents a new genus which should be classified into a new family, the Rigidotrichidae, together with the genera Uroleptus, Territricha, and Afrophrya nov. gen., the latter comprising Rigidothrix-like stichotrichs with cyrtohymenid oral apparatus. The conspicuous size and shape make R. goiseri a biogeographic flagship likely confined to Africa.

Reconciling classical and molecular phylogenies in the stichotrichines (Ciliophora, Spirotrichea), including new sequences from some rare species

We performed a comparative morphological and molecular study on oxytrichid and urostylid stichotrichs (=part of the former hypotrichs). Included are new small subunit (18S) ribosomal RNA (rRNA) gene sequences from five rare oxytrichids ( Gonostomum namibiense, Cyrtohymena citrina, Hemiurosoma terricola, Onychodromopsis flexilis, Orthoamphisiella breviseries) and published sequences, based on cultures provided by the senior author, of two key stichotrichid genera, viz., Gastrostyla and Engelmanniella. These and other sequences, altogether 27 species representing 23 genera, were used to analyze how 18S rRNA-based phylogenetic trees can be reconciled with the morphological and ontogenetical data. In 18S rRNA trees, the oligotrichine family Halteriidae invariably clusters within the oxytrichid clade, usually near Oxytricha granulifera, type species of the genus. This position is hardly supported by morphological and ecological evidence and, especially, it contradicts the current ontogenetic findings; possibly, it is an artifact caused by taxa undersampling and/or special molecular evolutionary events. In contrast, most morphological and DNA sequence data of the stichotrichs can be harmonized with the CEUU ( Convergent Evolution of Urostylids and Uroleptids) hypothesis which suggests that the urostylid midventral pattern evolved from an oxytrichine ancestor, developing a second time within the Oxytrichidae. The systematic position of one of the two key genera could be clarified with the 18S rRNA sequences: Gastrostyla is a stylonychine oxytrichid. Based on the molecular data and a reassessment of ontogenesis, a new genus, Styxophrya nov. gen., is established for Onychodromus quadricornutus Foissner, Schlegel & Prescott, 1987.

Phylogenetic relationships among 28 spirotrichous ciliates documented by rDNA

The contiguous sequence of the SSU rDNA, ITS 1, 5.8S, ITS 2, and ∼1370 bp at the 5 ′ end of the LSU rDNA was determined in 25 stichotrichs, one oligotrich, and two hypotrichs. Maximum parsimony, neighbor-joining, and quartet-puzzling analyses were used to construct individual phylogenetic trees for SSU rDNA, for LSU rDNA, and ITS 1 + 5.8S + ITS 2, as well as for all these components combined. All trees were similar, with the greatest resolution obtained with the combined components. Phylogenetic relationships were largely consistent with classical taxonomy, with notable disagreements. DNA sequences indicate that Oxytricha granulifera and Oxytricha longa are rather distantly related. The oligotrich, Halteria grandinella, is placed well within the order Stichotrichida. Uroleptus pisces and Uroleptus gallina probably belong to different genera. Holosticha polystylata (family Holostichidae) and Urostyla grandis (family Urostylidae) are rather closely related. These rDNA sequence analyses imply the need for some modifications of classical taxonomic schemes.

Histone H4 genes in some stichotrichous ciliates

Two or more macronuclear molecules encode histone H4 among eight stichotrichs ( Sterkiella nova , Sterkiella histriomuscorum , Stylonychia mytilus , Stylonychia lemnae , Pleurotricha lanceolata , Oxytricha granulifera , Sterkiella sp. (Aspen), and Paraurostyla viridis ). Only one macronuclear molecule encodes histone H4 in Uroleptus sp. Histone H4 molecules have been sequenced in five of the stichotrichs. Codon bias is extreme. The encoded amino acid sequences (104 amino acids) are identical. They differ significantly from the histone H4 sequences encoded by the hypotrichs, Euplotes aediculatus and Moneuplotes crassus (both 107 amino acids). Three major and five minor blocks of conserved nucleotide sequences are present throughout the ∼1150 bp 5′ noncoding leaders in the five stichotrichs. These conserved sequences may serve in regulation of gene function. However, all five 5′ leaders also contain different ORFs encoding amino acid sequence with similarity to sequences in GenBank. Except possibly for the ORF in Stylonychia mytilus and an ORF in Pleurotricha lanceolata , the ORFs appear not to be significant. The 50 bp in the ends of the macronuclear molecules contain an anomalous base composition that may be important in genome processing. The micronuclear histone H4 gene in Sterkiella nova contains an IES in the 5 leader, and the ORF in Sterkiella histriomuscorum contains a single IES.

Phylogenetic position of the ciliates Phacodinium (Order Phacodiniida) and Protocruzia (Subclass Protocruziidia) and systematics of the spirotrich ciliates examined by small subunit ribosomal RNA gene sequences

The small subunit rRNA (SSrRNA) genes were sequenced for Protocruzia sp2, Phacodinium metchnicoffi, Holosticha multistylata, and Halteria grandinella. All four genera are placed within the Class Spirotrichea with strong bootstrap support in both distance matrix and parsimony tree construction methods and by maximum likelihood analysis using quartet puzzling. Protocruzia sp2 groups with Protocruzia sp1 with 100% bootstrap support, and the 5.6% genetic difference between them strongly argues that they are different species although they are morphologically quite similar. The Protocruzia species branch first in the spirotrich clade at a deep level, supporting their recognition as a Subclass Protocruziidia. Phacodinium branches after Euplotes at a deep level, confirming the conclusion that others have reached that this genus is related to the hypotrich and stichotrich spirotrichs. Phacodinium is assigned to its own family and order, and we conclude that the deep branching within the spirotrichs argues for its own subclass, the Subclass Phacodiniidia. Consistent with the partial SSrRNA sequences and with the sequence of a polymerase gene, Halteria groups within the stichotrich clade, supporting the argument that the oligotrichs are not monophyletic as currently conceived. Finally, Holosticha, which has been assigned to the Order Urostylida, groups outside the stichotrichs with parsimony analysis, which is consistent with this ordinal assignment. However, it is associated with Halteria and Oxytricha granulifera in the other analyses. Additional stichotrich sequences obviously are required before we can confidently begin revision of the Subclass Stichotrichia.

Cloning and characterization of the Oxytricha granulifera chaperonin containing tailless complex polypeptide 1 gamma gene.

Here we report the cloning and characterization of the Oxytricha granulifera CCTgamma (chaperonin containing tailless complex polypeptide 1) gene encoding a protein that consists of 559 amino acids. The derived amino acid sequence shares 68% identity with Tetrahymena pyriformis CCTgamma and 58% identity with Mus musculus CCTgamma. The O. granulifera CCTgamma gene is located on a 2.07-kbp macronuclear gene-sized piece. Its transcription initiation site was determined by primer extension analysis. The expression of the CCTgamma gene was investigated by northern blot hybridization of the coding region with exponentially growing cells, heat shocked cells, and cells treated with 50 microM CdCl2. After heat shock, a decrease in the amount of the transcript compared to that of exponentially growing cells could be shown. In contrast, higher amounts of the transcript could be detected after treatment with CdCl2.

Evidence of a cadmium-thionein and the glycine cleavage system in Oxytricha granulifera.

This work presents the further purification of a Cd-linking protein in Oxytricha granulifera by reverse-phase chromatography. This protein contains 25% cysteine and no aromatic amino acid. It may be considered as a chelatin with some similarity to metallothioneins. During the purification of another Cd-linking compound, we were able to demonstrate that the H protein precursor of glycine cleavage is present in Oxytricha. This is the first finding of the presence of this system in Protozoa.

Effects of Cadmium in Stylonychia lemnae, Stylonychia notophora and Oxytricha granulifera: Isolation of a Cadmium‐Binding Protein

ABSTRACT The effects of cadmium on three ciliates are reported here. Cultures of Stylonychia lemnae, Stylonychia notophora and Oxytricha granulifera were treated with different doses of Cd according to tolerance. The two species of Stylonychia are very sensitive to the metal, white O. granulifera tolerates higher doses. Adding 50 μM of Cd to the medium did not damage cells. The accumulated metal is almost totally present in the particulate fraction after day 3. Two Cd‐Zn linking fractions were separated from the soluble fraction of culture treated on day 1. The first protein linking 17 μg Cd/mg showed an ultraviolet absorption spectrum similar to that of Cd‐thioneins. Preliminary amino acid analyses indicated that it contained 13% cysteine. The second protein, linking 60 μg Cd/mg, was a glycoprotein. Its ultraviolet absorption spectrum and amino acid analysis showed that this binding protein was far from being a metallothionein: its cysteine content was very low and aromatic and cyclic residues were present. This Cd‐linking compound seems to be unique, since it was very different both from metallothioneins and chelatins isolated by other protozoa. The protective role of these chelating proteins is discussed.

Molecular evolution in hypotrichous ciliates: Sequence of the small subunit ribosomal RNA genes fromOnychodromus quadricornutus andOxytricha 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.

Morphologie und Morphogenese des Bodenciliaten Oxytricha granulifera sp.n. (CiIiophora, Oxytrichidae)

Oxytricha granulifera sp.n. differs from other members of the genus by its subpellicular granules and the strongly shortened dorsal kinety 4. The overall pattern of the morphogenetic events is similar to that known from other Oxytrichidae. However, the oral primordium evolves de novo between the left marginal cirral row and the postoral cirri. The six anlagen of the frontoventral cirri are of different origin. Two anlagen of the proter evolve from parental frontal cirri, two from the opisthe, and one includes basal bodies of the proter and opisthe. Two anlagen of the opisthe evolve from the oral primordium, and three primordia originate from the postoral cirri. Frontal cirrus 1 evolves from the paroral membrane in the proter, and from the oral primordium and the anlagen of the frontoventral cirri in the opisthe. The genus Oxytricha can be subdivided into several groups with regard to the origin of its oral primordium and the development of the frontoventral cirri. The morphogenesis of the dorsal kineties in the Hypotrichida is reviewed. Seven different modes of origin are distinguished. We conclude that morphogenetic features cannot be used in the classification of the Hypotrichida at the generic level, because we have too little information to decide whether special morphogenetic features are important at the generic or species level.