Protist最新文献

The present study documents the discovery of the first European population of Colpodidium caudatum (Ciliophora, Colpodidiidae) in a water drain in a school playground in Manzanares (Ciudad Real, Spain). This species has been documented on every continent except Antarctica and Europe, until now. The ciliate was isolated from wet run-off soil collected from the water drain and was grown in semi-permanent cultures in the laboratory. The infraciliature of the ciliate was revealed using silver carbonate impregnation and cell measurements were taken from living and silver-impregnated specimens. A comparative analysis of published data from various populations of C. caudatum across the globe showed high intraspecific morphological variability in this species. To differentiate between species within the Colpodidium genus, a dichotomous key is presented. This investigation shows that C. caudatum is a ciliate that is found all over the world and is particularly associated with terrestrial habitats that are periodically flooded.

Cryptophytes are single celled protists found in all aquatic environments. They are composed of a heterotrophic genus, Goniomonas, and a largely autotrophic group comprising many genera. Cryptophytes evolved through secondary endosymbiosis between a host eukaryotic heterotroph and a symbiont red alga. This merger resulted in a four-genome system that includes the nuclear and mitochondrial genomes from the host and a second nuclear genome (nucleomorph) and plastid genome inherited from the symbiont. Here, we make use of different genomes (with potentially distinct evolutionary histories) to perform a phylogenomic study of the early history of cryptophytes. Using ultraconserved elements from the host nuclear genome and symbiont nucleomorph and plastid genomes, we produce a three-genome phylogeny of 91 strains of cryptophytes. Our phylogenetic analyses find that that there are three major cryptophyte clades: Clade 1 comprises Chroomonas and Hemiselmis species, Clade 2, a taxonomically rich clade, comprises at least twelve genera, and Clade 3, comprises the heterotrophic Goniomonas species. Each of these major clades include both freshwater and marine species, but subclades within these clades differ in degrees of niche conservatism. Finally, we discuss priorities for taxonomic revision to Cryptophyceae based on previous studies and in light of these phylogenomic analyses.

Ciliates Infundibulorium cameli from the faeces of the free-ranging dromedary from Oman were studied using a set of methods of the light and immunofluorescence microscopy and molecular phylogeny. With the use of molecular genetic methods, it was confirmed that the cysts found in the samples simultaneously with trophozoites actually belong to the species I. cameli. Tubulin cytoskeleton organization of trophozoites and cysts of this species were described for the first time. A striking morphological similarity between species I. cameli and Buxtonella sulcata was demonstrated, including the organization of ciliature. Different isolates of I. cameli and B. sulcata formed a common clade on the phylogenetic tree. The level of evolutionary divergence between the 18 S rRNA sequences of I. cameli, B. sulcata and species closest to them according to the results of molecular phylogenetic analysis was estimated. It was demonstrated that the divergence between I. cameli and B. sulcata is extremely low compared to members of other genera included in the analysis. Taxonomic position of I. cameli and B. sulcata was discussed in according to the data of comparative morphology and molecular phylogeny

Based on scanning electron microscopy observations, a new species of the coccolithophore genus Calciopappus (Syracosphaeraceae, Prymnesiophyceae) is described from the surface waters off Bergen and from the lower photic zone of sub-tropical and tropical waters. Morphological, coccolith rim structure and biometric analyses strongly support separation of this morphotype from the two described Calciopappus species, but inclusion of it within the genus. The new form differs from the other species in being noticeably smaller and in morpho-structural details of each of the three coccolith types that form the coccosphere: (1) the body coccoliths have an open central area; (2) the whorl coccoliths have a wide central opening and two thumb-like protrusions; and (3) the appendage coccoliths are curved. On this basis, the species is formally described as Calciopappus curvus sp. nov., its systematic affinity is discussed and compared with other extant coccolithophores.

Dinoflagellate genomes have a unique architecture that may constrain their physiological and biochemical responsiveness to environmental stressors. Here we quantified how nitrogen (N) starvation influenced macromolecular allocation and C:N:P of three photosynthetic marine dinoflagellates, representing different taxonomic classes and genome sizes. Dinoflagellates respond to nitrogen starvation by decreasing cellular nitrogen, protein and RNA content, but unlike many other eukaryotic phytoplankton examined RNA:protein is invariant. Additionally, 2 of the 3 species exhibit increases in cellular phosphorus and very little change in cellular carbon with N-starvation. As a consequence, N starvation induces moderate increases in C:N, but extreme decreases in N:P and C:P, relative to diatoms. Dinoflagellate DNA content relative to total C, N and P is much higher than similar sized diatoms, but similar to very small photosynthetic picoeukaryotes such as Ostreococcus. In aggregate these results indicate the accumulation of phosphate stores may be an important strategy employed by dinoflagellates to meet P requirements associated with the maintenance and replication of their large genomes.

Ciliates in the order Pleurostomatida are found free-living in many habitats including within biofilms, but some (e.g. Pseudoamphileptus spp.) are ectocommensal on various hosts. Due to issues involving overall undersampling, the exact diversity and molecular phylogeny of this group remain largely underexplored. To combat this deficiency, detailed investigations were undertaken in northern China. As a result of these studies, we provide the morphological descriptions of two new species. Pseudoamphileptus apomacrostoma sp. nov., a new ectocommensal species, is characterized by the broadly oval cell shape, numerous scattered contractile vacuoles, and unique densely bounded extrusomes; Amphileptus qingdaoensis sp. nov., a marine form, is characterized by possessing oblong extrusomes with a conical anterior end, a single contractile vacuole and 5–7 left and 18–23 right kineties. In addition, a new population of Amphileptus orientalis Zhang et al., 2022, a freshwater representative, was documented and an improved diagnosis is provided. The phylogenetic analyses based on the SSU rDNA sequences imply that the genus Pseudoamphileptus is monophyletic whereas the genus Amphileptus is paraphyletic. The new molecular sequences presented here further support the establishment of two new species.

Parasitic euglenids have rarely been studied. We found parasitic euglenids in two species of ostracods (Cyprinotus cassidula, Dolerocypris sinensis) and two species of rhabdocoels (Mesostoma lingua, Microdalyellia armigera) in a rice field. These parasites grew and proliferated inside the host body. These parasites had pellicle strips, one emergent flagellum, and a red stigma, but no chloroplasts, and showed euglenoid movement. Inside the living host, they did not have emergent flagella and moved only by euglenoid movement, but when the host died or the parasites were isolated from the host, they extended their flagella and switched to swimming movement. We conclude that the parasites found in the four hosts that we examined are of the same species, considering the morphological characteristics and identities in the nSSU and nLSU rDNA sequences of those parasites. Molecular phylogenetic analysis showed that the parasite formed a clade with the free-living photoautotrophic species of Euglenaformis, with moderate statistical support. Therefore, the parasite is a secondary osmotroph derived from a photoautotrophic ancestor. Based on the results of morphological observation and molecular phylogenetic analysis, we propose a new species of parasitic euglenid, Euglenaformis parasitica sp. nov.

Oceanic phytoplankton serve as a base for the food webs within the largest planetary ecosystem. Despite this, surprisingly little is known about species composition, function and ecology of phytoplankton communities, especially for vast areas of the open ocean. In this study we focus on the marine phytoplankton microflora from the vicinity of the Marquesas Islands in the Southern Pacific Ocean collected during the Tara Oceans expedition. Multiple samples from four sites and two depths were studied in detail using light microscopy, scanning electron microscopy, and automated confocal laser scanning microscopy. In total 289 taxa were identified, with Dinophyceae and Bacillariophyceae contributing 60% and 32% of taxa, respectively, to phytoplankton community composition. Notwithstanding, a large number of cells could not be assigned to any known species. Coccolithophores and other flagellates together contributed less than 8% to the species list. Observed cell densities were generally low, but at sites of high autotrophic biomass, diatoms reached the highest cell densities (1.26 × 10⁴ cells L⁻¹). Overall, 18S rRNA metabarcode-based community compositions matched microscopy-based estimates, particularly for the main diatom taxa, indicating consistency and complementarity between different methods, while the wide range of microscopy-based methods permitted several unknown and poorly studied taxa to be revealed and identified.

In this paper, we describe a new naked amoeba species, Mayorella marianaensis sp. n., order Dermamoebida, isolated from the bottom of the Pacific Ocean (>3,000 m depth) in the vicinity of the Mariana Trench, based on morphological and molecular data. The newly discovered species was identified based on morphological and molecular data. This is the first time that a Mayorella species was discovered in the deep sea (>1,000 m). Mayorella marianaensis is an irregularly rectangular naked amoeba (30–120 × 11–60 µm), with a narrow frontal hyaline area. Four to 15 conical sub-pseudopodia, and three kinds of floating forms are identified. Trophozoites have a thick cell coat consisting of two distinct layers. The small subunit ribosomal RNA gene phylogeny showed that M. marianaensis is classified into Dermamoebida, and is a sister clade to other Mayorella species whose sequences are available. BLAST analysis revealed that M. marianaensis is most similar to Coronamoeba villafranca and Mayorella sp. JJP-2003, with sequence identities of 92.43% and 88.30%, respectively.