A guide to the biology and taxonomy of the Echinosteliales

Abstract

Haskins EF, Clark J 2016 -A guide to the biology and taxonomy of the Echinosteliales. Mycosphere 7(4), 473-491, Doi 10.5943/mycosphere/7/4/7 AbstractThis guide is an attempt to consolidate all information concerning the biology of the Echinosteliales, including uniform species descriptions for all of the species, and to make this available to interested persons in an open access journal. The Echinosteliales are a small group of myxomycetes with relatively minute sporangia and a unique plasmodial trophic stage (a protoplasmodium). These protoplasmodia, which are a defining characteristic of the order, are relatively small (20-150 μm in diameter) amoeboid stages with sluggish protoplasmic streaming and plasmodial movement which, as far as it is known, do not form a reticulum or undergo fusion with other plasmodia, but do undergo binary plasmotomy after reaching an upper size limit with each plasmodium produces a single sporangium. The minute sporangia produce a relatively limited number of spores and, except for one stalk-less species, they have a distinctive stalk consisting of a fibrillose tube having amorphous material in the lower region and closing at the upper end to produce a solid region. This morphology, along with developmental and DNA studies indicate that this order is probably the evolutionary basal group of the dark-spored myxomycetes.Key words -amoeboflagellate -Barbeyella -Clastoderma -Echinostelium -plasmodiumSemimorula -sporangia IntroductionThe minute sporangia of Echinostelium minutum, Clastoderma debaryanum and Barbeyella minutissima were discovered and named between 1874 and 1914. However, they were seldom collected and little was known of their developmental history except for Guliema Lister's early studies on spore germination, swarm cells and dividing myxamoebae; see Haskins (1988) for a discussion of her workbooks. However, it was the culture studies of Alexopoulos (1960), Olive (1960), and McManus (1961) that determined their basic biology and stimulated the search for additional species; with the descriptions of thirteen new Echinostelium species, two new Clastoderma species, and a new genus and species Semimorula liquescens (Haskins et al. 1983). The Echinosteliales are a relatively small order of myxomycetes with minute sporophores, that are generally designated sporocarps (produce internal spores) and they have a distinctive shape and size and are therefore sporangia. These sporangia, except for their minute size, are similar in structure and form to the vast majority of the sporocarps of the other orders of myxomycetes. Sporangia normally consist of two parts − the sporotheca which contains the spores, and the stipe which lifts the sporotheca off of the substrate (presumably for better spore dispersal). The stipe, which is present in all but one species in the order, consists of three continuous regions: the

A Non‐Flagellated Member of the Myxogastria and Expansion of the Echinosteliida

“…The genus Echinostelium is characterised by minute fruiting bodies, c. 10-500 lm in height, the largest species being, ironically, Echinostelium minutum (Haskins and Clark 2016). All 16 recognised species possess stalked fruiting bodies (Haskins and Clark 2016;Lado and Pando 1997;Whitney 1980), with the exception of the somewhat aberrant Semimorula liquescens (Fiore-Donno et al 2009;Haskins et al 1983).…”

Echinostelium australiense (Myxomycetes: Echinosteliaceae), a new species of slime mould described from Western Australia

“…The dark colouration of the sporotheca, stalk, and spores in E. australiense is unusual for the genus, which more typically has a pale sporotheca, a hyaline to pale brown stalk of uniform colour, and pale or hyaline spores (Haskins & Clark 2016). It is easily distinguished from the other species with spore-like bodies (E. apitectum, E. coelocephalum, E. colliculosum, E. ladoi, and E. novozhilovii) by the diagnostic characters listed above, which do not occur in combination within this grouping.…”

“…The stalks of the genus Echinostelium are typically cylindrical tubes with a small, solid, translucent, colourless apical region (Haskins & Clark 2016). The apical region in E. australiense is typical except for the grey-brown colouring for the uppermost 10 µm.…”

“…Kowalski and C. pachypus Nann.-Bremek. (Haskins & Clark 2016) or black as in C. confusum K.J. Knight & Lado (Knight & Lado 2020).…”

“…Echinostelium is a genus of myxomycetes (slime moulds) in which the inconspicuous sporocarps generally occur on the bark of living trees, with occasional occurrences on vines or various types of dead plant material (Keller & Brooks 1976;Whitney 1980;Haskins & Clark 2016) and very rarely on the weathered dung of herbivorous animals (Novozhilov & Schnittler 2008). Due to a short-lived life cycle strategy and the diminutive size of sporocarps, mostly less than 0.5 mm in height with the exception of E. novozhilovii A.Vlasenko, which can reach a height of 2.5 mm (Vlasenko et al 2018), new records and new species are usually observed from material recovered using the moist chamber technique and examination of substrate samples under a dissecting microscope.…”