Cymbopleura huohuaensis sp. nov. (Cymbellaceae; Bacillariophyceae), a new species from Sichuan Province, China

Cymbopleura huohuaensis sp. nov. is identified as a new species and described from stone surfaces in Huohua Lake, Sichuan Province, China. A detailed morphological description of the new species is presented, based on light and scanning electron microscopy. Cymbopleura huohuaensis sp. nov. has the features that assign it to the genus Cymbopleura, including the raphe with dorsally deflected terminal fissures and ventrally curved central raphe ends, punctate-lineate striae, and the absence of apical pore fields and stigmata. There are five features that easily distinguish the new species from the other similar taxa within the genus: 1) linear-lanceolate central area, 2) mostly slit-like, partly T-shaped, V-shaped or irregularly-shaped areolae, 3) strongly reverse-lateral raphe, 4) slightly truncate to obtusely rounded ends and 5) the highest density of areolae (30–50 in 10 μm). Among the currently described species of Cymbopleura, the new species is in general most similar to C. subaequalis var. pertruncata in valve shape and possessing a reverse-lateral raphe, but is easily distinguished from that taxon by the size and shape of valve, shape of central area, and the degree of asymmetry about the apical axis and its notable lack of an intermissio. This species might be better placed in the C. austriaca group due to its lack of an intermissio. These findings increase our understanding the morphology and distribution of the genus Cymbopleura in China.

New and poorly known “araphid” diatom species (Bacillariophyta) from regions near Lake Titicaca, South America and a discussion on the continued use of morphological characters in “araphid” diatom taxonomy

Based on two Andean Altiplano samples and on light and scanning electron microscopy analyses, we present six new species of “araphid” diatoms in the genus Pseudostaurosira, P. aedessp. nov., P. frankenaesp. nov., P. heteropolarissp. nov., P. oblongasp. nov., P. occultasp. nov., and P. pulchrasp. nov. Additional data are provided for four other known taxa, Nanofrustulum cataractarum, N. rarissimum, P. sajamaensis and P. vulpina, the latter species corresponding to a stat. nov. based on a variety of P. laucensis. Each taxon is described morphologically and compared with closely related published taxa, using characters such as axial area, virgae, vimines, areolar shape, volae, internal striae depositions, spines, flaps and apical pore fields, which are not usually used for species distinction within the genus. It is our intention that the detailed morphological descriptions of each taxon and the elaborate comparative tables we provide serve as a basis for correction of neo and paleo-databases for the Altiplano to produce a better account of autecological data and ecological change in the region. Some arguments for our continued use of a morphologically based approach are given in the context of rapid environmental degradation in the Andes and the difficulties in applying molecular approaches in countries such as Bolivia.

First Report of the Marine Benthic Dinoflagellate Bysmatrum subsalsum from Korean Tidal Pools

Dense patches were observed in the tidal pools of the southern area of Korea. To clarify the causative organisms, the cells were collected and their morphological features were examined using light and scanning electron microscopy (SEM). In addition, after establishing strains for the cells the molecular phylogeny was inferred with concatenated small subunit (SSU) and large subunit (LSU) rRNA sequences. The cells were characterized by a nucleus in the hypotheca, strong reticulations in thecal plates, the separation of plates 2a and 3a, the tear-shaped apical pore complex, an elongated rectangular 1a plate and the absence of the right sulcal list. The thecal plate formula was Po, X, 4′, 3a, 7″, 6c, 4S, 5′′′, 2′′′′. Based on these morphological features, the cells were identified as Bysmatrum subsalsum. In the culture, the spherical cysts of B. subsalsum without thecal plates were observed. Molecular phylogeny revealed two ribotypes of B. subsalsum are identified; The Korean isolates were nested within the ribotype B consisting of the isolates from China, Malaysia and the French Atlantic, whereas the ribotype A includes only the isolates from the Mediterranean Sea. In the phylogeny, B. subsalsum and B. austrafrum were grouped. This can be supported by the morphological similarity between the two species, indicating that the two species may be conspecific, however B. subsalsum may distinguish from B. austrafrum, because of differences in the types of eyespots reported in previous studies. These findings support the idea that there is cryptic diversity within B. subsalsum.

Pseudostaurosira crateri sp. nov. (Fragilariaceae, Bacillariophyta), a new small araphid, fossil diatom species from the Pleistocene (Atlantic Forest, Brazil)

Pseudostaurosira crateri sp. nov. is described from fossil material analyzed from a Quaternary sediment core retrieved from the Colônia basin (located in the Brazilian Coastal Plain, Atlantic Forest, São Paulo Metropolitan Region). Light and scanning electron microscopy revealed its morphology and enabled its comparison with morphologically similar species from European and African rivers and lakes. The new species features wide and short vimines, a particular characteristic of the genus Pseudostaurosira, in addition to many other exclusive features that distinguish it from any other species in the genus reported to date. Some of these characteristics are: (i) apical pore fields composed of small poroids placed within cavernous troughs carved deep into the valve, (ii) absence of blisters or depositions along the valve mantle edge, (iii) small-sized valve, (iv) presence of incipient or rudimentary spines located on raised virgae at the valve face/mantle junction, and (v) internal accumulations of siliceous material on the volae appearing as concentric discs partially occluding the depression into which the areolae open internally. We further discuss the morphological features of similar species ascribed to the genera Pseudostaurosira, Pseudostaurosiropsis, Staurosirella, Frankophila, and Popovskayella based on literature information. Finally, this study contributes to the knowledge on diatom diversity and its biogeography, especially those from tropical regions, in addition to providing a taxonomical basis for its use as biological markers for paleoenvironmental reconstruction.

Staurosirella paranaensis sp. nov., a new epiphytic freshwater diatom (Bacillariophyceae) from the Paraná River floodplain, Brazil, South America

A new diatom species, Staurosirella paranaensis, is described only from epiphytic samples on the macrophyte Eichhornia azurea in a lake from the Upper Paraná River Floodplain in Brazil. Description of the new taxon is based on morphological characteristics observed using light and scanning electron microscopy. The new species is characterized by short elliptic valves with an axial area narrowly lanceolate, sometimes giving the impression of having a zig-zag form due the alternating nature of the striae. The lineolate striae, running uninterrupted from valve face to mantle. Spines are solid, thin, spatulate with two prominences at the top, located at the costae. Apical pore fields are inconspicuous, located at both apices and equally developed on both valves. Girdle elements variable in number, open, lacking pores, ligulated, and with valvocopula being much larger. The species previously identified in the region as the “catch-all” taxon “Staurosirella (Staurosira) pinnata” is placed in the genus Staurosirella based on the striae bearing well-developed internal vimines delimiting typically long areolae. Comparisons with similar species ascribed to the genus Staurosirella are provided to highlight the peculiar characteristics of S. paranaensis.

Three new needle-shaped Fragilaria species from Central America and the Tibetan Plateau

Three new needle-shaped Fragilaria species from freshwater lake Apastepeque in El Salvador (Fragilaria salvadoriana sp. nov., F. maarensis sp. nov.) and subsaline lake Nam Co on the Tibetan Plateau (F. huebeneri sp. nov.) are described and compared based on light and scanning electron microscopy observations and morphometric analyses. Fragilaria salvadoriana sp. nov. is characterized by narrowly linear-lanceolate, sometimes centrally constricted valves, subcapitate to rarely capitate apices, and a distinct, dented appearing central area. Striae are composed of 2−5 occluded areolae. It can be differentiated from similar needle-shaped species by the valve outline, relatively low striae density, and shark fin-shaped spines. Characteristic of F. maarensis sp. nov. are a very narrowly lanceolate valve outline and subcapitate apices. The apical pore field is composed of 2–3 rows of poroids and acute, irregularly oriented spines are present at the junction between valve face and mantle. This taxon is clearly different from other Fragilaria species, displaying a high length-to-width ratio and a low number of areolae per stria. The Tibetan species, F. huebeneri sp. nov., forms long ribbon-like colonies linked together by spatula-shaped spines. Valves have subcapitate apices, a spindle- to needle-shaped outline and an indistinct central area. Striae are alternate and composed of 3–5 areolae per stria. Teratological forms of F. huebeneri sp. nov. were commonly observed in the sediment trap samples. Fragilaria salvadoriana sp. nov. and F. maarensis sp. nov. were found in a warm, tropical crater lake characterized by low conductivity and dissolved oxygen content, medium alkaline pH, and magnesium-calcium-bicarbonate-rich waters. Fragilaria huebeneri sp. nov. was frequent in a large, high elevation lake with increased specific conductivity, alkaline pH and sodium-bicarbonate-rich waters. The new species are compared to morphologically similar species from the genus Fragilaria Lyngbye and ecological preferences are discussed.

Kurtkrammeria tiancaiensis sp. nov. a new cymbelloid species (Bacillariophyceae) from Lijiang Laojunshan National Park in Yunnan Province, China

During a survey of freshwater diatoms from a mountain lake, Lake Tiancai, Laojunshan National Park, Hengduan Mountain Range, Lijiang City, Yunnan Province, China, a new Kurtkrammeria species, Kurtkrammeria tiancaiensis sp. nov. was recorded. A detailed morphological description of K. tiancaiensis is presented, based on light and scanning electron microscopy. The main features of K. tiancaiensis include slightly dorsiventral valves with narrowly rounded, or slightly protracted ends, a wide central area, apical pore fields at both poles and lack of stigmata. The new species is compared with K. treinishii, K. weilandii, K. lacusglacialis and K. eileencoxiae (≡ Gomphonema eileencoxiae), all of which show similar valve outlines to K. tiancaiensis, but differ in details of size, striae density, puncta density, number of apical pore fields, shape of the central area and/or presence of stigmata.

Gomphonema frequentiformis (Metzeltin & Krammer) comb. nov. (Bacillariophyta): ecology and taxonomy of a Neotropical diatom

The transfer of Encyonopsis frequentiformis Metzeltin & Krammer to the genus Gomphonema Ehrenberg is proposed based on observations using light and scanning electron microscopy. The taxon is characterized by lanceolate heteropolar valves, with both apices strongly capitate, two apical pore fields, and elongated areolae slit-like and the internal stigma opens in a slit. Heteropolarity of the specimens measured and other shared similarities with the genus Gomphonema (APF, areolae, external and internal aperture of the isolated pore, pseudosepta at both apices) allows us to classify this species into the genus Gomphonema. Morphological, ecological and distribution data in South America are presented and discussed based on available literature for this Neotropical taxon.

Redefinition of the Dinoflagellate Genus Alexandrium Based on Centrodinium: Reinstatement of Gessnerium and Protogonyaulax, and Episemicolon gen. nov. (Gonyaulacales, Dinophyceae)

The genus Centrodinium contains oceanic and predominantly tropical species that have received little attention. Three species of Centrodinium were examined using thecal plate dissociation, scanning electron microscopy, and molecular sequences. The apical horn of Centrodinium intermedium and C. eminens is formed by the elongation of the fourth apical plate, and a second apical split into two plates. In C. punctatum two apical plates (2′ and 4′) almost completely encircle the apical pore plate (Po), while the contact with the plate 1′ in the ventral side is much reduced, and the plate 3′ does not reach the Po. Moreover, its left posterior lateral sulcal plate is longer than its right pair, while reversed in the typical Centrodinium spp. The sulcal posterior plate of C. punctatum is located in the left-ventral side below the plates 1′′′ and 2′′′, while the sulcal posterior plate located in the right face below the plates 4′′′ and 5′′′ in the typical Centrodinium spp. Phylogenetic analyses based on the small and large subunit of the rRNA gene showed that Centrodinium spp. and Alexandrium affine/A. gaarderae clustered as a sister clade of the Alexandrium tamarense/catenella/fraterculus groups. The clade of the subgenus Gessnerium, and the clade of the type species of Alexandrium, A. minutum, with four divergent species, clustered in more basal positions. The polyphyly of Alexandrium is solved with the split into four genera: (1) Alexandrium sensu stricto for the species of the clade of A. minutum and four divergent species; (2) the reinstatement of the genus Gessnerium for the species of the clade of A. monilatum; (3) the reinstatement of genus Protogonyaulax for the species of the tamarense/catenella/fraterculus groups, and (4) the new genus Episemicolon gen. nov. for A. affine and A. gaarderae. New combinations in the genera Gessnerium, Protogonyaulax, and Episemicolon are proposed.

Morphological reconsideration of the araphid genus Pseudostaurosira (Bacillariophyceae), a revision of Gedaniella, Popovskayella and Serratifera, and a description of a new Nanofrustulum species

Background and aims – As a result of the description of many new species, reanalyses of type material, and information becoming available on valve morphogenesis in small araphid diatoms lacking a rimoportulae, the existing classification scheme at the genus level needs revision. Because morphological information has increased manyfold since the system provided by Williams & Round (1987), it may now be possible to find distinguishing characters in order to produce a more stable and useful framework, encompassing a morphogenetic perspective, which could then guide the placement of newly discovered taxa. This new framework could also be used to help assess the molecular information generated for the group, based on which many new genera are being erected, but perhaps without proper pondering of morphological data. Methods – A thorough review was made of available published information on the ultrastructure of small-celled araphid diatoms lacking rimoportulae. In addition, image databases were searched, and new light and scanning electron microscopical observations made of some hitherto undescribed species. Key results and conclusions – We provide a table of putative distinguishing features for nine genera (Nanofrustulum, Opephora, Pseudostaurosira, Pseudostaurosiropsis, Punctastriata, Sarcophagodes, Stauroforma, Staurosira and Staurosirella), together with a discussion on their value for discriminating these small diatoms using a morphogenetic perspective. Based on our findings, we amend the genus Pseudostaurosira, establishing wide and short vimines as its most characteristic feature. We use our system in describing a new species from Bolivia, which we place in Nanofrustulum based on its quasifract copulae, the distinguishing trait of the genus. The new species is distinguished from its congeners by its heteropolar valves, apical pore field features, and the multiseriate areolae. We also examine the three genera Popovskayella, Gedaniella, and Serratifera, the latter two recently erected based on molecular information. Since none of these latter genera pass the morphogenetic evaluation we think is essential, we place them in synonymy with other genera and provide the consequent nomenclatural changes. Finally, we make several new combinations in Nanofrustulum, Pseudostaurosira, Sarcophagodes and Staurosirella.