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Fruit body-forming protists: Myxomycetes and Myxomycete-like organisms Acrasia, Eumycetozoa
... As such, protosteloid amoebae are usually considered microbial predators. Following this predatory amoeboid stage, they eventually mature to form clear to transparent fruiting bodies that typically consist of one to eight spores held by a non-septate needle-like stalk (Spiegel et al. 2007, Schnittler et al. 2012. Under certain conditions (i.e., environmental condition disturbance), the protosteloid amoebae fruiting bodies undergo spore dispersal until such conditions improve, whereas the spores will be able to germinate fresh protosteloid amoebae again . ...
... In fact, up to this date, no single record of its ecology in the Philippines and in tropical Southeast Asia has been reported. Thus, this leaves a wide gap regarding protosteloid amoebae diversity and distribution within the Eumycetozoan group (Spiegel et al. 2007, Schnittler et al. 2012). Therefore, the primary objective of this study is to assess for the first time the diversity and distribution of protosteloid amoebae across varying elevational belts, two different leaf litter types, and aspect or slope direction of a mountain using Mt. ...
... Для него характерны отрицательный фото-и положительный гидро-и трофотаксис. При неблагоприятных условиях миксамебы и жгутиконосные клетки образуют микроцисты, тогда как плазмодий превращается в склероций, состоящий из многоядерных сферул, или макроцист (Schnittler et al., 2012;Keller et al., 2022). Для миксомицетов характерен смешанный тип питания. ...
... Миксомицеты -одна из немногих групп протистов, представители которой формируют спорофоры, которые можно длительно хранить в гербариях (Schnittler et al., 2012;Stephenson, Schnittler, 2017). Большинство видов имеет сравнительно разнообразную морфологию структур спорофоров и спор, что позволило использовать их признаки для построения традиционной "морфологической" системы миксомицетов (Martin, 1949(Martin, , 1960Krzemieniewska, 1960;Martin, Alexopoulos, 1969;Nannenga-Bremekamp, 1974, 1991Farr, 1976;Martin et al., 1983;Novozhilov, 1993;Lado, Pando, 1997;Neubert et al., 1993Neubert et al., , 1995Neubert et al., , 2000Poulain et al., 2011aPoulain et al., , 2011bGmoshinskiy et al., 2021). ...
... Для него характерны отрицательный фото-и положительный гидро-и трофотаксис. При неблагоприятных условиях миксамебы и жгутиконосные клетки образуют микроцисты, тогда как плазмодий превращается в склероций, состоящий из многоядерных сферул, или макроцист (Schnittler et al., 2012;Keller et al., 2022). Для миксомицетов характерен смешанный тип питания. ...
... Миксомицеты -одна из немногих групп протистов, представители которой формируют спорофоры, которые можно длительно хранить в гербариях (Schnittler et al., 2012;Stephenson, Schnittler, 2017). Большинство видов имеет сравнительно разнообразную морфологию структур спорофоров и спор, что позволило использовать их признаки для построения традиционной "морфологической" системы миксомицетов (Martin, 1949(Martin, , 1960Krzemieniewska, 1960;Martin, Alexopoulos, 1969;Nannenga-Bremekamp, 1974, 1991Farr, 1976;Martin et al., 1983;Novozhilov, 1993;Lado, Pando, 1997;Neubert et al., 1993Neubert et al., , 1995Neubert et al., , 2000Poulain et al., 2011aPoulain et al., , 2011bGmoshinskiy et al., 2021). ...
Myxomycetes are amoeboid fungus-like organisms (Amoebozoa) with a unique life cycle characterized by a great morphological diversity of fruiting bodies. Due to the similarity of these structures to the fruiting bodies of some representatives of Ascomycota and Basidiomycota, myxomycetes have been classified as fungi since the first known scientific description in 1654. Only in the XIX century, when their life cycle was studied, the difference of this group from fungi became clear. During the same period, microscopic structures of fruiting bodies, as well as ornamentation of the spore surface, began to be considered as diagnostic features. Due to this, in the period from the end of XIX to the middle of XX century, a rather stable system was formed. However, as further studies have shown, both macro- and micromorphological characters are often quite variable, depend on environmental conditions, and often result from a convergent evolution, which causes difficulties in defining species and taxonomic units of higher ranks. Since the first decade of the 21st century, thanks to the development of molecular genetic methods and accumulation of data on nucleotide sequences of marker genes together with the improvement of microscopic studies, it has been possible to obtain data on the evolutionary relationships of different groups of myxomycetes. A milestone in this process was the publication of the first phylogenetic system of myxomycetes in 2019. This work was the starting point for a number of studies on the relationships of different groups of myxomycetes at a lower taxonomic level. Thus, there has been a surge in the number of studies that bring us closer to constructing a natural system. The latest iteration of the myxomycete system, incorporating all modifications and enhancements as of June 2024, is presented.
Миксомицеты (Myxomycetes)-амебоидные грибообразные организмы (Amoebozoa) с уникальным жизненным циклом, характеризующиеся большим морфологическим разнообразием спорофоров. Благодаря схожести этих структур с плодовыми телами некоторых представителей отделов Ascomycota и Basidiomycota, с момента первого известного научного описания в 1654 г. миксомицеты относили к грибам. Только в XIX в., когда удалось установить особенности их жизненного цикла, стала понятна обособленность этой группы от грибов. В результате с конца XIX до середины XX вв. сложилась достаточно стабильная таксономическая система, основанная главным образом на морфологических признаках спорофоров и спор. Однако было показано, что эти признаки довольно изменчивы и зависят от условий окружающей среды, а также могут быть результатом конвергентной эволюции. Это часто вызывает затруднения при идентификации видов и таксонов более высокого ранга. В первой декаде XXI в., благодаря развитию молекулярно-генетических и микроскопических методов, а также накоплению данных о нуклеотидных последовательностях маркерных генов, удалось получить первые данные об эволюционных взаимоотношениях ряда таксонов. Знаковой вехой развития систематики миксомицетов стала публикация в 2019 г. первой филогенетической системы. В настоящее время продолжаются попытки построения филогений различных таксонов миксомицетов и поиски их соответствия с системами, построенными на морфологических признаках. В работе приводится вариант системы миксомицетов с учетом всех изменений и дополнений по состоянию на июнь 2024 года. Ключевые слова: история микологии, маркерные гены, морфология, таксономия, Amoebozoa.
... The Myxomycetes are typically divided into six orders Ceratiomyxales, Echinosteliales, Liceales, Trichiales, Physarales and Stemonitales (Schnittler & Spiegel 2012). Stalk structure shows different characteristics in different taxonomic groups. ...
... The current species concept for myxomycetes is based almost entirely upon morphological features of the fruiting bodies and their spores, which allow identification to the species level (Lister and Lister, 1925;Martin and Alexopoulos, 1969;Schnittler and Mitchell, 2000;Schnittler et al., 2012;Stephenson, 2011). Since trophic stages of myxomycetes (amoeboflagellates and plasmodia) display little or no meaningful taxonomic characters, studies of fruiting bodies from field collections or moist chamber cultures are usually the only way to tell species apart. ...
In this chapter, the results obtained from recent studies of myxomycete ecology are discussed, with special emphasis on their distribution patterns in particular habitats, the relationships that exist between myxomycetes and other organisms, and the effect of disturbance events on myxomycete communities. It is important to note that most of the available data are based on collections of fruiting bodies, which probably represent (in a literal sense) only the tip of the iceberg, since it is possible that these reflect only a minor fraction of the real diversity of myxomycetes in a particular habitat. Therefore it appears unlikely that a single method will be universally applicable for assessing myxomycete diversity in all habitats and on all substrates. The approaches, techniques, and their potential limitations are discussed herein, along with recent advances (e.g., moist chamber cultures, environmental PCR, metagenomics, and barcoding attempts) that have been applied to studies of myxomycete ecology and will undoubtedly increase our understanding of myxomycete communities in the future.
... The myxomycetes, so-called plasmodial slime moulds, are protists characterised by a peculiar life cycle with an alternative amoeboflagellate stage, a multinuclear plasmodium (two distinct trophic stages), and a macroscopically recognisable sporophore bearing spores (reproductive sporocarpic stage) (for details, see Everhart and Keller 2008;Schnittler et al. 2012;Stephenson and Schnittler 2017). Currently, myxomycetes are considered undoubted members of the supergroup (kingdom) Amoebozoa (Adl et al. 2012;Baldauf et al. 2000;Kang et al. 2017;Pawlowski 2014). ...
Myxomycetes is one of the largest groups of protists belonging to Amoebozoa, with ca 1,000 species recognised and more than 4,000 names in use. Historically, myxomycetes were considered fungi or protozoans which, however, fell under the provisions of the former International Code of Botanical Nomenclature (ICBN), currently the International Code of Nomenclature for algae, fungi, and plants (ICN). Attempts to apply the International Code of Zoological Nomenclature (ICZN) to myxomycetes were rare and inconsistent; thus, we argue that Myxomycetes is not a truly ambiregnal group (i.e. one falling under both Codes). Recently, nomenclatural novelties within Myxomycetes have been proposed using ICZN rules, and the application of zoological orthography to myxomycete higher-level taxa in the recent amoebozoan phylogenies is increasingly common. We summarise the consequences of application of either ICN or ICZN to Myxomycetes. In our opinion, nomenclatural stability within Myxomycetes is best served by strict application of ICN. Either treating myxomycetes as falling under ICZN or considering them an ambiregnal group would cause serious nomenclatural instability, mainly owing to the incompatibility of the two Codes as to the date of the starting point of nomenclature and to the appearance of numerous homonyms.
... With recent advances in phylogeny (see review in Schnittler et al. 2012), it became clear that the classical system of myxomycetes, consisting of five orders (Echinosteliales, Liceales, Trichiales, Physarales, Stemonitales and the unique genus Ceratiomyxa) cannot be maintained. Current research has revealed Ceratiomyxa to be indeed a sister group to all other myxomycetes. ...
The coprophilous myxomycete Kelleromyxa fimicola (Dearn. & Bisby) Eliasson was first described in 1929 as Licea fimicola Dearn. & Bisby. Based on the superficial resemblance of its sporocarps to those of Licea biforis, the species was placed within the Liceales, an order assigned by molecular phylogenies to the bright-spored clade of myxomycetes. However, detailed studies of the morphology and life cycle of K. fimicola revealed several characters of the dark-spored order Physarales. To elucidate the systematic position of Kelleromyxa, we obtained three partial and one complete sequence of the SSU rDNA, which demonstrated a clear relationship of K. fimicola to the order Physarales. However, the obtained sequences are not closely related to any of the two known families of Physarales, supporting the erection of a monotypic family for this species. Along with morphological observations, our data support the exclusion of K. fimicola from the order Liceales and placement among the order Physarales within the dark-spored clade of myxomycetes.
The Volyn biota, fossilized organisms with a minimum age of 1.5 Ga, were found in cavities in granitic pegmatites from the Korosten Pluton, NW Ukrainian shield. Fossilization was due to an influx of hydrothermal fluorine-rich waters, which silicified the outermost part of the organisms, thus preserving the 3D morphology. Details of the morphology (investigated by scanning electron microscopy) show that the majority of the specimens are filamentous, of a large variety with diameters ranging from ∼ 10 to ∼ 200 µm, thin filaments with typical branching and thick filaments with ball-shaped outgrowths and dented surface. Filaments can be straight or conical, curvilinear, or strongly curved, up to millimeters in length, some with a central channel. Some filaments show indications of segmentation and are grown as sessile organisms onto substrate; others show both intact ends, indicating a non-sessile, free-living lifestyle. Objects with flaky morphology and agglutinating filaments are interpreted as fossil biofilms. Other objects are hollow and show a large variety of forms; spherical objects are scarce. Infrared spectroscopy indicates the presence of chitosan in one filament type, electron microprobe analysis of nanometer-sized inclusions in filaments identified the presence of Bi(Te,S) minerals, and both observations are compatible with the interpretation as fungi-like organisms. Stable C- and N-isotope data of bulk samples are in the range of -31 ‰ to -47 ‰ δ13C and of +3 ‰ to +10 ‰ δ15N, indicating possible methanogens as part of the subsurface microecosystem. The Volyn biota indicate that at 1.5 Ga complex forms of life existed in the continental deep biosphere, well above the microscopic level, including fungi-like organisms resembling eukaryotes.
Neben den Echten Pilzen (Fungi) gibt es weitere Organismen, die wie Pilze aussehen, aber nicht zum Verwandtschaftskreis der Echten Pilze gehören. Wie Echte Pilze bilden sie Hyphen oder kleine Fruchtkörper mit Sporen. Diese pilzähnlichen Organismen wurden früher als Pilze betrachtet, bis abweichende morphologische Merkmale und molekulare Sequenzdaten zeigten, dass sie zu anderen Großgruppen gehören. Noch heute werden sie jedoch von Mykologen bearbeitet, weshalb sie im Folgenden vorgestellt werden. In ◘ Tab. 6.1 sind wesentliche Unterscheidungsmerkmale für Echte Pilze und pilzähnliche Organismen aufgelistet.
In this chapter, the results obtained from recent studies of myxomycete ecology are discussed, with special emphasis on their distribution patterns in particular habitats, the relationships that exist between myxomycetes and other organisms and the effect of disturbance events on myxomycete communities. It is important to note that most of the available data are based on collections of fruiting bodies, which probably represent (in a literal sense) only the tip of the iceberg because it is possible that these reflect only a minor fraction of the real diversity of myxomycetes in a particular habitat. Therefore, it appears unlikely that a single method will be universally applicable for assessing myxomycete diversity in all habitats and on all substrates. The approaches, techniques, and their potential limitations are discussed herein, along with recent advances (e.g., moist chamber cultures, environmental PCR, metagenomics and barcoding attempts) that have been applied to studies of myxomycete ecology and will undoubtedly increase our understanding of myxomycete communities in the future.
Phylogenetic relationships within the taxonomically difficult species complex Lepidoderma chailletii-carestianum (Myxogastria, Amoebozoa) were investigated by partial sequences of three independent genetic markers (18S rRNA, elongation factor 1 alpha, and cytochrome c oxidase subunit 1 genes). The resulting phylogenies were largely congruent in their topologies. Together with the analysis of morphological traits of fruiting bodies, the results supported the hypothesis that L. chailletii and L. carestianum are two separate valid species. Within the morphospecies L. chailletii, two clades were found that are quite divergent from L. chailletii sensu stricto, one of them clustering closely with L. alpestroides but morphologically differing from it. The second part of the cytochrome oxidase subunit 1 gene showed significant variation due to RNA editing; this mitochondrial genetic marker is likely useful for barcoding and phylogenetic reconstructions in dark-spored myxomycetes.
Since the sporophores of the myxomycetes are the primary basis of taxonomy in the myxomycetes, an understanding of the development and range of variations of the various morphological structures is essential to constructing a valid system. A review of the morphology of the stipe, peridium, capillitium, and spores and their developmental aspects was undertaken and the resulting morphological hypotheses tested against recent advancements in DNA phylogeny, isozyme and DNA population, and genetic reproduction studies.
Hyperamoeba flagellata is a fresh-water protist of uncertain taxonomic position. It exists in three living forms: as an amoeba, a flagellate and a cyst. The ultrastructure of the flagellated stage of H. flagellata is investigated here by TEM for the first time. Special attention was paid to the structure of the flagellar apparatus. There is one long smooth flagellum only which is directed anteriorly. It emerges from the flagellar basal body (kinetosome) located at the apical end of the cell. Two cones of microtubules extend from the flagellar base towards the nucleus. The outer cone originates from the lateral side of the flagellar kinetosome, while the inner cone arises from an MTOC associated with the flagellar kinetosome by a short fibrillar rootlet. The second (barren) kinetosome lies ventrally and is directed to the right side of the cell. It has two microtubular rootlets which pass laterally in the same direction. The microtubular cones overlap the anterior end of the nucleus. A dictyosome lies between the basal bodies and the nucleus. Mitochondria with tubular cristae have an electron dense core which is orientated in a longitudinal axis. The structure of the flagellated stage of H. flagellata is compared with flagellated cells of protostelids and cercomonads. It is proposed that this organism may represent a link between protostelids and cercomonads.
A taxonomic study was made of the type specimens of 21 stipitate Licea species. Relevant characters were examined by light microscope and by SEM. Evidence of synonymy was found in five of the taxa, Licea tropica with L. bulbosa, L. cristallifera with L. eleanorae, L. longa and L. capitata with L. floriformis var. aureospora, and L. tanzanica with L. scyphoides. One taxon Licea capitatoides var. fujiokana is recombined as a variety of a different species, Licea rugosa var. fujiokana. A new name Licea verrucospora, and a new status was given to Licea scyphoides var. reticulata. One species, Licea takahashii was excluded as it is an immature form of another genus. Detailed standardized descriptions are made of each species examined, with comments on the most relevant taxonomic characters. Light and scanning electron micrographs of relevant morphological details are included. Nomenclatural information is given for each taxon. A key to the stipitate Licea species is proposed.
The plasmodium of the slime mould Physarum polycephalum is a large
amoeba-like cell consisting of a dendritic network of tube-like
structures (pseudopodia). It changes its shape as it crawls over a plain
agar gel and, if food is placed at two different points, it will put out
pseudopodia that connect the two food sources. Here we show that this
simple organism has the ability to find the minimum-length solution
between two points in a labyrinth.
This is the first report on the diversity of small free-living amoebae (FLA) in carbonate precipitating habitats in karst caves. Of 11 samples from nine different habitats in four Slovenian karst caves ten samples were positive for FLA, four strains were successfully isolated and transferred to clonal monoxenic cultures, including Acanthamoeba castellanii genotype T4, Echinamoeba silvestris, Hartmannella vermiformis, and a new vahlkampfiid amoeba Allovahlkampfia spelaea gen. nov., sp. nov. The latter was isolated from a stromatolitic stalagmite, a typical biogenic speleothem. Echinamoeba silvestris was identified from an aerophytic algal community and Acanthamoeba and Hartmannella were isolated from a cave pool with floating calcite rafts. The grazing of FLA on bacteria may help in creating conditions that enhance carbonate precipitation.
Our study was done to determine if cave crickets (Ceuthophilus gracilipes gracilipes) are able to transport dictyostelid cellular slime molds into and within caves. Large cave crickets were captured from Pigeon Roost Cave in northwestern Arkansas. Crickets were individually washed to remove dictyostelid spores, and fecal pellets collected aseptically from the washed crickets. Five species of dictyostelids, assigned to two genera (Dictyostelium and Polysphondylium), were recovered from the surface of six crickets, and a single species (D. sphaerocephalum) from one sample of fecal pellets. Since cave crickets forage outside the cave, they can introduce dictylostelids to caves from out-side sources, and can serve as vectors for transporting dictyotelids within caves. The present study is the first to demonstrate that cave-dwelling invertebrates are capable of transporting these organisms.
Considers the life cycles of myxomycetes and the ecologically significant aspects of individual stages and events in these cycles. The existence of 2 distinct vegetative stages with different characteristics adds greatly to the complexity of the reactions of myxomycetes with their environments. One of the most tantalizing problems is largely unanswered: what are the relative proportions of the different stages of the life cycle under natural conditions, in terms both of duration and biomass?-from Author
A revised six-kingdom system of life is presented, down to the level of infraphylum. As in my 1983 system Bacteria are treated as a single kingdom, and eukaryotes are divided into only five kingdoms: Protozoa, Animalia, Fungi, Plantae and Chromista. Intermediate high level categories (superkingdom, subkingdom, branch, infrakingdom, superphylum, subphylum and infraphylum) are extensively used to avoid splitting organisms into an excessive number of kingdoms and phyla (60 only being recognized). The two 'zoological' kingdoms, Protozoa and Animalia, are subject to the International Code of Zoological Nomenclature, the kingdom Bacteria to the International Code of Bacteriological Nomenclature, and the three 'botanical' kingdoms (Plantae, Fungi, Chromista) to the International Code of Botanical Nomenclature. Circumscriptions of the kingdoms Bacteria and Plantae remain unchanged since Cavalier-Smith (1981). The kingdom Fungi is expanded by adding Microsporidia, because of protein sequence evidence that these amitochondrial intracellular parasites are related to conventional Fungi, not Protozoa. Fungi are subdivided into four phyla and 20 classes; fungal classification at the rank of subclass and above is comprehensively revised. The kingdoms Protozoa and Animalia are modified in the light of molecular phylogenetic evidence that Myxozoa are actually Animalia, not Protozoa, and that mesozoans are related to bilaterian animals. Animalia are divided into four subkingdoms: Radiata (phyla Porifera, Cnidaria, Placozoa, Ctenophora), Myxozoa, Mesozoa and Bilateria (bilateral animals: all other phyla). Several new higher level groupings are made in the animal kingdom including three new phyla: Acanthognatha (rotifers, acanthocephalans, gastrotrichs, gnathostomulids), Brachiozoa (brachiopods and phoronids) and Lobopoda (onychophorans and tardigrades), so only 23 animal phyla are recognized. Archezoa, here restricted to the phyla Metamonada and Trichozoa, are treated as a subkingdom within Protozoa, as in my 1983 six-kingdom system, not as a separate kingdom. The recently revised phylum Rhizopoda is modified further by adding more flagellates and removing some 'rhizopods' and is therefore renamed Cercozoa. The number of protozoan phyla is reduced by grouping Mycetozoa and Archamoebae (both now infraphyla) as a new subphylum Conosa within the phylum Amoebozoa alongside the subphylum Lobosa, which now includes both the traditional aerobic lobosean amoebae and Multicilia. Haplosporidia and the (formerly microsporidian) metchnikovellids are now both placed within the phylum Sporozoa. These changes make a total of only 13 currently recognized protozoan phyla, which are grouped into two subkingdoms: Archezoa and Neozoa; the latter is modified in circumscription by adding the Discicristata, a new infrakingdom comprising the phyla Percolozoa and Euglenozoa). These changes are discussed in relation to the principles of megasystematics, here defined as systematics that concentrates on the higher levels of classes, phyla, and kingdoms. These principles also make it desirable to rank Archaebacteria as an infrakingdom of the kingdom Bacteria, not as a separate kingdom. Archaebacteria are grouped with the infrakingdom Posibacteria to form a new subkingdom, Unibacteria, comprising all bacteria bounded by a single membrane. The bacterial subkingdom Negibacteria, with separate cytoplasmic and outer membranes, is subdivided into two infrakingdoms: Lipobacteria, which lack lipopolysaccharide and have only phospholipids in the outer membrane, and Glycobacteria, with lipopolysaccharides in the outer leaflet of the outer membrane and phospholipids in its inner leaflet. This primary grouping of the 10 bacterial phyla into subkingdoms is based on the number of cell-envelope membranes, whilst their subdivision into infrakingdoms emphasises their membrane chemistry; definition of the negibacterial phyla, five at least partly photosynthetic, relies chiefly on photosynthetic mechanism and cell-envelope structure and chemistry corroborated by ribosomal RNA phylogeny. The kingdoms Protozoa and Chromista are slightly changed in circumscription by transferring subphylum Opalinata (classes Opalinea, Proteromonadea, Blastocystea cl. nov.) from Protozoa into infrakingdom Heterokonta of the kingdom Chromista. Opalinata are grouped with the subphylum Pseudofungi and the zooflagellate Developayella elegans (in a new subphylum Bigyromonada) to form a new botanical phylum (Bigyra) of heterotrophs with a double ciliary transitional helix, making it necessary to abandon the phylum name Opalozoa, which formerly included Opalinata. The loss of ciliary retronemes in Opalinata is attributed to their evolution of gut commensalism. The nature of the ancestral chromist is discussed in the light of recent phylogenetic evidence.
To evaluate the relevance of chemical characters as additional tools for the taxonomy of myxomycetes, sporocarp pigments of sixteen taxa of the genera Arcyria and Arcyodes (both Trichiales) were analysed by a thin-layer chromatography method that is easy to perform and reproduce. Focusing on the notoriously difficult group of red-coloured Arcyria species, surprisingly high correspondence for pigment patterns of all investigated specimens belonging to a certain morphospecies was found. The use of pigments for species differentiation is demonstrated by a key for the pigment patterns of Arcyria incl. Arcyodes incarnata. Results of pigment analyses are compared with the classical taxonomy based on morphological characters. A cladistic analysis of the relationships in the genus using both pigments and morphological characters is presented.
The frequency of occurrence of Acrasieae was determined in 28 temperate and tropical countries on five continents. Twenty-nine different cellular slime molds, including five new to science, were isolated. Diversity is greatest in the tropics and decreases as latitude increases. Eight species are cosmopolitan. The 11 species found in temperate forest also occur in the tropics; no endemics to temperate areas have been found. Half the species are endemic to the tropics and subtropics but the majority of these are pantropical. On the basis of frequency distributions six cosmopolitan species show definite responses to a climatically controlled temperature gradient. Two other cosmopolitan species Dictyostelium mucoroides and Polysphondylium pallidum are relatively unresponsive to climate or vegetation. The responses to a climatic temperature gradient may be direct but more likely are related to substrate.
In the Pan 4 isolate of Didymium iridis, a heterothallic line was spontaneously derived from an apomictic one. Genetical and cytological evidence shows that in the heterothallic state amoebal clones are self-sterile and cross-fertile, whereas in the apomictic condition each clone produces plasmodia without benefit of crossing.
A new technique has been designed to collect protostelids repeatedly on a standardized substrate that has been introduced into a habitat known to contain an assemblage of species of protostelids. Four species of protostelids were detected after 1 week of placing sterilized wheat straw into a leaf litter habitat. After 8 weeks, a total of eight species were found. All of these species were also present on samples of litter taken from the same site. Moreover, at least one species of protostelid fruited on 75 of the 80 straws examined. The most common species detected were Nematostelium ovatum, N. gracile, and Schizoplasmodiopsis pseudoendospora. These species also appear most frequently when plating leaf litter from this site. This technique has potential use in the study of protostelid ecology.
Fonticula alba fits no presently recognized genus of the Acrasiomycetes. The slime mold grows and fruits well at 25-28 C with Klebsiella pneumoniae upon weakly buffered nutrient agar. The myxamoebae are small, variable in form and dimensions, uninucleate or less commonly binucleate and with nucleoli indistinct. Myxamoebae form no streams but aggregate along definite paths to form low rounded mounds. From these mounds narrow tapering columns of cells develop vertically, up to 1.0 mm, each bounded by a thin, tube-like covering that is closed above and extends downward over a broader basal reservoir of cells. Later the covering ruptures apically and the cells within ascend, as if projected under pressure, and collect into a spherical droplet to differentiate as spores. When mature, the naked sorus thus formed may rest upon the emptied hyaline tube for several da before the structure collapses. In no other cellular slime mold are sorocarps known to be formed in a similar manner. Myxamoebae that fail to aggregate differentiate individually as microcysts.
Two new cellular slime molds are described from New Jersey. Acrasis rosea, a new species with a pink pigment in all its cells, produces fruiting bodies with branching chains of spores. It has been isolated on an orange bacterium and several pigmented fungi. Acrasis probably occupies an advanced position in the Guttulinaceae. The second organism, Protostelium mycophaga, is described as a new genus and species. Its cells also contain a pink pigment. It grows well on Rhodotorula and several other fungi, especially pigmented ones. During sporulation a single amoeba arises on a slender stalk and encysts at its apex. The genus is tentatively considered a primitive member of the Acytosteliaceae.
Preface 1. A brief introduction to Dictyostelium discoideum and its relatives 2. A history of research on Dictyostelium discoideum 3. The evolutionary biology of Dictyostelium 4. The genome and genetics 5. Membranes and organelles of Dictyostelium 6. Cell motility and the cytoskeleton 7. The transition from growth to development: from starvation to self sustaining cAMP signal relay 8. Chemotaxis and aggregation 9. Differentiation and adhesion in the aggregate 10. Behavior of cells in the slug 11. Culmination 12. Formation and germination of spores 13. Resources References Index.
A survey of the biosystematic studies in the myxomycetes indicates that the currently recognized morphospecies are generally species complexes consisting of a number of genetically isolated regional allopatric and/or sympatric biological species and numerous small (rarely large) apomicitic clones. Other variations include a single biological species with or without apomictic clones, or apomictic clones without a biological species. Stalk and sporangial color, columella shape, and sporangial cluster morphotypes, which are produced by variations at a few genes, also occur within a genetic group. Biotypes that have small plasmodia, rapid life cycles, and dwarf or reduced numbers of sporangia can be isolated from ephemeral or low nutrient habitats and are also part of a larger genetic group. This information indicates that many of the recently described species are probably based on restricted clonal lines, which should not be recognized at the species level. Also, some commonly accepted morphospecies are only morphological variants, which can be found within a single biological species. Thus, the description of new species should be based upon an extensive collection of specimens so that these variations and small clonal populations can be excluded.
Nivicolous myxomycetes are an ecological group of species growing in alpine and subalpine regions of the world near to the melting snow. Extensive field work was done in the mountain areas of the Iberian Peninsula from 1991 to 2002 which demonstrates the richness and variety of the myxobiota in this Mediterranean region. Among the areas with optimum conditions of geography, climate and vegetation, 123 localities were sampled from ten mountain ranges. Almost 1500 field collections were made and a first list of 48 different species is presented here. The altitudinal distribution and phenology of the sporulation of these myxomycetes are analyzed. Working hypotheses on how abiotic factors can influence the development of nivicolous species and some adaptative characters of these species are also presented.
Evolutionary relations are better represented by new classifications than by the traditional two kingdoms.
The morphology and phylogenetic affinity of Hyperamoeba isolated from human feces is described. During its life cycle, it switches reversibly from flagellate to aflagellated amoebae and is capable of forming cysts. It grows aerobically. Under anaerobic conditions it persists but does not replicate. The amoeboflagellate has a single nucleus with a distinct nucleolus. Its mitochondria possess tubular cristae and a central electron dense body, similar to that of plasmodial slime molds. A single contractile vacuole is evident. The flagellate has one detectable anterior flagellum but two basal bodies are visible at the ultrastructure level. The flagellar apparatus is very similar to that found in some Eumycetozoa, especially the myxogastrids. The uninucleate cyst has a bi-layered endocyst and a membranous, irregular shaped, faintly laminated ectocyst that harbors bacterial inclusions. Phylogenetic reconstructions based on nuclear small subunit ribosomal gene sequence comparisons show that Hyperamoeba is closely related to the plasmodial slime mold Physarum polycephalum. These protists share a most recent common ancestry that excludes all other taxa in the database. This phylogenetic relationship is supported by detailed similarities in both mitochondrial and flagellar apparatus ultrastructure.
A B S T R A C T A new genus and species of the Protosteliida (Mycetozoa), Ceratiomyxella tahitiensis, was isolated from dead plant material-var. tahitiensis from Tahiti and var. neotropicalis from Brazil and Colombia. The sporocarps have deciduous spores borne singly on slender hollow stalks; zooeysts with anteriorly flagellate planonts are produced. The trophic stage is comprised of uninucleate to plurinucleate amoeboid cells and reticulate plasmodia; the uninucleate cells become flagellate in water. The prespore cells and spores are plurinucleate. Sexuality has not been demonstrated. Var. tahitiensis has globose spores and produces its zooeysts just after spore germination, whereas var. neotropicalis has subglobose spores and forms zooeysts later in the life cycle. The species is thought to show phylogenetic relationships with Ceratiomyxa, which was recently transferred to the Protosteliida by Olive. THE PROTOSTELIDS, or Protosteliida, constitute the subclass Protostelia of the Mycetozoa (Olive, 1970). They are a common and widespread group of primitive mycetozoans, which are thought to be ancestral to both the dictyostelids of the cellular slime molds and the myxomycetes. Of the isolates in our laboratory which have remained undescribed, two similar ones from the tropicsone from Tahiti and the other from Brazil-have proved of particular interest from the standpoint of their possible relationship to Ceratiomyxa. The latter genus, formerly included in the myxomycetes, has recently been transferred to the Protosteliida under the family name Ceratiomyxidae (Olive, 1970). The two isolates are described here as varieties of a new genus and species, which has a number of characteristics indicating phylogenetic affinities with Ceratiomyxa. We have just recently obtained a third isolate from Colombia which resembles the one from Brazil, but it has not been studied in any detail and will not be included in the following discussion.
I report here the discovery of a single isolate of a new species of
cellular slime mould, Dictyostelium caveatum, in bat guano from
Blanchard Springs Cavern, Arkansas. Amoebae of this species form common
aggregates with all species that have been tested and interfere with
their morphogenesis in a dramatic way. The D. caveatum amoebae induce a
delay of morphogenesis while they consume all of the amoebae of the
other species by phagocytosis. Morphogenesis is reinitiated and fruiting
bodies containing only D. caveatum spores are erected.
Eumycetozoans, the myxomycetes, protostelids, and dictyostelids, were first hypothesized to be a monophyletic group by L.S. Olive, who suggested that the primitive members of the group were similar to some of the extant protostelids. A review of morphological evidence supporting some aspects of this hypothesis is presented along with explicit explanations of the shortcomings of morphological data as tests of other aspects. For the hypothesis to be supported, modified, or rejected, data from other areas such as the sequences of the nuclear ribosomal small subunit genes (SSrDNA) will have to be used. Presently, sequences for this gene are known only from Physarum polycephalum and Dictyostelium discoideum. These two slime molds are treated as separate, deep clades in the grand eukaryote phylogenies derived from the sequences of SSrDNA. That is, each species represents an independent lineage that diverged early in the history of the eukaryotes. Insufficient taxon sampling may account for the molecular trees which suggest that the dictyostelids and myxomycetes are not members of a monophyletic group. We have begun to examine the SSrDNA sequence in the protostelid Protostelium mycophaga. Preliminary phylogenetic reconstructions using 11 eukaryotic outgroups suggest that the protostelids, myxomycetes, and dictyostelids are members of a single monophyletic group which may be most closely related to the Chromista. It is interesting that these results coincide with earlier phylogenetic hypotheses based on the morphological characters of these slime molds. Key words: dictyostelids, myxomycetes, protostelids, ribosomal DNA, slime molds.
ABSTRACT The most commonly encountered protostelids are nominal members of the genus Protostelium Olive & Stoianovitch. These are Protostelium mycophaga Olive & Stoianovitch and P. irregularis Olive & Stoianovitch. Both species share the common features of long-stalked fruiting bodies with single, uninucleate, deciduous spores and trophic states that consist solely of uninucleate amoebae, but they are quite different with respect to their detailed structure at both the light and electron microscopic levels. Based on this evidence, it seems unlikely that the species are congeneric, and it is proposed that P. irregularis be assigned to Soliformovum n. g. Examination of other species of Protostelium indicates that P. nocturnum Spiegel should be retained in the genus and that P. expulsum Olive & Stoianovitch should be reassigned to Soliformovum. The group most closely related to Protostelium, under this new concept, is the genus Planoprotostelium Olive & Stoianovitch, while Soliformovum is best treated as a genus of Eumycetozoa incertae sedis, though it does share some similarities with the group that includes the genera Ceratiomyxella Olive & Stoianovitch, Nematostelium Olive & Stoianovitch, and Schizoplasmodium Olive & Stoianovitch.
ABSTRACT Reinvestigation of the type population of the sorocarp-forming ciliate Sorogena stoianovitchae Bradbury & Olive, 1980 using the Fernández-Galiano technique and various electron-microscopy techniques (scanning electron microscopy, freeze-fracture and ultrathin sections) expands the observations reported in the original description of the species, Sorogena stoianovitchae is a colpodid ciliate with oral ciliature consisting of 25 ciliated paroral dikinetids on the right and 3-5 small adoral organelles on the left of an elongated and domed oral slit, resembling that of the genus Platyophrya. Sorogena stoianovitchae divides in the free swimming condition and not in a division cyst, as is the case in the colpodids sensu stricto (s. str.), e.g. Colpoda, Bresslaua. or Tillina, As shown in a detailed light-microscopy study, morphogenesis in S. stoianovitchae is of the stomatic mode typical for certain colpodid ciliates. Based on the wealth of new information the phylogenetic position of S. stoianovitchae is discussed at some length and arguments are given in favor of the following classifications: S. stoianovitchae Bradbury & Olive, 1980 currently sole member of the family Sorogenidae Bradbury & Olive, 1980; order Sorogenida Foissner, 1985;subclassColpodiaFoissner, 1985; class Colpodea Small & Lynn, 1981. This investigation facilitates the discovery of further members of this genus reported primarily from the tropical and subtropical zone.