The Experts below are selected from a list of 186 Experts worldwide ranked by ideXlab platform
Nora Dotzler - One of the best experts on this subject based on the ideXlab platform.
-
frankbaronia velata nov sp a putative peronosporomycete Oogonium containing multiple oospores from the lower devonian rhynie chert
Zitteliana, 2013Co-Authors: Michael Krings, Thomas N Taylor, Nora Dotzler, Carla J HarperAbstract:Spherical to pyriform microfossils containing multiple smooth-walled spherules from the Lower Devonian Rhynie chert are described as oogonia of a new fossil peronosporomycete based on congruencies in basic morphology to the polyoosporous oogonia of certain extant Saprolegniales. Because the new fossils also resemble Frankbaronia polyspora, a putative peronosporomycete described previously from the Rhynie chert, they are assigned to the fossil genus Frankbaronia and formally proposed as a new species, F. velata. Surrounding the Oogonium is a conspicuous sheath of consolidated mucilage, produced and secreted by the Oogonium during development. The discovery of F. velata adds to our understanding of the microbial diversity in early terrestrial ecosystems, and contributes to the documentation of the evolutionary history of the Peronosporomycetes.
-
A fossil peronosporomycete Oogonium with an unusual surface ornament from the Carboniferous of France.
Fungal biology, 2010Co-Authors: Michael Krings, Thomas N Taylor, Jean Galtier, Nora DotzlerAbstract:A new fossil peronosporomycete from the upper Visean (Mississippian) of France occurs as a globose Oogonium at the tip of a thin-walled hypha. The Oogonium surface is prominently ornamented by densely spaced, long and subtle, straight or once to several times furcated thread-like extensions; many possess an opaque, bulb-like swelling at base. Antheridia adpressed to the Oogonium are clavate and paragynous. This fossil represents only the third record of an unequivocal peronosporomycete from the Carboniferous, and thus provides important details about the evolutionary history of this group of organisms.
Michael Krings - One of the best experts on this subject based on the ideXlab platform.
-
frankbaronia velata nov sp a putative peronosporomycete Oogonium containing multiple oospores from the lower devonian rhynie chert
Zitteliana, 2013Co-Authors: Michael Krings, Thomas N Taylor, Nora Dotzler, Carla J HarperAbstract:Spherical to pyriform microfossils containing multiple smooth-walled spherules from the Lower Devonian Rhynie chert are described as oogonia of a new fossil peronosporomycete based on congruencies in basic morphology to the polyoosporous oogonia of certain extant Saprolegniales. Because the new fossils also resemble Frankbaronia polyspora, a putative peronosporomycete described previously from the Rhynie chert, they are assigned to the fossil genus Frankbaronia and formally proposed as a new species, F. velata. Surrounding the Oogonium is a conspicuous sheath of consolidated mucilage, produced and secreted by the Oogonium during development. The discovery of F. velata adds to our understanding of the microbial diversity in early terrestrial ecosystems, and contributes to the documentation of the evolutionary history of the Peronosporomycetes.
-
A fossil peronosporomycete Oogonium with an unusual surface ornament from the Carboniferous of France.
Fungal biology, 2010Co-Authors: Michael Krings, Thomas N Taylor, Jean Galtier, Nora DotzlerAbstract:A new fossil peronosporomycete from the upper Visean (Mississippian) of France occurs as a globose Oogonium at the tip of a thin-walled hypha. The Oogonium surface is prominently ornamented by densely spaced, long and subtle, straight or once to several times furcated thread-like extensions; many possess an opaque, bulb-like swelling at base. Antheridia adpressed to the Oogonium are clavate and paragynous. This fossil represents only the third record of an unequivocal peronosporomycete from the Carboniferous, and thus provides important details about the evolutionary history of this group of organisms.
W. Wallace Martin - One of the best experts on this subject based on the ideXlab platform.
-
Two new species of Couchia parasitic in midge eggs.
Mycologia, 2000Co-Authors: W. Wallace MartinAbstract:Two new species of Couchia are described as parasites in the eggs of midges. Couchia amphora sp. nov. typically produces terminal flask-shaped zoo- sporangia with occasional secondary zoosporangia arising by basipetalous succession. Oogonia contain oospores, which usually fill the Oogonium. Couchia limnophila sp. nov. typically produces broadly ellip- soidal zoosporangia which are single and terminal, but sympodial renewal may rarely occur. Oospores of C. limnophila do not usually fill the Oogonium. The new species are contrasted with the previously de- scribed C. circumplexa which, like C. limnophila, typ- ically produces broadly ellipsoidal zoosporangia and which, like C. amphora, usually produces oogonia whose oospores fill the Oogonium. Couchia circum- plexa differs from both new species in renewing its zoosporangia by internal proliferation. Typical mor- phological forms and configurations of appressorial complexes produced by each of the three species are useful in species determination, however such use- fulness is limited by the intergradation of forms among the three species. Drawings and full descrip- tions are included to aid in identification of the new species.
Masahiko Idei - One of the best experts on this subject based on the ideXlab platform.
-
Gametogenesis and Auxospore Development in
2016Co-Authors: Masahiko Idei, Kensuke Toyoda, Keigo Osada, Tamotsu Nagumo, Shinya Sato, David G. MannAbstract:cGametogenesis and auxospore development have been studied in detail in surprisingly few centric diatoms. We studied the development of sperm, eggs and auxospores in Actinocyclus sp., a radially symmetrical freshwater diatom collected from Japan, using LM and electron microscopy of living cultures and thin sections. Actinocyclus represents a deep branch of the ‘radial centric ’ diatoms and should therefore contribute useful insights into the evolution of sexual reproduction in diatoms. Spermatogenesis was examined by LM and SEM and involved the formation of two spermatogonia (sperm mother-cells) in each spermatogonangium through an equal mitotic division. The spermatogonia produced a reduced ‘lid ’ valve, resembling a large flat scale with irregular radial thickenings. Sperm formation was merogenous, producing four sperm per spermatogonium, which were released by dehiscence of the ‘lid ’ valve. The sperm were spindle-shaped with numerous surface globules and, as usual for diatoms, the single anterior flagellum bore mastigonemes. One egg cell was produced per Oogonium. Immature eggs produced a thin layer of circular silica scales before fertilization, while the eggs were still contained within the Oogonium. Sperm were attracted in large numbers to each egg and were apparently able to contact the egg surface via a gap formed between the long hypotheca and shorter epitheca of the Oogonium and a small underlying hole in the scale-case. Auxospores expanded isodiametrically and many new scales were added to its envelope during expansion. Finally, new slightly-domed initial valves were produced at right angles to the Oogonium axis, after
-
gametogenesis and auxospore development in actinocyclus bacillariophyta
PLOS ONE, 2012Co-Authors: Masahiko Idei, Kensuke Toyoda, Keigo Osada, Tamotsu Nagumo, Shinya Sato, David G. MannAbstract:cGametogenesis and auxospore development have been studied in detail in surprisingly few centric diatoms. We studied the development of sperm, eggs and auxospores in Actinocyclus sp., a radially symmetrical freshwater diatom collected from Japan, using LM and electron microscopy of living cultures and thin sections. Actinocyclus represents a deep branch of the ‘radial centric’ diatoms and should therefore contribute useful insights into the evolution of sexual reproduction in diatoms. Spermatogenesis was examined by LM and SEM and involved the formation of two spermatogonia (sperm mother-cells) in each spermatogonangium through an equal mitotic division. The spermatogonia produced a reduced ‘lid’ valve, resembling a large flat scale with irregular radial thickenings. Sperm formation was merogenous, producing four sperm per spermatogonium, which were released by dehiscence of the ‘lid’ valve. The sperm were spindle-shaped with numerous surface globules and, as usual for diatoms, the single anterior flagellum bore mastigonemes. One egg cell was produced per Oogonium. Immature eggs produced a thin layer of circular silica scales before fertilization, while the eggs were still contained within the Oogonium. Sperm were attracted in large numbers to each egg and were apparently able to contact the egg surface via a gap formed between the long hypotheca and shorter epitheca of the Oogonium and a small underlying hole in the scale-case. Auxospores expanded isodiametrically and many new scales were added to its envelope during expansion. Finally, new slightly-domed initial valves were produced at right angles to the Oogonium axis, after a strong contraction of the cell away from the auxospore wall. At different stages, Golgi bodies were associated with chloroplasts or mitochondria, contrasting with the constancy of Golgi–ER–mitochondrion (G-ER-M) units in some other centric diatoms, which has been suggested to have phylogenetic significance. Electron-dense bodies in the vacuole of Actinocyclus are probably acidocalcisomes containing polyphosphate.
-
Early stage oogonial structure in Actinocyclus.
2012Co-Authors: Masahiko Idei, Kensuke Toyoda, Keigo Osada, Tamotsu Nagumo, Shinya Sato, David G. MannAbstract:A, B, LM. E–F, TEM. A. Peripheral focus of a fully elongated Oogonium containing a single nucleus with a nucleolus (arrow), located just beneath the girdle. Scale bar = 10 µm. B. A young Oogonium before thin sectioning: note the unequal epi- and hypothecae. Scale bar = 10 µm. C. The same Oogonium as in Fig. 5B after thin sectioning. The cell is still fully enclosed by the hypotheca and epitheca. Note a thin layer of scales (appearing as a black line) surrounding the cytoplasm, several scales being formed beneath the cell membrane (circles), and a small discontinuity in the scale layer (arrow). Within the vacuole are several bodies containing ‘frothy’ electron-dense material (double arrows), as well as smaller grey bodies that probably represent lipid. Scale bar = 10 µm. D. Enlargement of C showing a pear-shaped nucleus (with a single nucleolus) elongated towards a centrosome (arrowhead) and overlying split in the scale case (white arrow). Scale bar = 2 µm. E. Detail of the centrosome located at the tip of the nucleus and subtending many radiating microtubules. Scale bar = 1 µm. F. A peripheral part of the cell showing Golgi bodies associated with chloroplasts; note also the mitochondria and a vesicle (arrow) containing a scale beneath the cell membrane. Scale bar = 1 µm.
-
Middle stage oogonial structure in Actinocyclus.
2012Co-Authors: Masahiko Idei, Kensuke Toyoda, Keigo Osada, Tamotsu Nagumo, Shinya Sato, David G. MannAbstract:A, LM. B, D, E, TEM. C, SEM. A, B. The same elongated, dehisced Oogonium, which has split apart within the hypotheca, leaving one of the hypothecal band attached to the epitheca. Scale bars = 10 µm. B shows a complete layer of scales around the cell, scale forming vesicles (circles), and a nucleus located at the side, beneath the girdle of the Oogonium. Note the distal band attached to the inside of the epivalve (arrows). Scale bars, 10 µm. C. An Oogonium at ± the same developmental stage as A, showing a deeper hypotheca than epitheca (towards the top, lacking girdle bands) and an exposed cell covered by a siliceous layer visible between the thecae. Scale bar = 10 µm. D. Detail of the nucleus in the cell shown in Fig. 6B, showing the broken edge of the hypotheca (left), the layer of scales (two scales thick), scale-forming vesicles (arrows), and mitochondria and chloroplasts (but no Golgi bodies) surrounding the nucleus. Scale bar = 2 µm. E. Detail of scale silicadepositing vesicle (SDV), showing two membranes externally (arrowheads), representing the plasma membrane and the outer membrane of thescale SDV, and a single one internally (arrows). Note numerous closely-spaced pores in the nuclear envelope and no associated Golgi bodies. Scale bar = 0.5 µm.
-
Details of scale SDV in Actinocyclus.
2012Co-Authors: Masahiko Idei, Kensuke Toyoda, Keigo Osada, Tamotsu Nagumo, Shinya Sato, David G. MannAbstract:A–D, TEM. A. A part of Oogonium showing a Golgi body associated with a chloroplast, and a scale SDV slightly separated from a layer of scales (arrow). Scale bar = 1 µm. B. Enlargement of the scale SDV of Fig. 7A, showing the SDV membranes (arrows) and the plasma membrane (arrowheads), which in this case has separated from the Oogonium wall, probably as an artifact of specimen preparation. Note that the SDV membranes here are continuous but the silica within discontinuous. Scale bar = 0.5 µm. C. Detail of scale SDV (arrows), sectioned tangentially near its periphery, showing individual vesicle-like membrane profiles containing silica: these represent finger-like extensions of the SDV before fusion. Scale bar = 1 µm. D. Detail of a Golgi body associated with a chloroplast (therefore with chloroplast ER) and apparently producing many vesicles containing dark content (e.g. arrows). Scale bar = 1 µm.
David G. Mann - One of the best experts on this subject based on the ideXlab platform.
-
Gametogenesis and Auxospore Development in
2016Co-Authors: Masahiko Idei, Kensuke Toyoda, Keigo Osada, Tamotsu Nagumo, Shinya Sato, David G. MannAbstract:cGametogenesis and auxospore development have been studied in detail in surprisingly few centric diatoms. We studied the development of sperm, eggs and auxospores in Actinocyclus sp., a radially symmetrical freshwater diatom collected from Japan, using LM and electron microscopy of living cultures and thin sections. Actinocyclus represents a deep branch of the ‘radial centric ’ diatoms and should therefore contribute useful insights into the evolution of sexual reproduction in diatoms. Spermatogenesis was examined by LM and SEM and involved the formation of two spermatogonia (sperm mother-cells) in each spermatogonangium through an equal mitotic division. The spermatogonia produced a reduced ‘lid ’ valve, resembling a large flat scale with irregular radial thickenings. Sperm formation was merogenous, producing four sperm per spermatogonium, which were released by dehiscence of the ‘lid ’ valve. The sperm were spindle-shaped with numerous surface globules and, as usual for diatoms, the single anterior flagellum bore mastigonemes. One egg cell was produced per Oogonium. Immature eggs produced a thin layer of circular silica scales before fertilization, while the eggs were still contained within the Oogonium. Sperm were attracted in large numbers to each egg and were apparently able to contact the egg surface via a gap formed between the long hypotheca and shorter epitheca of the Oogonium and a small underlying hole in the scale-case. Auxospores expanded isodiametrically and many new scales were added to its envelope during expansion. Finally, new slightly-domed initial valves were produced at right angles to the Oogonium axis, after
-
gametogenesis and auxospore development in actinocyclus bacillariophyta
PLOS ONE, 2012Co-Authors: Masahiko Idei, Kensuke Toyoda, Keigo Osada, Tamotsu Nagumo, Shinya Sato, David G. MannAbstract:cGametogenesis and auxospore development have been studied in detail in surprisingly few centric diatoms. We studied the development of sperm, eggs and auxospores in Actinocyclus sp., a radially symmetrical freshwater diatom collected from Japan, using LM and electron microscopy of living cultures and thin sections. Actinocyclus represents a deep branch of the ‘radial centric’ diatoms and should therefore contribute useful insights into the evolution of sexual reproduction in diatoms. Spermatogenesis was examined by LM and SEM and involved the formation of two spermatogonia (sperm mother-cells) in each spermatogonangium through an equal mitotic division. The spermatogonia produced a reduced ‘lid’ valve, resembling a large flat scale with irregular radial thickenings. Sperm formation was merogenous, producing four sperm per spermatogonium, which were released by dehiscence of the ‘lid’ valve. The sperm were spindle-shaped with numerous surface globules and, as usual for diatoms, the single anterior flagellum bore mastigonemes. One egg cell was produced per Oogonium. Immature eggs produced a thin layer of circular silica scales before fertilization, while the eggs were still contained within the Oogonium. Sperm were attracted in large numbers to each egg and were apparently able to contact the egg surface via a gap formed between the long hypotheca and shorter epitheca of the Oogonium and a small underlying hole in the scale-case. Auxospores expanded isodiametrically and many new scales were added to its envelope during expansion. Finally, new slightly-domed initial valves were produced at right angles to the Oogonium axis, after a strong contraction of the cell away from the auxospore wall. At different stages, Golgi bodies were associated with chloroplasts or mitochondria, contrasting with the constancy of Golgi–ER–mitochondrion (G-ER-M) units in some other centric diatoms, which has been suggested to have phylogenetic significance. Electron-dense bodies in the vacuole of Actinocyclus are probably acidocalcisomes containing polyphosphate.
-
Early stage oogonial structure in Actinocyclus.
2012Co-Authors: Masahiko Idei, Kensuke Toyoda, Keigo Osada, Tamotsu Nagumo, Shinya Sato, David G. MannAbstract:A, B, LM. E–F, TEM. A. Peripheral focus of a fully elongated Oogonium containing a single nucleus with a nucleolus (arrow), located just beneath the girdle. Scale bar = 10 µm. B. A young Oogonium before thin sectioning: note the unequal epi- and hypothecae. Scale bar = 10 µm. C. The same Oogonium as in Fig. 5B after thin sectioning. The cell is still fully enclosed by the hypotheca and epitheca. Note a thin layer of scales (appearing as a black line) surrounding the cytoplasm, several scales being formed beneath the cell membrane (circles), and a small discontinuity in the scale layer (arrow). Within the vacuole are several bodies containing ‘frothy’ electron-dense material (double arrows), as well as smaller grey bodies that probably represent lipid. Scale bar = 10 µm. D. Enlargement of C showing a pear-shaped nucleus (with a single nucleolus) elongated towards a centrosome (arrowhead) and overlying split in the scale case (white arrow). Scale bar = 2 µm. E. Detail of the centrosome located at the tip of the nucleus and subtending many radiating microtubules. Scale bar = 1 µm. F. A peripheral part of the cell showing Golgi bodies associated with chloroplasts; note also the mitochondria and a vesicle (arrow) containing a scale beneath the cell membrane. Scale bar = 1 µm.
-
Middle stage oogonial structure in Actinocyclus.
2012Co-Authors: Masahiko Idei, Kensuke Toyoda, Keigo Osada, Tamotsu Nagumo, Shinya Sato, David G. MannAbstract:A, LM. B, D, E, TEM. C, SEM. A, B. The same elongated, dehisced Oogonium, which has split apart within the hypotheca, leaving one of the hypothecal band attached to the epitheca. Scale bars = 10 µm. B shows a complete layer of scales around the cell, scale forming vesicles (circles), and a nucleus located at the side, beneath the girdle of the Oogonium. Note the distal band attached to the inside of the epivalve (arrows). Scale bars, 10 µm. C. An Oogonium at ± the same developmental stage as A, showing a deeper hypotheca than epitheca (towards the top, lacking girdle bands) and an exposed cell covered by a siliceous layer visible between the thecae. Scale bar = 10 µm. D. Detail of the nucleus in the cell shown in Fig. 6B, showing the broken edge of the hypotheca (left), the layer of scales (two scales thick), scale-forming vesicles (arrows), and mitochondria and chloroplasts (but no Golgi bodies) surrounding the nucleus. Scale bar = 2 µm. E. Detail of scale silicadepositing vesicle (SDV), showing two membranes externally (arrowheads), representing the plasma membrane and the outer membrane of thescale SDV, and a single one internally (arrows). Note numerous closely-spaced pores in the nuclear envelope and no associated Golgi bodies. Scale bar = 0.5 µm.
-
Details of scale SDV in Actinocyclus.
2012Co-Authors: Masahiko Idei, Kensuke Toyoda, Keigo Osada, Tamotsu Nagumo, Shinya Sato, David G. MannAbstract:A–D, TEM. A. A part of Oogonium showing a Golgi body associated with a chloroplast, and a scale SDV slightly separated from a layer of scales (arrow). Scale bar = 1 µm. B. Enlargement of the scale SDV of Fig. 7A, showing the SDV membranes (arrows) and the plasma membrane (arrowheads), which in this case has separated from the Oogonium wall, probably as an artifact of specimen preparation. Note that the SDV membranes here are continuous but the silica within discontinuous. Scale bar = 0.5 µm. C. Detail of scale SDV (arrows), sectioned tangentially near its periphery, showing individual vesicle-like membrane profiles containing silica: these represent finger-like extensions of the SDV before fusion. Scale bar = 1 µm. D. Detail of a Golgi body associated with a chloroplast (therefore with chloroplast ER) and apparently producing many vesicles containing dark content (e.g. arrows). Scale bar = 1 µm.
