Description of Cystodiscus elachistocleis sp. nov. (Cnidaria: Myxosporea) parasitizing the gallbladder of Elachistocleis cesarii from Brazil, based on morphological and molecular analyses

Numerous pseudoplasmodia containing myxospores belonging to the genus Cystodiscus were found in the gallbladder of Elachistocleis cesarii from Mato Grosso State, Brazil. Herein, we describe Cystodiscus elachistocleis sp. nov., using morphological and small subunit ribosomal DNA sequences. The mature myxospores were ellipsoid to ovoid, measuring in average 10.6 (9.8–11.2) μm in length and 6.2 (5.6–6.6) μm in width. Polar capsules were pyriform and equal in size measuring in average 3.6 (2.8–4.3) μm in length and 2.6 (2.2–3.1) μm in width. Polar filaments had 2–4 coils. The myxospores had 3–5 transverse ridges. The phylogenetic analysis showed Cystodiscus elachistocleis sp. nov. as a sister species of Cystodiscus cf. immersus 1, in a subclade formed by species that parasitize the amphibians gallbladder. This is the first species of Cystodiscus described parasitizing a species of Elachistocleis and the third species of Cystodiscus described in Brazil.

Morphology, Morphogenesis, and Molecular Phylogeny of a New Freshwater Ciliate, Quadristicha subtropica n. sp. (Ciliophora, Hypotrichia)

The morphology and the regulation of cortical pattern associated with the cell size, division, and phylogenetic position of a new hypotrichous ciliate, Quadristicha subtropica n. sp. collected from a freshwater pond in southern China, were investigated. Quadristicha subtropica n. sp. is characterized as follows: size in vivo 60–115 μm × 25–45 μm; 19–21 adoral membranelles; buccal cirrus near anterior end of endoral and paroral; cirrus IV/3 at about level of buccal vertex; right marginal row begins ahead of buccal vertex; 11–16 right and 12–19 left marginal cirri; and dorsal cilia about 5 μm long. The basic morphogenetic process in Q. subtropica n. sp. is consistent with that of the type species, Quadristicha setigera. Phylogenetic analyses based on small subunit ribosomal DNA sequence data reveal that the systematic position of Q. subtropica n. sp. is rather unstable with low support values across the tree and the genus Quadristicha is not monophyletic.

Isolation of the Parasite Enterocytospora artemiae From Chinese Grass Shrimp (Palaemonetes sinensis)—First Report in Asia

Chinese grass shrimp (Palaemonetes sinensis) is an economically important crustacean in Chinese aquaculture. Recently, we found that shrimp in Panjin city were infected with microsporidia, a group of fungi. The hepatopancreas of several infected shrimp showed white turbidity and pathological changes that negatively affected the health and appearance of the shrimp. Histopathology and transmission electron microscopy were used to examine the development of the parasite within its parasitophorous vacuole. Our results indicated that microsporidia developed asynchronously within the same parasitophorous vacuole. The spores were predominantly small, and rod or oval-shaped. The sizes of fresh spores were approximately 3.1 × 2.4 μm and fixed spores were 1.9 × 1.1 μm. The polar filament was isofilar with 5–6 coils and the thickness was 103.2 nm. Merogonial divisions occurred by binary fission and sporogonial division occurred by plasmotomy. The small subunit ribosomal DNA sequence (1295 bp) from the parasite was highly similar to the previously reported parasite Enterocytospora artemiae (99% nucleotide identity, JX915760). Using maximum likelihood to analyze the phylogenetic relationships, we found that this microsporidian should be grouped within Clade IV, an Enterocytospora-like clade, of the Microsporidia phylum. Based on this parasite’s life cycle characteristics, morphology, and small subunit ribosomal DNA sequence, the parasite described here is likely E. artemiae, which has previously only been described in Europe and North America. Thus, this is the first report of E. artemiae both in Asia and economically important shrimp.

Molecular Detection and Subtyping of Human Blastocystis and the Clinical Implications: Comparisons between Diarrheal and Non-diarrheal Groups in Korean Populations

Blastocystis has recently been recognized as the most common eukaryotic microbe of the human gut. We investigated the prevalence of Blastocystis and their subtypes in diarrheal and non-diarrheal groups and the associated clinical parameters. A total of 324 stool samples were obtained from 196 diarrheal and 128 non-diarrheal subjects. Blastocystis subtypes were determined by sequencing the small subunit ribosomal DNA (SSU rRNA) gene. Demographic, clinical and laboratory data were collected and analyzed by diarrhea and Blastocystis status. The overall rate of Blastocystis positivity was 9.0% (29/324) but was significantly higher in the non-diarrheal group (18.0% vs. 3.1%, P<0.0001). Of the 6 Blastocystis-positive diarrheal patients, 3 (50.0%), none (0.0%), 2 (33.3%), and 1 (16.7%) were infected with subtypes ST1, ST2, ST3, and multiple subtypes, respectively. Of the 23 Blastocystis-positive non-diarrheal patients, 4 (17.4%), 1 (4.3%), and 18 (78.3%) were infected with subtypes ST1, ST2, and ST3, respectively. Blastocystis was less common in the diarrheal than the non-diarrheal group (odds ratio, 0.144; 95% confidence interval, 0.057–0.365, P<0.001). Of the 3 subtypes, ST3 was more frequently observed in the non-diarrheal than diarrheal group (78.3% vs. 33.3%, P=0.0341). Collectively, Blastocystis was found in both the diarrheal and non-diarrheal groups and ST3 was the most common subtype in Korea.

Comparative Studies on the Polymorphism and Copy Number Variation of mtSSU rDNA in Ciliates (Protista, Ciliophora): Implications for Phylogenetic, Environmental, and Ecological Research

While nuclear small subunit ribosomal DNA (nSSU rDNA) is the most commonly-used gene marker in studying phylogeny, ecology, abundance, and biodiversity of microbial eukaryotes, mitochondrial small subunit ribosomal DNA (mtSSU rDNA) provides an alternative. Recently, both copy number variation and sequence variation of nSSU rDNA have been demonstrated for diverse organisms, which can contribute to misinterpretation of microbiome data. Given this, we explore patterns for mtSSU rDNA among 13 selected ciliates (representing five classes), a major component of microbial eukaryotes, estimating copy number and sequence variation and comparing to that of nSSU rDNA. Our study reveals: (1) mtSSU rDNA copy number variation is substantially lower than that for nSSU rDNA; (2) mtSSU rDNA copy number ranges from 1.0 × 104 to 8.1 × 105; (3) a most common sequence of mtSSU rDNA is also found in each cell; (4) the sequence variation of mtSSU rDNA are mainly indels in poly A/T regions, and only half of species have sequence variation, which is fewer than that for nSSU rDNA; and (5) the polymorphisms between haplotypes of mtSSU rDNA would not influence the phylogenetic topology. Together, these data provide more insights into mtSSU rDNA as a powerful marker especially for microbial ecology studies.

A new species of Hedruris (Nematoda: Hedruridae) from freshwater turtles, its life cycle and biogeographic distribution of the genus

We describe Hedruris dratini n. sp. (Nematoda, Hedruridae) from Hydromedusa tectifera and Phrynops hilarii in Argentina based on morphological and molecular characters. Also, we provide information about its life cycle. The new species differs from other species of the genus by possessing the excretory pore, nerve ring and deirids at equal distance from the anterior end. Additionally, H. dratini n. sp. has mammilated eggs and males possess nine pairs of caudal papillae. The subadults and adults of H. dratini n. sp and H. orestiae were characterized by sequencing the small subunit ribosomal DNA (18S). We present for the first time a life cycle of a species of Hedruris that includes an amphipod as intermediate host and a reptile as definitive host. Furthermore, we analysed the host and geographic distribution of all Hedruris species. Although the genus has a cosmopolitan distribution and parasitizes a great host diversity, the majority of species have a Gondwanian distribution, with amphibians being the preferred hosts.

Nematodes as evolutionary commuters between marine, freshwater and terrestrial habitats

Nematodes are the only major metazoan group which is persistently abundant and diverse across marine, freshwater and terrestrial ecosystems. This could be the result of a few major habitat transitions followed by extensive diversification, or numerous habitat transitions followed by moderate diversification. To pinpoint habitat transitions, we superposed nematode habitat associations on an available phylum-wide phylogenetic tree based on small subunit ribosomal DNA sequences (≈2730 SSU rDNA sequences covering ≈1750 nematode taxa). Our analysis revealed at least 30 major habitat transitions within the phylum Nematoda. These transitions as well as their directionality were unevenly spread over the 12 major clades. Most transitions reside in Clades 1–6, and these transitions are bidirectional. Members of Clades 8–12 showed five full transitions, and these took place exclusively from terrestrial to marine systems. We relate our results to the distinct secretory–excretory systems in Clades 1–6 and Clades 8–12, as well as to differences in water permeability of the nematode cuticle. Hence, the phylum Nematoda is characterized by a relatively large number of habitat transitions followed by moderate diversification. The identification of multiple habitat transitions at a low taxonomic level will facilitate future investigations into the mechanisms underlying this unusual ecological flexibility.

Dinobryon taiyuanensis (Chrysophyta, Dinobryaceae), a new freshwater species described from Shanxi province, China

A new freshwater species of Chrysophyceae, Dinobryon taiyuanensis, is described from Linde Lake in Shanxi province, China. This new species is similar to D. sertularia, the type species of the genus, in the shape of the lorica and organization of the colony. The cells have two heterokont flagella surrounded by a lorica and occurred both as free-living, solitary cells or in branched colonies. The lorica of our new species like a bent or S-shaped cone, and shorter than the lorica in D. sertularia. In addition to describing the morphological features of D. taiyuanensis, a phylogenetic analysis based on sequences of the nuclear small subunit ribosomal DNA (SSU rDNA) and internal transcribed spacer (including internal transcribed spacer 1, 5.8S rDNA and internal transcribed spacer 2) placed this alga in single clade with a considerable sequence distance from the other Dinobryon species. Thus, results of both morphological comparisons and phylogenetic analysis based on molecular data suggest this alga as a new species, increasing the total number of recognized freshwater Chrysophyta species in China.

Genetic diversity analysis of an isolate of microsporidia infesting Athetis lepigone

In this study, PCR amplification, cloning and sequencing analysis were adopted to explore genetic diversity of microsporidia (LEP9557) infecting Athetis lepigone. The small subunit ribosomal DNA (SSU rDNA), internal transcribed spacer (ITS) and intergenic spacers (IGS) of ribosomal RNA (rRNA) were cloned from the strain and sequenced. By means of multiple sequence alignment, we found that the three gene regions had different levels of polymorphism. There was greater polymorphism in ITS (74 variable sites) and IGS (55.59%) regions than in the SSU rDNA (17 variable sites). Phylogenetic analysis was performed using Kimura 2-parameter with neighbor joining and the results showed that LEP9557 had a close relationship with Nosema bombycis. Sequences of each clone were submitted to Genbank (Accession number: MF150254-MF150258). All of the results indicated the presence of genetic diversity in LEP9557, which established the foundation for identifying the phylogeny and relationships with other microsporidian strains, and had significant biological meaning for maintaining the survival and population continuity of the strain.

Phylogenetic analysis of Rhizoclonium (Cladophoraceae, Cladophorales), and the description of Rhizoclonium subtile sp. nov. from China

The genus Rhizoclonium (Cladophoraceae, Cladophorales) accommodates uniserial, unbranched filamentous algae, closely related to Cladophora and Chaetomorpha. Its taxonomy has been problematic for a long time due to the lack of diagnostic morphological characters. To clarify the species diversity and taxonomic relationships of this genus, we collected and analyzed thirteen freshwater Rhizoclonium specimens from China. The morphological traits of these specimens were observed and described in detail. Three nuclear gene markers small subunit ribosomal DNA (SSU), large subunit ribosomal DNA (LSU) and internal transcribed spacer 2 (ITS2) sequences were analyzed to elucidate their phylogenetic relationships. The results revealed that there were at least fifteen molecular species assignable to Rhizoclonium and our thirteen specimens were distributed in four clades. On the basis of morphological and molecular evidence we propose the new species, R. subtile sp. nov.