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

Systematic review of the genera Rhabdostyla Kent 1880 and Orborhabdostyla Foissner et al. 2010 (Ciliophora, Peritrichia, Epistylididae)

The genus Rhabdostyla is one of the oldest of the family Epistylididae, it was described over 120 years ago and has more than 40 species considered valid. This group went through several systematic changes throughout its existence and due to the lack of taxonomic information, said to be essential, for most species that compose it, some of these changes are still questioned. In order to better understand and validate the species and relationships identified for this genus, the present work makes a brief review for the genus Rhabdostyla and its related genera, Opisthostyla and Orborhabdostyla. A 18S-rDNA phylogenetic analysis was also performed to understand the relationship between these groups. As a result of this review, 45 diagnoses were compiled and reorganized for the current model, accompanied by new graphical representations for the species considered valid for the genus Rhabdostyla and its associates. The major changes that the genus underwent, such as synonymy and separation to a new genus, were discussed in light of new phylogenetic information, but despite this, other information is still needed for a better validation of these changes.

Clinico-histopathological and phylogenetic analysis of protozoan epibiont Epistylis wuhanensis associated with crustacean parasite Lernaea cyprinacea from ornamental fish in Iran

Parasitic infestations are one of the most concerning problems limiting ornamental fish farming. In addition to the direct economic losses due to the major mortalities, parasites may significantly negatively impact the body shape, coloration, growth rate, and health condition of the fish. The results of the study highlight the importance of comprehensive parasitological analysis in the diagnosis and treatment of parasitic infections in ornamental fish farms. The presence of multiple parasites in the affected fish emphasizes the need for effective biosecurity measures, such as extending the quarantine period for newly imported fish, closely monitoring fish populations, and implementing isolation units to prevent the spread of infections. By implementing these preventative measures, ornamental fish farmers can reduce the risk of parasitic infections and ensure the health and well-being of their fish populations. This, in turn, can lead to increased profitability and sustainability for their business. Overall, the current study aimed to conduct a clinical, histopathological, and phylogenetic analysis of the epibiont ciliated protozoan Epistylis wuhanensis and the copepod crustacean Lernaea cyprinacea in a freshwater ornamental fish farm in Iran. Furthermore, it provides valuable insights into the prevalence and impact of parasitic infections in ornamental fish farms and underscores the need for continued research and the development of effective preventative measures to address this issue. A total of 60 symptomatic freshwater ornamental fish, including 30 guppy (Poecilia reticulata) and 30 sailfin molly (Poecilia latipinna), were packed in polyethylene bags filled with oxygenated pond water and transported to the Ornamental Fish Clinic, Faculty of Veterinary Medicine, University of Tehran, for parasitological analysis. Following the clinical examination, histopathological analysis was performed on 10% NBF (neutral buffered formalin)-fixed samples from affected tissues, including the skin, skeletal muscle, and liver, to identify any pathological changes associated with the parasitic infections. Furthermore, the DNA was extracted from the 99% ethanol-fixed samples using a commercial DNA extraction tissue kit (SinaPure DNA, Iran), and PCR was performed using Peri18S-F1 (5'-ACC TGG TTG ATC CTG CCA GT-3') and Peri18S-R1 (5'-TGC AGG TTC ACC TAC GGA AA-3') (first reaction), and Peri18S-F2 (5'-CCG CGG TAA TTC CAG CTC-3') and Peri18S-R2 (5'-GAT CCC CTA ACT TTC GTT CTT GA-3') (second round) primers for the identified parasites. Finally, the PCR products were sequenced using Sanger dideoxy sequencing methods, and the resulting sequences were compared to sequences in the BLAST search program to provide a comprehensive picture of the current parasite-based disorder. The crustacean L. cyprinacea and the epibiont sessilid E. wuhanensis were identified in the examined ornamental guppy (6/30) and sailfin molly (6/30), with an overall parasitic prevalence of 20.00% (12/60). Ciliates were found in all tissue lesions but not in fish without lesions. A great number of the ciliated protozoan E. wuhanensis were found attached to the integumentary area of L. cyprinacea. Microscopically, oval to round granulomatous lesions were observed in cutaneous and skeletal muscles. Lymphoplasmacytic dermatitis and myositis were also observed. The crustacean L. cyprinacea serves as a mechanical vector for E. wuhanensis infection and spreads the disease in ornamental fish farming operations. For the first time in Iran, we successfully presented diagnostic morphological and molecular data on sessilids isolated from L. cyprinacea. Based on the findings of the current study, such parasitic infections may cause significant economic losses following invasion of the integument area of fish, eventually leading to death, if treatment is neglected or inadequate. Furthermore, the findings of the analysis were used to develop effective diagnostic approaches for the affected fish, as well as recommendations for improved health conditions to prevent future outbreaks of parasitic infections. However, further research is needed to determine the precise mechanisms of crustacean attachment and host-crustacean-peritrich protozoan interactions. Furthermore, the direct and indirect effects of various environmental factors on the emergence and spread of the current disease should be considered.

On four epibiotic peritrichous ciliates (Protozoa, Ciliophora) found in Lake Weishan Wetland: morphological and molecular data support the establishment of a new genus, Parapiosoma gen. nov., and two new species

During a study on the diversity of ciliated protists in Lake Weishan Wetland, the largest wetland in northern China, four epibiotic sessilid peritrichs were isolated from aquatic host animals. Two of them, i.e., Epistylis cambari Kellicott, 1885 and Epistylis lwoffi Fauré-Fremiet, 1943, were known species whereas the other two, i.e., Parapiosoma typicum gen. nov., sp. nov. and Orborhabdostyla gracilis sp. nov., are new to science. The new genus Parapiosoma gen. nov. is characterized by its branched non-contractile stalk, everted peristomial lip, obconical macronucleus and transverse silverlines. Two species are assigned to the new genus, namely Parapiosoma typicum sp. nov. and Parapiosoma gasterostei (Fauré-Fremiet, 1905) comb. nov. Morphologically, P. typicum sp. nov. is recognized by its goblet-shaped zooids, single-layered peristomial lip, dichotomously branched stalk, and infundibular polykinety 3 (P3) containing three equal-length rows. Orborhabdostyla gracilis sp. nov. is characterized by its slender zooid, curved macronucleus, and three equal-length rows in infundibular P3. Improved diagnoses and redescriptions of E. cambari and E. lwoffi are provided including, for the first time, data on the ciliature of E. cambari. Phylogenetic analyses based on SSU rDNA, ITS1-5.8S rDNA -ITS2, and LSU rDNA sequence data strongly support the assertion that the family Epistylididae comprises morphospecies with different evolutionary lineages and indicate that Parapiosoma gen. nov. may represent a new taxon at family level.

New considerations on the phylogeny of Sessilida (Protista: Ciliophora: Peritrichia) based on multiple-gene information, with emphasis on colonial taxa

The subclass Peritrichia, containing two orders Sessilida and Mobilida, is a major group of ciliates with worldwide distribution and high species diversity. Several studies have investigated the phylogeny of peritrichs; however, the evolutionary relationships and classification of some families and genera within the Sessilida remain unclear. In the present study, we isolated and identified 22 peritrich populations representing four families and six genera and obtained 64 rDNA sequences to perform phylogenetic analyses and assess their systematic relationships. Ancestral character reconstruction was also carried out to infer evolutionary routes within the Sessilida. The results indicate: (1) family Vaginicolidae is monophyletic and acquisition of the typical peritrich lorica represents a single evolutionary divergence; (2) core epistylidids evolved from a Zoothamnium-like ancestor and experienced spasmoneme loss during evolution; (3) Campanella clusters with species in the basal clade and shows stable morphological differences with other epistylidids, supporting its assignment to a separate family; (4) the structure of the peristomial lip may be a genus-level character rather than a diagnostic character for discriminating Epistylididae and Operculariidae, thus a redefinition of Operculariidae should be carried out when more species have been investigated; (5) some characters, such as lifestyle (solitary or colonial), spasmoneme and living habit (sessile or free-swimming), evolved repeatedly among sessilids indicating that species with non-contractile stalks or that are free-swimming have multiple evolutionary routes and might derive from any sessilid lineage without a lorica. The close phylogenetic relationships of some morphologically distinct sessilids imply that the diagnoses of some genera and families should be improved.

Integrative Studies on Three Epibiotic Epistylis Species (Protozoa, Ciliophora, Peritrichia) in Lake Weishan Wetland, Northern China, Including the Establishment of a New Species

Three epibiotic Epistylis species, i.e., Epistylis weishanensis sp. nov., Epistylis daphniae Fauré-Fremiet, 1905, and Epistylis pygmaeum (Ehrenberg, 1838) Foissner et al., 1999, were investigated based on their living morphology, infraciliature, and small subunit (SSU) rDNA sequence data. Epistylis weishanensis sp. nov. is characterized by its double-layered peristomial lip, contractile vacuole located on the dorsal wall of the infundibulum, infundibular polykinety 3 (P3) composed of three equal-length rows that terminate above infundibular polykinety 1 (P1), 50-62 silverlines between the peristome and the trochal band, and about 30 silverlines between the trochal band and the scopula. Based on previous and newly obtained data for E. daphniae and E. pygmaeum, improved diagnoses and redescriptions are provided including, for the first time, data on their infraciliature. Phylogenetic analyses reveal that all three species do not group within the major clade of Epistylis, supporting the assertion that the genus Epistylis should be an assemblage of morphospecies and therefore needs to be revised.

The Morphology, Taxonomy, and Phylogenetic Analyses of Five Freshwater Colonial Peritrich Ciliates (Alveolata, Ciliophora), Including the Descriptions of Two New Species

The morphology and phylogeny of two new sessilid species, Zoothamnium weishanicum n. sp. and Epicarchesium sinense n. sp., two insufficiently known species, Zoothamnium arbusculaEhrenberg, 1831 and Zoothamnium hentscheliKahl, 1935, and a well-known species, Carchesium polypinum (Linnaeus, 1767) Ehrenberg, 1838, collected from freshwater habitats of China, were investigated. Zoothamnium weishanicum n. sp. is characterized by its inverted bell-shaped zooids, double-layered peristomial lip, alternately branched stalk, and two different-length rows in infundibular polykinety 3 (P3). Epicarchesium sinense n. sp. is recognized by its asymmetric-pyriform zooids, single-layered peristomial lip, conspicuous cortical blisters on the pellicle, dichotomously branched stalk, and P3 containing one short inner row and two long outer rows. Based on previous and newly obtained data of the three known species, improved diagnoses and redescriptions are provided including, for the first time, data on the infraciliature of Z. arbuscula and Z. hentscheli. In addition, we analyzed the phylogeny of each species based on SSU rDNA sequence data.

Integrative Studies on a New Ciliate Campanella sinica n. sp. (Protista, Ciliophora, Peritrichia) Based on the Morphological and Molecular Data, With Notes on the Phylogeny and Systematics of the Family Epistylididae

During an investigation on freshwater peritrichs, a new colonial sessilid ciliate, Campanella sinica n. sp., was isolated from aquatic plants in an artificial freshwater pond in Qingdao, China. Specimen observations of this species were performed both in vivo and using silver staining. C. sinica n. sp. is characterized by the appearance of the mature colony, which is up to 2 cm high and contains more than 1,000 zooids, the asymmetric horn-shaped zooids, strongly everted and multi-layered peristomial lip, the slightly convex peristomial disc, and the well-developed haplokinety and polykinety, which make more than four circuits of the peristome before descending into the infundibulum. The small subunit ribosomal DNA (SSU rDNA), 5.8s rDNA and its flank internal transcribed spacers (ITS1-5.8s rDNA-ITS2), and large subunit ribosomal DNA (LSU rDNA) are sequenced and used for phylogenetic analyses which reveal that the family Epistylididae Kahl, 1933 is non-monophyletic whereas the genus Campanella is monophyletic and nests within the basal clade of the sessilids. The integrative results support the assertion that the genus Campanella represents a separate lineage from other epistylidids, suggesting a further revision of the family Epistylididae is needed. We revise Campanella including the transfer into this genus of a taxon formerly assigned to Epistylis, which we raise to species rank, i.e., Campanella ovata (Nenninger, 1948) n. grad. & n. comb. (original combination Epistylis purneri f. ovata Nenninger, 1948). In addition, we provide a key to the identification of the species of Campanella.

Morphology, phylogenetics and pathology of "red sore disease" (coinfection by Epistylis cf. wuhanensis and Aeromonas hydrophila) on sportfishes from reservoirs in the South-Eastern United States

The aetiological agents of red sore disease (RSD) reportedly comprise a taxonomically ambiguous stalked ciliate (a species of Epistylis) and Aeromonas hydrophila. The taxonomic identity of each pathogen remains provisional: using supra-specific morphological features for the ciliate and culture-based methods that cannot delineate bacterial strain. On 7 and 9 November 2017 and 28 May 2020, biologists and anglers reported a local epizootic (Hiwassee and Chattahoochee river basins; Georgia) wherein some moribund fish presented RSD-like lesions. The ciliates were assigned to Epistylis by morphology. The ciliate is regarded as Epistylis cf wuhanensis, as nucleotide sequences from its small subunit ribosomal DNA were identical to those of Epistylis wuhanensis. The bacterium was identified as Aeromonas hydrophila by phenotypic markers and nucleotide sequences from the DNA gyrase subunit B; our sequences comprised 3 strains and phylogenetically were recovered sister to strains of Eurasian origin. Histological sections of lesions revealed effacement or partial deterioration of the epithelium covering scales, scale loss, haemorrhaging, necrosis, oedema, and extensive inflammatory infiltrate in the dermis. This is the first nucleotide sequence information for the symbionts implicated in RSD.

Fins infestation induced by Myxobolus xiantaoensis in yellow catfish Tachysurus fulvidraco Richardson, 1846: Some pathophysiological and molecular insights

The myxozoan parasite Myxobolus xiantaoensis is a fin pathogen of commercially important yellow catfish Tachysurus fulvidraco Richardson, 1846, in the freshwater ponds of China. In the present work, four geographical isolates of M. xiantaoensis were sampled from the fins of yellow catfish. It was found that the spores of four isolates exhibited few markable differences in morphometrics. The small subunit ribosomal DNA (SSU rDNA) sequences of four isolates were conspecific to the SSU rDNA sequence of M. xiantaoensis. No genetic level variation was observed, even in the characteristically more variable internal transcribed spacer (ITS) region. This absence of variability suggests high gene flow as a result of panmixia in the parasitic populations. ITS phylogeny placed four isolates of M. xiantaoensis in a clade together with myxozoans species infecting Siluriformes. The M. xiantaoensis infection inflicted severe hemorrhages on epidermis of ray-fins, which grew into inflammatory epithelial hyperplasia and lytic cartilage signs. The histochemical analysis of infected fins biopsies is characterized by damage of collagen components of cartilage, resulting in weakness, breaks, and missing fin rays. These tissue sections also had a remarkable inflammatory response around the fin cartilage, with the absence of mature spores and chondrocytes. These results indicate that the fin cartilage damage appeared before the development of tissue inflammation and the parasitic infestation of the fins. The present four geographical isolates of M. xiantaoensis were identified by a holistic approach of species characterization based on biological, morphological, and molecular evidence. These four isolates showed some morphological and genetic variations but within the intraspecific range.

Morphology and molecular phylogeny of three Epistylis species found in freshwater habitats in China, including the description of E. foissneri n. sp. (Ciliophora, Peritrichia)

The peritrich genus Epistylis is speciose, however many species lack complete morphological description based on modern criteria and/or molecular data. In the present study, one new species, i.e., E. foissneri n. sp., and two morphologically similar species, i.e., E. hentscheli Kahl, 1935 and E. vaginula Stokes, 1884, collected from freshwater habitats in China, were studied. Epistylis foissneri n. sp. is characterized by its extremely slender zooids encased in a gelatinous sheath, symmetrically dichotomously branched stalk, trochal band located at mid-body, contractile vacuole located on dorsal wall of infundibulum, infundibular polykinety 3 (P3) composed of three equal-length rows that terminate above infundibular polykinety 1 (P1), 105-110 silverlines between the peristome and the trochal band, and about 110 silverlines between the trochal band and the scopula. Epistylis hentscheli is characterized by its asymmetric pyriform zooids (average length ca. 160 μm in vivo), dichotomously branched stalk with transverse striations on the surface of the upper portion, P3 three-rowed and terminating slightly above P1, 60-75 silverlines between the peristome and the trochal band, and 55-90 silverlines between the trochal band and the scopula. Epistylis vaginula is characterized by its elongated body shape (about 100 μm in length in vivo), dichotomously branched and smooth stalk, P3 three-rowed and terminating above P1, 80-100 silverlines between the peristome and the trochal band, and 45-80 silverlines between the trochal band and the scopula. The small subunit ribosomal DNA gene (SSU rDNA) of these three species was sequenced and supported the validity of each. Phylogenetic analyses based on SSU rDNA sequence data revealed that all three morphospecies group with other congeners within the major clade of Epistylis.

Morphology and molecular analyses of four epibiotic peritrichs on crustacean and polychaete hosts, including descriptions of two new species (Ciliophora, Peritrichia)

Four epibiotic sessilid peritrichs, i.e., Zoothamnium wilberti n. sp., Baikalonis microdiscus n. sp., Epistylis anastatica (Linnaeus, 1767) Ehrenberg, 1830, and Rhabdostyla commensalisMöbius, 1888, were isolated from one syllid polychaete and three crustacean hosts in Qingdao, China. For each species, specimens were observed both in vivo and following silver staining. Their SSU rDNA was also sequenced for phylogenetic analyses. Zoothamnium wilberti n. sp. is characterized by the appearance of its colony, which is up to 350 μm high, and usually has fewer than 16 zooids, and the dichotomously branched stalk with transverse wrinkles, the conspicuously conical peristomial disc, and infundibular polykinety 3 comprising three isometric ciliary rows. Baikalonis microdiscus n. sp. can be recognized by its barrel-shaped zooid, small peristomial disc, smooth and short stalk, and its unusual infundibular polykinety 3 comprising a long inner row and a short outer row. Two poorly known species, i.e., Epistylis anastatica and Rhabdostyla commensalis, are redescribed and redefined. Phylogenetic analyses reveal that: (i) R. commensalis is closely related to the family Astylozoidae rather than to the morphologically similar Epistylididae; (ii) B. microdiscus n. sp. is sister to the family Scyphidiidae; (iii) E. anastatica groups with vorticellids and ophrydiids, which further supports the polyphyly of the genus Epistylis; and (iv) Z. wilberti n. sp. is nested within the Zoothamniidae, as expected.

Morphological and molecular identification of epibiontic sessilid Epistylis semiciculus n. sp. (ciliophora, Peritrichia) from Procambarus clarkia (Crustacea, Decapoda) in China

Data on sessilinasis from Procambarus clarkia are limited. This study investigates sessilid diversity in Hubei Province, China in 2016. Procambarus clarkia pereopods were covered by two sessilid morphotypes in April and May, and the gills were adhered by one of these two morphotypes (morphotype I) in January. Identifying the two morphotypes according to their morphological characters through live observations and protargol-stained method is difficult. Both morphotypes show almost identical morphological characteristics: zooids present vase-shaped, the length-to-width ratio is 2:1, the semicircle-shaped peristomial disk is evidently above the peristomial lip, single contractile vacuole is located below the peristomial lip, and the oral infraciliature shows identical arrangement which can be distinguished from other Epistylis. However, the morphometric data of the two morphotypes are significant different: body size of morphotype I is 78.9–103.8 × 32.1–54.6 μm, whereas that of morphotypes II is 136.7–171.5 × 60.9–88.0 μm. To further identify the two morphotypes, molecular regions including small subunit ribosomal DNA (SSU rDNA) sequences, large subunit ribosomal DNA (LSU rDNA) sequences, and ITS1-5.8S-ITS2 sequences were used. Results supported that the two morphotypes are single species of genus Epistylis rather than distinct species based in their distinct size ranges and temporal presence events. We assigned it the name E. semiciculus n. sp. with respect to the semicircular peristomial disk. Overall, these findings emphasized the importance of using molecular data to solve the identification confusion caused by ontogenetic processes. This study is the first morphological and molecular characterization of a sessilid isolated from P. clarkia under aquaculture conditions.

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The first identification of epibiontic sessilid from Procambarus clarkia.

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Different attachment sites of sessilids in spring and winter.

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Two morphotypes of a new Epistylis with significant different morphometric data.

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Species descriptions include morphological (vivo and stained) and molecular data.

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Present Epistylis distinguished by body shape, contractile vacuole and infraciliature.

First molecular identification of Vorticella sp. from freshwater shrimps in Tainan, Taiwan

Freshwater shrimps are the most common crustaceans kept in an aquarium. This study was a survey seeking parasites infecting cultured freshwater atyid shrimps at aquarium stores in Tainan, Taiwan. We observed that atyid shrimps were infested with Vorticella and Scutariella. Scutariella is a common shrimp parasite; thus, we focused on Vorticella infection in the atyid shrimps. Vorticella aequilata-like pop TW, a freshwater peritrich ciliate, was isolated from the atyid shrimps. The morphological characteristics were investigated using live observations. Specimens from the population showed identical arrangement of the infraciliature and identical ITS1-5.8SITS2 region sequences. The zooids are bell-shaped, 40-58 μm wide and 47-70 μm in long in vivo. The food vacuole is variable in shape and is located in the middle of the cell. ITS1-5.8S-ITS2 sequences of Vorticella aequilata-like pop TW did not match any available sequences in GenBank. Phylogenetically, Vorticella aequilata-like pop TW clusters with the other Vorticella within the family Vorticellidae and nests with Vorticella aequilata in the subclade. Above all, the morphological characteristics and molecular analyses show that the investigated Vorticella is a Vorticella aequilata-like species. The phylogenetic analyses of ciliates based on the ITS1-5.8S-ITS2 sequences reveal that the Vorticella genus consists of Vorticella morphospecies and that taxonomic revision of the genus is needed. Morphometric criteria and molecular analysis were used to describe and identify the Vorticella specie and this study presents the first molecular identification analysis of the Vorticella species in the cultured atyid shrimps in Tainan, Taiwan.

First record of two ectoparasitic ciliates of the genus Trichodina (Ciliophora: Trichodinidae) parasitizing gills of an invasive freshwater fish, Micropercops swinhonis, in Tibet

Although high diversity of parasitic ciliates has been reported in China, little is known about the species from high altitude areas, especially in Tibet. To investigate the species of parasitic ciliates in Tibet, a project was initiated in the Chabalang wetland in 2013. Two Trichodina species, namely, Trichodina sp. and T. reticulata Hirschmann & Partsch, 1955, were isolated from gills of an invasive fish, Micropercops swinhonis for the first time. In the present study, we provided the morphological, morphometrical, and molecular characterizations of the two species and conducted the phylogenetic analyses of mobilids based on the small subunit ribosomal RNA gene (SSU rDNA) sequences. Both morphological characters and morphometric data of the T. reticulata agreed well with previous studies. Although two partial SSU rDNA sequences were obtained in the present study, only the sequence of T. reticulata population in the present study was thought to be reliable. The other sequence may not belong to the other species. Thus, we regarded the other species isolated in the present study as Trichodina sp. to avoid the wrong or confused species identification. Morphologically, Trichodina sp. is distinguished mainly by its large body shape with a broad adhesive disk, robust and obliquely quadrilateral blades, and well-developed rays. T. reticulata is mainly characterized with the 8-12 spherical or elliptical granules in the central zone of adhesive disk. Phylogenetic analyses consistently showed the two ectoparasites clustered with freshwater species of the genus Trichodina within the order Mobilida. Our study extended the host range of T. reticulata and supplemented the molecular data. Also, results reveal that invasion of exotic fish may cause a potential threat to native fish by introducing or dispersing parasitic ciliates.