| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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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