| 1. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
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Entomoneis annagodheisp. nov., a new marine diatom (Entomoneidaceae, Bacillariophyta) from the west coast of Sweden
- 2020
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Ingår i: Diatom Research. - : Informa UK Limited. - 0269-249X .- 2159-8347. ; 35:3, s. 269-279
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Tidskriftsartikel (refereegranskat)abstract
- The genusEntomoneisincludes diatoms with an elevated bilobate keel, a sigmoid raphe canal and numerous girdle bands. It is known to inhabit various environments, from freshwater to marine, both plankton and benthos. During a phytoplankton investigation in the Kungalv estuary on the west coast of Sweden, we observed numerous cells belonging toEntomoneis. Further morphological investigations performed with light and electron microscopy allowed us to describeEntomoneis annagodhei, sp. nov., with a unique set of morphological characters. Most importantly, a still undocumented character proved to be an oblique transapical fascia across the centre of the valve. Other distinctive features of this species are a pronounced raphe canal with dense raphe fibulae, very fine striation, resolvable only with electron microscopy, external lanceolate slit-like opening of the central nodule, and fine, linear to undulate external ridges running more or less parallel and adjacent to the raphe and valve margin. The morphological characters and morphometry are discussed in comparison with similar taxa. Our results contribute to the under-appreciated diversity ofEntomoneis, especially inhabiting the marine plankton.
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| 2. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
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Gomphonemopsis ligowskii, a new diatom (Bacillariophyceae) from the marine Antarctic and a comparison to other Gomphonemopsis
- 2018
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Ingår i: Diatom Research. - : Informa UK Limited. - 0269-249X .- 2159-8347. ; 33:1, s. 97-103
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Tidskriftsartikel (refereegranskat)abstract
- A new marine diatom, Gomphonemopsis ligowskii, is described. Gomphonemopsis ligowskii was found as an epiphyte on the brown macrophyte, Desmarestia anceps, collected from King George Island, Antarctica in January 2016. This species is the first of the genus described from a polar region. It is a small and relatively rare taxon that is characterized by its unique shape and the presence of uniseriate striae, composed of round poroidal areolae on its valve face. The striae are arranged in parallel rows on either side of the axial area, and a row of rounded areolae on both sides of the valve mantle is confined to the wider part of the valve (headpole). A description of valve ultrastructure as well as a comparison with related taxa are provided.
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| 3. |
- Chevalier, Mathieu
(författare)
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Planktonic diatom community dynamics in a tropical flood-pulse lake: the Tonle Sap (Cambodia)
- 2019
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Ingår i: Diatom Research. - 0269-249X .- 2159-8347. ; 34, s. 1-22
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Tidskriftsartikel (refereegranskat)abstract
- It has been proposed that, within flood-pulse systems, seasonally dynamic conditions promote extremely high levels of biodiversity. In this paper, we aim to understand how variation in environmental conditions and habitat availability, across space and time, influences the structure and composition of plankton diatom communities within the Tonle-Sap Lake (Cambodia) during two flood-pulse cycles. We hypothesize that (i) communities vary considerably across space and time, (ii) environmental filtering accounts for a substantial portion of the variation in community composition, and (iii) shifts in meta-community structure occur seasonally, due to variation in both environmental conditions and habitat availability. A principal component analysis and a permutational multivariate analysis of variance were used to characterize spatio-temporal variations in environmental conditions, community structure and composition. Determinants of community variations across space were identified by redundancy analyses and variation partitioning, while seasonal changes in meta-community structure were assessed by investigating temporal changes in beta-diversity. Our results indicate that (i) spatial variations in community structure and composition are largely influenced by the seasonal flood-pulse, (ii) environmental filtering is the most likely process driving the compositional changes, and (iii) changes in diatom life-form community provide insights into the hydrological functioning of the Tonle Sap. We conclude that the survey of diatom communities may constitute a relevant sensor of hydrological change in the system and could be used to derive regionally specific hypotheses about how global climate change is impacting the lake's functioning.
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| 4. |
- Katrantsiotis, Christos, et al.
(författare)
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Morphological study of Cyclotella distinguenda with a description of a new fossil species Cyclotella paradistinguenda sp nov from the Agios Floros fen, SW Peloponnese, Greece in relation to other Cyclotella species
- 2016
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Ingår i: Diatom Research. - 0269-249X .- 2159-8347. ; 31:3, s. 243-267
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Tidskriftsartikel (refereegranskat)abstract
- In a previous palaeoenvironmental study based on a high-resolution diatom record from a core sampled at the Agios Floros fen, SW Peloponnese, Greece, Cyclotella distinguenda was reported as exhibiting two morphs with distinct central area and stria arrangement, as well as a specific distribution throughout the sequence. In the present paper, we examine this morphological variability through detailed observations using light and scanning electron microscope combined with a simple statistical approach. Our new data suggest that the two morphs present substantial and constant differences in the structure and size of their central areas, the structure and number of their striae, the arrangement of their marginal fultoportulae/density of costae between fultoportulae, the shape of their rimoportulae and their alveolar chambers. On the basis of these morphological and stratigraphic variations one morph is described as a new species, Cyclotella paradistinguenda sp. nov., while the other is assigned to C. distinguenda and is also consistent with the original description of this taxon. The two species share well-defined central areas without fultoportulae, almost equal length striae and one rimoportula situated on a costa within the ring of marginal fultoportulae. Cyclotella paradistinguenda sp. nov. can be distinguished by a combination of the following characteristics: (1) large central area (1/3 of valve diameter), smooth or decorated with puncta and depressions, flat or concentrically undulated, (2) distinct, narrow striae (12-15/10 mu m) consisting of one or two short rows of areolae of the same size expanding into three rows at the mantle, (3) marginal fultoportulae on each first to third costae (4) poorly developed alveolar chambers and rimoportula. Based on the stratigraphic distribution and the associated flora in the Agios Floros sequence, it can be inferred that C. paradistinguenda sp. nov. is tolerant of shallower water conditions with lower nutrient availability and/or higher pH than C. distinguenda.
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| 5. |
- Lobban, Christopher S., et al.
(författare)
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Licmosphenia revisited : transfer to Licmophora, redescription of L. clevei Mereschkowsky and descriptions of three new species
- 2015
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Ingår i: Diatom Research. - 0269-249X .- 2159-8347. ; 30:3, s. 227-236
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Tidskriftsartikel (refereegranskat)abstract
- Licmosphenia Mereschkowsky (Licmophorales: Licmophoraceae) is distinguished from Licmophora C. Agardh almost entirely by the presence of an apical window in the septum of the valvocopula. Recently, SEM images of three new species, all with coarse striae, showed that the valve morphology was indistinguishable from a group of Licmophora species including L. ehrenbergii, and gene sequence data showed Licmosphenia sister to the few available Licmophora spp. Two questions remain: (1) what is the structure of Licmosphenia spp. with fine striae? and (2) what would further molecular evidence contribute to understanding whether these genera are distinct or not? New LM and SEM observations on Licmosphenia species and sequence data from additional Licmophora species now answer these questions. Valve ultrastructure of a new, finely striated species with a small apical aperture, from Mallorca, Spain, is similar to finely striated Licmophora species, and the position of Licmosphenia in the phylogenetic tree is now within the Licmophora clade. The presence of apical apertures in two morphological groups of Licmophora suggests that the apical window has arisen at least twice. Licmophora is the older genus name and we therefore formally transfer all Licmosphenia species to it. In addition to Licmophora garyi from Mallorca, we describe a curved species from the Adriatic, Licmophora arcuata, similar to L. grunowii but with much coarser striae, and a species from Guam with a very large apical aperture, L. pisciformis. We also designate an epitype for Licmosphenia clevei Mereschkowsky, the type species of that genus.
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| 6. |
- Pennesi, Chiara, et al.
(författare)
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Morphological discoveries in the genus Diploneis (Bacillariophyceae) from the tropical west Pacific, including the description of new taxa
- 2017
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Ingår i: Diatom Research. - 0269-249X .- 2159-8347. ; 32:2, s. 195-228
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 7. |
- Plikk, Anna, 1982-, et al.
(författare)
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Diatom assemblages from an Eemian palaeolake in Northern Europe with morphological observations of rare Aulacoseira sp. resting spores
- 2021
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Ingår i: Diatom Research. - 0269-249X .- 2159-8347. ; 36:4, s. 313-321
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Tidskriftsartikel (refereegranskat)abstract
- An overview of the diatom flora of the last interglacial (Eemian) lacustrine gyttja deposit at Sokli, northeastern Finland is presented together with descriptions including photomicrographs of resting spores similar to the Aulacoseira islandica-skvortzowii group, not found in recent material from Europe. Comparisons are made with literature data on similar taxa. The morphology of the resting spores (e.g., the number of striae and areolae in 10 mu m) links them to the A. islandica-skvortzowii group, but the lack of vegetative cells in the Sokli record makes the determination of true synonymy difficult. The presence of spores similar/related to the A. islandica-skvortzowii group in the Sokli Eemian palaeolake may reflect a more widespread distribution of this group in the past.
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| 8. |
- Ulanova, Anna, et al.
(författare)
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Lunella garyae sp nov - A new polyhalobous diatom from the English Channel coast
- 2006
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Ingår i: Diatom Research. - 0269-249X .- 2159-8347. ; 21:2, s. 415-426
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Tidskriftsartikel (refereegranskat)abstract
- A new benthic polyhalobous diatom species, Lunella garyae, is described from supralittoral limestone rock pools at Dancing Ledge, English Channel coast, England. The detailed morphology of this species is examined using scanning electron microscopy (SEM) and light microscopy (LM). The new species is compared with the two previously described Lunella species and with some other morphologically similar diatom taxa. The identity of the genus Lunella is discussed.
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| 9. |
- Öberg, Helena, 1974-, et al.
(författare)
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Morphology, valve ultrastructure and stratigraphical variability of Discostella taxa in a tropical crater lake, northern Tanzania
- 2009
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Ingår i: Diatom Research. - Bristol : Biopress Ltd. - 0269-249X .- 2159-8347. ; 24:2, s. 341-356
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Tidskriftsartikel (refereegranskat)abstract
- Morphological and ultrastructural variability of Discostella Houk et Klee (Bacillariophyceae) valves from a small crater lake in northern Tanzania have been examined under scanning electron microscope (SEM) and light microscope (LM). Three types of Discostella are described; Discostella woltereckii, as well as a small variety of D. woltereckii denoted Discostella woltereckii var. minor Öberg, Risberg et Stabell and an unidentified species, Discostella sp. The diatom record during the last ~100 years is dominated by D. woltereckii and D. woltereckii var. minor. The lithology and diatom stratigraphy of a 36 cm sediment surface core show a period of low lake level with extensive aquatic vegetation from around AD 1600. Sometime around AD 1900 there is a substantial rise in the lake water level indicated by an increase in euplanktonic Aulacoseira ambigua and facultative planktonic Discostella spp.
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| 10. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
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COCCONEIS POTTERCOVEI SP NOV AND COCCONEIS PINNATA VAR. MATSII VAR. NOV., TWO NEW MARINE DIATOM TAXA FROM KING GEORGE ISLAND, ANTARCTICA
- 2010
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Ingår i: Diatom Research. - 0269-249X. ; 25:1, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- Details of two new small marine taxa of the genus Cocconeis Ehrenberg are described; C. pottercovei sp. nov. and C. pinnata var. matsii var. nov., which were observed as epipelic and epiphytic in Potter Cove, King George Island, Antarctica. Descriptions are based on both light and scanning electron microscope observations. C. pottercovei belongs to the group of Cocconeis taxa that bear very short and marginal striae on the rapheless valve while C. pinnata var. matsii belongs to the C. costata Gregory complex. They are mainly differentiated from the other similar taxa by stria number, stria arrangement and structure on both raphe and rapheless valves. A comparison with closely resembling taxa is given.
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| 11. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
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Entomoneis grisslehamnensis, a New Diatom (Bacillariophyceae) from the Baltic Coast of Sweden with taxonomic and ecological notes on Entomoneis paludosa (W. Smith) Reimer
- 2023
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Ingår i: Diatom Research. - 0269-249X. ; 38:1, s. 55-68
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Tidskriftsartikel (refereegranskat)abstract
- The diatom genus Entomoneis includes species with panduriform frustules characterized by a bilobate, elevated keel, sigmoid raphe canal and numerous open, porous girdle bands. During a phytoplankton survey along the Baltic coast of Sweden, we observed numerous Entomoneis cells, some belonging to the well-known Entomoneis paludosa, while others remained unknown. Morphological and ultrastructural studies of the unknown species were performed with light microscopy (LM), scanning (SEM) and transmission (TEM) electron microscopy, and revealed a unique set of morphological characters. Live cells of Entomoneis grisslehamnensis sp. nov. contain one plate-like plastid and show various degrees of torsion about the apical axis. Microscopic features of cleaned frustules are discussed in comparison with similar species. Most importantly, every 2nd to 5th virga is strongly elevated, uniseriate striae are composed of quadrangular areolae with finely perforated hymenes; the winged keel with a discernible raphe canal is structurally strengthened by raphe fibulae with a flattened wing area, and the main part of the valve bulges towards the margins; striation is decussate on the wings and there is one row of raphe canal areolae at the central area. In addition to describing this new species of an underappreciated, yet cosmopolitan diatom genus, we contribute to the taxonomy of E. paludosa with LM, SEM and TEM details, some of which were not sufficiently noted in original descriptions or re-examination of type material and other specimens made by Dalu et al. [2015. A re-examination of the type material of Entomoneis paludosa (W. Smith) Reimer and its morphology and distribution in African waters. Fottea 15: 11-25] and Long et al. [2022. Ultrastructure of three species of Entomoneis (Bacillariophyta) from Lake Qinghai of China, with reference to the external areola occlusions.
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| 12. |
- Al-Handal, Adil Y, 1952, et al.
(författare)
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Navithidium gen. nov., a new monoraphid diatom (Bacillariophyceae) genus based on Achnanthes delicatissima Simonsen
- 2021
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Ingår i: Diatom Research. - 0269-249X. ; 36:2, s. 133-141
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the ultrastructure of Achnanthes delicatissima Simonsen in materials collected from the Swedish Baltic coast. Valve structure differs markedly from that of Achnanthes sensu lato, particularly in the absence of cribrate areolae which separates Achnanthes from all other members of the family Achnanthaceae. Comparing this species with those recently described achnanthoid genera, such as Scalariella Riaux-Gobin & Witkowski and Madinithidium Witkowski, Desrosiers & Riaux-Gobin revealed morphological differences that warrant the erection of a new genus, Navithidium. Owing to the small size of the frustules, it is difficult to identify Navithidium delicatissima in light microscopy due to similarities with some closely related taxa like Achnanthidium pseudochamaepinnularia (which is here transferred to Navithidium). A comparison with related genera is provided and discussed. © 2021 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
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| 13. |
- Håkansson, Hannelore
(författare)
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A compilation and evaluation of species in the general Stephanodiscus, Cyclostephanos and Cyclotella with a new genus in the family Stephanodiscaceae
- 2002
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Ingår i: Diatom Research. - 0269-249X. ; 17:1, s. 1-139
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Forskningsöversikt (refereegranskat)abstract
- 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 (Kutzing) Brebisson, 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 cribium 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 Hakansson 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 Opus generis: Puncticulata comta (Ehrenberg) Hakansson comb.
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| 14. |
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| 15. |
- Riaux-Gobin, C, et al.
(författare)
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New Amphicocconeis species off Mascarenes (Western Indian Ocean) and related taxa
- 2011
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Ingår i: DIATOM RESEARCH. - 0269-249X. ; 26:1-2, s. 175-188
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Tidskriftsartikel (refereegranskat)abstract
- Two new species were found on coral sediments of Mascarene archipelago: Amphicocconeis mascarenica sp. nov., relatively frequent in Réunion and rare in Rodrigues Islands, and A. rodriguensis sp. nov., relatively rare in Rodrigues and scarce in Réunion. Comparison was made with A. disculoides and A. debesii (Hustedt) De Stefano, and with species pertaining to Psammococconeis Garcia (P. brasiliensis and P. disculoides sensu Garcia). The Mascarenes taxa do not have simple raphe endings but terminal raphe fissures bent to the same side, which is a characteristic feature shared by Amphicocconeis taxa. Amphicocconeis rodriguensis has a raphe valve relatively similar to that of A. debesii (Hustedt) De Stefano, but with a denser striation; furthermore, the valvocopula of the sternum valve is narrow with simple to chiselled fimbriae. Amphicocconeis rodriguensis sternum valve is close to that of A. debesii (Hustedt) De Stefano. Amphicocconeis mascarenica shows a number of striae relatively low on both valves and both valvocopulae are generally extended and present rows of alternated small holes, which seems a unique feature for Amphicocconeis.
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| 16. |
- Riaux-Gobin, C, et al.
(författare)
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Species of the Cocconeis peltoides group with a marginal row of unusual processes (Mascarenes and Kerguelen Islands, Indian Ocean)
- 2011
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Ingår i: DIATOM RESEARCH. - 0269-249X. ; 26:3-4, s. 325-338
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Tidskriftsartikel (refereegranskat)abstract
- Two diatoms related to Cocconeis peltoides Hustedt (Bacillariophyceae), from coral reef environments (Mascarenes, Western Indian Ocean), are proposed as a new Cocconeis variety and a new C. species: Cocconeis peltoides var. archaeana Riaux-Gobin et Compère and Cocconeis sigillata Riaux-Gobin et Al-Handal. Cocconeis peltoides and the two new taxa possess an unusual marginal row of small processes on their sternum valve, internally opening as curb-like structures. Several other Cocconeis species, encountered during sampling campaigns in Kerguelen (Southern Ocean, Indian Ocean sector), also share such processes, including Cocconeis hauniensis Witkowski and Cocconeis germainii Riaux-Gobin, Witkowski et Romero. The shared characteristics of these taxa are examined and compared in detail.
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| 17. |
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| 18. |
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