Raphe Endings Research Articles

Tetramphora croatica sp. nov.—A new brackish-water species from Lake Vransko, Croatia

The genus Amphora sensu lato was considered highly heterogeneous for a long time. Modern microscopy and molecular analyses revealed significant differences in cell morphology and structure, thus suggesting polyphyly of the genus. New findings resulted in separation and description of several amphoroid genera. Recently, the genus Tetramphora Mereschkowsky was re-established based on ultrastructural and molecular analyses. The genus is widely spread in marine and brackish habitats. Recent observations of contemporary flora and cores from Lake Vransko (Croatia) revealed a new species of Tetramphora. The new species is characterized by having large semi-elliptical valves with arched dorsal margin and biarcuate ventral margin, length of 49.0–78.0 µm and width between 7.5–12.0 µm. The raphe is discontinuous, with proximal raphe ends externally covered with large siliceous flap. Striae are uniseriate, composed of small round to elongated areolae. Based on this unique combination of characters visible on light and scanning electron microscope, a new species Tetramphora croatica sp. nov. is described.

New and interesting Luticola species (Bacillariophyta) from the mangroves of Nosy Be Island, NW Madagascar

Abstract Madagascar is an isolated island characterized by a high degree of endemism at all taxonomic levels. Diatom assemblages of the region are still poorly known and sporadic sampling events in various habitats (e.g. lagoons, mangroves) have revealed a large number of taxa that could not be identified. This study presents detailed descriptions of two new species of Luticola: L. nosybeana and L. madagascarensis, collected from mangrove roots on Nosy Be Island. Comparisons with the described congeners showed that the density of striae in Luticola nosybeana is higher than that in L. belawanensis and proximal raphe endings terminate as irregular, shallow grooves. Luticola madagascarensis differs from L. similis in the shape of proximal raphe endings, which are short and expanded in the latter, while continue with irregular, shallow, elongated L-shaped grooves in L. madagascarensis. Luticola nosybeana and L. madagascarensis can be distinguished under a light microscope by the shape of the central area (bow-tie shaped in L. madagascarensis and deltoid in L. nosybeana) and isolated pores (robust and well visible in L. madagascarensis, poorly discernible in L. nosybeana). The two new species are unique in their habitat preferences: while all known congeners are freshwater, the new species inhabit estuarine mangroves.

Ninastrelnikovia lateritica sp. nov., a new and rare freshwater diatom species from the rocky pools of the Western Ghats, India with a note on the genus Ninastrelnikovia Lange-Bertalot & A.Fuhrmann (Bacillariophyta)

Ninastrelnikovia lateritica sp. nov., a new and rare freshwater biraphid diatom species was discovered from a rocky ephemeral pool of the Kaas plateau, Western Ghats, and described on the basis of light and scanning electron microscopy observations. A morphological comparison with the two other described Ninastrelnikovia taxa is provided. This new species can easily be separated from its congeners by the shape of the valve apex and absence of any second inflation along the valve margin, as well as the shape and structure of the external distal raphe ends and internal proximal raphe ends. The members of Ninastrelnikovia are characterized by two morphological types of valves. Valves on the ends of colonies exhibit one set of morphological features while valves located in the middle of colonies show another set of morphological features. Morphological details of the valves are discussed.

Achnanthidium neotropicum sp. nov., a new freshwater diatom from Lake Apastepeque in El Salvador (Central America)

A new freshwater diatom recovered from modern and subfossil sediments of Lake Apastepeque in El Salvador, Achnanthidium neotropicum sp. nov., is described based on light and scanning electron microscopy observations. The species is characterized by valves with linear, sometimes centrally constricted (mainly in large cells), outlines, broadly rounded to subrostrate apices, and often rectangular fascia. Striae are composed of 3–4 rounded to slit-like areolae. It can be separated from similar species by valve outline, together with striae density, and number of areolae per stria. Based on the straight distal raphe endings this species can be assigned to the A. minutissimum complex. The new species is compared to morphologically resembling species from the genus Achnanthidium Kützing.

A new species of Genkalia (Bacillariophyta) from mountain lakes within the Sichuan Province of China

A new diatom species, Genkalia alpina sp. nov., was identified in high elevation lakes in the Mugecuo Scenic Area within the Sichuan Province of China. The area is located in the northern foot of the Hengduan Mountains between the western edge of the Sichuan Basin and the Qinghai-Tibet Plateau, belongs to the subtropical humid monsoon climate, at an altitude of 2600–3800m, with lake water originating mostly from the melting mountain snow. Light and scanning electron microscopy revealed that G. alpina valves are linear with two undulated margins and apices that are subcapitate in larger specimens, but slightly shorter in smaller specimens. The central area is elliptical, and the external proximal raphe ends are straight, or slightly deflected towards the primary valve side. Terminal raphe fissures are strongly bent towards the secondary side and they extend to mantle. Uniseriate striae continue uninterrupted from the valve face to the mantle. The present study is the first report of Genkalia species in China, and expands the geographical distribution of the genus, as well as the known diatom diversity of China.

Three new Hantzschia species (Bacillariophyta) from the Maritime Antarctic Region

Following an earlier revision of the genus Hantzschia (Bacillariophyta) in the Maritime Antarctic Region, several at present unidentified or poorly known taxa of this aerophilic genus have been investigated using both light and scanning electron microscopy. Based on the morphological analysis of the observations, three new species are currently described: Hantzschia australabundans sp. nov., H. zidarovae sp. nov. and H. zikmundiana sp. nov. The new species differ from comparable taxa in valve outline, structure of the internal proximal raphe endings and structure of the striae and areolae. Additional observations are presented on Hantzschia amphioxys and its forma muelleri, H. abundans and H. incognita, based on observations of Antarctic populations from the South Shetland Islands, Vega Island and James Ross Island. Brief notes on the ecology of all reported species are added.

Adlafia moseri and A. tjibaoui two new diatom species (Bacillariophyta) from New Caledonia with further observations on Adlafia muscora and Kobayasiella saxicola

During a recent survey of epilithic diatoms in running waters of New Caledonia, two unknown Adlafia Moser, Lange-Bertalot & Metzeltin species were found. Both species are described as new based on light and scanning electron microscopy (LM and SEM). Adlafia moseri sp. nov., is characterised by its margins morphology, its large size and its low stria density, clearly visible in LM. Adlafia tjibaoui sp. nov. shows a very long internal intermissio with curved proximal raphe endings and a very high stria density. Since the generitype Adlafia muscora (Kociolek & de Reviers) Moser, Lange-Bertalot & Metzeltin was poorly described, its diagnosis is emended based on more detailed scanning electron microscopy observations. Kobayasiella saxicola (Manguin) Lange-Bertalot, only described in light microscopy, occurs frequently in some running waters in New Caledonia. An emended description of this taxon is likewise proposed based on additional SEM data.

Planothidium juandenovense sp. nov. (Bacillariophyta) from Juan de Nova (Scattered Islands, Mozambique Channel) and other tropical environments: A new addition to the Planothidium delicatulum complex

Planothidium juandenovense sp. nov. (Bacillariophyta) is described from the marine tropical environments of Juan de Nova I. (Mozambique Channel), Rodrigues I. (Mascarene Archipelago) and from Guam (Northern Mariana Is., Pacific). This small and relatively rare taxon has short multiseriate striae on the sternum valve (SV), hooked raphe valve (RV) terminal raphe endings and no SV cavum or hoof-shaped area. This taxon has similarities with Planothidium delicatulum (Kutz.) Round et Bukht. and Planothidium septentrionale (Ostrup) Round et Bukht. ex Rumrich et al., but also differences: e.g. a relatively narrow and rhombic SV sternum, void of areolae, with vestigial radiate structures and an uninterrupted marginal SV elevated crest or 'crista marginalis'. P. juandenovense sp. nov. is compared to some other Achnanthales with short SV striae. Cocconeis quarnerensis var. lanceolata Jurilj and Planothidium quarnerense f. rhombica (Giffen) comb. nov. may be close to our new taxon.

Description of the new freshwater diatom genus Okhapkinia gen. nov. from Laos (Southeast Asia), with notes on family Sellaphoraceae Mereschkowsky 1902

A new monotypic diatom genus from Laos is described, Okhapkinia alexandrii Glushchenko, Kulikovskiy et Kociolek gen. et sp. nov. The new genus is described on the basis light and scanning electron microscope observations. This genus is similar morphologically to the genus Sellaphora Mereschkowsky on the basis of several shared features. These features include presence of uniseriate striae, internal hymenate pore occlusions, large, elongate helictoglossae, round depressions at the valve face mantle junction, straight internal raphe slit, presence of longitudinal lines positioned on either side of the axial area, and striae arrangement and shape. The new genus is diagnosed by having an external, undulate raphe slit, absence of polar bars, presence of massive basal siliceous layer, and presence of rims and external thickenings around the areolae, central raphe ends curved to different sides internally and very prominent elongated hymenes internally. In all of these features the new genus differs from Sellaphora. The shared features between Okhapkinia gen. nov. and Sellaphora suggest the new genus should be assigned to the Sellaphoraceae Mereschkowsky. Similarites between Okhapkinia gen. nov. and other newly-described genera are discussed. We consider the newly described genus Altana Kulikovskiy, Lange-Bertalot et Metzeltin, which shares the feature of external silica outgrowths with Okhapkinia gen. nov. to be part of the family Cavinulaceae D.G. Mann. The genus Buryatia Kulikovskiy, Lange-Bertalot et Metzeltin described from Lake Baikal may represent another genus closely related to Sellaphora, and suggest it is also a member of the family Sellaphoraceae.

Morphological investigation and transfer of Naviculadicta parasemen Lange-Bertalot to the genus Rexlowea Kociolek & Thomas

We document the size diminution series and valve morphology of the diatom Naviculadicta parasemen Lange-Bertalot in Lange-Bertalot & Genkal, described originally from the Yugorsky Peninsula and nearby islands, northwest Siberia. Based on material from the northeastern Arctic, the features of the valve structure, undulate raphe with dilated external proximal raphe ends, organization of the striae, and change in orientation of the striae near the apices suggest a close affinity with the monotypic genus Rexlowea. We effect the transfer of N. parasemen to Rexlowea, making the new combination R. parasemen. Several features of R. navicularis, the generitype, are missing from R. parasemen, including septa and pseudosepta. It may therefore be necessary to emend the description of Rexlowea as additional species are referred to the genus, but we will await discovery of additional species before formal emendation.

A new Muelleria species (Bacillariophyta) from the Maritime Antarctic Region

During a survey conducted on the soil diatom flora of newly exposed areas due to the retreat of the Ecology Glacier (King George Island, South Shetlands) an unknown Muelleria taxon was observed that could not be identified using the currently available literature. Based on detailed morphological observations using LM and SEM microscopy the unknown taxon has been described as new for science - Muelleria olechiae sp. nov. The new species is characterized in having typically bifurcated terminal raphe fissures, elongated, deflected proximal raphe endings and a lack of canal puncta. It was observed in several soil samples, but always in relatively low abundances.

Muelleria pseudogibbula, a new species from a newly recorded genus (Bacillariophyceae) in China

The genus Muelleria is reported for the first time from China in this paper. The new diatom species Muelleria pseudogibbula sp. nov. was observed during a survey of diatoms from Zoige Wetland, Sichuan Province, China. The morphological characters of this new species were documented by light and scanning electron microscope and compared with similar species. M. pseudogibbula is characterized by its lanceolate to linear-lanceolate valve outline with rounded apices, two longitudinal canals running parallel to each side of the raphe, proximal ends of the raphe deflected to the same directions and finishing before the first row of areolae, and curved distal raphe ends, forming two divergent branches.

Morphological discoveries in the genus Diploneis (Bacillariophyceae) from the tropical west Pacific, including the description of new taxa

Epiphytic diatoms on seaweeds and seagrasses were collected from tropical regions in the western Pacific Ocean (i.e., Siladen Island, Celebes Sea, Indonesia; Guam; Palau). Fifteen species of Diploneis are described in detail with light and scanning electron microscopy including six species new to science, D. cerebrum, D. claustra, D. craticula, D. crispa, D. rimosa and D. weissflogiopsis. Valve structure in Diploneis is particularly complicated, and two new distinctive structures are described for the first time: (1) central external raphe endings with flaps or rolled flaps and (2) internal globular papillae near the marginal ends of the virgae. In addition, we confirm that openings on the inner surface of the longitudinal canals are of taxonomic value. The structural complexities encountered in Diploneis require the study of a great many more taxa before a meaningful revision of the genus can be undertaken. Its diversity in warm waters is a rich resource for new Diploneis taxa to further our understanding of the genus.

Two new species of Achnanthidium Kützing (Bacillariophyceae) from Kolli Hills, Eastern Ghats, India

Two new freshwater species of Achnanthidium Kutzing are described from Eastern Ghats Mountain range of Peninsular India based on light and scanning electron microscopy observations. Achnanthidium initium sp. nov. belongs to the group of Achnanthidium taxa that have terminal raphe fissures curved to opposite sides of the valve. This taxon is characterized by distinctive fascia, raphe endings extending to the valve margin, lineate distal raphe endings and 2-5 linear areola per striae. Achnanthidium linannulum sp. nov. belongs to the group of Achnanthidium taxa with terminal raphe fissures curved to the same side of the valve. This species is characterized by the presence of occluded areolae near the margin, striae orientation and the weakly bent internal distal ends of the raphe. These new species are known only from their type locality, oligotrophic Masilla Waterfalls from Kolli Hills, Eastern Ghats.

Navicula amoyensis sp. nov. (Bacillariophyceae), a new benthic brackish diatom species from the Jiulong River estuary, Southern China

Based on the light and scanning electron microscopy observations, we present a detailed description of a new brackish diatom Navicula amoyensis sp. nov. Samples were collected from an intertidal sand flat in the Jiulong River estuary, Southern China. The key diagnostic features of this species include the simple terminal raphe endings, broad terminal area, two rows of perpendicular apical pores, a wide contracted girdle region with pectinate margin and internal proximal raphe endings with a raised siliceous rib and accessory rib. Furthermore, the main taxonomic features of N. amoyensis sp. nov. and the genera Hippodonta and Navicula are also discussed in detail.

New and interesting Eunotia (Bacillariophya) taxa from the Democratic Republic of the Congo, tropical central Africa

Background and aims - Large-celled Eunotia species from tropical central Africa are documented in order to define morphological variation within species and to describe new or poorly documented taxa. Methods - Samples were collected from the Congo River between Kisangani and Bumba in the Democratic Republic of the Congo. These samples were prepared for diatom analysis and examined according to standard methods and documented using both light and scanning electron microscopy. Key results - A single population of Eunotia zygodon is used to demonstrate the high degree of change in gross cell morphology during its life cycle, changes previously observed in cultures of this genus. Cells of this taxon from each extremity of the reproductive cycle could be, and probably often were, placed in discrete taxa during sample analysis, especially as this taxon occurs rather infrequently. We also describe Eunotia leonardii as new to science. It has an undulate valve margin and is closely related to Eunotia serra and Eunotia georgii but differs in respect to overall cell size and the structure of the terminal raphe endings. The bi-undulate Eunotia papilio var. africana is raised to the rank of species and named Eunotia fuseyi as it is clearly a discrete taxon from E. papilio s. str.

A new Navicula (Bacillariophyta) species from low-elevation carbonate springs affected by anthropogenic disturbance

Diatom assemblages in carbonate spring habitats at low elevations, with low discharge, and affected by direct human impacts were studied only recently and in some geographic areas. We describe and characterize the ecology of a new Navicula species from springs with these characteristics within the basin of the River Adige in the south-eastern Alps and Alpine foothills (Province of Verona, Italy). Navicula veronensis sp. nov. is in the group of species around N. cincta but has distinct outline, size, central area, and proximal raphe endings. The availability of data on the distribution of the new species in streams of the Island of Cyprus allowed to quantitatively compare the ecological preferences, niche position, and niche breadth of Navicula veronensis sp. nov. with those of allied species. The new species was found to be characteristic of medium-high conductivity freshwaters, rich in sulphates and chloride, often nitrate enriched and affected by marked discharge fluctuations and seasonal desiccation. Niche position however differed only slightly from those of morphologically-similar species, with the exception of Navicula dealpina that was found to be characteristic of oligotrophic, calcium-bicarbonate rich environments with medium(-low) conductivity. Canonical Correspondence Analysis clearly showed that the most influential environmental variables determining the diatom assemblages of low-elevation carbonate springs affected by anthropogenic disturbance were nitrate enrichment, spring morphology alteration (in particular for water abstraction), and low discharge.

Petroplacus gen. nov. (Bacillariophyta): a new genus of diatom from Lake Baikal

The valve morphology of two raphid diatom taxa from the littoral zone of Lake Baikal has been studied by means of light and electron microscopy. Their characters show obvious affinities to the genera Placoneis and Petroneis. Due to distinctive characters of the internal and external valve structure, however, the two taxa cannot be placed in either of these two genera or any other existing genus. Thus we have described the new genus Petroplacus to accommodate them. Its distinctive characters are: linear-elliptic or broadly-linear valves with protracted rostrate apices, fine radial striation including semi-regular short intercalary striae, the external straight central fissures deep in the T-shaped grooves, direct internal raphe endings and small round poroids internally covered by simple volae. Two species are included: Petroplacus lizae, the generitype, and P. tectum. To date, these species have been found only on the sandy substrate of the western shore of Lake Baikal.

Humidophila komarekiana sp. nov. (Bacillariophyta), a new limnoterrestrial diatom species from King George Island (Maritime Antarctica)

During a survey of the non-marine diatom flora of King George Island (South Shetland Islands), an unknown Humidophila taxon was recorded. Detailed light and scanning electron microscopy observations indicated that the unknown taxon could not be identified based on the currently available literature. The new species is described as Humidophila komarekiana sp. nov. and is characterized in having strictly linear valves with parallel margins and broadly rounded, never protracted apices, a filiform raphe with almost indistinct, straight proximal and distal raphe endings. The striae are composed of one, irregularly shortened areola. The mantle areolae are interrupted at the apices. The new species is compared with similar taxa in the Antarctic Region and worldwide. Notes on the ecology of the new species are added.

Two new Platessa (Bacillariophyceae) from Amazonia: Platessa guianensis spec. nov., and P. itoupensis spec. nov.

Recent investigations in the deep rainforest of Amazonia in French Guiana and in the north of Brazil revealed the presence of two new Platessa species. Detailed light (LM) and scanning electron microscope (SEM) observations were used to describe the morphology and the ultrastructure of these new monoraphid diatoms, Platessa guianensis and P. itoupensis. They display the taxonomic features characteristic of the genus Platessa, namely almost flat valves, straight raphe fissures and uni- to multiseriate striae with specific features such as the ornementation of the striae and the morphology of the groove surrounding the raphe endings. These two Platessa are the first ones described from Amazonia. They are compared with the two types of two similar species described originally from Indonesia (i.e. Platessa brevicostata and Platessa cataractarum) whose original materials are also here re-illustrated in LM and SEM. The taxonomical diagnosis is completed with comments on ecology issues. In addition, we proposed the recombination of three Achnanthes into Platessa based on published literature.