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 in vivo ca. 60–120 × 20–40 μm, 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.     

The ecology of two species of primitive ciliated protozoa commonly found in standing freshwaters (Loxodes magnus stokes and L. striatus penard)

The distribution of Loxodes magnus and L. striatus (Karyorelictida) was investigated in two eutrophic waters (Esthwaite Water and Priest Pot, English Lake District). In the benthos, these species were most abundant at the sediment surface, at deeper sites, and when the bottom water was oxygenated. In the plankton, in Priest Pot, they were found only in the oxygen deficient summer hypolimnion. Experimental studies suggested that L. magnus and L. striatus required access to oxygen. Loxodes was apparently excluded from the oxygenated Priest Pot epilimnion by several adverse factors, one of which was bright light. It was concluded that the ecology of L. magnus and L. striatus resembles, in many ways, that of the advanced ciliates which were found associated with Loxodes.     

Phylogeny and systematic revision of the karyorelictid genus Remanella (Ciliophora,Karyorelictea) with descriptions of two new species

We present here the systematic relationships and taxonomy of some newly collected karyorelictid ciliates from the genus Remanella isolated from the intertidal zone in China. Three species were investigated using observation in vivo and silver staining methods, of which two new species were identified: R. macrostoma sp. nov. and R. achroma sp. nov. Small subunit (SSU) rRNA genes were sequenced for six species and phylogenetic analyses indicated that the genus Remanella is paraphyletic, with three Loxodes species nesting within it. The monophyly of Remanella, however, could not be rejected through the approximately unbiased (AU) test (p = 0.311 > 0.05) and therefore we considered Remanella to be a valid genus. Based on a critical review of the literature, the validity of all nominal species of Remanella was discussed. Remanella unirugosa and R. multicorpusculata were regarded as junior synonyms of R. rugosa and R. granulosa respectively. We also presented here an illustrated taxonomic key based on morphologic and morphometric characteristics and containing all Remanella species considered identifiable in this revision.     

The effects of photosynthetically raised pH and light on some ciliated Protozoa in a eutrophic pond

Some ciliated Protozoa (e.g. Loxodes magnus, L. striatus, Spirostomum teres, S. ambiguum and Frontonia leucas) are abundant during summer in the hypolimnion of a eutrophic pond in north-west England but are absent from the epilimnion. The work described in this paper was begun with the aim of investigating the suggestion that high pH values caused by phytoplankton photosynthesis contributed to the exclusion of these ciliates from the epilimnion. In July 1973, phytoplankton photosynthesis and high pH were found only in the epilimnion, hence conditions were compatible with the above suggestion. Ciliates were, therefore, kept in the laboratory in hypolimnion water and were exposed to phytoplankton photosynthesis, both with and without pH increase. It was found that Loxodes died under both treatments hence there is no evidence that high pH is lethal to Loxodes. It seemed possible, therefore, that either light or toxins released by algae during photosynthesis are lethal to Loxodes. L. magnus was, therefore, exposed to light in the absence of phytoplankton (in filtered hypolimnion water) both in the laboratory and in the pond and it was found that light was lethal. High light intensities might, therefore, contribute to the exclusion of at least Loxodes species from the surface water of the pond, although other adverse factors are probably operative since Loxodes species do not migrate into the epilimnion at night.     

Morphological Characterizations of Four Species of Parallelostrombidium (Ciliophora,Oligotrichia), with a Note on the Phylogeny of the Genus

The morphology and phylogeny of four oligotrichid ciliates, Parallelostrombidium paraellipticum sp. n., P. dragescoi sp. n., P. jankowskii (Xu et al. 2009) comb. n., and P. kahli (Xu et al. 2009) comb. n., are described or redescribed based on live observation, protargol stained material, and SSU rRNA gene sequences. The new species P. paraellipticum sp. n. is characterized by its obovoidal cell shape, adoral zone composed of 17–21 collar, 9–11 buccal, and two thigmotactic membranelles, and extrusomes attached in one row along the girdle kinety. The new species P. dragescoi sp. n. is distinguished from its congeners by its obovoidal cell shape and a lack of thigmotactic membranelles. Based on ciliary patterns recognizable in the original slides, Omegastrombidium jankowskii Xu et al. 2009 and O. kahli Xu et al. 2009 should be transferred to the genus Parallelostrombidium Agatha 2004. Phylogenetic analyses based on SSU rRNA gene sequence data demonstrate that all four new sequences cluster with previously described congeners. The genus Parallelostrombidium is separated into two clusters, suggesting its non‐monophyly and probably corresponding to the two subgenera proposed by Agatha and Strüder‐Kypke (2014), as well as their morphological difference (cell dorsoventrally flattened vs. unflattened).     

Morphology and Phylogeny of Two New Pleurostomatid Ciliates,Epiphyllum shenzhenense n. sp. and Loxophyllum spirellum n. sp. (Protozoa,Ciliophora) from A Mangrove Wetland,South China

ABSTRACT. The morphology, infraciliature, and small subunit (SSU) rRNA gene sequences of two new pleurostomatid ciliates, Epiphyllum shenzhenense n. sp. and Loxophyllum spirellum n. sp., isolated from a mangrove wetland near Shenzhen, South China, were investigated. Epiphyllum shenzhenense n. sp. is morphologically characterized by leaf‐shaped cell about 150 × 35 μm in vivo, usually with four contractile vacuoles, 20–29 right kineties and 10–26 left kineties, ca. four macronuclear nodules, and two types of extrusomes (i.e. short spindle‐shaped and long bar‐shaped). As a new species, L. spirellum n. sp. is distinguished from its congeners by its posterior dorsal margin twisted onto the left side, the distribution of extrusomes (evenly arranged along the oral slit, the posterior end, and clustered to 7–13 warts on dorsal margin), the subterminally positioned contractile vacuole, the number of kineties (8–10 on right side, 4–5 on left side), and its genetic distance from congeners. Phylogenetic trees based on the SSU rRNA gene sequence for both organisms were constructed, which indicate that Epiphyllum is a distinct genus and occupies a basal position in the Pleurostomatida clade; L. spirellum n. sp. falls well into the Loxophyllum clade, which has a close relationship with Litonotus and Spiroloxophyllum.     

Photosensitivity in the Ciliated Protozoon Loxodes: Pigment Granules,Absorption and Action Spectra,Blue Light Perception,and Ecological Significance1

ABSTRACT. The ciliate Loxodes has a faint yellow-brown coloration due to large numbers of electron-dense granules located in the pellicle. Absorption and action spectra both indicate the presence of a blue-light receptor, which may be a flavin. Absorbance is minimal at wavelengths greater than 500 nm; there is a major peak at 360 nm and a pronounced shoulder at 435 nm. An action spectrum based on light-induced escape from oxic water shows a peak at 435 nm and a peak or shoulder at 360 nm. The pigment will generate superoxide when illuminated in the presence of oxygen. Loxodes living in an oxygen gradient in a spectrophotometer cell swims into and remains in anoxic water at light levels ≤10 Wm^-2. Loxodes can be exposed to light levels of 2–20 Wm^-2 in stratified lakes so its photobehavior can explain its periodic absence from oxic water. Photosensitivity in Loxodes may function as part of a predator-avoidance strategy.     

Photobehavior of the Ciliated Protozoon Loxodes: Taxic,Transient, and Kinetic Responses in the Presence and Absence of Oxygen1

ABSTRACT. Behavioral responses to light at different oxygen tensions were studied in the ciliate Loxodes striatus. In the absence of O₂ it does not react to light. In the presence of O₂ it reacts to light as if the pO₂ had been further increased, with the induction of positive geotaxis, a transient phobic response, and finally with a permanent kinetic response (increased swimming velocity and a decreased rate of tumbling). Cells treated with cyanide behave as cells in an anoxic environment and do not react to light. It is concluded that the light response is due to the photochemical production of oxygen radicals and that the sensory receptors for O₂ and for light are identical. The three types of behavioral response (geotaxis, transient, and kinetic responses) are discussed in terms of their adaptive significance for the orientation of Loxodes in the natural environment.     

Nitrate respiration by Protozoa (Loxodes spp.) in the hypolimnetic nitrite maximum of a productive freshwater pond

SUMMARY.

• 1 The ciliated protozoon Loxodes dominated the microfaunal community living in the anoxic hypolimnion of Priest Pot, a small productive pond. Its peak abundance close to the oxic-anoxic boundary was always associated with a peak in nitrite (NO₂) concentration. Both peaks were usually found in water containing μ1 μmol O₂ 1^-1.
• 2 The microfauna were concentrated on a 30 μim sieve. The number of Loxodes in the sieve retentate correlated well with the activity of nitrate reductase in the same material, implying that the enzyme was located in Loxodes. It is unlikely that residual bacterial contamination could have accounted for the activity.
• 3 A doubling of specific electron transport system activity was associated with the transition across the oxic–anoxic boundary. This is consistent with the switch to nitrate respiration and the lower energy yield it provides.
• 4 Dissimilatory nitrate reduction was deduced to be the source of the nitrite peak. Nitrate was supplied by both run-off and nitrification.
• 5 It is suggested that Loxodes participates in the dissimilatory sequence of a condensed nitrogen cycle functioning across the oxic—anoxic boundary.

     

Morphological Description and Molecular Phylogeny of Two Species of Levicoleps (Ciliophora,Prostomatida), L. taehwae nov. spec. and L. biwae jejuensis nov. subspec., collected in Korea

Two colepid ciliates, Levicoleps taehwae nov. spec. and L. biwae jejuensis nov. subspec., were collected from the brackish water of the Taehwa River and a small freshwater pond in Jeju Island, South Korea, respectively. Their living morphology, infraciliature, and small subunit (SSU) rRNA gene sequences were determined using standard methods. Barrel‐shaped L. taehwae nov. spec. is a small ciliate with an average size of 45 × 25 μm in vivo, about 15 ciliary rows each composed of 12 monokinetids and two perioral dikinetids, and two 20 μm‐long caudal cilia. The sequence length and GC content of the SSU rRNA gene are 1,669 bp, 44.5%. This novel species is similar in body size to Coleps hirtus, and has six armor tiers and hirtus‐type tier plates, and the same number of ciliary rows as C. hirtus; however, it can be distinguished from the latter by the absence of armor spines and its sequence similarity of SSU rRNA gene is about 92.8% which indicates that it is a distinct form. Levicoleps biwae jejuensis nov. subspec., is a medium colepid ciliate which has a barrel‐shaped body, about 22 somatic kineties and 16 transverse ciliary rows, three mini adoral organelles, and four 15 μm‐long caudal cilia. The sequence length and GC content of the SSU rRNA gene are 1,666 bp and 44.4%.     

Description of a New Freshwater Ciliate Epistylis wuhanensis n. sp. (Ciliophora,Peritrichia) from China,with a Focus on Phylogenetic Relationships within Family Epistylididae

Two populations of Epistylis wuhanensis n. sp., a new freshwater peritrich ciliate, were isolated from different freshwater ponds located in Hubei, China. Their morphological characteristics were investigated using live observation, protargol impregnation, and scanning electron microscopy (SEM). Specimens from the two populations showed identical arrangement of the infraciliature and identical small subunit ribosomal RNA (SSU rRNA) gene and ITS1‐5.8S‐ITS2 sequences. The zooids present bell‐shaped and 90–175 × 27–54 μm in vivo. Macronucleus is variable in shape and located in the middle of cell. Pellicle is usually smooth with 139–154 and 97–105 striations above and below the trochal band, respectively. SSU rRNA gene and ITS1‐5.8S‐ITS2 sequences of E. wuhanensis n. sp. did not match any available sequences in GenBank. Phylogenetically, E. wuhanensis n. sp. clusters with the other Epistylis within the family Epistylididae, but is distinct from the major clades of Epistylis. Above all, the morphological characteristics and molecular analyses support that the present Epistylis is a new species. Expanded phylogenetic analyses of sessilids based on both SSU rRNA gene sequences and ITS1‐5.8S‐ITS2 sequences reveal that the genus Epistylis consists of Epistylis morphospecies and taxonomic revision of the genus is needed.     

Morphology,Morphogenesis, and Molecular Phylogeny of Anteholosticha multicirrata n. sp. (Ciliophora,Spirotrichea) with a Note on Morphogenesis of A. pulchra (Kahl, 1932) Berger, 2003

Two marine urostylid ciliates, Anteholosticha multicirrata n. sp. and Anteholosticha pulchra (Kahl, 1932) Berger, 2003, were collected from South Korea. These species were identified based on morphology, morphogenesis, and SSU rRNA gene sequence comparison. Anteholosticha multicirrata n. sp. is characterized by the following features: body size 90–125 × 30–45 μm in vivo, shape slender to ellipsoidal in outline, with yellow‐greenish cortical granules distributed along and between dorsal kineties and cirri; single contractile vacuole positioned on left at mid‐body; three frontal, five to seven frontoterminal, one buccal, one to two pretransverse and four to six transverse cirri; three complete dorsal kineties; one left and one right marginal cirral row; about 117 macronuclear nodules; and three to four micronuclei observed during morphogenesis. In addition, based on the observations of morphogenesis, we found that A. pulchra has pretransverse cirri, which were not described in detail in previous studies. Nuclear small subunit ribosomal RNA (SSU rRNA) gene was used to analyse their phylogenetic relationship, and the gene tree supports that the genus Anteholosticha is a highly polyphyletic group.     

Morphology and Molecular Phylogeny of Two New Marine Euplotids,Pseudodiophrys nigricans n. g., n. sp., and Paradiophrys zhangi n. sp. (Ciliophora: Euplotida)

ABSTRACT. The morphology, infraciliature, and molecular phylogeny of Pseudodiophrys nigricans n. g., n. sp., and Paradiophrys zhangi n. sp., isolated from a sandy beach near Qingdao, China, were investigated. Pseudodiophrys is characterized by the Diophrys‐like ciliature pattern, but having only a single, reduced undulating membrane. Pseudodiophrys nigricans, the type species by monotypy, is described from live and silver‐impregnated specimens. Paradiophrys zhangi is similar to the type species Paradiophrys irmgard but can be recognized by its border body and the number (7 vs. 8–10) and arrangement (in rows vs. sparsely distributed) of the frontoventral cirri. Small subunit (SSU) rRNA gene sequence data support the validity of both species. Phylogenetic analyses based on the SSU rRNA gene sequence data currently available for uronychiids and other related taxa indicate that P. nigricans is most closely related to Diophrys scutum and Diophrys apoligothrix, while P. zhangi clusters most closely with Apodiophrys ovalis within a clade that also includes two other Paradiophrys species.     

Morphological and Molecular Description of Three New Species of the Cyrtophorid Genus Chlamydodon (Ciliophora,Cyrtophoria)

This study investigates the morphology and molecular characteristics of three new cyrtophorid ciliates isolated from China seas: Chlamydodon salinus n. sp., Chlamydodon caudatus n. sp., and Chlamydodon paramnemosyne n. sp. Of these, C. salinus n. sp. differs from its congeners through a combination of body size, a cross‐striated band that is not continuous, the presence of 30–34 somatic kineties, 11–15 nematodesmal rods, and 13 contractile vacuoles. Chlamydodon caudatus n. sp., meanwhile, is characterized by having a conspicuous tail, a continuous cross‐striated band, 34–40 somatic kineties, about 15 contractile vacuoles, and 20–24 nematodesmal rods. Compared with other Chlamydodon species, the third new one, C. paramnemosyne n. sp., could be identified by its continuous cross‐striated band, 16–18 somatic kineties, 5 contractile vacuoles, and 9–12 nematodesmal rods. Based on the sequence of the small subunit (SSU) rRNA gene, the phylogeny of these three new species was analyzed, indicating that they all clustered with other congeners to form a monophyletic assemblage. Based on previous studies and the present work, a brief revision of the genus Chlamydodon is supplied, and a key to aid the identification of Chlamydodon species is given.     

Morphological and molecular characterization of Aspidisca hongkongensis spec. nov. (Ciliophora,Euplotida) from the South China Sea

The morphology and infraciliature of a new ciliate, Aspidisca hongkongensis spec. nov., a large marine form isolated from the coastal waters near Hong Kong, were investigated. It differs from the congeners by the combination of cell size (about 90×60 μm in vivo), 9–11 conspicuous dorsal ridges, one fine and seven strong frontoventral cirri, six membranelles in anterior portion of adoral zone, and 17–23 membranelles in posterior portion of adoral zone. The comparison with similar congeners clearly supports the distinction of this new species based on morphological and small subunit (SSU) rRNA gene sequence studies. The SSU rRNA gene sequence similarity within the genus is about 75.3–92.1% which indicates that this is a distinct form. Phylogenetic trees based on SSU rRNA gene information show that A. hongkongensis groups with A. leptaspis.     

Morphology,morphogenesis and phylogeny of Anteglaucoma orientalis n. sp. (Ciliophora,Oligohymenophorea), a freshwater hymenostomatid from northeastern China

A new hymenostomatid ciliate, Anteglaucoma orientalis n. sp., isolated from a freshwater pond in Harbin, northeastern China, was investigated using live observation and silver staining methods. Anteglaucoma orientalis is characterized as follows: size in vivo about 50–60 × 30–35 μm; oval body shape; buccal area occupies about 25% of body length; 28–36 somatic kineties; membranelle 1 having six or seven basal body rows, membranelle 2 five to seven rows, and membranelle 3 three rows; single macronucleus with one micronucleus attached. Morphogenesis of the genus Anteglaucoma is revealed for the first time. The main events during binary fission are as follows: morphogenesis begins with proliferation of kinetosomes in the middle part of postoral kinety 1, and kinetosomes of this primordial field multiply and organize to finally form the paroral membrane and membranelles 1–3 of the opisthe; the parental apparatus in the proter does not take part in the stomatogenetic process. Phylogenetic analyses based on SSU rRNA gene sequences show that Anteglaucoma orientalis n. sp. clusters with the type species, A. harbinensis Pan et al., 2017, with full support.     

Morphological and Molecular Identification of a New Ciliate,Zoothamnium palmphlatum nov. spec. (Ciliophora,Peritrichia) from North China

A new peritrichous ciliate, Zoothamnium palmphlatum nov. spec., was collected from an estuary in Yantai, China. It was investigated, using both live observation and silver staining. The new species can be identified by a palm‐shaped colony consisting of highly developed and alternately arranged secondary branches, a double‐layered peristomial lip, and an infundibular polykinety 3 composed of two parallel kinetosomal rows. Phylogenetic analyses of the small subunit (SSU) rRNA gene sequence show that Z. palmphlatum clusters with other members of the family Zoothamniidae. Furthermore, the comparison of primary and secondary SSU rDNA structures indicates that Z. palmphlatum is distinctly different from its morphologically similar species (93.2–97.0% in sequence similarity) in combination of H10 and H31 regions. Although Z. palmphlatum shares highest sequence similarity with Zoothamnium mucedo (98.9%), the new species has distinctly different structures in the H11, H12, H18, and H31 regions compared to Z. mucedo, which indicates that sequence similarity may not determine the similarity of the secondary structure.     

Two New Diophrys‐Like Genera and Their Type Species,Apodiophrys ovalis n. g., n. sp. and Heterodiophrys zhui n. g., n. sp. (Ciliophora: Euplotida), with Notes on Their Molecular Phylogeny

ABSTRACT. Based on both morphological and molecular information, two new euplotid genera Apodiophrys n. g. and Heterodiophrys n. g. are described in the present paper. Apodiophrys n. g. is defined as sculptured Diophryinae with bipartite adoral zone; frontoventral cirri arranged in Diophrys‐pattern; marginal cirri located in two clearly separated groups. Heterodiophrys n. g. is recognizable by the combination of Diophrys‐like frontoventral cirri and the unique structure of several marginal cirri that are arranged in a long row. The type species for both new genera, Apodiophrys ovalis n. sp. and Heterodiophrys zhui n. sp., collected from southern China sea, are described. The small subunit rRNA (SSU rRNA) gene sequences for both new taxa are determined. Phylogenetic analyses based on these data indicate that Apodiophrys is most closely related to Paradiophrys, which then clusters with Uronychia species. Thus, Apodiophrys–Paradiophrys is separated from other typical Diophrys‐like genera in the SSU rRNA gene trees. The new genus Heterodiophrys is basal to the sister group of Diophrys–Diophryopsis, hence belongs to the “core”Diophrys‐complex.     

Observations over 24 hours on the quantity of algae inside grazing ciliated protozoa

Summary The numbers of cells of the alga Scenedesmus (S. quadricauda and S. denticulatus) inside natural populations of grazing ciliated protozoa from a eutrophic pond (Loxodes magnus and L. striatus) were counted at 4 h intervals over two 24 h periods. There were no diel fluctuations in number of algal cells inside the protozoa, therefore the grazing rates were probably more or less constant over 24 h. L. magnus contained more algae than the smaller L. striatus. S. quadricauda was the more abundant Scenedesmus species in the phytoplankton and both Loxodes species contained more S. quadricauda than S. denticulatus, although the ratio S. denticulatus cells/S. quadricauda cells was greater inside the ciliates than in the phytoplankton.