Thalassiosira sundarbana sp. nov. (Bacillariophyta), an estuarine diatom from Sundarbans mangrove ecoregion based on morphology and molecular phylogeny

A new species of diatom, Thalassiosira sundarbana, is described based on light and scanning electron microscopy along with molecular phylogeny. The specimen was collected from Chemaguri creek of the Indian part of Sundarbans mangroves, and subsequently a clonal culture was established. Thalassiosira sundarbana possess variable numbers of occluded processes, and one labiate process on the valve face. Valve margin is ribbed and areolae are fasciculated on the valve face. Two rings of strutted processes are present on valve face. Strutted processes are also scattered on the valve face apart from the presence of two rings. Valvocopula and copula have rows of pore, and pleurae are hyaline. Bayesian analyses of nuclear encoded small subunit (SSU) rDNA and plastid encoded rbcL gene confirmed that T. sundarbana is phylogenetically novel. Salinity tolerance experiment with the clonal culture of T. sundarbana showed that this isolate can grow in salinity ranging from 10–35 psu. The maximum growth rate was observed in 15 psu salinity (0.5 divisions 24 h^?1). On the basis of morphological features and molecular phylogeny, this clonal isolate is considered as a new estuarine species of Thalassiosira.     

Morphology and molecular phylogeny of Thalassiosira sinica sp. nov. (Bacillariophyta) with delicate areolae and fultoportulae pattern

Thalassiosira Cleve is one of the most species-rich marine diatom genera. Previous studies have mainly focused on polar and temperate areas, but recent studies on material from Asian waters suggested that a high and undescribed species diversity of Thalassiosira occurs in Asia. On the basis of plankton samples collected from the South China Sea, a new species, T. sinica sp. nov. Y. Li & Y. Q. Guo is described. The morphology of the cells was examined by light and scanning electron microscopy. The hypervariable region of the nuclear large-subunit ribosomal DNA and the relatively conserved region of the nuclear small-subunit ribosomal DNA were sequenced for information on phylogenetic relationships. The living cells are usually solitary and drum-shaped. The areolae on the valve are delicate, small and arranged in fascicles. In addition to a regular ring of marginal fultoportulae on the valve edge, T. sinica possesses one central fultoportula and a number of fultoportulae arranged into 2–3 irregular rings on the valve face. A rimoportula located inside the ring of marginal fultoportulae possesses a long and strong external tube. The valvocopula and the copulae have rows of pores, but the pores on the valvocopula are larger than those on the copulae. Thalassiosira sinica appears to be included in subgroup C sensu Gedde because of a rimoportula with a distinct external tube located on the valve face. The molecular phylogeny, inferred from both SSU and LSU sequences, does, however, not support the validity of subgroup C, as the closest allies of T. sinica here turned out to be T. diporocyclus and T. lundiana, species in which the rimoportulae are located on the valve margin.     

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 and molecular phylogeny of two new soil ciliates,Hemiurosomoida warreni nov. spec. and Hemiurosoma clampi nov. spec. (Ciliophora,Hypotrichia) from Tibet

Two novel hypotrichous ciliates, Hemiurosomoida warreni nov. spec. and Hemiurosoma clampi nov. spec., isolated from soil in the Lhalu Wetland and Motuo Virgin Forest in Tibet, respectively, were investigated using live observation and protargol staining. Hemiurosomoida warreni nov. spec. strongly resembles the type species H. longa but can be distinguished by its body size in vivo (110–145 × 30–40 μm vs. 50–100 × 18–40 μm), number of adoral membranelles (25–38 vs. 15–22), and numbers of right (29–39 vs. 14–23) and left (26–35 vs. 13–23) marginal cirri, transverse cirri (3 vs. 4 or 5) and macronuclear nodules (4–8 vs. 2). Hemiurosoma clampi nov. spec. is characterized by its vermiform body shape, colourless cortical granules distributed in irregular rows, two macronuclear nodules, three frontal cirri, one buccal cirrus, four frontoventral cirri ranged in a line, two transverse cirri, lacking postoral ventral and pretransverse ventral cirri, and marginal rows that are not posteriorly confluent. Phylogenetic analyses based on SSU rDNA gene sequences suggest that Hemiurosomoida is not monophyletic. A close relationship is revealed between Hemiurosomoida warreni nov. spec., Parakahilella macrostoma, Hemiurosoma clampi nov. spec., and the type species Hemiurosoma terricola. As expected, all these species are classified within the “non-oxytrichid Dorsomarginalia”.     

Morphology,morphogenesis and molecular phylogeny of a new marine ciliate,Trichototaxis marina n. sp. (Ciliophora,Urostylida)

The live morphology, infraciliature and morphogenesis of a new urostylid ciliate, Trichototaxis marina n. sp., collected from coastal water in Qingdao, China, were studied based on the observations of live and silver stained specimens. The new species is characterised as follows: body very flexible and contractile, slight to brick-reddish in colour due to irregularly-shaped, brick-red pigments; ca. 70 adoral membranelles; about 17 frontal cirri arranged in a bicorona; average 67 midventral pairs, the right base of each pair being conspicuously larger than the left base; five to seven transverse cirri; constantly two frontoterminal, one buccal and two pretransverse ventral cirri; two or three left marginal rows; right and innermost left marginal rows with 56–92 and 66–106 cirri, respectively; six bipolar dorsal kineties; more than 100 macronuclear nodules. The characteristic morphogenetic feature in T. marina is the development of the left marginal rows, that is, only one left marginal row is newly built the other one or two being retained from the parental cell. Phylogenetic analyses based on small subunit ribosomal gene sequence data reveal a close relationship of T. marina with members of family Pseudokeronopsidae.     

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.     

Morphology and molecular phylogeny of the anaerobic freshwater ciliate Urostomides spinosus nov. spec. (Ciliophora,Armophorea, Metopida) from China

The morphology and molecular phylogeny of a new metopid ciliate, Urostomides spinosus nov. spec., discovered in a freshwater ditch in Qingdao, China, were investigated using live observation, morphometry and protargol staining as well as molecular phylogenetic methods. Diagnostic features of the new species include a broadly obpyriform body carrying three posterior spines, eight somatic kineties, five preoral dome kineties with specialized row 3, adoral zone composed of about 28 membranelles, making a 270° turn around body axis. Phylogenetic analyses of the SSU rDNA sequence revealed that the genus Urostomides is monophyletic, but its interspecific relationships remained unresolved. Moreover, a closer relationship of the new species with the morphologically similar Urostomides campanula was not supported by the molecular data.     

Morphology and molecular phylogeny of a new brackish pleurostomatid ciliate,Loxophyllum paludosum sp. n. (Ciliophora,Litostomatea, Haptoria), from a mangrove wetland in China

A new ciliate species of the genus Loxophyllum Dujardin, 1841, Loxophyllum paludosum sp. n., is described from a mangrove wetland near Daya Bay in Guangdong Province, southern China, based on morphological and molecular analyses. The new species can be distinguished from its congeners by a combination of the following characters: (1) 12–14 right kineties and 4–6 left kineties; (2) two macronuclear nodules and one micronucleus; (3) a single contractile vacuole located terminally; (4) extrusomes bar-shaped, evenly spaced along entire ventral margin, and clustered to form 5–7 warts along dorsal margin; and (5) presence of three ridges on the left side of cell. The new species is divergent from its congeners from 0.4% to 6.7% (5–104 nucleotide sites) based on the small subunit (SSU) rRNA gene sequence data. The validity of the new species is also supported by molecular phylogenetic trees inferred from SSU rRNA gene sequences.     

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

The living morphology, infraciliature, morphogenesis and phylogenetic position of a new hypotrichous ciliate, Heterourosomoida sinica n. sp., discovered in saline soil in Northwest of China, were investigated. Heterourosomoida sinica n. sp. is characterized as follows: body size about 70–95 × 20–30 μm in vivo, ellipsoid or elongate; cortical granules dark green, 0.5 μm across, arranged around dorsal cilia and in short irregular rows on ventral side; consistently 18 frontoventral-transverse cirri; left and right marginal rows composed of 17–24 and 13–21 cirri, respectively; two macronuclear nodules and one or two micronuclei. The detailed morphogenesis of a species of Heterourosomoida is reported for the first time. The ontogenesis on dorsal side is basically similar to that in Urosomoida-species and the process on ventral side is characterized by: 18 frontoventral-transverse cirri develop from six anlagen with the anlagen V and VI formed in the primary mode. Phylogenetic analyses based on SSU rDNA sequence data reveal that Heterourosomoida sinica n. sp. clusters with Kleinstyla dorsicirrata and forms a clade with the type species H. lanceolata.     

Morphology and taxonomy of Stephanodiscus vestibulis sp. nov. (Bacillariophyta)

A new species Stephanodiscus vestibulis is described from an eutrophic, hardwater habitat in western North America. Under the light microscope it resembles, and has perhaps been confused with, certain other small species of the genus. Structural features of the valve resolved by SEM, however, show that it is unique. The new species is particularly characterized by arch-like vestibules over the external openings of the marginal strutted processes. Other features include central and marginal strutted processes with three satellite pores, internally domed criba on the puncta and a single labiate process.     

Gambierdiscus (Gonyaulacales,Dinophyceae) diversity in Vietnamese waters with description of G. vietnamensis sp. nov.

Viet Nam has a coastline of 3200 km with thousands of islands providing diverse habitats for benthic harmful algal species including species of Gambierdiscus. Some of these species produce ciguatera toxins, which may accumulate in large carnivore fish potentially posing major threats to public health. This study reports five species of Gambierdiscus from Vietnamese waters, notably G. australes, G. caribaeus, G. carpenteri, G. pacificus, and G. vietnamensis sp. nov. All species are identified morphologically by LM and SEM, and identifications are supported by molecular analyses of nuclear rDNA (D1–D3 and D8–D10 domains of LSU, SSU, and ITS1-5.8S-ITS2 region) based on cultured material collected during 2010–2021. Statistical analyses of morphometric measurements may be used to differentiate some species if a sufficiently large number of cells are examined. Gambierdiscus vietnamensis sp. nov. is morphologically similar to other strongly reticulated species, such as G. belizeanus and possibly G. pacificus; the latter species is morphologically indistinguishable from G. vietnamensis sp. nov., but they are genetically distinct, and molecular analysis is deemed necessary for proper identification of the new species. This study also revealed that strains denoted G. pacificus from Hainan Island (China) should be included in G. vietnamensis sp. nov.     

Morphology and molecular phylogeny of the marine diatom genus Nagumoea (Bacillariophyceae) from Japan

The canal-bearing diatom genus Nagumoea, described based on only morphological evidence, was tentatively assigned to the order Bacillariales, although its phylogenetic position remained unclear. Because three isolates of Nagumoea (SK002, SK024 and SK053) were successfully established from Japanese coasts, we performed their morphological observations and molecular phylogenetic analyses to discuss the phylogeny and taxonomic position of this genus. Strains SK002 and SK024 were identified as Nagumoea africana, whereas SK053 conformed with Nagumoea serrata. There was high interspecific divergence between N. africana and N. serrata in the rbcL sequences (8.03–8.17%), indicating their distinctness. Furthermore, intraspecific variations were detected within N. africana (2.35%) in the rbcL, implying its cryptic diversity. The maximum likelihood and Bayesian phylogenetic trees inferred from the plastid rbcL, psbC and nuclear 18S rDNA genes recovered Nagumoea as monophyletic with strong statistical support and embedded within an unresolved, poorly supported lineage containing Achnanthes, Craspedostauros, Staurotropis and Undatella in the canal-bearing order Bacillariales (= the family Bacillariaceae). Although the constrained tree based on the monophyly of Nagumoea and the other canal-bearing clade (Surirellales and Rhopalodiales) was statistically rejected by the topology tests, the phylogenetic position of Nagumoea with other Bacillarialean members remains equivocal. The possession of two plastids positioned fore and aft, observed in the present study, and lack of keel, typical of the Bacillariales, indicate the possibility of Nagumoea being part of the ingroup of the Bacillariales or its closely related outgroup.     

Morphology,morphogenesis and molecular phylogeny of a freshwater ciliate,Monomicrocaryon euglenivorum euglenivorum (Ciliophora,Oxytrichidae)

The morphology, morphogenesis and molecular phylogeny of the oxytrichid ciliate, Monomicrocaryon euglenivorum euglenivorum (Kahl, 1932) Foissner, 2016, isolated from freshwater in a seaside park, Guangzhou, China, were investigated. Monomicrocaryon euglenivorum euglenivorum can be recognized as follows: caudal cirri in midline of body; dorsal kinety 1 without a one-kinetid-wide gap; transverse cirri acicular or rod-shaped with a fringed distal end; right marginal row commences at level of buccal vertex or anterior to buccal vertex. The main events during binary fission are as follows: (1) the proter retains the parental adoral zone of membranelles entirely; (2) frontoventral-transverse cirral anlagen I–VI 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 postoral ventral, two pretransverse ventral and five transverse cirri, respectively; (3) dorsal morphogenesis is in the typical Oxytricha-pattern, but fragmentation of dorsal kinety 3 is indistinct; and (4) three caudal cirri are formed, one at the posterior end of each of dorsal kineties 1, 2 and 4. Phylogenetic analyses based on SSU rDNA sequences showed that M. euglenivorum euglenivorum clustered with Kleinstyla dorsicirrata and Heterourosomoida lanceolata rather than with its congener M. elegans. The genus Monomicrocaryon is not monophyletic in this study; however, its monophyly is not rejected by the AU test.     

Morphology,Morphogenesis and Molecular Phylogeny of a New Obligate Halophile Ciliate,Schmidtiella ultrahalophila gen. nov., spec. nov. (Ciliophora,Hypotrichia) Isolated from a Volcanic Crater on Sal (Cape Verde Islands)

A new hypotrichous ciliate, Schmidtiella ultrahalophila gen. nov., spec. nov., was isolated from a solar saltern on the island of Sal, Cape Verde. The possession of only one short dorsal kinety clearly distinguishes S. ultrahalophila from other known hypotrichous genera and species. Further diagnostic characters include: a flexible and slender body, an average size of 85 × 15 μm in vivo; a bipartite adoral zone with two hypertrophied frontal adoral membranelles and nine to twelve ventral adoral membranelles; three frontal, one parabuccal, two frontoventral, two or three postoral ventral, and two or three frontoterminal cirri; and marginal cirral rows variable in number, usually one on each side. Ontogenetic data indicate the following: the frontal‐ventral cirri originate from six or five anlagen; the proter inherits the parental adoral zone; the frontal and ventral cirri originate from five or six anlagen; and the marginal cirral rows and the dorsal kinety tend to originate intrakinetally. Additional marginal rows are rarely derived from de novo anlagen. Based on its morphology, morphogenesis and its SSU rRNA phylogenetic placement, the new species should be assigned to the order Sporadotrichida Fauré‐Fremiet, 1961. Due to low taxon sampling, however, its exact position in this order remains enigmatic.     

Fine structure and 18S rDNA phylogeny of a marine araphid pennate diatom Plagiostriata goreensis gen. et sp. nov. (Bacillariophyta)

A marine araphid pennate diatom Plagiostriata goreensis is described from the sand grains of Goree Island, Dakar, Republic of Senegal, based on observations of fine structure of its frustule. The most striking feature of the species is its striation, which is angled at approximately 60° across the robust sternum. The other defining features of the species are its one highly reduced rimoportula and apical pores located at both ends of the valve margin. In the 18S rDNA phylogeny, the species appears as a member of a ‘small‐celled clade’ of araphid pennate diatoms that consist of Nanofrustulum, Opephora and Staurosira. The results of the phylogenetic analyses suggest that the distinct characters of the diatom; namely, oblique striae and apical pores, may have been acquired independently. However, it remains unclear whether the rimoportula of P. goreensis is a reduced state or P. goreensis acquired its morphologically curious rimoportula independently after the loss of an ancient rimoportula at the root of the small‐celled clade.     

Morphology and molecular phylogeny of Holostichides terrae nov. spec. (Ciliophora: Spirotrichea) with discussion on the possible non-monophyly of Holostichides

In a study to investigate ciliate diversity, we discovered a new soil ciliate. Holostichides terrae nov. spec. was examined and identified based on observations of living cells and stained specimens. In addition, the nuclear SSU rRNA gene along with morphology was analyzed to infer its phylogenetic position. The new species closely resembles H. dumonti, but can be distinguished by the morphology of the pharynx (with rod-shaped structure vs. lacking) and the number of frontoterminal cirri (invariably two vs. usually more than two). Molecular analyses indicate that the genus Holostichides is not monophyletic, and H. terrae is closely related with the genera Birojimia and Hemicycliostyla, both of which have a pharynx with rod-shaped structures, as also seen in H. terrae.     

Morphology and small subunit rRNA gene sequence of Uronemita parabinucleata n. sp. (Ciliophora,Uronematidae), with an improved generic diagnosis

The morphology and infraciliature of a new species, Uronemita parabinucleata n. sp., isolated from intertidal sediments in a coastal region in northern China, were investigated using live observation and silver impregnation methods. The new species is characterized by an in vivo body size of about 20–50 × 10–25 μm, 22 or 23 somatic kineties, two macronuclear nodules, and one caudal cilium. Its small subunit ribosomal RNA gene (SSU rDNA) was sequenced and compared with those of other Uronemita species to reveal nucleotide differences. Phylogenetic analyses indicated that Uronemita is monophyletic and that the new species clusters with its congener Uronemita filificum, with full support provided by both Bayesian inference and maximum likelihood algorithms. Based on previous studies and the present study, an improved diagnosis of the genus Uronemita is supplied, which has been absent since the establishment of this genus. A key to the Uronemita species is also provided.     

Morphology and phylogeny of Prorocentrum caipirignum sp. nov. (Dinophyceae), a new tropical toxic benthic dinoflagellate

A new species of toxic benthic dinoflagellate is described based on laboratory cultures isolated from two locations from Brazil, Rio de Janeiro and Bahia. The morphology was studied with SEM and LM. Cells are elliptical in right thecal view and flat. They are 37–44 μm long and 29–36 μm wide. The right thecal plate has a V shaped indentation where six platelets can be identified. The thecal surface of both thecal plates is smooth and has round or kidney shaped and uniformly distributed pores except in the central area of the cell, and a line of marginal pores. Some cells present an elongated depression on the central area of the apical part of the right thecal plate. Prorocentrum caipirignum is similar to Prorocentrum lima in its morphology, but can be differentiated by the general cell shape, being elliptical while P. lima is ovoid. In the phylogenetic trees based on ITS and LSU rDNA sequences, the P. caipirignum clade appears close to the clades of P. lima and Prorocentrum hoffmannianum. The Brazilian strains of P. caipirignum formed a clade with strains from Cuba, Hainan Island and Malaysia and it is therefore likely that this new species has a broad tropical distribution. Prorocentrum caipirignum is a toxic species that produces okadaic acid and the fast acting toxin prorocentrolide.