Cirral Anlagen Research Articles

Morphology and morphogenesis of a soil urostylid ciliate, Paragastrostyla terricola (Foissner, 1988) Berger, 2006 (Ciliophora: Hypotrichia)

ABSTRACT The soil urostylid ciliate Paragastrostyla terricola, isolated from northern China, was studied for its morphology and morphogenesis using live observation and protargol impregnation. The main ontogenetic features of P. terricola are as follows: (a) in the proter, the anterior portion of the parental adoral zone of membranelles is retained, while only the posterior part is renewed; undulating membranes anlage undergo, like most hypotrichs, depolymerisation of old undulating membranes and differentiation of new structures; (b) usually eight frontoventral cirral anlagen are formed, the penultimate anlage produces the midventral row and the rightmost anlage produces three frontoterminal cirri; (c) marginal and dorsal kineties anlagen are formed intrakinetally; one caudal cirrus is formed at the posterior end of each dorsal kinety; (d) the macronuclear nodules fuse into a single mass during the process. http://www.zoobank.org/urn:lsid:zoobank.org:pub:A150EE18-03BF-46B4-9E5B-48273FBA2CFF

Morphology, Morphogenesis and Molecular Phylogeny of Two Freshwater Ciliates (Alveolata, Ciliophora), with Description of Pseudosincirra binaria sp. nov. and Redefinition of Pseudosincirra and Perisincirra

Ciliated microeukaryotes are insufficiently investigated despite their ubiquity and ecological significance. The morphology and morphogenesis of a new Stichotrichida species, Pseudosincirra binaria sp. nov., and the known Perisincirra paucicirrata Foissner et al., 2002, are here studied using live observations and protargol staining methods. The new species is characterized by having one buccal, one parabuccal and three frontal cirri, one frontoventral row extending to the posterior half of the cell, three left and two right marginal rows and three dorsal kineties with the left kinety conspicuously bipartite, along with one caudal cirrus at the rear end of each kinety. During morphogenesis, there exist five frontal-ventral cirral anlagen with anlagen IV and V forming a frontoventral row in the proter, and four cirral anlagen with only anlage IV generating a frontoventral row in the opisthe. The anlagen for marginal rows and dorsal kineties develop intrakinetally. The new population of Perisincirra paucicirrata corresponds well with other isolates regarding morphology and cell development. Phylogenetic analyses based on small subunit ribosomal gene sequence data revealed that both Perisincirra and Pseudosincirra are deeply clustered in the clade consisting of species from the genera Deviata and Heterodeviata, supporting the placement of both genera into the family Deviatidae Foissner, 2016.

Multi-gene-based investigation on the molecular phylogeny of the hypotrichous family Strongylidiidae (Protista, Ciliophora), with notes on the ontogeny of a new genus and new species

Ciliates in the subclass Hypotrichia have long been difficult to classify as they are one of the most polymorphic and highly differentiated groups, leading to their systematics remaining unresolved. Phylogenetic relationships within the hypotrich family Strongylidiidae have been ambiguous due to discordance between the morphological and genetic data. In this study, a new strongylidiid genus Heterouroleptus is established, mainly based on the novel mode of origin of the ventral cirral rows: left ventral cirral row (LVR) originates from frontal–ventral–transverse cirral anlagen (FVTA) III (anterior portion), IV (middle portion), and V (rear portion); right ventral cirral row comes from the entire FVTA VI. A new species, Heterouroleptus weishanensis gen. nov., sp. nov., is investigated along with the morphometric and molecular data from a population of Strongylidium wuhanense. Eight new sequences and nuclear gene markers (single-gene and multi-gene) are provided to analyze the phylogenetic relationships of strongylidiids, with the COI gene utilized to uncover further genetic information at species level and below. The results reveal that: (1) Strongylidiidae is monophyletic and has a close relationship with Dorsomarginalia; (2) Heterouroleptus gen. nov. forms a clade that is sister to all the other strongylidiids; (3) Hemiamphisiella Foissner, 1988 and Pseudouroleptus Hemberger, 1985 should not be synonyms, and both genera should be subdivided due to their variable morphological characteristics; (4) LVR originating from three anlagen is a plesiomorphy of Strongylidiidae. The discovery of the origin of the LVR not only contributes to the establishment of the genus Heterouroleptus, but also helps to improve the diagnosis of the family Strongylidiidae.

Morphology, morphogenesis and molecular phylogeny of a new soil ciliate, Lamtostyla paravitiphila nov. spec. (Ciliophora, Hypotrichia)

The morphology and morphogenesis of Lamtostyla paravitiphila nov. spec., a novel soil hypotrichous ciliate collected from eastern China, were investigated based on live observations and protargol-stained specimens. The new species is morphologically characterized as follows: seven to twelve macronuclear nodules, cortical granules absent, 19–26 adoral membranelles, three or four frontoventral cirri, the amphisiellid median cirral row extends to about mid-body and composed of 12–18 cirri, two or three transverse cirri, 27–39 left and 30–41 right marginal cirri, three almost bipolar dorsal kineties. Morphogenetically, it is characterized by the initial formation of six frontal-ventral-transverse cirral anlagen as primary primordia. Notably, the amphisiellid median cirral row and the posterior frontoventral cirrus (or cirri) contribute to the development of the frontal-ventral-transverse cirral anlagen, while the buccal cirrus may not participate in this process. Phylogenetic analyses based on small subunit ribosomal DNA sequence data indicate that the Lamtostyla species with available molecular data do not form a monophyletic group.

Morphological, ontogenetic, and phylogenetic research of a poorly known non-dorsomarginalian ciliate: Erniella filiformis Foissner, 1987 (Protista, Ciliophora, Hypotrichia)

Erniella Foissner, 1987 is a poorly known genus with its available information limited solely to morphological characteristics. In this study, the type species E. filiformis, isolated from highly saline water in China, was investigated for morphology, morphogenesis, and phylogeny based on small subunit ribosomal DNA sequences. The main characteristic events during morphogenesis in Erniella filiformis are as follows: (1) in the proter, only the posterior part of the parental adoral zone is renewed and undulating membranes anlage is formed from the dedifferentiation of the old structure; (2) the oral primordium is formed intrakinetally in the opisthe; (3) frontoventral-transverse cirral anlagen II–IV develop in the primary mode, anlage V develops intrakinetally in the proter; and (4) the right frontoventral row is formed by a single anlage. The phylogenetic analyses indicate that Erniella forms a monophyletic group with Bistichella, Keronopsis, Lamtostyla, Orthoamphisiella, Parabistichella, Paraholosticha, and Uroleptoides.

Three closely-related subclasses Phacodiniidia Small & Lynn, 1985, Protohypotrichia Shi et al., 1999, and Euplotia Jankowski, 1979 (Protista, Ciliophora): A new contribution to their phylogeny with reconsiderations on the evolutionary hypotheses

The huge variety of species and worldwide distribution of ciliated protists in class Spirotrichea continue to make it one of the most complicated and confused groups in Ciliophora, despite significant research interest in the unique molecular genetics of these organisms. In this study, the morphological and molecular information were integrated, and it is inferred from a new perspective for the evolutionary relationship among Phacodiniidia, Protohypotrichia, Hypotrichia and Euplotia. Our results indicate that Kiitricha and Caryotricha, two members in Protohypotrichia, may represent two parallel branches of evolution; Euplotidae and Aspidiscidae represent the most recently diverged taxa within Euplotida, followed by Certesiidae, Gastrocirrhidae, and Uronychidae. Further, representative morphological characters (e.g. fronto-ventral-transverse cirral anlagen, undulating membranes, marginal cirri and caudal cirri) were stochastically mapped on phylogenies to speculate evolutionary path and morphological characters of the evolutionary transition node groups were assumed.

Morphology, morphogenesis and molecular phylogeny of a novel saline soil ciliate, Urosoma quadrinucleatum n. sp. (Ciliophora, Hypotrichia)

The morphology and morphogenesis of a new saline soil hypotrichous ciliate, Urosoma quadrinucleatum n. sp., collected from northwestern China, were studied based on live observations and protargol stained specimens. The new species is characterized as follows: size in vivo 90–130 × 20–30 μm; body outline elongate-elliptical with both ends broadly rounded; four macronuclear nodules; cortical granules present; paroral in front of endoral; usually 16 frontal-ventral-transverse cirri. Urosoma quadrinucleatum n. sp. has almost the same morphogenetic characteristics as its congeners U. gigantea and U. salmastra, and differs from other three congeners whose morphogenesis is known in the formation of the frontal-ventral-transverse cirral anlagen as well as the development of marginal and dorsal kineties anlagen. The sequence differences among U. quadrinucleatum n. sp. and other Urosoma species further support the validity of the present organism as novel species. Further, U. quadrinucleatum n. sp. clusters with U. salmastra in the phylogenetic analyses based on small subunit ribosomal RNA gene (SSU rDNA) sequence data.

Doublets of the unicellular organism Euplotes vannus (Alveolata, Ciliophora, Euplotida): the morphogenetic patterns of the ciliary and nuclear apparatuses associated with cell division.

Ciliated protists are one of the most diverse and highly differentiated group among unicellular organisms. Doublets occur in ciliates when two cells fuse into a single individual. Doublets contain two major cellular components (either cell in a doublet) and have traditionally been considered as developmental anomalies. Nevertheless, doublets can divide or even conjugate effectively, which may represent dispersal forms of the life stages. In addition, morphogenesis, as an important process in the life cycle, will provide important insights into the complex differentiation mechanism and various physiological phenomena. However, morphogenetic studies focusing on doublets of ciliates are very limited, which has become an obstacle to understand their complete life history. Here we isolated a doublet strain from the marine species Euplotes vannus (Müller, 1786) Diesing, 1850 and investigated its morphogenetic events during asexual reproduction. Our results indicate that: (1) the opisthe's oral primordium develops de novo beneath the cortex; (2) the frontoventral and transverse cirral anlagen, cirrus I/1, and marginal anlagen in both dividers develop de novo separately; (3) the dorsal kinety anlagen, the three rightmost ones of which produce three caudal cirri for the proter, occur within the parental structures in the mid-body region; (4) the opisthe acquires two caudal cirri, one from the end of each two rightmost kineties; and (5) there are two macronuclei and one micronucleus in the doublet and they divide amitotically and mitotically, respectively. Finally, we speculate that this special differentiation may be an adaptive form to adverse environments.

Ontogenesis and systematic position of a new hypotrichous ciliate, Chaetospira sinica sp. nov., with an improved diagnosis of the poorly defined family Chaetospiridae Jankowski, 1985 (Protozoa, Ciliophora, Hypotrichia).

Ciliates are unique single-celled organisms that play important roles in ecological, environmental, evolutionary, and ontogenetic research. In the present study, phylogenetic analyses based on 18S rRNA gene sequence data reveal that Chaetospira sinica sp. nov. clusters with Stichotricha aculeata with strong to full support (97% ML, 1.00 BI), but is not closely related to members of Spirofilidae Gelei, 1929 to which Chaetospira and Stichotricha have previously been assigned. Phylogenetic analyses, together with morphological and morphogenetic data from Chaetospira sinica sp. nov., support the validity of family Chaetospiridae Jankowski, 1985. Chaetospira and Stichotricha are here assigned to the family Chaetospiridae, the improved diagnosis of which is as follows: non-dorsomarginalian Hypotrichia with flask-shaped body; oral region extending along narrow anterior neck region; lorica usually present; two ventral and two marginal cirral rows, all distinctly spiraled or obliquely curved; pretransverse and transverse cirri absent. The basic morphogenetic features in C. sinica sp. nov. can be summarized as: (1) the oral primordium for the opisthe develops de novo and the parental adoral zone is completely retained by the proter; (2) all ventral cirral anlagen and marginal anlagen developed intrakinetally; (3) three dorsal kineties anlagen formed intrakinetally in each daughter cell; and (4) macronuclear nodules fuse into a single mass. Exconjugant cells were also isolated and their morphologic and molecular data are provided.

Morphology, morphogenesis and molecular phylogeny of Lamtostyla granulifera sinensis subsp. nov. (Ciliophora, Hypotrichia) from a wetland in China

The morphology, morphogenesis and molecular phylogeny of a hypotrichous ciliate, Lamtostyla granulifera sinensis subsp. nov., isolated from northern China, were investigated. This population appeared highly similar in morphology to L. granulifera Foissner, 1997. However, on detailed investigation some non-overlapping features were identified, i.e., the body shape and the arrangement of the cortical granules. These differences suggested the separation at subspecies level. Furthermore, the morphogenesis of the new subspecies is described, which is characterized by: (1) the posterior part of the parental adoral zone of membranelles is renewed; (2) the amphisiellid median cirral row is formed from two anlagen; and (3) the frontoventral-transverse cirral anlagen II to VI generate one transverse cirrus each. Phylogenetic analyses based on SSU rDNA sequence data show that Lamtostyla species are scattered in different clades. The monophyly of the genus Lamtostyla is also rejected by the AU test in this study.

Morphology, morphogenesis and phylogeny of a new soil ciliate, Bistichella sinensis n. sp., and morphology of two oxytrichids (Ciliophora, Hypotrichia)

The living morphology, infraciliature, morphogenesis and phylogenetic position of a new soil ciliate, Bistichella sinensis n. sp. collected from Northwest of China, were investigated. The new species is characterized by an elongate-oval body, two macronuclear nodules, colourless cortical granules, three frontal and three or four buccal cirri, three frontal rows with 7–10 cirri in total, and usually-two frontoventral rows with the left one usually terminating at 90% down length of body. The main morphogenetic features of the novel species are as follows: (1) the posterior part of the parental adoral zone is renewed; (2) frontal-ventral cirral anlagen III to V each forms a frontal row, and anlagen VI to n each produces a frontoventral row; (3) marginal rows and dorsal kineties develop intrakinetally. Furthermore, the phylogenetic analyses based on small subunit ribosomal DNA reveal close relationship between Bistichella sinensis n. sp., Parabistichella, Uroleptoides, Lamtostyla, Keronopsis, Paraholosticha and Orthoamphisiella. The in vivo morphology and the infraciliature of the Chinese populations of Monomicrocaryon euglenivorum fimbricirratum and Laurentiella strenua are basically identical to previous descriptions. Improved diagnoses for M. euglenivorum and its two subspecies, as well as a redescription of a Chinese population of L. strenua are supplied.

Conjugation in the eukaryotic single-celled organism Euplotes aediculatus (Protozoa, Ciliophora): A focus on nuclear divisions, morphogenesis and pheromones

Ciliates are unique in having nuclear dimorphism (i.e., possessing both a germline micronucleus and a somatic macronucleus in one cell), and undergo dramatic changes during their sexual process (known as conjugation). Here we investigate the nuclear events and morphogenetic processes during conjugation in the freshwater species Euplotes aediculatus. In addition, three conjugation-related pheromone genes were sequenced and analyzed. The results indicate that: (i) the 65-hour-long conjugation process includes five nuclear divisions, i.e., three prezygotic divisions (mitosis, meiosis I and II) and two postzygotic divisions; (ii) the ciliature reorganizes twice during conjugation with the frontoventral-transverse cirral anlagen regenerating during both morphogenetic events and breaking apart in a 3:3:3:2:2 pattern; and (iii) each of three pheromone genes contains a 444 bp coding region and encodes 147 amino acid polypeptides. These results suggest a broadly shared morphogenetic pattern during conjugation in Euplotes species and provide new information for studies on the evolutionary history of pheromone genes.

Morphology, cell division, and phylogeny of Notohymena antarctica Foissner, 1996 and Engelmanniella mobilis (Engelmann, 1862) Foissner, 1982 (Ciliophora, Hypotrichia)

The morphogenesis of two hypotrich ciliates, Notohymena antarctica Foissner, 1996 and Engelmanniella mobilis (Engelmann, 1862) Foissner, 1982, were investigated using protargol staining. The main events of the oxytrichid Notohymena antarctica during binary fission are as follows: (1) the oral primordium of the opisthe is formed apokinetally left of transverse cirrus II/1; (2) six streaks of frontal-ventral-transverse cirral anlagen are segmented in the ordinary pattern 1: 3: 3: 3: 4: 4 from left to right, which form three frontal, four frontoventral, one buccal, three ventral, two pretransverse ventral and five transverse cirri; (3) marginal anlagen are formed intrakinetally and the right marginal anlagen develop much earlier than those on the left. Phylogenetic analyses based on SSU rDNA sequence data indicate that Notohymena is monophyletic. A remarkable morphogenetic feature in E. mobilis is the mode of formation of the right marginal rows. In this paper, we clarified that the right marginal anlagen of E. mobilis are formed and develop to the right of the parental outer right marginal row, and that the grandparental (inner) right marginal row and great-grand parental (the outermost) left marginal row are resorbed. It is the first time to report a population of E. mobilis with comprehensive information, i.e. the morphology, ontogeny and molecular sequence.

Redescription and phylogenetic position of the terrestrial ciliates Gastrostylides dorsicirratus and Heterourosomoida lanceolata (Hypotricha, Dorsomarginalia)

The morphology and infraciliature of two soil hypotrichous ciliates, Heterourosomoida lanceolata (Shibuya, 1930) Singh and Kamra, 2015 and Gastrostylides dorsicirratus (Foissner, 1982) Foissner, 2016, were investigated using live observation and protargol staining. The Chinese population of H. lanceolata differs slightly from other populations in the body size in vivo, the relative length of the adoral zone, the number of right and left marginal cirri, the total number of dorsal bristles, and the number of micronuclei. The Chinese population of G. dorsicirratus corresponds well with Austrian and Indian populations. We also document the morphogenetic processes during binary fission of G. dorsicirratus, including the formation of the frontoventral-transverse cirral anlagen in a primary pattern. In addition, phylogenetic analyses based on SSU rDNA sequence data reveal that the two populations of G. dorsicirratus for which data are available cluster together with full support and form a clade with Heterourosomoida sinica and two populations of H. lanceolata.

Redescription, Morphogenesis, and Molecular Phylogeny of Pseudosincirra longicirrata nov. comb., With Establishment of a New Genus Pseudosincirra nov. gen. (Ciliophora, Hypotrichia).

The morphology and morphogenesis of Pseudosincirra longicirrata nov. gen. and nov. comb., isolated from southern China, were investigated with living observation and protargol staining. Our population is similar to the original population in living characteristics and ciliary patterns. The main determinable morphogenetic features of P. longicirrata nov. comb. are the presence of five frontoventral-transverse cirral anlagen (FVT-anlagen) and a dorsomarginal kinety anlage. According to the origin of FVT-anlagen IV and V in proter, it can be determined that P. longicirrata nov. comb. possesses two frontoventral rows and one right marginal row. Hence, a new genus, Pseudosincirra nov. gen., is proposed, and the diagnosis of P. longicirrata nov. comb. is improved. The new genus is diagnosed as follows: adoral zone of membranelles and undulating membranes is in a Gonostomum pattern; there are three enlarged frontal cirri, one buccal cirrus, and one parabuccal cirrus; postperistomial cirrus and transverse cirri are lacking; there are two more or less long frontoventral rows and one right and two or more left marginal rows; cirri within all rows very widely spaced; dorsal kinety pattern is of Urosomoida type, that is, three dorsal kineties and one dorsomarginal kinety; and caudal cirri are present. Phylogenetic analyses based on the small subunit ribosomal (SSU rDNA) sequence data indicate that P. longicirrata nov. comb. clusters with Deviata and Perisincirra. It is considered that Pseudosincirra nov. gen. and Perisincirra paucicirrata should be assigned to the family Deviatidae; fine cirri, and cirri within all rows being relatively widely spaced, should be considered as plesiomorphies of Deviatidae; and Deviatidae is closely related to Dorsomarginalia or Strongylidium–Hemiamphisiella–Pseudouroleptus.

Morphology, ontogeny and molecular phylogeny of a new urostylid ciliate, Bakuella (Pseudobakuella) guangdongica n. sp. (Ciliophora, Hypotrichia) from southern China

The morphology, morphogenesis, and molecular phylogeny of Bakuella (Pseudobakuella) guangdongica n. sp., isolated from southern China, were investigated. The new species is characterized by a body length of 150–225 μm in vivo; 35–42 adoral membranelles; 3–5 buccal, two frontoterminal, 7–12 transverse and two pretransverse ventral cirri; midventral complex comprised of 10–20 pairs and two rows extending to transverse cirri; posterior part of marginal rows slightly overlapping; colorless cortical granules about 1 μm across, arranged in small groups; soil habitat. Its main ontogenetic features are: (1) in the proter, the parental adoral zone of membranelles is completely renewed by new structures; (2) in the opisthe, the oral primordium originates apokinetally, some old midventral cirri join the formation of frontoventral-transverse cirral anlagen; (3) the anlagen for marginal rows and dorsal kineties develop intrakinetally; and (4) the numerous macronuclear nodules fuse into a single mass before dividing. Phylogenetic analyses based on the SSU rDNA sequence suggest the non-monophyly of the genus Bakuella.

Morphology, morphogenesis and molecular phylogeny of a novel soil ciliate, Afrokahliella paramacrostoma n. sp. (Ciliophora, Hypotrichia)

A soil hypotrich ciliate, Afrokahliella paramacrostoma n. sp., was discovered in China. Its morphology, morphogenesis and molecular phylogeny were investigated using standard methods. The new species is characterized as follows: body about 140–180 × 60–70 μm in vivo, cortical granules absent, contractile vacuole positioned about 40% down length of body, 5–9 macronuclear nodules, 34–49 adoral membranelles, 3–5 buccal and 3–6 parabuccal cirri, usually two frontoventral rows, three or four left and two or three right marginal rows, three dorsal kineties and one dorsomarginal kinety; 1–3 and one or two caudal cirri located at the ends of dorsal kineties 1 and 2, respectively. The ontogenetic process is characterized by: (1) the marginal anlagen on each side develop in the outer right and the inner left marginal rows, respectively; (2) five frontoventral-transverse cirral anlagen, anlagen II–IV develop in secondary mode; (3) dorsal morphogenesis follows a typical Urosomoida-pattern, no parental dorsal kineties are retained; (4) caudal cirri are generated at the ends of dorsal kineties 1 and 2. Phylogenetic analyses based on SSU rDNA sequence data reveals that Afrokahliella paramacrostoma n. sp. is closely related to Parakahliella macrostoma and Hemiurosomoida longa.

Description and Morphogenesis of a Chinese Population of Bakuella granulifera Foissner, Agatha and Berger, 2002 (Ciliophora, Hypotricha).

In this study, the morphology and morphogenesis of Bakuella granulifera Foissner, Agatha, and Berger, 2002, isolated from soil in the Chanba National Wetland Park, Xi'an, China, were studied based on invivo observations and protargol staining. The Chinese population is distinctly smaller than the type population from Namibia. Details of the ontogenetic process are provided for the first time and are summarized as follows: (1) the parental adoral zone is partly retained; (2) the left of the endoral forms a rather wide anlage and the proximal adoral membranelles are renewed; (3) the parental midventral complex contributes to the formation of the FVT cirral anlagen; (4) the marginal rows anlagen and dorsal kineties anlagen develop intrakinetally; (5) no caudal cirri are produced; and (6) the macronuclear nodules fuse to a single mass. In combination with previous studies, these findings suggest that the genus Bakuella is ontogenetically diverse.

Morphology, morphogenesis and molecular phylogeny of the new soil ciliate Sterkiella paratricirrata n. sp. (Ciliophora, Hypotrichia, Oxytrichidae)

ABSTRACT The morphology and morphogenesis of a new soil hypotrichous ciliate, Sterkiella paratricirrata n. sp., collected from north China, were studied using live observation and protargol staining. The new species is characterised as follows: body elliptical, 70–100 × 35–50 µm in vivo, an average of 26 adoral membranelles, 16 frontoventral-transverse cirri with three transverse cirri closely positioned and four frontoventral cirri arranged in triangle, two macronuclear nodules and resting cyst with polygon wrinkles. The ontogenetic process in Sterkiella paratricirrata n. sp. is characterised by anterior portions of anlagen II and III of the opisthe proliferate and merge with the disaggregating cirri II/2 and III/2, respectively, to form anlagen II and III of the proter; segmentation of the frontoventral-transverse cirral anlagen generated in a 1:2:2:3:4:4 pattern. Based on the phylogenetic tree, the monophyly of Sterkiella is not supported. Sterkiella paratricirrata n. sp. forms a clade with Rigidohymena candens and R. quadrinucleata with high support, while it has a long distance with the morphologically similar species, S. tricirrata. http://www.zoobank.org/urn:lsid:zoobank.org:pub:1872D857-30EF-4E4C-85B8-82CCFE465D56

The insights into the systematic relationship of Gastrostyla-affinitive genera, with report on a new saline soil ciliate genus and new species (Protozoa, Ciliophora)

BackgroundHypotrichia are a group with the most complex morphology and morphogenesis within the ciliated protists. The classification of Gastrostyla-like species, a taxonomically difficult group of hypotrichs with a common ventral cirral pattern but various dorsal and ontogenetic patterns, is poorly understood. Hence, systematic relationships within this group and with other taxa in the subclass Hypotrichia remain unresolved.Results18S rRNA gene sequence of a new Gastrostyla-like taxon was obtained. Phylogenetic analyses based on the 18S rRNA gene sequences indicate that this ciliate represents a new genus that is closely related to Heterourosomoida and Kleinstyla within the oxytrichid clade of the Hypotrichia. However, the position of this cluster remains unresolved. All three genera deviate from the typical oxytrichids by their incomplete (or lack of) dorsal kinety fragmentation during morphogenesis. Morphology and morphogenesis of this newly discovered form, Heterogastrostyla salina nov. gen., nov. spec., are described. Heterogastrostyla nov. gen., is characterised as follows: more than 18 fronto-ventral-transverse cirri, cirral anlagen V and VI develop pretransverse cirri, and dorsal ciliature in Urosomoida-like pattern.ConclusionsSimilar to the CEUU-hypothesis about convergent evolution of urostylids and uroleptids, we speculate that the shared ventral cirral patterns of Gastrostyla-like taxa might have resulted from convergent evolution.