Valve Face Fultoportulae Research Articles

A new freshwater species Conticribra sinica (Thalassiosirales, Bacillariophyta) from the lower reaches of the Yangtze River, China

A new freshwater diatom species Conticribra sinica sp. nov. Yu, You et Wang from three lakes in the lower reaches of the Yangtze River, China, is described here using a combination of morphological and molecular data from ribosomal DNA genes. The primary distinguishing characteristic of C. sinica was the presence of a non-plicate or slightly-plicate valve face and a single ring marginal fultoportulae that was located at the junction between the valve face and the mantle. There were 4-11 valve face fultoportulae that were located at the subcenter of the valve face. In addition, a single rimoportula replaced a marginal fultoportulae. Areolae loculate were open to the outside by irregularly circular foramina or slit foramina that are radially arranged. Internally, cribra were continuously arranged long a radial arrangement of areolae. Characteristics of the new species with other similar species of Conticribra. Phylogenetic analysis of the nuclear small subunit (SSU) rDNA sequences and nuclear large subunit (LSU) rDNA gene sequences revealed that C. sinica in a single clade at a considerable sequence distance from the other Conticribra species.

Rimocostatus bugojnicus gen.et. sp. nov. (Coscinodiscophyceae, Bacillariophyta) – a new fossil diatom genus from Gračanica, Bugojno palaeolake in Bosnia and Herzegovina

A new freshwater fossil diatom taxon Rimocostatus bugojnicus gen. et sp. nov, from Miocene sediments at the Gračanica site, Bugojno palaeolake in Bosnia and Herzegovina, is described. The main morphological feature of the genus is the presence of marginal rimoportulae with simple, round external openings positioned on interfascicles on the valve mantle and stalked, large, wide internal slits, positioned on every costa. Marginal and valve face fultoportulae are absent. With these characteristics, the species shows similarities to both marine and freshwater species, known from recent, and primarily from fossil, diatom deposits. Thus, Rimocostatus bugojnicus gen. et sp. nov. is an important find for understanding the evolution of centric diatom species.

Stephanodiscus coruscus sp. nov., a new species of diatom (Bacillariophyta) from June Lake, California (USA) with close affiliation to Stephanodiscus klamathensis

Modern and fossil populations of a Stephanodiscus Ehrenberg species from June Lake, California (USA) were analysed using light and scanning electron microscopy (SEM). Stephanodiscus valves were a major constituent of almost all analysed samples, often dominating fossil assemblages dating back several thousand years. The most commonly observed Stephanodiscus specimen in the samples bore a striking resemblance to the extinct Late Pliocene species Stephanodiscus klamathensis, particularly under light microscopy. The population size range, ultrastructure, and other defining characteristics closely matched published information on S. klamathensis. However, under SEM, internal views of the specimens from June Lake showed an important difference; specimens lacked valve face fultoportulae, whereas S. klamathensis is characterized by the presence of two valve face fultoportulae, each with three satellite pores near the centre of the valve. Additional differences in valve size range, absence of fultoportulae on the valve face, and the fact that S. klamathensis is an extinct species (observed in diatomites deposited from Late Pliocene to Pleistocene) with no closely related living relatives, necessitates describing this Stephanodiscus as a new species. To date, Stephanodiscus coruscus has been observed only in June Lake, California; most Stephanodiscus that share strong morphological similarities to this species have only been observed in ancient fossil diatomites. Thus, Stephanodiscus coruscus Jeff. R. Stone, Edlund & Streib sp. nov. is not only a new species but also provides a rare glimpse into the likely types of environments that S. klamathensis and other similar ancient Stephanodiscus may have inhabited in the late Pliocene. Character variations between S. coruscus and S. klamathensis reveal potential patterns of evolution in freshwater lineages, such as character loss, over time.

Two new Tertiarius (Bacillariophyta, Coscinodiscophyceae) species from Mariovo Neogene Basin, Macedonia

The morphology, biostratigraphy and ecology of two new species, Tertiarius jurijlii and Tertiarius mariovensis are presented. The valve morphological variation and ultrastructure are described by light and scanning electron microscopy. Tertiarius juriljii is distinguished by the presence of hyaline area on the valve face; central area comprised of areolae arranged in single short or long radial rows; presence of small to large granules on the interstriae; and valve face fultoportulae arranged in radial rows around the valve center. Comparatively, in Tertiarius mariovensis the hyaline area around the central area is missing, and the taxon is characterized by tri- to biseriate striae in the central part of the valve face becoming uniseriate towards the valve centre and stalked rimoportula positioned between two costae inside the alveolar opening. Both species are found in nonmarine sediments of Pliocene age from Mariovo Basin, Macedonia.

Description of the pseudocryptic species Conticribra weissflogiopsis sp. nov. (Thalassiosirales, Bacillariophyta) isolated from brackish waters in Korea, based on its cingulum structure and molecular analysis

We describe the new fultoportulate diatom species, Conticribra weissflogiopsis, isolated from brackish waters in Korea, based on morphological characters and molecular data. The new species is characterized by having areolae venation with internal (semi-) continuous cribra, a flat valve face, a single marginal rimoportula replacing a marginal fultoportula, a subcentral ring of the valve face fultoportulae, and a dextral pattern of cingulum structure. The overall valve structure of C. weissflogiopsis resembles that of C. weissflogii; however, the cingulum structure differs between the two species—C. weissflogiopsis has a dextral offset of band opening in the cingulum, whereas C. weissflogii has a sinistral offset. Phylogenetic analysis of the nuclear small subunit ribosomal DNA (SSU rDNA) revealed that C. weissflogiopsis is located in the Conticribra clade. Further, the pairwise genetic distance based on the SSU rDNA and the internal transcribed spacer 2 (ITS2) indicated that C. weissflogiopsis is a distinct Conticribra species. On the basis of the morphology and molecular phylogeny, we expand the hypothesis regarding the morphological evolution of Conticribra species.

Morphology of some fossil lacustrine centric species from the western United States assigned to the genus Cyclotella (Bacillariophyta), including four described as new

During consideration of fossil centric diatoms from a variety of non-marine localities in the western USA, we encountered four new species and two previously known taxa that should be assigned to the genus Cyclotella (F.T. Kützing) A. de Brébisson. We detail the morphological features of these species, and discuss their relevance to other members of the Cyclotella. These fossil species are studied in light and scanning electron microscopes, and can be assigned to several morphological groups with respect mainly to the structure of alveolae as well as positon(s) of rimoportula(e) and marginal fultoportulae. Presence of loculate areolae with internal domed cribra and external foramina, or both areolae and valve face fultoportulae in the central area are characteristics found in all of these Cyclotella taxa.

Pliocaenicus tanimurae, a new Pliocene diatom species from Aguni Island, Okinawa Prefecture, southwestern Japan

Pliocaenicus tanimurae sp. nov., from Early Pliocene sediment of the Fudenzaki Formation, Aguni Island, Okinawa Prefecture, southwestern Japan is described here. The new species is round to elliptical with a slightly tangential undulated valve face. Valve face of the elliptical valves are more elliptical than the valves themselves. Several valve face fultoportulae in the valve center form a circle. Costae alternate thicker (sometimes slightly recessed) and thinner with mantle fultoportulae located on slightly recessed thicker costae. Both valve face and mantle fultoportulae have three satellite pores. Alveoli have centrifugal ‘roofing over’. One rimoportula is located near the edge of the marginal area of the valve face at the base of a costa. The new species is shown in light microscopy and scanning electron microscopy photographs and compared with similar taxa of P. costatus (Loginova, Lupikina & Khursevich) Flower, Ozornina & A.I.Kuzmina, P. seczkinae Stachura-Suchoples, Genkal & Khursevich and P. omarensis (Kuptsova) Stachura-Suchoples & Khursevich.

Description ofConticribra tricircularis, a new genus and species of Thalassiosirales, with a discussion on its relationship to other continuous cribra species ofThalassiosira Cleve (Bacillariophyta) and its freshwater origin

A new diatom genus Conticribra is erected to accommodate C. tricircularis, described from a freshwater Pliocene deposit in Trout Creek, Oregon (USA). The genus accommodates species possessing: (i) loculate areolae with (semi-) continuous cribra; (ii) non-plicated valve face; (iii) rimoportula located on the valve mantle, replacing a fultoportula. Conticribra tricircularis has no valve face fultoportulae and can easily be distinguished by its marginal fultoportulae with four satellite pores arranged in three rings. Three species are transferred to the new genus from Thalassiosira sensu lato. Using evidence from the fossil record and recent molecular data, a hypothesis concerning the freshwater origin of Conticribra is discussed.

New data on the morphology, taxonomy, ecology, and distribution of Stephanodiscus agassizensis Håkansson et Hickel (Bacillariophyta)

The study of samples from various waterbodies (rivers, lakes, reservoirs, and seas) has shown that S. agassizensis manifests a significant morphological variability of qualitative and quantitative characters (the valve diameter and its relief, the mantle height, and the presence and arrangement valve face fultoportulae) which distinguish this species from other species with similar a morphology (S. neoastraea, S. heterostylus, S. alpinus, and S. maximus). Original and literature data on the morphology, ecology, and distribution of S. agassizensis has allowed the author to specify its taxonomic position, refer the species to the synonymy of S. neoastraea, and extend the diagnosis of the latter.

PLIOCAENICUS SECZKINAE SP. NOV., FROM LAKE EL'GYGYTGYN IN CHUKOTKA (NE RUSSIA)

Pliocaenicus seczkinae Stachura-Suchoples, Genkal & Khursevich, sp. nov. was described from the phytoplankton samples and surface bottom deposits of Lake El'gygytgyn located in central Chukotka, NE Russia. The species is distinguished from the nominate variety of P. costatus mainly by the different structure of the valve face fultoportulae, which open externally with distinct short tubes and are flanked by two satellite pores. The tubes are located in small depressions within the radial rows of areolae. These observations have important implications for the entire genus, as up until now all known Pliocaenicus species had external fultoportulae openings lacking tubuli. Pliocaenicus seczkinae is the second known species of the genus Pliocaenicus to be found in modern populations.

STEPHANODISCUS MIYAGIENSIS SP. NOV. FROM PLEISTOCENE SEDIMENT IN NORTHEASTERN JAPAN

Stephanodiscus miyagiensis sp. nov., is described from Pleistocene freshwater sediment in Onikobe, northeastern Japan. The species is characterized by fascicles of many areolae rows, a sharp curve of the valve face/mantle junction, the presence of valve face fultoportulae with 2-4 satellite pores, mantle interfascicles and the occasional presence of two mantle fultoportulae together at the end of either a valve or mantle interfascicle. This new species is compared to other similar species of Stephanodiscus including S. carconensis Grunow, S. suzukii Tuji & Kociolek and S. niagarae Ehrenberg.

The centric diatom genus Cyclotella, (Stephanodiscaceae: Bacillariophyta) from Florida Bay, USA, with special reference to Cyclotella choctawhatcheeana and Cyclotella desikacharyi, a new marine species related to the Cyclotella striata complex†

A.K.S.K. Prasad and J.A. Nienow. 2006. The centric diatom genus Cyclotella, (Stephanodiscaceae: Bacillariophyta) from Florida Bay, USA, with special reference to Cyclotella choctawhatcheeana and Cyclotella desikacharyi, a new marine species related to the Cyclotella striata complex. Phycologia 45: 127–140. DOI: 10.2216/05-13.1A new marine species of the centric diatoms of the genus Cyclotella, Cyclotella desikacharyi A.K.S.K. Prasad collected from several localities in Florida Bay, USA, where it is a dominant part of the planktonic assemblage, is described by means of light and scanning electron microscopy. Cyclotella desikacharyi is characterized by the presence of dense striae (14–19 in 10 µm) in the marginal zone and small granules all through the surface of the valve, including the central area, fultoportulae on the valve mantle located on every second or third interstria, each surrounded by three satellite pores, a pronounced tangential undulation, 3–17 valve-face fultoportulae in an arc on the uplift of the undulation and numerous discoid plastids. The new species is compared with Cyclotella striata complex; C. desikacharyi closely resembles C. striata in valve dimensions and in the structure and arrangement of alveolate striae, and in the presence of three satellite pores surrounding each fultoportula on the valve mantle; it differs from it in the stria density and the presence of siliceous granules on the entire valve surface. The new species is compared with the other closely related marine members of the genus, Cyclotella stylorum and Cyclotella litoralis. Cyclotella choctawhatcheeana Prasad, originally described from the northern Gulf Coast of Florida, is also recorded in several localities in Florida Bay and its global distribution is discussed. The evolution of euryhalinity in the genus Cyclotella is also discussed in brief.

STEPHANODISCUS NEOASTRAEA AND STEPHANODISCUS HETEROSTYLUS (BACILLARIOPHYTA) ARE ONE AND THE SAME SPECIES

Stephanodiscus neoastraea Håkansson et Hickel is distinguished from S. heterostylus Håkansson et Meyer by the absence of valve face fultoportulae. Scanning electron microscopy analyses (SEM) revealed, that cultures established from a single cell of S. neoastraea and/or S. heterostylus persistently contained a mixture' of cells with and without valve face fultoportulae. Amplification of the ITS2 spacer region of the nuclear encoded rRNA transcription unit yielded a single band in an agarose gel electrophoresis for three “mixed” cultures tested. Furthermore, sequencing of the ITS2 region resulted in unambiguous sequences that were identical for each strain investigated. Ambiguous peaks which may originate from sequencing a mixture of different templates did not appear in the electropherogram. Thus, no, one or several valve face fultoportulae appear in the same species. Absence or presence of fultoportulae is not a useful character for differentiating S. neoastraea and S. heterostylus. Presence or absence of tubular processes on the valve face is a variable character, clearly expressed in clonal culture, and thus cannot be used for species discrimination. The species name S. heterostylus is a “nomen nudum”, and thus invalid.

A COMPILATION AND EVALUATION OF SPECIES IN THE GENERAL STEPHANODISCUS, CYCLOSTEPHANOS AND CYCLOTELLA WITH A NEW GENUS IN THE FAMILY STEPHANODISCACEAE

Systems of classification are not hat racks, objectively presented to us by nature. They are dynamic theories developed to express particular views about the history of organisms. Evolution has produced a set of unique species ordered by differing degrees of genealogical relationship. Taxonomy, the search for this natural order, is the fundamental science of history. D.J. Gould (1987) This paper includes species investigated through many years starting with original material from museum collections. A great number of species in the genera Stephanodiscus Ehrenberg, Cyclostephanos Round and Cyclotella (Kützing) Brébisson, all in the family Stephanodiscaceae Makarova, are presented with holo-, lecto- and/or neotypes, type locality and information concerning nomenclature. A typus generis is given for each genus. Errors in the literature are pointed out and corrected. Species in the genus Stephanodiscus have the characteristic fasciculate morphology, they have fultoportulae, rimoportulae with their external tubular (long or short) extension and areolae internally with a domed cribrum both on the valve face and on the mantle. The typus generis is Stephanodiscus niagarae. Species in the genus Cyclostephanos have also the fasciculate structure, the fultoportulae, but their areolae have a domed cribrum only on the valve face and are flat on the mantle, their rimoportulae have only a simple external opening, often connected with a spine and a marginal alveolate structure, even though in some species weakly developed, which differentiate these species from those in the genus Stephanodiscus. The typus generis: Cyclostephanos novaezeelandiae. The genus Cyclotella includes species which have a smooth central area, none to several valve face fultoportulae, a simple alveolate marginal striation and the rimoportulae with an external round or slit-like opening, located on the mantle interrupting the ring of mantle fultoportulae. In some species complexes, however, the external opening of the rimoportula can be found on the valve face, near the valve face/mantle junction. The typus generis selected is C. distinguenda. Some other described species are transferred to the new genus Puncticulata Håkansson gen. nov. encompassing the species with an areolate central area consisting of areolae and valve face fultoportulae, in some species only fultoportulae in others only areolae, a complex alveolate striated marginal area, rimoportulae on the valve face at the end of a shortened interstriae. The typus generis: Puncticulata comta (Ehrenberg) Håkansson comb. nov.

PHENOTYPIC VARIATION OF LIFE-CYCLE STAGES IN CLONES OF THREE SIMILAR CYCLOTELLA SPECIES AFTER INDUCED AUXOSPORE PRODUCTION

Auxospore production was induced in clonal cultures of three morphologically similar Cyclotella species, C. meneghiniana, C. gamma and C. quillensis to determine the pattern of variation of the frustule morphology through the life-cycle. Investigations were made by light and electron microscopy. The Cyclotella species have in common the tangential undulation of the smooth central area, striated marginal area, presence of valve face and mantle fultoportulae with three satellite pores and at least one rimoportula. Each of the three species produced two size groups with slightly different valve morphology. The morphological characters of the two size groups can cause identification difficulties, especially when found together. This paper presents an interspecific comparison of the morphology of the siliceous cell wall of the initial cells and their descendants. Auxospore production was induced in a small portion of the cells 3–12 days after transfer into seawater based saline medium (7.5 %). The initial cells showed species-specific structures and have taxonomic potential in delimitation of the Cyclotella taxa. Initial cell valves were hemispherical or domed, but cells with a relatively flat central area were found, complicating identification. The complex morphology of initial cells found in this investigation has shown that C. wulfiae is the initial cell of C. meneghiniana.

A STUDY OF VARIATION IN VALVE MORPHOLOGY OF THE DIATOM CYCLOTELLA MENEGHINIANA IN MONOCLONAL CULTURES: EFFECT OF AUXOSPORE FORMATION AND DIFFERENT SALINITY CONDITIONS

Cyclotella meneghiniana was collected from an artificial pond Kosharskij near Feodosia, Crimea, isolated and cultured under different conditions (freshwater, 2‰, 4‰, 8‰, and 16‰ salinity). Detailed light- and electron microscope investigations were made of specimens from monoclonal cultures of C. meneghiniana and comparisons made with type material of both C. meneghiniana and C. kuetzingiana, which are conspecific. Cells cultured under different salinity conditions were very similar, showing only slight differences in the number of valve face fultoportulae, in the pattern of the satellite pores of the mantle fultoportulae, and in the lengths of the striae. New cultures started from single initial cells isolated from 3 of the 4 monoclonal cultures at 8‰or 16‰ salinity conditions, and grown in 16‰ salinity showed greater morphological variability, with differences in the pattern and number of the marginal striae, the number and placement of valve face fultoportulae, and the pattern of the satellite pores of the mantle fultoportulae. “Abnormal” cells or valves were found in some of the cultures in the highest salinity, especially after isolation of initial cells. Many of the morphological differences recognized in this investigation are probably part of the life cycle of C. meneghiniana but some may be due to environmental influence.

CYCLOTELLA WULFIAE, A NEW DIATOM FROM A BRACKISH LAKE IN GERMANY

A new diatom species, Cyclotella wulfiae, is described from the brackish lake Grosser Binnensee, Germany. The new species is distinguished by its size, the concentric undulation of the valve face centre, 2–14 valve face fultoportulae scattered or organized in a ring, lack of spines, gentle angle of the valve face/mantle junction and the varied width of the internal costae, a new feature in Cyclotella. Comparison of the fine structure with the closely related species C. meneghiniana, C. gamma and C. quillensis showed that the combination of characters of C. wulfiae does not belong to any of the previously described species. C. wulfiae was found only once (July 1975) associated with abundant C. meneghiniana.

STEPHANODISCUS KHURSEVICZAESP. NOV. FROM PLEISTOCENE SEDIMENTS OF LAKE BAIKAL

A new species, Stephanodiscus khurseviczae, has been found in Lake Baikal in sediments from the Pleistocene. The diameter of the cells of this species varies between 12.5 and 28 μm. Areolae are placed densely and evenly over the valve surface and there are no distinct fascicles of areola rows. The foramina of the areolae have a characteristic form: polygons with rounded corners. There are one to four valve face fultoportulae (with two or three satellite pores) near the centre. Some characters of this species are similar to those of diatoms described earlier: to S. grandis Churs. & Log., in the arrangement of areolae; to S. binatus Hakansson & Kling, in the form of foramina. However, there are enough differences between the new species and those described earlier to justify its separation.

A COMPARATIVE STUDY OF SPECIES IN THESTEPHANODISCUS NIAGARAE-COMPLEX AND A DESCRIPTION OFS. HETEROSTYLUSSP. NOV.

The Stephanodiscus niagarae-complex is comprised of large, planktonic, morphologically variable species with dissimilarly shaped valves (heterovalvy). The species are characterized by a set of subtle morphological features causing controversy in species distinction. In this paper we present a comparative study based on a re-investigation of the original material for the following species: S. niagarae, S. rotula, S. aegyptlacus, S. neoastraea, S. galileensis and S. agassizensis. New material from Farmoor Reservoir (England), Loch Neagh (Ireland) and a lake in the Rift Valley (East-Africa) was also analyzed. The position of the valve face fultoportulae is used as a character to differentiate two groups. In one group the position of the fultoportulae is the same on each valve face, whereas in the other group the positions are different. A third group is lacking fultoportulae. A new species, S. heterostylus is described based on material from Farmoor.