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Achnanthes longipes. Fig. 3. Abundant auxosporulation (arrows) following intercrossing between clones in mixed culture. Fig. 4. Chain of abnormal cells (a-f) produced after vegetative cell enlargement in clone 9. Several cells (especially a, b) are unusually elongate along the pervalvar axis and in some (c, d) the cell contents have degenerated ; in cell b the protoplast has contracted away from the frustule (arrow). Note that no stalk is present. Fig. 5. A chain of normal cells with its stalk (arrow). Scale bars represent : Fig. 3, 100 µm; Figs 4 and 5, 20 µm.

Achnanthes longipes. Fig. 3. Abundant auxosporulation (arrows) following intercrossing between clones in mixed culture. Fig. 4. Chain of abnormal cells (a-f) produced after vegetative cell enlargement in clone 9. Several cells (especially a, b) are unusually elongate along the pervalvar axis and in some (c, d) the cell contents have degenerated ; in cell b the protoplast has contracted away from the frustule (arrow). Note that no stalk is present. Fig. 5. A chain of normal cells with its stalk (arrow). Scale bars represent : Fig. 3, 100 µm; Figs 4 and 5, 20 µm.

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Article
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Monoecious, bisexual and unisexual clones of Achnanthes longipes were isolated from the Black Sea and studied in laboratory culture. Clones differed in their growth characteristics : in monoecious clones the cells formed tufted aggregations while in other clones they were more dispersed. Bisexual and unisexual clones exhibited intraclonal (monoecio...

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Context 1
... was a further difference between group A clones, which will henceforth be called monoecious clones, and the essentially non-monoecious group B clones. This concerned the distribution of cells in culture. Solitary cells and short, ribbon-like chains of 4-8 cells (Fig. 5) were produced by all clones, either attached to the Petri dish or motile. In non-monoecious clones, attached cells and colonies were dispersed more or less evenly across the substratum (Fig. 1), while in monoecious clones they often formed tufts, in which the mucilage stalks were clustered close together (Fig. 2). Similar aggregations ...
Context 2
... enlargement, seems to bring about genetic or cytological damage, producing abnormal development. This was observed in clones 5 and 9 (monoecious and unisexual, respectively). Immediately after vegetative enlargement of these clones, new sub- clones were isolated, in which most of the cells became strongly elongate along the pervalvar axis ( Fig. 4 ; contrast Fig. 5). The cell contents seemed disorganized and no stalks were formed. Following division, daughter cells generally did not separate but formed very long, twisted, ribbon-like colonies. Only a few cells were solitary and ...

Citations

... Принимая во внимание принцип подвижности/неподвижности гамет, можно ожидать, что у тех двудомных видов, у которых гаметы как мужского, так и женского гаметангиев одинаково подвижны (IB и IC типы по Гайтлеру), либо подвижна только одна из гамет в гаметангии (тип IA1, физиологическая транс-анизогамия), внутриклоновое воспроизведение будет наблюдаться в обоих скрещивающихся клонах. Схема скрещивания, описанная для двудомной (Рощин, 1994) и транс-анизогамной (Chepurnov, Mann, 1997) N. lanceolata подтверждает это предположение. Было установлено, что у этого вида клоны обоих полов способны к нечастому внутриклоновому воспроизведению (Рощин, 1994). ...
... Очень сложная система скрещивания была описана у Achnanthes longipes Chepurnov, Mann, 1997. Обнаружены "однодомные", "бисексуальные" и "однополые" клоны. ...
... Tabularia fasciculata (C. A. Agardh) Williams et Round,24,26,28,40,42,43,44,56,58,59,60,62,63,68,69,83,89,91,92,98,100 Tabularia tabulata (C. A. Agardh) Snoeijs,25,26,28,38,40,42,43,44,51,55,59,62,63,68,70,79,83,91 Compère,25,26,28,40,42,43,44,49,53,62,63,68,70,72,83,95,96 Примечание. 1) -неоогамные типы воспроизведения обозначены согласно классификации Л. Гайтлера ; оогамия центрических не во всех случаях подтверждена в цитируемой оригинальной работе (отсутствует наблюдение сперматогенеза); 2) -буквенные обозначения соответствуют границам фаз жизненного цикла так, как указано на рисунке 8; 3) -коэффициент восстановления размеров клеток (соотношение между размером родительских клеток и размером образующихся инициальных клеток); принято допущение, что меньшие гаметангии дают инициальные клетки меньшего размера и наоборот; 4) -у центрических был измерен размер оогониев; 5) -инбредные клоны обнаруживали иные типы (детали см. в работе [Chepurnov, Mann, 1997 Subrahmanyan, 1946;von Stosch & Drebes, 1964;Drebes, 1974;Idei et Drebes, 1974von Stosch, 1982 Thwaites, 1848;Karsten, 1928;Skabichevskij, 1929;Cleve-Euler, 1951;Поповская, Скабичевский, 1970;Gibson & Fitzsimons, 1990;Jewson, 1992b Karsten, 1928;Cupp, 1943;Drebes, 1974;Barron et al., 1989;Crawford, 1995;Hoppenrath et al., 2009 Coscinodiscus -apiculatus Ehrenberg -asteromphalus Ehrenberg -biconicus Van Breemen Hofker, 1928;Holmes, , 1967Drebes, , 1974Findlay, 1969;Werner, 1971;Schmid, 1994 Smith, 1856;Karsten, 1897;Müller, 1906;Hustedt, 1923;Schmidt, 1923;Cholnoky, 1933;Rieth, 1940Rieth, , 1953Cleve-Euler, 1951;Bruckmayer-Berkenbusch, 1954;von Stosch, 1951;Erben, 1959;Migita, 1967aMigita, , 1967cDrebes, 1974;Crawford, 1974Crawford, , 1975Рощин, 1986a, 1990bКустенко, 1991;Idei & Chihara, 1992 Karsten, 1928;Cupp, 1943;Drebes, 1974 Pseudosolenia -calcar-avis (Schultze) B. G. Sundström § 1 Кустенко, 1991 Rhizosolenia -bergonii H. Peragallo § -hebetata f. semispina (Hensen) Gran -setigera Brightwell § -styliformis T. Brightwell 4 Cupp, 1943;Ramsfjell, 1959;Drebes, 1974Belt et al., 2002 Stephanopyxis -palmeriana (Greville) Grunow § -turris (Greville) Ralfs § 2 von Stosch & Drebes, 1964;Drebes, , 1969Drebes, , 1974Drebes, , 1979Steele, 1967 Bachmann, 1903;Iyengar & Subrahmanyan, 1944;Geitler, 1952a;Rao, 1971; Hoops Cupp, 1943;Migita, 1967aMigita, , 1967bКустенко & Рощин, 1974;Hoppenrath et al., 2009;Godhe et Cupp, 1943;Drebes, 1974Drebes, , 1979Schmid, 1984;Horner, 2002;Mills & Kaczmarska, 2006 von Stosch, 1982;Chepurnov et al., 2004 Bacteriastrum -hyalinum Lauder § 1 Drebes, 1967Drebes, , 1972von Stosch, 1982;Hoppenrath et al., 2009 Продолжение таблицы П.2 ...
Book
Full-text available
The monograph concerns items related to reproductive biology of diatoms including such sections as sex and principles of sex determination in diatoms, their life cycles, patterns of sexual reproduction, sex distribution and mating systems, factors inducing sexual reproduction, inheritance coupled with sex, reproductive boundaries and distribution of diatoms, phylogeny of diatoms in the light of reproductive characteristics, etc. The book is dedicated for specialists in algology, hydrobiolody, reproductive biology; for students and graduate students in the relevant areas of study. (in Russian)
... According to modern views, reproduction with gametes similar in morphology and behavior that form in different gametangia, is referred to as isogamy [29] and belongs to the IC category in Geitler's system [19]. This type of sexual process was previously described, e.g., from Nitzschia reversa W. Smith sensu Krammer & Lange-Bertalot [29], Achnanthes longipes [7], Navicula protracta Grunow [28], and from a number of other species of raphid diatoms. ...
... paludosa are isogamous morphologically (spherical in shape) and behaviorally (do not show motility). Complete isogamy is also characteristic of Amphora arcus Gregory [30,40], Achnanthes longipes [7], and Haslea ostrearia (Bory) Simonsen [15]. Members of the genus Nitzschia exhibit complete isogamy like that in N. reversa [29], behavioral anisogamy with morphological isogamy as in N. recta Hantzsch ex Rabenh [27], and a combination of morphological and behavioral anisogamy as in N. longissima (Brébisson ex Kützing) Grunow [13]. ...
... In some species (A. longipes, N. longissima, etc.), homothallic reproduction may occur along with heterothallism [7,13]. ...
... Heterothallic and homothallic behaviour have been demonstrated in different species of Sellaphora and Pseudo-nitzschia (see Poulíčková et al. 2015, andQuijano-Scheggia et al. 2009a, respectively), and both allomictic and automictic behaviour in different species of Neidium, Sellaphora, and Nitzschia Poulíčková et al. 2015;Poulíčková 2008a;Rovira et al. 2015). Moreover, complex controls on mating behaviour are evident in Achnanthes longipes, where clones can be 'monoecious', 'bisexual' and 'unisexual' (Chepurnov & Mann 1997, 1999. ...
Chapter
This chapter contains sections titled:IntroductionCentric DiatomsPennate Diatom Life Cycles and ReproductionAuxospore Development and StructureInduction of Sexual ReproductionAcknowledgments
... According to modern views, reproduction with gametes similar in morphology and behavior that form in different gametangia, is referred to as isogamy [29] and belongs to the IC category in Geitler's system [19]. This type of sexual process was previously described, e.g., from Nitzschia reversa W. Smith sensu Krammer & Lange-Bertalot [29], Achnanthes longipes [7], Navicula protracta Grunow [28], and from a number of other species of raphid diatoms. ...
... paludosa are isogamous morphologically (spherical in shape) and behaviorally (do not show motility). Complete isogamy is also characteristic of Amphora arcus Gregory [30,40], Achnanthes longipes [7], and Haslea ostrearia (Bory) Simonsen [15]. Members of the genus Nitzschia exhibit complete isogamy like that in N. reversa [29], behavioral anisogamy with morphological isogamy as in N. recta Hantzsch ex Rabenh [27], and a combination of morphological and behavioral anisogamy as in N. longissima (Brébisson ex Kützing) Grunow [13]. ...
... In some species (A. longipes, N. longissima, etc.), homothallic reproduction may occur along with heterothallism [7,13]. ...
Article
Sexual reproduction and the life cycle of the marine pennate diatom Entomoneis cf. paludosa are described. The reproduction in this species is characterized by morphological and behavioral isogamy. Two gametangia are involved in the sexual process, each of which produces two gametes.
... An aliquot of the Clot lagoon sample was spread over the surface of a 2% agar plate (made with 35 psu seawater) and a monoclonal culture of the new species (Nit952CAT) was established by isolating a single cell from the agar surface by micropipette. The culture was maintained in a 1:1 mixture of WC (Guillard & Lorenzen, 1972) and R (Chepurnov & Mann, 1997) medium. ...
Article
A previously unknown member of the Bacillariaceae was discovered almost simultaneously in four different brackish coastal wetlands on the Atlantic and Mediterranean coasts of the Iberian Peninsula. It appears to tolerate a wide range of salinities but was never common in samples where it occurred. The frustules were consistently hantzschioid (i.e. with the raphe systems always on the same side of the frustule) and the valve outline was asymmetrical about the apical plane, two features that have until recently been considered characteristic of Hantzschia. Molecular phylogenies based on rbcL and LSU rDNA indicated, however, that the new species does not belong in Hantzschia but among the several disparate lineages that comprise the paraphyletic genus Nitzschia. This finding, coupled with the recent discovery of other diatoms with constant hantzschioid symmetry but with a morphology very similar to the type species of Nitzschia, is discussed in relation to the status and characterization of Hantzschia as an independent genus. It is concluded that, while a core of hantzschioid species may exist that can be classified together, corresponding to the traditional understanding of the genus Hantzschia, there is no single morphological feature common to all of them that can be used to diagnose the group and differentiate it from the various hantzschioid lineages that are separate from true Hantzschia and currently placed in e.g. Nitzschia or Cymbellonitzschia. Testing whether a hantzschioid species does or does not belong to Hantzschia will in many cases require molecular evidence. Although the new coastal species does not belong to the same lineage as the type species of Nitzschia, N. sigmoidea, it is described for the moment as N. varelae Carballeira, D.G. Mann & Trobajo, sp. nov., until there is a better understanding of generic limits in the Bacillariaceae following a wider molecular and morphological survey of that family.
... Smith) Okuno (SZCZP665) from Sao Miguel Island in Azores. In still other monoraphid diatoms such as Achnanthes longipes the breeding system is much more complex than in Schizostauron, with differentiation between monoecious, unisexual and bisexual clones (Chepurnov & Mann 1997). ...
... In its sexual reproduction, Schizostauron sp1 is similar to several other monoraphid diatoms, since two gametes per gametangium are normally formed in Achnanthes (Geitler 1932;Mizuno 1994;Roshchin 1994), Achnanthidium, Planothidium, Eucocconeis and Lemnicola (Geitler 1932(Geitler , 1958b(Geitler , 1973(Geitler , 1977(Geitler , 1980, referred to as 'Achnanthes'). Chepurnov & Mann (1997) reported that the gametangia sometimes produce only a single gamete in Achnanthes. Here, however, the 'reduced type' of auxosporulation (Geitler's type IIA2a) was exhibited by a minority of the clones, and in most cases auxosporulation was of the 'normal type', where both gametangia produced two gametes. ...
Article
The focus of this paper is the sexual reproduction and phylogeny of Schizostauron Grunow, which were studied using clonal cultures isolated from the Indian Ocean coast of Mozambique near Tofo and Bazaruto. Taxa of Schizostauron were characterized by light and electron microscopy and a phylogeny derived from three genes (rbcL, psbC and short subunit). Schizostauron was established in the second half of the 19th century, then forgotten, with its taxa included in Cocconeis or Achnanthes sensu lato. Schizostauron, together with Astartiella and perhaps also Kolbesia and Karayevia, seems to form a third lineage of monoraphid diatoms, which are related to biraphid diatoms belonging to the Stauroneidaceae and Parlibellus, but not to the two other lineages of monoraphids (Achnanthes and the Achnanthidiaceae-Cocconeidaceae group). In culture, size reduction was followed by release of gametes and auxosporulation in mixtures of clones. Despite some morphological differences, four clones from the Bazaruto population proved to be sexually compatible, one of the clones being sexually compatible with the three others. Before gametogenesis, cells gathered in groups of two to eight through active movement. Some groups of cells surrounded themselves by weakly visible mucilage. Reproduction was isogamous morphologically, and apparently also behaviourally. Growing auxospores were surrounded by the empty irregularly arranged frustules of parental cells. In numerous aspects the pattern of sexual reproduction of Schizostauron is similar to that of Achnanthes sensu stricto. The rbcL identity matrix (IDM) for sexually compatible clones ranged between 0.998 and 0.984. One clone derived from the Tofo population had an IDM below 0.900 and was sexually isolated from the remaining clones. A description of Schizostauron davidovichiorum sp. Nov. is provided.
... Another dominant hypothesis proposes that mating types are important because they promote outbreeding and prevent same clone fusions [13]. This hypothesis has a strong appeal, as inbreeding can indeed be detrimental in many higher animals and plants [14], and high levels of inbreeding are harmful in some protists [15]. However, many protists that have a diploid vegetative stage are heterozygous for mating type loci in their adult state. ...
Article
Full-text available
While sex requires two parents, there is no obvious need for them to be differentiated into distinct mating types or sexes. Yet this is the predominate state of nature. Here, we argue that mating types could play a decisive role because they prevent the apparent inevitability of self-stimulation during sexual signalling. We rigorously assess this hypothesis by developing a model for signaller-detector dynamics based on chemical diffusion, chemotaxis and cell movement. Our model examines the conditions under which chemotaxis improves partner finding. Varying parameter values within ranges typical of protists and their environments, we show that simultaneous secretion and detection of a single chemoattractant can cause a multifold movement impediment and severely hinder mate finding. Mutually exclusive roles result in faster pair formation, even when cells conferring the same roles cannot pair up. This arrangement also allows the separate mating types to optimize their signalling or detecting roles, which is effectively impossible for cells that are both secretors and detectors. Our findings suggest that asymmetric roles in sexual chemotaxis (and possibly other forms of sexual signalling) are crucial, even without morphological differences, and may underlie the evolution of gametic differentiation among both mating types and sexes. © 2015 The Authors.
... Our work was based on the biological criterion, which allows one to obtain objective confirmation of the conspecificity of the studied clones. The reproduc tive compatibility of the 0.1117 E and 0.1119 I clones with the 0.1119 B, 0.1119 C, 0.1119 G, 0.1119 L, 0.1119 P, 0.1119 W, and 0.1125 B clones indicates, first, the specific unity of all the obtained clones and, second, the dioecy that determines the heterothallic mode of reproduction of this species, which was previ ously determined in many other species among pen nate diatoms [2,3,12,15,16,18]. ...
Article
Full-text available
The inter- and intraclonal variability of the morphology and ultrastructure of the frustule of Nitzschia rectilonga Takano, 1983 was investigated. This study showed a wider intraclonal variability than in the diagnosis of the species. An emended diagnosis of the species is provided; a twofold reduction in the density of striae that are visible under a light microscope was found compared to electron-microscope images.
... Other mechanisms that affect cell size of diatoms like vegetative cell enlargement (von Stosch 1965), vegetative auxosporulation (Nagai et al. 1995;Nagai & Imai 1997;Sabbe et al. 2004), apomixis or abrupt cell size reduction (Locker 1950;von Stosch 1965;Chepurnov & Mann 1997;Chepurnov et al. 2004) could also not be ruled out as possible explanation for the cell size differences observed in this study as bacteria may possibly serve as an additional external trigger for one of these mechanisms. ...
Article
Vegetative cell division in diatoms often results in a decreased cell size of one of the daughter cells, which during long-term cultivation may lead to a gradual decrease of the mean cell size of the culture. To restore the initial cell size, sexual reproduction is required, however, in many diatom cultures sexual reproduction does not occur. Such diatom cultures may lose their viability once the average size of the cells falls below a critical size. Cell size reduction therefore seriously restrains the long-term stability of many diatom cultures. In order to study the bacterial influence on the size diminution process, we observed cell morphology and size distribution of the diatoms Achnanthidium minutissimum, Cymbella affiniformis and Nitzschia palea for more than two years in bacteria-free conditions (axenic cultures) and in cultures that contain bacteria (xenic cultures). We found considerable morphological aberrations of frustule microstructures in A. minutissimum and C. affiniformis when cultivated under axenic conditions compared to the xenic cultures. These variations comprise significant cell length reduction, simplification and rounding of the frustule contour and deformation of the siliceous cell walls, features that are normally found in older cultures shortly before they die off. In contrast, the xenic cultures were well preserved and showed less cell length diminution. Our results show that bacteria may have a fundamental influence on the stability of long-term cultures of diatoms.
... Other mechanisms which affect cell size of diatoms like vegetative cell enlargement (von Stosch 1965), vegetative auxosporulation (Nagai et al. 1995;Nagai and Imai 1997;, apomixis or abrupt cell size reduction (Locker 1950;von Stosch 1965;Chepurnov and Mann 1997;Chepurnov et al. 2004) could also not be ruled out as possible explanation for the cell size differences observed in this study as bacteria may possibly serve as an additional external trigger for one of these mechanisms. ...