Figs 10-16
Diploneis interrupta, SEM. Fig. 10. Internal valve view showing slightly radiate transapical striae and hyaline areas (arrowheads); Fig. 11. Internal view showing raised central nodule and central raphe endings; Fig. 12. Internal view of apex with raphe endings and cribra closing the areolae; Fig. 13. External valve view showing longitudinal canals (arrowhead) and striation; Fig. 14. External valve view of apex with hooked terminal raphe fissure and three large scattered rounded openings (arrowheads) among the row of fine pores on the longitudinal canals; Fig. 15. External view of valve centre showing slightly depressed quadrangular central area and central raphe endings; Fig. 16. Internal valve view showing the multiseriate striation and robust virgae. Scale bars represent 5 μm (Figs 10, 13), 2 μm (Figs 11, 14-15) and 1 μm (Figs 12, 16).
Source publication
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 were described in detail through scanning electron and light microscopy, including six species new to science, D. cerebrum, D. claustra, D. craticula...
Citations
... can be constricted in the middle, such strongly constricted species are few and hence Hagelstein's (1939) comparison with Progonoia intercedens. The nominate form of Diploneis interrupta is much larger and less constricted than the present species, and the wall structure is much different (Pennesi et al. 2017;figs. 10-17): the external opening is a narrow, transapical slit occluded internally by poroid plates. ...
... Diploneis caffra, D. gravelleana, and D. carolinensis are further examples of simulacra. Pennesi et al. (2017) previously showed a series in Diploneis, viz., Diploneis weissflogii (A. Schmidt) Cleve, Diploneis weissflogiopsis Lobban & Pennesi, and Diploneis claustra Lobban & Pennesi, the first being the only one widely reported in Micronesia whereas the two simulacra were found only with SEM. ...
Diploneis gravelleana Hagelstein was described in 1939 from Puerto Rico but may later have been confused with Diploneis interrupta var. caffra Giffen, described in 1960 from South Africa. Both are small (ca 20 µm in length), strongly constricted species indistinguishable in light microscopy. When we found a similar species in Micronesia, we needed to determine if it matched either of these species. We obtained mud samples from the US Virgin Islands containing D. gravelleana and unmounted type material of Giffen’s original material for SEM imaging. All three populations differed ultrastructurally and hence the Micronesian species is described as Diploneis carolinensis sp. nov. Lobban & Witkowski. Diploneis carolinensis was found in mangrove samples from Yap and Palau. These simulacra suggest that D. caffra may not be as widely distributed as supposed.
... From the literature it has been observed that most of the Diploneis sp. are marine and also aerophilic (Taylor et al., 2014). The present record Diploneis litoralis is more similar with the morphotypes described by (Pennesi et al., 2017). The diverse range of morphotypes of Diploneis sp. are more or less related (Droop, 1994). ...
Present investigation records diversity of pennate diatom species belonging to seven genera viz. Thalassionema, Nitzschia, Bacillaria, Psammodictyon, Hantzschia, Haslea and Diploneis, in brackish water of Budhabalanga river estuary, Odisha coast. The study comprises morphological and taxonomical enumeration of the species found in samples of the estuary. Light and scanning electron microscopy (SEM) of raw and cleaned diatom samples were described. A total of 10 brackish water diatom taxa were enumerated of which 2 species each from the genus Nitzschia, Thalassionema and Diploneis and one each from others were enumerated and identified. Haslea subsalina sp. nov. described as a new species under genus Haslea.
... 59; Lobban et al. (2012), p. 291, pl. 46, figs 2-4; Pennesi et al. (2017), figs 51-57. Samples: Moen1_Halimeda, Moen1_Padina Dimensions: 22.5-34.7 µm long, 11.8-19.4 ...
In order to contribute understanding of the biodiversity of seaweed-associated diatoms at Moen Island in Chuuk lagoon, Micronesia in the tropical western Pacific, we collected four macroalgae (Halimeda sp., Padina sp., Sargassum sp., Dictyota sp.) that were distributed throughout at 5 subtidal sites of reef flat. These are the first records of diatoms from Chuuk, Federated States of Micronesia. A total 148 taxa belonging to 30 families and 49 genera were briefly documented with the identification references, dimension and illustrations, but many taxa could only be identified to genus. There is much similarity to the flora of Guam, but 16 records are new for the region. Four nomenclatural changes were necessary in consequence of the findings of Ruck et al. (2016) on Surirellales and Rhopalodiales.
Diploneis zhui sp. nov. was observed in epilitic diatom communities from Jiuzhaigou National Nature Reserve. The species is described herein based on light microscopy (LM) and scanning electron microscopy (SEM) and ecological information of the type locality is provided. The species is characterized by linear to linear-elliptic valves with broadly rounded ends, 18–39 μm long, and 9.5–11.0 μm wide and partly biseriate striae, 16–18 in 10 μm. The species is compared with most similar taxa from other regions. The discovery of a new diatom species confirms the importance of Jiuzhaigou not only in terms of species richness and endemicity, but also for the biodiversity of freshwater karst ecosystems.
The present study enhances knowledge of the biodiversity of diatoms in Chuuk, Micronesia following our 2018 study on the seaweed-associated diatoms. We collected planktonic samples of diatoms from five sites of reef flats using a 20 μm mesh net, and two samples of seaweeds with epiphytes by hand from an islet on the barrier reef. In addition, the seaweed-associated diatoms from our 2018 study were analysed using scanning electron microscopy. A total of 109 diatom taxa are documented in the present study. Of these, 70 species were from net samples, and 39 species from the seaweed-associated diatoms. Thirty-one species are newly recorded from Micronesian waters. Most taxa are benthic or tychoplanktonic; euplanktonic diatoms were rare. The occurrence of benthic diatoms from the water column might be related to the Chuuk environmental conditions which include shallow water, strong light intensity and high grazing pressure, to which benthic diatoms seem to be able to better adapt than planktonic diatoms.
The Atlas is an illustrated catalog of recent and extinct diatoms and silicoflagellates from the sediments of the Daginsky Mud Volcano. Diatom flora (278 species and varieties belonging to 99 genera) is represented by different ecological groups, but the abundance of marine and brackish-water species and the presence of silicoflagellates indicates the predominant influence of lagoon waters on the formation of sediments. The systematic part of the Atlas includes taxonomic references and micrographs of 170 taxa of diatoms and 3 taxa of silicoflagellates.
We demonstrated the use of the OpenSees framework for structural and geotechnical system simulations (National Science Foundation-Pacific Earthquake Engineering Center-PEER) and the ABAQUS software for finite element analysis to infer the performance of the cell valve in the diatom Diploneis serrata (the strength and stiffness of the cell wall's valve interstriae) under sheer and normal loads. The visualization of finite element analysis together with ultrastructural microscopic studies, both morphological and molecular (using 18S rDNA markers) helped us to resolve and classify the diatom Diploneis serrata collected from a microcosm made of intertidal submerged benthic shore rocks from Kenting National Park, Taiwan. The neat equilateral triangle pattern of the areolae in D. serrata allow us to construct a physical description of the striae structure. Based on the unique triangular areola in D. serrata, the structure of different areola shapes was simulated, and the difference in structural stability was discussed. The result shows the triangular areolae subjected to shear loads provided significantly larger stiffness and strength we deduce as a structural reinforcement strategy against predation. Based on the strength of the physical simulation structure, we attempt further to infer the possible evolutionary and environmental adaptation significance of the areola arrangement pattern. This line of thinking may help resolve difficult taxa within the diatoms, a task that could aide their use as ecological biomarkers in field observations.
Hyalosira gene sequences are divided into two clades within different families. We examined authentic material of Hyalosira (isotype material of H. obtusangula, synonymous with H. delicatula) and voucher specimens of published sequences, and pooled our observations of Hyalosira-like taxa from benthic and epizoic habitats in several parts of the globe. The two molecular clades corresponded to two morphological groups, with Hyalosira obtusangula associated with Grammatophoraceae. We emend the description and provide lectotypification for Hyalosira and propose Placosira to encompass the taxa in the other clade, associated with Rhabdonemataceae. We propose that Hyalosira has uniseriate to triseriate striae, sometimes different on valve face and mantle. Copulae in most species had shallow septa, though in one they were moderately deep. All species had girdle bands bearing two rows of areolae separated by a midrib. We name five new species of Hyalosira. Morphologies of taxa in the Placosira clade were superficially similar to Hyalosira but differed in having areolae with ricae, a single row of areolae on the girdle bands, and tubular rimoportulae on the valve-face mantle junction. Hyalosira hustedtiana Patrick should revert to its original position in Striatella until the appropriate genus can be determined. We emend Rhabdonematales to encompass Rhabdonemataceae, Grammatophoraceae and Tabellariaceae.
We present three new species, Diploneis implicatus, Diploneis lacustris and Diploneis pumicosus, from the littoral zone of Lake Baikal. Descriptions of these species are based on light and scanning electron microscopical features that distinguish them from other taxa. Diploneis implicatus exhibits external openings of each stria areola flanked by short siliceous thickenings of the vimenes and virgae forming a regular pattern on the external valve that is unique for the genus. Similar structures have previously been reported only in the distantly related and ecologically different Craticula citroides. Diploneis lacustris possesses a conopeum, uncommon in Diploneis and known only in Diploneis aokiensis from Japan. In our species, the conopeum is variable in structure and only developed in the apical quarter of the valve. The third species, Diploneis pumicosus, has a distinctive raphe system morphology similar to that in the single valve of Diploneis conopeospongiosa from Lake Baikal. All three species inhabit silty bottom habitats at depth of 20 m or more, and have so far been found in the southern basin of Lake Baikal. The diversity of Diploneis species in Lake Baikal is a rich resource for further understanding the genus.
