The subkingdom Protozoa now inclues over 65,000 named species, of which over half are fossil and approximately 10,000 are parasitic. Among living species, this includes approximately 250 parasitic and 11,300 free-living sarcodines (of which approximately 4,600 are foraminiferids); approximately 1,8000 parasitic and 5,100 free-living flagellates; approximately 5,600 parasitic "Sporozoa" (including Apicomplexa, Microspora, Myxospora, and Ascetospora); and approximately 2,5000 parasitic and 4,700 free-living ciliates. There are undoubtedly thousands more still unnamed. Seven phyla of PROTOZOA are accepted in this classification--SARCOMASTIGOPHORA, LABYRINTHOMORPHA, APICOMPLEXA, MICROSPORA, ASCETOSPORA, MYXOSPORA, and CILIOPHORA. Diagnoses are given for these and for all higher taxa through suborders, and reporesentative genera of each are named. The present scheme is a considerable revision of the Society's 1964 classification, which was prepared at a time when perhaps 48,000 species had been named. It has been necessitated by the acquisition of a great deal of nex taxonomic information, much of it through electron microscopy. It is hoped that the present classification incorporatesmost of the major changes that will be made for some time, and that it will be used for many years by both protozoologist and non-protozoologists.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1550-7408.1980.tb04228.x

A Newly Revised Classification of the Protozoa

The Mycetozoa include the cellular (dictyostelid), acellular (myxogastrid), and protostelid slime molds. However, available molecular data are in disagreement on both the monophyly and phylogenetic position of the group. Ribosomal RNA trees show the myxogastrid and dictyostelid slime molds as unrelated early branching lineages, but actin and β-tubulin trees place them together as a single coherent (monophyletic) group, closely related to the animal–fungal clade. We have sequenced the elongation factor-1α genes from one member of each division of the Mycetozoa, including Dictyostelium discoideum, for which cDNA sequences were previously available. Phylogenetic analyses of these sequences strongly support a monophyletic Mycetozoa, with the myxogastrid and dictyostelid slime molds most closely related to each other. All phylogenetic methods used also place this coherent Mycetozoan assemblage as emerging among the multicellular eukaryotes, tentatively supported as more closely related to animals + fungi than are green plants. With our data there are now three proteins that consistently support a monophyletic Mycetozoa and at least four that place these taxa within the “crown” of the eukaryote tree. We suggest that ribosomal RNA data should be more closely examined with regard to these questions, and we emphasize the importance of developing multiple sequence data sets.

/pdf/origin-and-evolution-of-the-slime-molds-mycetozoa-2xmljsbzbo.pdf

Origin and evolution of the slime molds (Mycetozoa)

A B S T R A C T The clonal isolation of Acrasieae from suspensions of soils or organic substrates may be accomplished by employing a dilute hay-infusion agar medium to the surface of which pregrown bacteria have been added as a source of nutrient for the myxamoebae. The method described permits quantitative sampling of cellular slime mold populations, and it has been used by the authors in a study of the occurrence and distribution of these organisms in North and Central American forests. AS A PREREQUISITE for investigating the occurrence and distribution of the Acrasieae in forest soils, a method was developed which makes possible the clonal isolation of these cellular slime molds. Hence it can be used in the comparison of populations from different localities or sources. Although the method was developed and has been employed mainly for the study of populations in forest soils, it is equally applicable to other substrates such as leaf litter, decaying plants, fruits and dung, if these are macerated prior to analyses. MATERIALS AND METHODS-Collection of samXples-Samples were collected at the soil surface or from the humus layer of forests, and, in the latter case, included a portion of the fermentation layer where decomposition is most active. Variation in slime mold populations from one site to another in a forest is considerable. Consequently, an adequate number of soils must be taken to ensure representative sampling of a particular forest population. Soils may be conveniently collected in 9-dr plastic vials with wide mouths and snap-on covers. These vials are light weight, sufficiently strong, inexpensive, and suitable for shipping by mail, if necessary. Samples are taken by scraping the soil surface with the mouth of the vial. If soils cannot be plated out immediately after collection, they should be stored at a temperature slightly above freezing. Numbers of Acrasieae diminish soon after collection, there being a 15-25% decrease after 8 weeks' storage at 4 C in a moist condition. The decrease may be explained largely by death of active myxamoebae with some loss of spore and cyst viability as well. Samples may be frozen, but freezing causes a sharper initial decrease in numbers than does

The acrasieae in nature. i. isolation.

Amoebae that make fruiting bodies consisting of a stalk and spores and classified as closely related to the myxogastrids have classically been placed in the taxon Eumycetozoa. Traditionally, there are three groups comprising Eumycetozoa: myxogastrids, dictyostelids, and the so-called protostelids. Dictyostelids and myxogastrids both make multicellular fruiting bodies that may contain hundreds of spores. Protostelids are those amoebae that make simple fruiting bodies consisting of a stalk and one or a few spores. Protostelid-like organisms have been suggested as the progenitors of the myxogastrids and dictyostelids, and they have been used to formulate hypotheses on the evolution of fruiting within the group. Molecular phylogenies have been published for both myxogastrids and dictyostelids, but little molecular phylogenetic work has been done on the protostelids. Here we provide phylogenetic trees based on the small subunit ribosomal RNA gene (SSU) that include 21 protostelids along with publicly available sequences from a wide variety of amoebae and other eukaryotes. SSU trees recover seven well supported clades that contain protostelids but do not appear to be specifically related to one another and are often interspersed among established groups of amoebae that have never been reported to fruit. In fact, we show that at least two taxa unambiguously belong to amoebozoan lineages where fruiting has never been reported. These analyses indicate that we can reject a monophyletic Eumycetozoa, s.l. For this reason, we will hereafter refer to those slime molds with simple fruiting as protosteloid amoebae and/or protosteloid slime molds, not as protostelids. These results add to our understanding of amoebozoan biodiversity, and demonstrate that the paradigms for understanding both nonfruiting and sporulating amoebae must be integrated. Finally, we suggest strategies for future research on protosteloid amoebae and nonfruiting amoebae, and discuss the impact of this work for taxonomists and phylogenomicists.

/pdf/eumycetozoa-amoebozoa-ssurdna-phylogeny-of-protosteloid-2xulg1lfbq.pdf

Eumycetozoa = Amoebozoa?: SSUrDNA Phylogeny of Protosteloid Slime Molds and Its Significance for the Amoebozoan Supergroup

The myxomycetes (plasmodial slime molds or myxogastrids) are a group of eukaryotic microorganisms usually present and sometimes abundant in terrestrial ecosystems Evidence from molecular studies suggests that the myxomycetes have a significant evolutionary history However, due to the fragile nature of the fruiting body, fossil records of the group are exceedingly rare Although most myxomycetes are thought to have very large distributional ranges and many species appear to be cosmopolitan or nearly so, results from recent studies have provided evidence that spatial distribution patterns of these organisms can be successfully related to (1) differences in climate and/or vegetation on a global scale and (2) the ecological differences that exist for particular habitats on a local scale A detailed examination of the global distribution of four examples (Barbeyella minutissima, Ceratiomyxa morchella, Leocarpus fragilis and Protophysarum phloiogenum) demonstrates that these species have recognizable distribution patterns in spite of the theoretical ability of their spores to bridge continents

https://www.discoverlife.org/pa/or/polistes/pr/2010nsf_macro/references/Stephenson_et_al(2)2008.pdf

Myxomycete diversity and distribution from the fossil record to the present

Two New Members of the Acrasiales

Three new species of Protostelium (Order Protostelida of the Mycetozoa) are described: P. irregularis, P. zonatum, and P. pyriformis, all with rather wide distribution and occurring on dead attached plant parts, less often in soil and humus. The latter two species differ from the first and from the other two known species, P. mycophaga Olive and Stoianovitch and P. arachisporum Olive, in the endogenous origin of the stalk. P. mycophaga var. crassipes, with vesicular stalk bases, is the third variety of that species to be described. A key to the genus is included. PROTOSTELIUM Olive and Stoianovitch (1960) is the type genus of the family Protostelidae, order Protostelida of the Mycetozoa (Olive and Stoianovitch, 1966a). Up to the present time it contains only two valid species, P. mycophaga Olive and Stoianovitch (1960) and P. arachisporum Olive (1962). In the present paper three new species and one new variety are described and additional developmental details on members of the genus are presented. Protostelium is characterized chiefly by its predominantly uninucleate, non-flagellate, phagotrophic, amoeboid cells and slender-stalked sporocarps that bear the deciduous spores singly. N\Jembers of the genus occur primarily on dead plant parts (pods, capsules, berries, flowers, etc.) that have remained attached to the plants, though some species are occasionally found in soil, humus, or rotting wood. The trophic stage ingests such foods as yeasts, fungal spores and bacteria. Methods for isolating and culturing protostelids in the laboratory have been described in an earlier publication (Olive, 1967), as have the photographic techniques used in the present research. While uninucleate amoebae and spores are characteristic of the group, plurinucleate cells or even aplanate multinucleate protoplasts appear in cultures of some species. The multinucleate ones, however, do not develop into the extensive reticulate plasmodia that characterize such genera as Schizoplasmodium and Schizoplasmodiopsis (Olive, 1967). Cell division is by binary fission, following which the nucleolar material reappears in each daughter nucleus as several separate bodies that eventually fuse into a single larger nucleolus more or less centrally positioned in the nucleus. It is common to find considerable range in cell and nuclear size within an isolate, which may indicate a range in ploidy, but there are no cytological data to substantiate the latter. I Received for publication 17 March 1969. This research was supported by grants GB-5508, GB7392, and GB-501 from the National Science Foundation. No evidence of sexuality has been observed. Typical sporulating cultures are regenerated from single spores. Plurinucleate protoplasts appear to arise by cell anastomosis as well as by nuclear division without cytokinesis. Such protoplasts may divide into smaller ones by plasmotomy. The amoebae commonly produce filose pseudopodia, especially when placed in water. However, under certain conditions, such as prolonged flattening between a cover slip and a thin agar layer ("sandwich" preparation), they frequently produce lobose pseudopodia instead. Ontogeny of the protostelid sporocarp has been described elsewhere (Olive and Stoianovitch, 1966a) and, with the exception of the two new species with bell-shaped or pyriform spores, is applicable to the genus Protostelium. The stalk-generating part of the culminating protoplast is typically hemispherical, with a narrow extension passing into the upper part of the eveloping stalk, but in the two exceptional species the steliogen is cylindric and the stalk of endogenous origin. The mature sporocarp typically consists of a narrow stalk tube terminated by a single spore, the whole being enveloped by a thin, closely applied sheath. At least one species does not have a demonstrable stalk tube. All species are characterized by having deciduous spores, though in some the spores fall off more readily than in others. The manner in which the spore separates from the stalk tip is not well understood. A key to the species and varieties of the genus is presented below. KEY TO THE GENUS PROTOSTELIUM Spores globose to subglobose Protoplasts orange-pigmented; spores averaging less than 15,g diam; microcysts fairly regular in outline .... . mycophaga Stalk with conspicuous vesicular enlargement at base .... var. crassipes Stalk without conspicuous basal enlargement

Monograph of the genus protostelium

SYNOPSIS. Two new species of the simple mycetozoan genus Schizoplasmodium—S. ovatum and S. gracile—are described, the former having ovate spores and the latter spherical ones. All stages of the life cycle are multinucleate. At sporulation the holozoic plasmodium segments into prespore cells which develop directly into long-stalked, single-spored sporocarps. Sexual reproduction was not observed. A new order—the PROTOSTELIDA—is proposed for this and related genera, which are believed to comprise a phylogenetically linked series, beginning with the amoebo-flagellate genus Cavostelium and evolving through Schizoplasmodium to Protostelium. The two families Cavostelidae (Cavostelium) and Protostelidae (Schizoplasmodium, Protostelium) are recognized.

Schizoplasmodium, a mycetozoan genus intermediate between Cavostelium and Protostelium; a new order of Mycetozoa.

A simple new mycetozoan with ballistospores

A number of isolates of the cellular slime mold, Acrasis rosea, differed from each other in the range of microorganisms on which they could grow and fruit. In a test for the possible occurrence of sexual reproduction and genetic recombination, two of the most widely divergent of these physiological races were studied further. Mixed colonies were obtained in agar plate cultures of Rhodotorula mucilaginosa, a yeast utilized by both. When spores from mature fruiting bodies or amoebae migrating out from the mixed colonies were isolated singly, regrown on Rhodotorula, and tested on a critical spectrum of food microorganisms, about 3-4% proved to be distinct from the original two strains. Although some of these new types remained stable for several transfers, they eventually reverted to one or both of the parental types. The possibilities of explaining the neotypes on the basis of diploidy, heterokaryosis, or mixed cytoplasmic effects are discussed. The occurrence of cell anastomoses and occasional binucleate cells favors the latter two possibilities.

Carmen Stoianovitch

Papers

Two New Members of the Acrasiales

Monograph of the genus protostelium

Schizoplasmodium, a mycetozoan genus intermediate between Cavostelium and Protostelium; a new order of Mycetozoa.

A simple new mycetozoan with ballistospores

Variation in the Cellular Slime Mold Acrasis rosea