Girdle View Research Articles

Newly identified resting stage cells of diatoms from sediments collected in Ago Bay, central part of Japan

Resting stage cells of six diatom species, Actinoptychus senarius, Biddulphia alternans, Lithodesmium variabile, Odontella longicruris, O. mobiliensis, and Detonula pumila were newly identified from bottom sediments of Ago Bay, central Japan. The resting stage cells of A. senarius, B. alternans and L. variabile are very similar in morphology to their vegetative cells; hence, these resting stage cells areresting The resting stage cells of O. longicruris and O. mobiliensis closely resemble the vegetative cells in morphology, therefore, they are regarded as resting cells. However, they have some morphological differences compared with the vegetative cells, indicating a possibility of them being resting The resting stage cells of D. pumila are quite different in morphology from the vegetative cells; therefore, these areresting spores. The morphology of the resting spore of D. pumila is circular in valve view. In girdle view, each valve shows the same shape, slightly vaulted, and has a distinct mantle. As a com- mon feature of the resting stage cells of the six species, the plastids show a darker color than those of vegetative cells, and are positioned unevenly in the cells.

A morphological study of epipsammic diatoms (Bacillariophyta) from the tropical Mexican Pacific, including two species of Aulacodiscus, and a description of the new species Cerataulus simsae Hernández-Becerril et Barón-Campis

Coastal phytoplankton samples were analyzed from two locations in the tropical Mexican Pacific Ocean. Three solitary, presumably epipsammic diatom species were studied in detail: Aulacodiscus petersii , A. scaber , and a new species of Cerataulus , C. simsae . Most morphological features previously described for A. petersii and A . scaber were also found in this study; however, we found great variation in the external tube of the rimoportulae in terms of size and complexity. Although C. simsae was less common, it also showed significant size and shape variation. The species has slightly undulated frustules in girdle view, with elliptical to circular valves; it also has two opposite, marginal ocelli that are not prominent, but rather almost flush with the valve face. The valves are usually covered by granules (marginal granules have a short peduncle) of different sizes that mask the areolae. A marginal ring of rimoportulae, with no large protrusion to the outside, but rather small “knobs”, was found in valves of the species. Cerataulus simsae is probably closely related to C . californicus . Cerataulus should be revised because its generic circumscription and relationships are unclear.

Morphology and ecology of Achnanthidium caravelense (Bacillariophyceae), a new species from Portuguese rivers

A new benthic freshwater diatom species belonging to the genus Achnanthidium Kutz. has been recorded from several watercourses in the North of Portugal. Achnanthid- ium caravelense Novais et Ector is described as a new species based on light and scanning electron microscopic observations, as well as on its ecological preferences as reconstructed from field observations. The most characteristic morphological features of this species are the different outline of the raphe valve (narrowly elliptic with linear margins) and the ra- pheless valve (narrowly elliptic to narrowly rhombic with moderately convex margins), the non-protracted broadly rounded apices and the length/width ratio. Furthermore, the areolae of the single row along the mantle are elongated and are more or less widely open, which is a characteristic discernible in girdle view under light microscopy. The species that A. caravelense resembles most is A. eutrophilum (LaNgE-BErt.) LaNgE-BErt.; nevertheless it can be distinguished from the latter by the different raphe valve outline, its higher valve length/width ratio and autecology. A. caravelense is common and abundant in soft waters with low to moderate nutrient content in the North of Portugal.

Diversity of the diatom genus Fragilariopsis in the Argentine Sea and Antarctic waters: morphology, distribution and abundance

Fragilariopsis species composition and abundance from the Argentine Sea and Antarctic waters were analyzed using light and electron microscopy. Twelve species (F. curta, F. cylindrus, F. kerguelensis, F. nana, F. obliquecostata, F. peragallii, F. pseudonana, F. rhombica, F. ritscheri, F. separanda, F. sublinearis and F. vanheurckii) are described and compared with samples from the Frenguelli Collection, Museo de La Plata, Argentina. F. peragallii was examined for the first time using electron microscopy, and F. pseudonana was recorded for the first time in Argentinean shelf waters. New information on the girdle view is included, except for the species F. curta, F. cylindrus and F. nana, for which information already existed. In the Argentine Sea, F. pseudonana was the most abundant Fragilariopsis species, and in Antarctic waters, F. curta was most abundant. Of the twelve species of Fragilariopsis documented, four occurred in the Argentine Sea, nine in the Drake Passage and twelve in the Weddell Sea. F. curta, F. kerguelensis, F. pseudonana and F. rhombica were present everywhere.

Climaconeis species (Bacillariophyceae: Berkeleyaceae) from western Pacific islands, including C. petersonii sp. nov. and C. guamensis sp. nov., with emphasis on the plastids

Plastids of Climaconeis (Okedenia) were originally characterized by Mereschkowsky as H-shaped in girdle view with pyrenoids but recent descriptions implicitly or explicitly indicate that the H-shape is seen in valve view. We observed five known taxa–one a variety that we raise to species rank–and two new species: C. silvae, C. riddleae, C. guamensis sp. nov. and C. inflexa (curved species); C. lorenzii (straight species with craticular bars); a straight species without bars that matches Navicula scopulorum var. triundulata = Climaconeis undulata comb. nov.; and a new straight species without bars, C. petersonii sp. nov. In the species with multiple plastids, plastids are plate-like, usually with a pyrenoid in the centre, arranged in pairs along the girdle faces of the cells. In some species with few plastids, including C. riddleae, and possibly C. inflexa, the pyrenoid is also visible in valve view between opposing plastids, such that these species do appear to have plastids that are H-shaped in valve view. We describe the two new species and confirm published SEM observations on other species, including features of the pores that help distinguish C. guamensis from the very similar C. riddleae.

An investigation of the fine structure, cell surface carbohydrates, and appeal of the diatom Extubocellulus sp. as prey for small flagellates

The fine structure and surface exopolymers of a coastal planktonic nanodiatom of the sparsely reported genus Extubocellulus were studied respectively by scanning electron microscopy and confocal microscopy in conjunction with fluorescent lectins. Monitoring the suitability of the species as prey food for other protists was also investigated by video microscopy coupled with digital film. Cells are rectangular in girdle view, with a pervalvar axis longer than the apical axis. Valves are almost circular with a diameter of 2.8 to 3.6 microm. The valve face bears randomly distributed areolae (ca. 50 in 10 microm), which may be either open or occluded. Two small raised ocelluli occur at the apices, with a rim devoid of perforations and about 6-7 porelli. Glucose and N-acetyl-glucosamine moieties present on the surface of the live diatom were labelled with fluorescent lectins, and a differential pattern of distribution for both carbohydrates was observed. The potential role of fluorescent lectins as cellular probes of taxonomic value in small diatoms is compared with that of nucleotide and antibody probes. We provide the first illustrative evidence of the presence of Extubocellulus sp. in the cytoplasm of the nanoflagellate Goniomonas amphinema and of the egestion of diatom frustules. Results obtained are discussed in the light of the present knowledge of the role of carbohydrate-protein interactions in phagocytosis of prey by free-living protozoa.

A DETAILED DESCRIPTION OF A DANISH STRAIN OF NITZSCHIA SIGMOIDEA, THE TYPE SPECIES OF NITZSCHIA, PROVIDING A REFERENCE FOR FUTURE MORPHOLOGICAL AND PHYLOGENETIC STUDIES OF THE GENUS

Nitzschia sigmoidea is the type species of the diatom genus Nitzschia. Recent evidence implies that the genus is polyphyletic. As a reference for future studies of the genus, we here provide a thorough morphological examination of the silica frustule, including new details of copulae and poroids, as well as compiling previously published information on the cellular ultrastructure. Observed specimens of Nitzschia sigmoidea are linear in frustule view and sigmoid in girdle view with a length of 346–359 μm, and a width of 9–13 μm. Both nitzschioid and hantzschioid cells are found. The raphe is highly eccentric, elevated on a keel, without a central nodule. The raphe ends externally in a hook-shaped terminal fissure, internally in a helictoglossa forming an excrescence. Tubular fibulae are slim and irregularly distributed with a density of 6–9 in 10 μm. A conopeum runs the entire length of the cell. The striae are uniseriate with 4–5 poroids in 1 μm, each with a hymen with a hexagonal pattern of perforations. Two types of copulae are found, both with two rows of poroids, 3.2–3.4 poroids in 1 μm. One type of copula is fimbriate with evenly distributed fimbriae, while the other type has a veil. Initially, growth of the diatom was restricted by lack of carbon in the freshwater medium, after addition of bicarbonate it grew well. HPLC analysis showed no domoic acid production by N. sigmoidea.

AN EMENDED DESCRIPTION OF DECUSSATA (PATRICK) LANGE-BERTALOT & METZELTIN THAT INCLUDES PROTOPLAST ORGANIZATION AND DETAILED VALVE AND CINGULUM ULTRASTRUCTURE

The subgenus DECUSSATA R.M. Patrick was recently elevated to generic status as Decussata (R.M. Patrick) H. Lange-Bertalot & Metzeltin in Lange-Bertalot (2000. Iconographica Diatomologica, 9, 670–673) to accommodate Navicula placenta Ehrenberg and its allies. The description of Decussata is based on characteristics of the valve: solitary cells, flat, broadly elliptic valves with various ends, and areolae with circular foramina arranged in regular quincunx patterns crossing at 60°-80°. A collection from Cedar Hills Sand Prairie in Black Hawk Co., Iowa (U.S.A.), had abundant live Decussata placenta (Ehrenberg) Lange Bertalot & Metzeltin in Lange-Bertalot, the generitype, and a collection from near Prava Reka, Macedonia, had numerous specimens of Decussata hexagona (Torka) Lange-Bertalot. These collections permitted a first observation of living Decussata and a detailed study of their valve and cingulum ultrastructure. Based on this material we place Decussata in the Order Mastogloiales and Family Mastogloiaceae, and provide an emended description of the genus to include details of valve ultrastructure including structure of the cingulum, areolae occluded by internal convex hymenes, and the protoplast characters of a central nucleus, two chloroplaste per cell, one toward each pole, H-shaped in girdle view, variably invaginated in valve view, with a pyrenoid in the plastid bridge.

Morphological investigations of the frustule, perizonium and initial valves of the freshwater diatom Achnanthes crenulata Grunow (Bacillariophyceae)

SUMMARYThe present study clarifies the fine structure of the vegetative frustules, initial valves and perizonium of Achnanthes crenulata Grunow. The valves of the vegetative cell are distinctly linear‐lanceolate with an undulate margin. The valve face is quite flat and in girdle view is smoothly curved as in species of Gephyria (Bacillariophyceae). However, the valve face of the initial cells is slightly rounded and does not have an undulate margin. Furthermore, the rapheless sternum is centrally positioned along the apical axis of the araphid initial valve. As this taxon develops from auxospore to initial valve, it forms only longitudinal perizonial bands; no transverse bands arise. The perizonium consists of three silicified bands: one large, central longitudinal plate and two bands that underlie this plate; these two bands are either open or closed. This taxon has several conspicuous structures compared to other marine species of Achnanthes, but the structure of the perizonium supports the position of A. crenulata within Achnanthes sensu stricto.

Pseudo-nitzschia seriata f. obtusa (Bacillariophyceae) raised in rank based on morphological, phylogenetic and distributional data

G.R. Hasle and N. Lundholm. 2005. Pseudo-nitzschia seriata f. obtusa (Bacillariophyceae) raised in rank based on morphological, phylogenetic and distributional data. Phycologia 44: 608–619.Pseudo-nitzschia seriata f. obtusa (Hasle) Hasle is raised in rank to P. obtusa (Hasle) Hasle & Lundholm, based on morphological, phylogenetic and distributional features. The most prominent distinctive morphological feature is the shape of the valve ends, which in girdle view are truncate in P. obtusa and pointed in P. seriata. Other differences are the transapical width, the number of striated bands and the fine structure of bands and valve striae. Phylogenetically, P. obtusa is found in a clade comprising species lacking a larger central interspace and a central nodule but possessing simple hymenate poroids. Within that clade, P. obtusa is most closely related to P. seriata and P. australis, which make up the sister group to P. obtusa. Pseudo-nitzschia obtusa is recorded from the Arctic regions of the Atlantic and the Pacific Oceans, whereas P. seriata is recorded from the Arctic and Temperate regions but only from the Atlantic Ocean. The relationship between P. obtusa and other morphologically and phylogenetically similar species of the genus is discussed. In growth studies under replete nutrient conditions, P. obtusa had a growth rate of 0.55–0.66 day−1 and an upper pH limit for growth of 9.1. No P. obtusa clones have yet been shown to produce the toxin, domoic acid.

Three extant species of Paralia (Bacillariophyceae) along the coast of Japan

Y. Sawai, T. Nagumo and K. Toyoda. 2005. Three extant species of Paralia (Bacillariophyceae) along the coast of Japan. Phycologia 44: 517–529.Three extant species of the genus Paralia (Bacillariophyceae) occur along the coast of Japan, two of them are new species. Observations of living populations suggested that significant characters for separating Paralia species are (1) structure of the mantle of the separation valve; (2) shape of the linking spines; (3) topography and morphology of valve face on the separation valve, and possibly (4) cingulum structures; and (5) rimoportula morphology. Some features vary but the structure of the separation valves in girdle view was stable in all specimens. Based on these criteria, we identified Paralia sulcata (Ehrenberg) Cleve and two new species, P. fenestrata Sawai & Nagumo sp. nov., and P. capitata Sawai & Nagumo sp. nov. from coast of Japan.

MORPHOLOGY AND ECOLOGY OF THE CENTRIC DIATOM TERPSIONE MUSICA EHRENBERG, BASED ON MATERIAL COLLECTED FROM CAIRO, EGYPT.

Specimens of the centric benthic diatom Terpsione musica Ehrenberg species belonging to family Biddulphiaceae, collected from different aquatic habitats in Cairo, Egypt were examined using LM and SEM in order to reveal more details about frustule structure and to reconfirm its identification. Ecology of this taxon aimed to be studied. Examination of T. musica revealed that the most characteristic features of this species are the presence of pseudosepta, which appear in girdle view as musical notation (from which the species derives its name) in addition to the presence of rimportula. Reconfirmation of the identification of T. musica was carried out to remove the confusion between this species and the related one; T. americana. Ecological studies of this species indicated that; although this species was recorded in many localities in The Greater Cairo; its maximum flourishment was observed in the ground seepages of Kobri El-Kobba (i.e. T. musica is a monomorphic specialist species), which characterized by slightly alkaline, brackish hard water with relatively high electrical conductivity and moderately high temperatures.

MORPHOLOGICAL INVESTIGATIONS OF ACHNANTHES JAVANICA GRUNOW AND A. SUBCONSTRICTA (MEISTER) COMB. NOV.

The morphology and fine structure of two marine mooraphid diatoms, Achnanthes javanica Grunow and A. subconstricta (Meister) comb. Nov. (= A javanica var. subconstricta Meister) have been investigated. Observations on the valves of type material (Grunow in Cleve & Möller 1878) of A. javanica show them to be lanceolate to linear in shape with a marginal ridge on the araphid valve but lacking terminal orbiculi. Conversely, A. subconsticta has a marginal ridge and special marginal spines as well as terminal orbiculi. From SEM observations in girdle view, A. subconstricta. These features support the view that A. subconstricta should be considered an independent species.

Planktonic centric diatom Minidiscus chilensis dominated sediment trap material in eastern Bransfield Strait, Antarctica

The planktonic centric diatom Minidiscus chilensis Rivera was collected over 1 yr in a sediment trap at 1000 m depth in one of the deep basins in the eastern Bransfield Strait, Antarctica. The valves of this diatom are 3 to 8 μm in diameter and quadrangular in girdle view. The center of each valve is prominently hyaline with 3 strutted processes and a labiate process. M. chilensis was observed in all of the sediment trap samples collected between December 25, 1998 and December 24, 1999. The flux of M. chilensisinto the trap varied considerably according to season, with the highest flux of 2.4 x 10 9 valves m -2 d -1 (87 % of total diatom valve flux) occurring in mid January when the mooring area was free of sea-ice. The dominance of M. chilensis among planktonic diatoms in Antarctic open waters has not been previously recorded. Our study suggests that M. chilensis should be included in future quantitative analyses and should be considered an important species for understanding the ecological structure of Antarctic waters.

A MORPHOLOGICAL STUDY OF CHAETOCEROS TENUISSIMUS MEUNIER, A LITTLE-KNOWN PLANKTONIC DIATOM, WITH A DISCUSSION OF THE SECTION SIMPLICIA, SUBGENUS HYALOCHAETE

The morphology of Chaetoceros tenuissimus Meunier, a little-known species, has been studied for the first time with electron microscopy. C. tenuissimus has been placed as a synomyn of C. simplex Ostenfeld since approximately 1930, and has been misidentified or neglected in routine phytoplankton counts. The cells are very small and solitary, square to rectangular in girdle view. The setae are narrow and straight, arising from the two poles of the valve at an angle of 45° to its apical axis. The valve face possesses an annulus, delimited by a hyaline rim. Costae and small areolae radiate from the annulus. A single rimoportula occurs within the annulus. The rimoportula opens externally in a flatened tube and internally by a simple slit. The setae exhibit spirals of minute pores and an intricate pattern of spiral and perpendicular costae; spines are regularly present. Similarities with closely related species in Section Simplicia are discussed.

FLORELLA PASCUENSIS SP. NOV., A NEW MARINE DIATOM SPECIES FROM EASTER ISLAND (ISLA DE PASCUA), CHILE

A new diatom species, Florella pascuensis Navarro, is described from marine waters around Easter Island, Chile. Examination in LM and SEM revealed that this diatom differs from the only other known species in the genus, F. portoricensis Navarro, by virtue of the morphology, orientation and number of its rimoportulae, weakly sigmoid sternum, and the presence at each pole of two longitudinal rows of large, dash-shaped areolae. The new species is compared to Striatella unipunctata (Lyngbye) C.A. Agardh, with which it can be easily confused in girdle view during routine LM observations.

Six new Actinella (Bacillariophyta) species from Papua New Guinea, Australia and New Zealand: further evidence for widespread diatom endemism in the Australasian region

Examination of sediment samples from oligo-and dystrophic ponds, lakes and streams in Papua New Guinea, Australia and New Zealand revealed a hitherto unknown diversity of the diatom genus Actinella Lewis. Six new species are proposed, viz. Actinella aotearoaia sp. nov., A. giluwensis sp. nov., A indistincta sp. nov., A. muylaertii sp. nov., A. parva sp. nov. and A. pulchella sp. nov. All species are heteropolar, both in girdle and valve view. Novel information on the genus Actinella includes the observations of two ribbon-shaped, valve-appressed plastids in A. aotearoaia and A. pulchella, and the presence of long mucilage stalks in A. aotearoaia. It is argued that, despite recent proposals to reduce the genera Actinella and Desmogonium Ehrenberg to the rank of subgenera of Eunotia, they should be kept separate until the taxonomic significance of their distinctive morphological features (such as heteropolarity) is fully assessed. The new species appear to be endemic to Australasia and have distinct biogeographies within this region. Except for A. aotearoaia, all species are present in Tasmania; A. indistincta and A. pulchella have also been found in New Zealand (Stewart Island). A. aotearoaia is common in several localities in New Zealand but was also found near Sydney on the Australian mainland. Actinella giluwensis has only been observed in material from Papua New Guinea. The record of A. punctata for the latter country constitutes the first confirmed record for this species outside North America and Europe. The discovery of the new Actinella species again confirms the importance of the Australasian region as a major centre of microalgal biodiversity and endemism.

MORPHOLOGY OF THE MARINE DIATOM NITZSCHIA NAVIS‐VARINGICA, SP. NOV. (BACILLARIOPHYCEAE), ANOTHER PRODUCER OF THE NEUROTOXIN DOMOIC ACID

A new marine diatom, Nitzschia navis‐varingica, sp. nov., isolated from Vietnamese waters, is described by light, transmission, and scanning electron microscopy, including thin sectioning. The new species has been found to produce the neurotoxin domoic acid (DA), better known from several species of Pseudo‐nitzschia Peragallo and one species of Amphora Ehrenberg. Production of DA is therefore more widespread among diatoms than previously thought. Taxonomically, the genus Nitzschia Hassall is exceptionally difficult, with about 900 described taxa. Grunow (in Cleve and Grunow 1880 divided the genus into 24 sections, and this system is still used with modifications. Nitzschia navis‐varingica, sp. nov. fits best into a group of sections that includes Dubiae, Bilobatae, most of the Lanceolatae, and Lineares, all sensu Grunow, as the cell is slightly indented in the middle in girdle view and has a moderately eccentric raphe and a weak longitudinal fold on the valve. Many species within these sections have features similar to N. navis‐varingica, but no species seems to be identical. Because both Pseudo‐nitzschia and Nitzschia belong to the family Bacillariaceae, it seems reasonable to look for further producers of DA in this family, including freshwater species, which mainly comprise species within the sections Dubiae, Bilobatae, Lanceolatae, and Lineares.

Entomoneis vertebralis sp. nov. (Bacillariophyceae); a new species from hypersaline environments

A hyaline Entomoneis species was isolated during a study of microbial mats from hypersaline environments in the Exportadora de Sal salt works, Guerrero Negro (Mexico). Morphological, ultrastructural and ecophysiological characteristics of the species were investigated. Live cells contained two plastids. In girdle view the frustules appeared bilobate, deeply constricted, with a junction line visible only near the central nodule. The margin of the wings was fibulate with 19–23 fibulae in 10 urn, some of which, at irregular intervals, appeared longer and ended in small puncta. After mild cleaning, neither valve body nor the sigmoid connecting bands appeared ornamented under the light microscope. Scanning electron microscopy revealed membranaceous valves without ornamentation and a strongly silicified fibulate keel. Furthermore, keels were the only part of the cell which could be found and recognized in cleaned field samples. This diatom species was able to grow over a salinity range of 15–50 ‰ and hence could be considered a euryhaline marine species.

NAVICULA PULCHRIPORA, A NEW SPECIES FROM THE COASTAL WATERS OF TEXAS, USA

A very small diatom, Navicula pulchripora Kaczmarska & Chan, was isolated from the warm coastal waters of South Texas, USA (27° 50' N, 97° 02″W). It is a motile, lightly silicified and fast-growing organism able to complete up to 3 doublings/day. It is free living when in exponential growth phase but it aggregates within gelatinous masses when approaching stationary phase. Cells contain one or two plate-like chloroplasts. In girdle view valves are convex and frustules rectangular. A frustule may contain up to 40 girdle bands. Valves are lanceolate, 3.7–6.6 μm long, 2.0–3.0 μm wide, with uniseriate, mainly parallel striae, 57–69 striae in 10 μm and 74–94 poroid areolae in 10 μm. In some aspects of cell structure N. pulchripora is similar to the marine members of the sections Minusculae (small size, shape and fine ornamentation), Microstigmaticae (wide girdle) and Pelagicae (plate-like chloroplast and wide girdle). It differs from the first section in having a wide girdle, from the second in lacking “butterfly” chloroplasts and from the third in lacking ribbon-shaped chloroplast and not forming chain-like colonies.