Myxomycetes is a group of eukaryotic organisms widely distributed in terrestrial ecosystems. In their life cycle, they have both vegetative mass with protozoan motility and highly specialized propagules. The morphological structure and physiological characteristics have both the features of “fungi” and “animals”. The unique evolutionary status and close relationships with the environment and human health make myxomycetes become model organisms in biology, genetics, physiology, ecology, information science, and other disciplines, with a wide range of scientific significance and essential application value. Since the 17th century, researchers have gradually expanded from the early classic taxonomy to various biological branches concerned in order to systematically and comprehensively understand myxomycetes, and have made significant progress in systematics, biology, ecology, and other fields in the past decades. This article briefly reviews the representative research progress and front-line scientific problems in myxomycetology concerning various fields, and prospectively predicts the future development of related fields.
Myxomycetes are a kind of eukaryotic organisms with unique characteristics and widely distributed in terrestrial ecosystems. They can regulate microbial communities in microhabitats, affect distribution of nutrition and biomass. Species diversity and influencing factors of myxomycetes have been the focus of myxomycete ecology research. In this paper, the occurrence of myxomycetes in different microhabitats and the research progress of abiotic and biological factors affecting species diversity as well as ecological functions of myxomycetes in ecosystems were reviewed.
For the purposes of revealing a variety of cytogenetic patterns of myxomycetes, research advances in biological characteristics, behaviors and related developmental mechanisms of myxomycetes at different stages of life cycle are reviewed. In addition, the phylogenetic relationship between myxomycetes and other groups of Amoebozoa is described, and the homologous characteristics in the various taxonomical groups are compared. The relationship between the ontogenic characteristics and phylogeny of myxomycetes is also expounded.
Dictyostelid cellular slime molds are a group of protist with habits and characteristics mediated between plant and animal. The biological characteristics and applications of dictyostelid cellular slime molds have essential research values because they are small, short cyclic and easily proliferous. The life cycle, biological characteristics, ecodiversity, explorations in connection with medical and medicinal science, relationship with other microorganism of dictyostelids are reviewed, and potential applications of dictyostelids in medical science, ecology, environment improvements, etc. in future are prospected.
In order to assess myxomycete resources and diversity in Greater Khingan and Lesser Khinggan Mountains, a field investigation has been carried out in the mountainous regions, and 1 355 samples were obtained in 32 collection sites from 2014 to 2018. On the basis of the data published and our own studies, 152 species belonging to 32 genera are recorded up to now. Number of collecting localities is expanded from 11 to 37. Thirty-four species, including Arcyria affinis, Arcyria virescens, Barbeyella minutissima, etc. are newly recorded in the regions, of which 25 species for Heilongjiang Province and 12 for Inner Mongolia. In this checklist, names of myxomycetes together with their substrates, collecting localities, literature concerned and accession number of collections deposited in Herbarium of the Mycological Institute of Jilin Agricultural University (HMJAU) are given.
Myxomycete is an important component of soil protist, but comprehensive information on its community composition and diversity pattern is lacking. In present study, soil samples were collected from deciduous broad-leaved forest, coniferous forest, and mixed forest in Baotianman Nature Reserve and the diversity of bright-spored myxomycetes in the soil was studied by using 18S high-throughput sequencing. In addition, the relationships between myxomycete community structure and soil environmental factors were analyzed by multivariate statistics. In total, 26 OTUs were obtained from 30 soil samples, belonging to seven genera of Trichiales. Four OTUs could be further annotated at species level and identified as Arcyria globosa, Hemitrichia serpula, Trichia scabra, and Trichia alpina. The α diversity of bright-spored myxomycete communities were significantly different between different forest types, and the highest diversity indices were observed in coniferous forest and the lowest in deciduous broad-leaved forest. The community structure in different forest types also differed significantly. Redundancy analysis showed that the bright-spored communities were related to soil water content, C:N ratio, available K and organic carbon. However, the total soil environmental factors could only explain 10.18% of the variations in community composition.
Myxomycetes from Pinus koraiensis forest and coniferous and broad-leaf mixed forest in Liangshui National Nature Reserve were investigated. A total of 242 samples of myxomycetes was collected and 50 species belonging to 17 genera of seven families in four orders were identified based on morphological characteristics. Nine species were newly recorded in Heilongjiang Province including Arcyria insignis, Cribraria paucidictyon and Physarum roseum, and the relative abundance was 16.67%. Ph. viride was the most dominant species in Liangshui National Nature Reserve. The species diversity of myxomycetes was higher in mixed forest (H′=2.06) than that in Pinus koraiensis pure forest (H′=1.71). Seventeen species were common to both forest types and the composition similarity (CS) was 50.75%. Vegetation type seems important for the species composition and diversity of myxomycetes.
Xingshan County in Yichang City of Hubei Province, being the north subtropical zone, is located in the eastern extension of Qinba Mountain Area stretching to Jianghan Plain and belongs to Three Gorges Reservoir Area. The humid climate and vegetation of mixed evergreen broad-leaved and deciduous broad-leaved forests are suitable for the growth of myxomycetes. The investigation of specific composition of myxomycetes in the county was conducted 10 times in different seasons from October 2016 to August 2018. Meanwhile, the substrate was also collected for moist chamber culture. A total of 215 myxomycetes specimens was obtained, belonging to 6 orders, 9 families, 25 genera and 56 species. Of which 25 species such as Cribraria aurantiaca, Licea variabilis and Pericaena corticalis were recorded for the first time in Hubei Province, and Cribraria martini was first reported in the subtropical region of China. It was found that June was the most suitable for propagation of myxomycetes, using decaying logs as substrate. The distribution of myxomycetes varied with different altitudes.
The ultrastructural characteristics of spore, myxamoeba and sorophore of Cavenderia fasciculata were observed, and comparison of ultrastructural characteristics was made between three known dictyostelids, Dictyostelium multiforme, D. minimum and C. fasciculata. The observation results showed that there were mitochondrial structures in spore, myxamoeba and sorophore of C. fasciculata. With cell differentiation, the inner structure of mitochondria is gradually destroyed and phagocytized by autophagic vesicles. The surface of spores has linear ornamentation.
The life cycle of Physarum cinereum was investigated in water agar medium and microscopic structure formation at five different stages during sporulation was observed. Spores of P. cinereum germinated by a V-shaped split method then produced watery white plasmodium of phaneroplasmodial type. The sporulation includes two periods, sporocarp formation and sporocarp maturity. The color of sporocarp changed from white to red-brown and finally black as spores developed during sporocarp maturity. Spores formed after capillitium formation during sporulation.
The life cycle and the microscopic structure at different stages of morphogenesis of Physarum pusillum was observed. The spore germination of P. pusillum was split type. Its swarm cells had two flagella, and the shorter one was not easy to observe. The plasmodial type is of phaneroplasmodium, and the sporulation process took about 12-13h. The microstructure observation showed that the lime knot and capillitium began to form about 6h after plasmodium uplift, and spores began to form about 9h after plasmodium uplift. The lime knot and capillitium formed before spore formation.
The volatile components in fruiting bodies of Polysphondylium violaceum and Cavenderia fasciculata were analyzed by phase microextraction gas chromatography/mass spectrometry. Thirty-two kinds of volatile components, including hydrocarbon, aldehydes, indoles, terpenes, ketones, esters and phenols, were identified from these two dictyostelid cellular slime molds. Of which 15 volatile components were identified from P. violaceum, and 27 from C. fasciculata. Eleven components were common in these two species. Some components seem applicable to making flavourings, and the further research on application of dictyostelid cellular slime molds needs to be developed.
